|
*.. .. .... .......-l.-. .a
-;f ..... .. a e .-ey M T -N;
a. ........... , s ~ - ~
4~- -.. .2., e ,.. , .. ,, v a s 3
C --- 4 44 e .- e. - -a e- - e -- -- e 4w
- .. we.* > a .. ma - - r- s - :- : E.i i M f i l i ? > -v
~~~~~~~~~~~~~~~ ~~. . . . . -a---v.- eaa..
.. .. ... ...4- ..,.- .... .. .. . , . . . -- 4 a < ,
..........a 3 4 - a a a a a r 4. a ., o a a n as
Z- aer e a/ -/ e + 2e a e e
4 4 = 4 ( g 9 e W e# %+ a49 e4 44 e N4 4% e E S4 m m i-. i r' Zi i il. i, e-M r n a,- ea 2- 4eei e
4 a a e -a e a a v a / a aa a e e a e sw a e a 4 = 4 * * a e a T e * a a , . a : . = 4 . 4 - a a a e e, a ; fi ---.!E .
.. . ... e a o a a a . a a a a a e a e a a e o e e + t
& f & 4 # 4 B i -xy a e /
a ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .. lol ......, ta a s e e* ,9 e s
4 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .. .. - e < > - + - - - - e - - o
5 5 = a v w 4en 9 4h a1 ,
... . . i . . . .,. . . - ,
V5 ic 4 1 ,,ea a a ,ay +a ee A eaa w -o e 4 aa t s
rm r-.",
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ .. .. .. .. .... .. .. ,. . ..
* : i e b e E .
4. e a a < a a e = - = e s -- -a i ;;e - a
.............a .2 4 a a e a a et 4 4 -e 4 a e 4 5 ws a
s a a e4 ee 44 4 aa *N **t oa ae, ah awe e =*a 34a .. ... . 3 4 % 4 9
a a a a -s e e e i a e s e a e av i e e 5 m i i x M * * * a rmen o a s e ....... .... se
.. ...........- te a e a o y
3 m e6 s a e a 5 V 4 2 m r ** A 9 e * a W I * * * ** * in;.0
a a e e a e a e \ s e a e i .+ 4 a + e e e e e f a e J. -4 s a :- 3 919/a
-:ja e a a as + s awa eav e<,s ev4 aara5e t a24 mee4% =smn
R e a . a a e e = a i a e o e4; s e * a i a
K .. . .a ,a .--- -s
as 4 i % e e t a 4 e e n eA N J M* e e aa ea ea ae aa 54 5% ae 5L,*3 4A 4 awassN 4 % aoFi i ri 4 a e e i a i t t% eti 4 % e eN 2 4- 4 3 % % 4 3 4 i a i 4 % zi 4 aaag 3 ga 4 &a9e d 6*7e %0 44N t 4 E/ MNa t 4 644 .L4 30e $$% 66 &WX um-M7EN ey ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ i '%;TZA3 $$466ee4% eA$%eia 4t99244md 1 r ."' A .v v ;. , e e e a e a e s e e s
R .. .... ... e s eaaa4waaaei+ws
-4 : . . . . . . ,. **
Yx_;,i . .......... o6aeaa aaes as Aeasea ae a
-:A .. .. .. a aea aa aa aaa raa e a U S .5 a a 4 s 1 4 2 4 4 4 e L e a e ae .g y ao a p 9 E 3 i e #4 26 a 1 2 1e E3 m 6 $ aD & 4 E 4 9=ii p* 9 % ju m 9 s 1 e a 5 0 6 s 3 # 4 3 & 3%
; "Im m f
-x I: -4 1
T::70 sM.,
> a - *e a 3 i i ** *Mie i q ; Az N-, m tiiKkW.R 1M Z 1 ,z11:z;-1- e zil77 10 n g 3 T T A P ;Ji,
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 4 a 4aa R *Tny f ~
Mea2 ~
.. i e s -* +e+ s 1 pun ,e as
M. ....,,aa,,=, n ,. *,es a a ~ m 4x-e
m w a ,3 s1 a2% *A94Ea -a44% .0, a, g i aa s ae ii ea a e a s4- 1 :q aa*ias** 4 n s a a t $ 4 54 7e a i a a aa ae a , 1 i 4 a a 24 3% # t 4 % 4 'k
-~~ ..... ....y43it38m t 14,23si1%e344 y .. .. .
lo- 4 -5%6
...,. . . .
Il i&; aggaa sa i V
is j --t .,,, a~~~~~~. .. .. .., r s
C L a , ..
i:, -j ia ws, fff e 1to sa=
T.:a
z
Ci cmi i i,
~ ~ ~ ~ : ".. s ,- r-ex-,
-.;z -. ... i,-
E;. t i, i 2 -;
... L N. D-el
.j i
A.:
;4Z
..
44
0 st,:F r -4
ssu.
-im .q I'V a 1 ; e +
-m i -4 t
P --. a y
e .4 -.41
0"p-
u -- JI
13
,uns$flW 1mw) ~ujV#WJ a~$fO $P9
Gi- of'the Panama Canal Museum
1 -1-
REPORT
OF THE
BOARD F CONSULTING ENGINEERS
FOR THE
PANAMA CANAL
WASH INGTON
GOVERNMENTHPRINTING OFFICE
1906
-%I-
/s
'o
REPORT
OF THE
BOARD OF CONSULTING ENGINEERS
FOR THE
PANAMA CANAL.
LETTERS OF TRANSMITTAL.
To the Senate and ouse of Representatives:
1 submit herewith the letter of the Secretary of War transmitting the report of the Board of Consulting Engineers on the Panama Canal and the report of the Isthmian Canal Commission thereon, together with a letter written to the chairman of the Isthmian Canal Commission by Chief Engineer Stevens. Both the Board of Consulting Engineers and the Canal Commission divide in their report. The majority of the Board of Consulting Engineers, eight in number, including the five foreign engineers, favor a sea-level canal, and one member of the Canal Coinmission, Admiral Endicott, takes the same view. Five of the eight American members of the Board of Consulting Engineers and five members of the Isthmian Canal Commission favor the lock canal, and so does Chief Engineer Stevens. The Secretary of War recommends a lock canal pursuant to the recommendation of the minority of the Board of Consulting Engineers and of the majority of the Canal Commission. After careful study of the papers submitted and full and exhaustive consideration of the whole subject I concur in this recommendation.
It will be noticed that the American engineers on the Consulting Board and on the Comission by a more than two to one majority favor the lock canal, whereas the foreign engineers are a unit against it. I think this is partly to be explained by the fact that the great traffic canal of the Old World is the Suez Canal, a sea-level canal, whereas the great traffic canal of the New World is the Sault Ste. Marie Canal, a lock canal. Although the latter, the Soo, is closed to navigation during the winter months, it carries annually three times the traffic of the Suez Canal. In my judgment the very able argument of the majority of the Board of Consulting Engineers is vitiated by their failure to pay proper heed to the lessons taught by the construction and operation of the Soo Canal. It must be borne in mind, as the Commission points out, iII
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
that there is no question of building what has been picturesquely termed the Straits of Panama;" that is, a waterway through which the largest vessels could go with safety at uninterrupted high speed. Both the sea-level canal and the proposed lock canal would be too narrow and shallow to be called with any truthfulness a strait, or to. have any of the properties of a wide, deep water strip. Both of them would be canals, pure and simple. Each type has certain disadvantages and certain advantages. But, in my judgment, the disadvantages are fewer and the advantages very much greater in the case of a lock canal substantially as proposed in the papers forwarded herewith; and I call especial attention to the fact that the chief engineer, who will be mainly responsible for the success of this mighty engineering feat, and who has therefore a peculiar personal interest in judging aright, is emphatically and earnestly in favor of the lock-canal project and against the sea-level project.
A careful study of the reports seems to establish a strong probability that the following are the facts: The sea-level canal would be slightly less exposed to damage in the event of war, the running expenses, apart from the heavy cost of interest on the amount employed to build it, would be less, and for small ships the time of transit would probably be less. On the other hand, the lock canal at a level of 80 feet or thereabouts would not cost much more than half as much to build and could be built in about half the time, while there would be very much less risk connected with building it, and for large ships the transit would be quicker; while, taking into account the interest on the amount saved in building, the actual cost of maintenance would be less. After being built it would be easier to enlarge the lock canal than the sea-level canal. Moreover, what has been actually demonstrated in making and operating the great lock canal, the Soo, a more important artery of traffic than the great sea-level canal, the Suez, goes to support the opinion of the minority of the Consulting Board of Engineers and of the majority of the Isthmian Canal Commission as to the superior safety, feasibility, and desirability of building a lock canal at Panama.
The law now on our statute books seems to contemplate a lock canal. In my judgment a lock canal, as herein recommended, is advisable. If the Congress directs that a sea-level canal be constructed its direction will, of course, be carried out. Otherwise the canal will be built on substantially the plan for a lock canal outlined in the accompanying papers, such changes being made, of course, as may be found actually necessary, including possibly the change recommended by the Secretary of War as to the site of the dam on the Pacific side.
THEODORE ROOSEVELT.
THE WHITE HouSE, February 19, 1906.
WAR DEPARTMENT,
Wahington, February 19, 1906.
SIR: I have the honor to forward herewith the report of the Board of Consulting Engineers for the Panama Canal, convened by your order of June 24, 1905, with the views of the Isthmian Canal Commission and of the chief engineer of the canal.
The report shows that all plans heretofore proposed for a canal, with elevations varying from zero (sea level) up to 100 feet, have received careful consideration, but the Board was unable to reach a unanimous agreement. The majority of its members are in favor of a so-called sea-level canal, and the minority recommends a lock canal with a summit level 85 feet above the sea. A choice between the two must rest upon their relative advantages and disadvantages.
IV i
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
Both the majority and minority contemplate "safe and commodious" harbors in Limnon and Panama bays. Though differing in details, such work in no way affects the type of canal, and consideration of the terminal harbors in connection therewith is here unnecessary.
The sea-level canal proposed by the majority consists of a continuous, winding waterway extending from Limon Bay to a properly-constructed dam near Panama Bay, provided with duplicate locks near Sosa Hill to overcome the difference in tidal fluctuations that exist at the two extremities of the canal.. The canal prism has a depth of 40 feet, a minimum bottom width of 150 feet in earth and 200 feet in rock, with suitable side slopes for the former and practically vertical sides for the latter. The floods of the Chagres are controlled by a dam built at Gamboa to a height of 180 feet above sea level, provided with sluice gates for regulating the discharge, which is made through the canal. Dams and levees exterior to the canal are provided for diverting five of the twenty-seven streams that cross the canal line and for preventing overflows in the vicinity of Panama.
The 85-foot level canal recommended by the niinoritv has a dam across the valley of the Chagres River near Gatun, with a crest 135 feet above sea level and 50 feet above the normal water surface of the reservoir or inland lake that is formed. The dam is provided with sluice gates for regulating the height of water in the reservoir, thereby controlling the floods of the Chagres. From Limon Bay to this dam the channel is 500 feet wide and 41 feet deep at mean tide. The difference of level from the channel at the foot of the dam to the surface of the lake (85 feet) is overcome by duplicate flights of three locks. The total length of this waterway is 30 miles, extending from the Gatun dam to Pedro Miguel. At Pedro Miguel duplicate locks, with one lift of 30 feet under' ordinary conditions, connect the summit level with another waterway whose surface at normal stage is 55 feet above mean sea level. This waterway is created by dams placed across the valley of the Rio Grande and adjacent depressions, and extends nearly 5 miles to Sosa Hill. Descent to the channel-55 feet at mean tide-in Panama Bay is effected by duplicate flights of two locks to the west of Sosa Hill.
Under the act of June 28, 1902, Congress requires that the canal across the Isthmusshall be of sufficient capacity and depth as shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use, and such as may be reasonably anticipated.
This law, in effect, fixes the minimum dimensions of the locks and the width and depth of the canal prism. The high-level canal employs locks with 900 feet usable length, 95 feet width, and 40 feet depth over the miter sills, somewhat smaller than the tidal locks recommended for the sea-level type.
Two ships now building for the Cunard Line will be, when completed, the largest afloat. Each is 800 feet in length over all and 88 feet beam, with a maximum loaded draft of 38 feet. As the smaller of the proposed locks is capable of floating vessels of 25 per cent greater tonnage than the new Cunarders, it is evident that the locks fully comply with the requirements imposed by Congress.
In the high-level canal, a vessel of the dimensions noted would have, with the exception of the 4.7 miles where the width is only 200 feet, ample leeway for safe navigation and good speed, without objectionable currents and without difficulties at the points where changes in course are necessary. There would also be ample depth throughout except at the approaches. It is true that the depth in the channel below the Gatun dam is 41 feet at mean tide (tidal range 2 feet) and in the channel,below the Sosa locks, is 45 feet at mean tide (tidal range 20 feet), but additional
VI REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. depths in both approaches, because of the character of the bottom, can be easily and economically secured by dredging, when demanded by the needs of commerce.
With the proposed sea-level canal conditions are different. The depth is but 2 feet greater than the draft of the ship, not sufficient to permit her to proceed under her own steam except at great risk; 21 miles of the canal-is not sufficiently wide for two such ships to pass; currents caused by the regulation of the Chagres and by the flow of other streams into the canal, and its many curves, combine to increase the difficulties and dangers of navigation. In short, the sea-level canal recommended is not "of sufficient capacity and depth" to "afford convenient passage for vessels of the largest tonnage and greatest depth," and can be made so only by materially increasing the depth and width, and at a considerable increase of time and money. If the suggested width of 150 to 200 feet is the greatest width economically permissible for a sea-level canal, the cost of the enlargement required must be prohibitive.
It therefore follows that the high-level canal more fully meets the requirements of Congress.
The majority of the Board makes objection that locks are unsafe for the passage of the great seagoing vessels contemplated by the act, due to the disastrous consequences that might result if the gates are injured by vessels entering; that the lifts- proposed are beyond the limit of prudent design for safe operation and administrative efficiency; that locks delay transit.
Lock navigation is not an experiment. All the locks are duplicated, thereby minimizing such dangers, and experience shows that with proper appliances and regulations the dangers are more imaginary than real. The locks proposed have lifts of about 30 feet, or less than those heretofore advocated by engineers of such high standing that the objection is believed to be not well founded. The delays due to lockages are more than offset by the greater speed at which vessels can safely navigate the lakes formed by the dams than is possible in the sea-level canal, and the arguments on this point in the minority report seem to me to be the more weighty.
The advocates of the sea-level canal express doubt as to the stability of the dams at Gatun and at La Boca, if founded on the natural soil, and advance the opinion that no such vast and doubtful experiment should be indulged in."
It appears, however, that the dams proposed are to be founded on impervious materials, thereby conforming to the views of the majority, and are to have such ample dimensions as to insure the compression of the mud and clay rather than its displacement. Furthermore, the estimates include an allowance for additional safeguards against seepage if subsequent detailed investigations show the necessity for extra precautions. The construction of earth dams to retain water 85 feet deep is not experimental, and as the dams proposed have greater mass and stability than similarly constructed dams of greater heights, it appears that the apprehensions as to the safety of the dams are unnecessary.
In the sea level-canal there are three stretches, aggregating 21 miles, out of about 43 miles between the shores of Limon Bay and Panama Bay, in which the bottom width is 150 feet; 19 miles have a bottom width of 200'feet; 1.5 miles near Panama have a width of 300 to 350 feet; the remainder, 1.5 miles near Mindi, has a bottom width of 500 feet.
Between the Gatun dam and Sosa locks, a distance of 41 miles, the high-level canal has a minimum depth of 45 feet; for 19 miles of this distance the least bottom width is 1,000 feet; 4.7 miles have a width of 200 feet; the remaining 17.5 miles have widths varying from 300 to 800 feet.
The sea-level canal gives tortuous navigation for the greater distance through a comparatively narrow gorge in which the largest vessels can not proceed under full headway, pass without risk,
I
REPORT OF' BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. ,4T11 or turn about. The high-level canal, for the greater distance, gives practically lake navigation in which vessels can proceed at full speed along straight courses, pass each other without delays or risks, and can turn about, if necessary.
The high-level canal has the additional advantage of "greater safety for ships and less danger of interruption to traffic, by reason of its wider, deeper, and straighter channels."
It also follows from these considerations that quicker passage with larger traffic is possible with the high-level canal.
The estimated, cost is $247,021,000 f or the sea-level canal, and $139,705,200 f or the 85-f ootlevel canal, a difference of $107,000,000. The lsthmian Canal Commission and the chief engineer regard the estimate for the sea-level canal as too low by at least $25,000,000, for reasons stated in their reports.
The advantage of less cost is greatly in favor of the 85-foot-level canal.
The estimated time for completing the sea-level canal is stated by the majority of the Board as from 12 to 13 years, by the Isthmnian Canal Commission and -the chief engineer from 18 to 20 years. The minority report estimates the time for completing the high-level canal at eight and one-half years, and this is regarded as conservative by the other competent authorities.
The advantage in practical speed of construction is in favor of the high-level canal.
The cost of operation and maintenance is an important consideration, and if measured solely by annual appropriations therefor the advantage is in favor of the sea-level canal. It is believed, however, that the difference is more than offset by the interest on the additional investment in the cost of a sea-level canal.
Besides serving the needs of commerce, the canal will give the military advantage to the country of providing a route for the speedy reinforcement of the fleet on either side of the continent, and military considerations must have due weight. Either type of canal is vulnerablethe high level the more so because of the lift locks which can be easily injured. Protection must be afforded in either case. A concentration of the locks simplifies the defense, and as guards are necessary they should be of sufficient strength to reduce to a minimum the danger of injury to locks and dams.
In view of the foregoing, I recommend the adoption of the type of canal proposed by the minority of the Board of Consulting Engineers, except so far as relates to the location of the locks at Sosa Hill.
The suggestion that the lake formed near Panama will be unsanitary does not seem well founded, as I am advised by the medical authorities of this Department that unsanitary conditions with respect to the lake can be avoided by proper precautions.
The great objection to the locks at Sosa Hill is the possibility of their destruction by the fire from an enemy's ships. If, as has been suggested to me by officers of this Department entitled to speak with authority on military subjects, these locks may be located against and behind Sosa Hill in such a way as to use the hill as a protection against such fire, then economy would lead to the retention of this lake. The lake would be useful to commerce as a means for relieving any possible congestion in the canal should the traffic be very great and would give, in case of need, a place for concentrating or sheltering the fleet. If, however, Sosa Hill will not afford a site with such protection, then it seems to me wiser to place the locks at Miraflores.
When I visited the Isthmus a year and a half ago and went over the site and talked with the then chief engineer I received a strong impression that the work of construction upon which the
United States was about to enter was of such world-wide importance and so likely to continue in
:4VI
VVJ60 REPORT OF BOARD ON CONSULTING ENGINEERS, PANAMA CANAL.
active use for centuries to come, that it was wise for the Government not to be impatient of the time to be taken or of the treasure to be spent. It seemed to me that the sea-level canal was necessarily so much more certain to satisfy the demands of the world's commerce than a lock canal that both time and money might well be sacrificed to achieve the best form, and this feeling was emphasized by reading the very able report of the majority. Bnt the report of the minority, in showing the actual result of the use of the locks in ship canals, in pointing out the dangers of so narrow and contracted a canal prism as that which the majority proposes, and in making clear the great additional cost in time and money of a seal-evel canal, has led me to a different conclusion.
We may well concede that if we could have a sea-level canal with a prism from 300 to 400 feet wide, with the curves that must now exist reduced, it would be pref erable to the plan of the minority, but the time and the cost of constructing such a canal are in effect prohibitory.
I ought not to close without inviting attention to the satisfactory character of the discussion of the two types of canal by the greatest canal engineers of the world, which insures to you and to the Congress an opportunity to consider all the arguments, pro and con, in reaching a proper conclusion.
Very respectfully, W~m. H. TAFT,
Secretary qfIT'r.
The PRESIDENT.
ISTHMIAN CANAL COMMISSION,
lWashington, D. C., February 6, 1906.
SIR: I have the honor to transmit herewith the conclusions and recommendations of the Isthmian Canal Commission and the dissenting views of Admiral Endicott upon the majority and minority reports of the Board of Consulting Engineers, advance copies of which, together with the proceedings of the Board, were furnished to the Commission in December last. Appended to the findings of the Commission is a letter to the Commission from the chief engineer, Mr. John F. Stevens, giving his views on the relative merits of a sea-level and a high-level canal.
Very respectfully,
T. P. SHONTS, Ota)nman.
To the honorable the SECRETARY OF WAR.
ISTHMIAN CANAL COMMISSION,
a'8s'gton, D. C., February 5, 1906.
MR. SECRETARY: The Isthmian Canal Commission has the honor to transmit herewith two reports which it has received from the Board of Consulting Engineers appointed by the President June 24, 1905, to consider plans for the construction of a canal across the Isthmus of Panama. The board was unable to reach a unanimous agreement. One of the reports is signed by eight members, and recommends a canal at sea level. The other is signed by the remaining five members, and recommends a canal with a summit level 85 feet above the sea, to be reached by locks.
Before proceeding to a review of these two reports -it is desirable to remove certain misapprehensions as to the meaning of the terms "canal at sea level" and "canal with locks" as defining the character of the completed waterway. In the popular mind the one means a waterway affording navigation without restriction, while the other means a waterway in which navigation is delayed and hampered by mechanical appliances, and decidedly inferior to the former. These conceptions are quite inaccurate.
The ideal waterway through the Isthmus would be a channel at the sea level, of which the width would be greater than the length of the vessels using it. With any less width it is liable to the accident of being completely blocked by the sinking of a vessel transverse to its axis. If vessels 900 feet long are to be accommodated, the width should be considerably greater than 900 feet. A channel of this size can not be considered and has never been proposed. The, enormous cost of the excavation has compelled all engineers who have considered the question to reduce the width to that strictly necessary to pass the largest vessels at greatly reduced speed. A width of 150 to 200 feet is now proposed, and is believed to be the greatest width economically permissible for the sea-level canal. It is very far, however, from furnishing unrestricted navigation. The speed of very large vessels, like the new Cunarders, must be reduced to 4 miles per hour or less, while two such vessels could not pass each other in the canal. Between this and the ideal canal are many degrees of size and convenience.
In a canal with locks, artificial lakes are created in which for considerable distances the navigation is entirely unrestricted. The advantages thus gained may more than counterbalance
the delay and risk in the use of locks, and it is quite conceivable that a canal with locks may be a better canal-that is, can be navigated in less time and with less risk than a canal at sea level.
A discussion of the relative advantages and disadvantages of the canal at sea level and the canal with locks is to be approached then without prejudice in favor of either as a means of transit.
S. Doc. 231, 59-1-2* Ix
X REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
SEA-LEVEL PLAN.
The plan recommended by the majority of the board is a canal at the sea level, following essentially the line heretofore adopted by Congress, except near the terminals, the depth to be 40 feet, and the width at bottom to be 150 feet where the side slopes are gentle, and 200 feet where the side slopes are nearly vertical, as in rock. The least area of cross section is 8,276 square feet. At the Panama end is a tide lock, having a usable length 1,000 feet, width 100 feet, and depth over the miter sills 40 feet. In Panama Bay the channel is to be 35 feet deep at extreme low water of spring tides, which will give the fll 40 feet provided elsewhere in the canal, except upon rare occasions.
To control the Chagres River, a dam of masonry, or of earth and masonry, is proposed at Gamboa, jnst off the line of the canal, built to a height 180 feet above the sea, forming a reservoir called Gamboa Lake, of which the maximum flow line is to be at elevation 170, into which the flood waters are to be received, but no design therefor is submitted.
This dam is to be fitted with controlling sluices by which a maximum discharge of 15,000 cubic feet per second is to be admitted to the canal prison, all in excess of that amount being temporarily stored until the subsidence of the flood. Of the tributaries entering the Chagres below Gamnboa, the most important are diverted entirely from the canal and conducted by separate channels to the sea. There will still remain a number of tributaries and other streams to be taken into the canal. Their volume is assumed by the Board to be such that, added to the 15,000 cubic feet to be admitted through the sluices, they will create currents of which the highest mean velocity is computed by the majority to be 2.6 miles per hour. Ordinarily the velocity will not exceed 1 mile per hour.
Extensive harbor improvements are proposed at Colon.
The cost of the canal under this plan is estimated by the majority at $247,000,000. From the nature of the case this estimate can not be made with great preision. The quantity of each class of work to be done can, as a rule, be accurately measured, but the unit price for~ each class must be largely a matter of judgment. It is the opinion of this Commission that the unit prices adopted by the Board are, upon the whole, judicious, except in the ase of rock excavation under water, which seems to us low, but is accepted'here for purposes of comparisson; and that otherwise the estimates are as near an approximation to the truth as can now be reached, in all except two items. These items are the excavation in Culebra Cut below elevation +10, given on page 51 as $20,242,877.50; and the completion of river diversions, regulation of rivers floxing-, into the canal, etc., given on page 58 as $3,500,000.
The first item covers 16,194,302 cubic yards of excavation, of which 11,439,612 cubic yards is below and the remainder above the level of the sea. The majority of the Board has adopted a uniform unit price of $1.25 per cubic yard for the whole. This price seems fair for the portion above the level of the sea. For the portion below, it seems to the Commission that the price of rock excavation under water, $2.50 per cubic yard, should be applied here as it is in the adjacent sections of the canal by the Board. If that be done, the cost of this item will be increased $14,299,515, and adding the usual 20 per cent for contingencies, the estimate will be increased $17,159,418.
The estimate, $3,500,000, of the cost of completing the river diversions, formation of dams across tributary streams, regulation of rivers which flow into the canal, etc., is believed to be too low. To show the magnitude of this feature of a sea-level canal, a table is presented giving the names of the more important streams which enter the site of the canal, the distance of the point of junction from the Caribbean end of the canal, the height above sea level of their junction with the Chagres', Obispo, or Rio Grande rivers, and the volume of discharge at igyh stage as far as observed or estimated. It must be remembered that while gaugings
of the Chagres at several points have been systematically carried through thfe river year COv Tering both low waters and floods, nothing of this sort has been done on the other streams, where gaugings have only been made desultorily, at such times and for such periods as were convenient. The discharges given in the table are in many instances obtained by distributing
i
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. X
the total discharge of a considerable number of tributaries of the Chagres among the individual ti-ibutaries, according to the areas of their drainage basins. There is no certainty that this gives. the maximum discharge for any one tributary, but the probability is that it does not.
Greatest ElevaName. Distance observed tion at Nam. isane.dis- mouth charge. above sea
level.
Streams diverted: Mites. Sec. feet. Feet.
Mindi.....................5
Gatun..................... 6.2 16,100 ..........
Trinidad.................. 9.6 18,500 ..........
Gigante, left bank........ 18.91 2,158 30 Cano, left bank.. ......... 19.84 9, 006 33
Streams not diverted:
Aojeta .................... 15.25 1,000 15
Agua Salude, right bank.. 16.30 2,306 25 Frijolito, right ban ...... 17.36 1,000 20 Frijoles Grande, right
bank.................... 17.98 3,740 26
Agua Bendita, left bank.. 21.26 300 35 Caimito Mulato, left bank 22.32 300 35 Baila Monos, left bank.... 22.81 1,775 45 Culo Seco, left bank....... 23.87 300 40 Pisco, right bank.......... 24.18 1,200 34
Juan Grande, right bank. 25.11 1,200 38 Carabali, left bank........ 25.42 760 40 Quatre Calles, right ban. 26.66 500 45 Obispo .................... 27. 90 3, 700 160
Mandingo, left bgnk ...... 28.80 1,500 45 Camacho, left bank....... 29.10 1, 349 165 Sardinilla................. 30.30 800 165
Rio Grande, right bank... 34.72 660 130 Mallejon, right bank 36. 89.............33
Pedro Miguel, left bank... 37. 07........... 15
Caimitillo, left bank ...... 37.82........... 13
Rio Cocoli................. 38.90........ ..........
Rio Cardenas ............. 39.40 .......... ..........
The Cano and the Gigante, the latter including its principal tributary, the Gigantito, are to be cut off by dams. The Trinidad will occupy the old channel of the Chagres River and the Chagres diversion. The Gatun will be cut off from the canal by the partly finished Gatun diversion, into which also will be conducted the Mindi River, which has not been gauged, but which is a stream of considerable importance. The others are to be taken into the canal. They must, however, be temporarily diverted during the excavation of the canal; and in the case of the Rio Grande this involves a tunnel seven-eighths of a mile long. In all the diversion channels together, the amount of excavation and levee building, with the necessary muck ditches and riprap levee and bank revetments, tunnels, etc., can not be less than 10,000,000 cubic yards. In view of the facts that in many cases the work is isolated and the field of operations narrow and contracted, that much special work, such as revetment, is required, and that the operations of excavation for channels and embankments for levees are separate and distinct, and that the material is not uniform, involving both earth and rock, the unit prices will be high.
The Cano and the Gigante are to be cut off by dams, lakes being thus created which will overflow through spillways provided in the divide near the heads of those streams. In this scheme four dams and three spillways are projected. The dam to close the Gigante will be about 2,800 feet long, that to close its main tributary, the Gigantito, will be about 490 feet long, and that to close the Cano about 820 feet long, the height in each case being about 75 feet above the ground, the depth to which the foundations must be sunk being unknown. A dam about 535 feet long and 25 feet high will be required to close a depression in the rim of one of the lakes. These and the spillways are expensive works'. Their locations have never been examined by
XII REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
borings or exact topography, with the exception of the Gigante spillway. Their cost can not be accurately estimated without further examinations, but under favorable circumstances cen hardly be less than $1,000,000.
The streams taken into the canal, whose beds at point of junction with the canal are considerably above the canal prismi, are to be discharged over masonry stepped aprons or through metallic discharge pipes, or these beds will be sloped and lowered so as to prevent objectionable currents at junction points." Tfhe elevation above sea level at which these streams reach the canal is given in the foregoing table, and varies from 13 to 165 feet. A provisional treatment of such important features of a sea level-canal should not be considered. From the point of view of thoroughness and permanency, the sloping and lowering of the beds so as to prevent objectionable currents at junction points would not be good practice. It may be surely anticipated that the accelerated velocity down the increased slope, unless its bottom and sides are lined with masonry, will operate with destructive effect both on the lowered channel and the bed and banks of the canal. Metallic discharge pipes are not adapted to this purpose on streams which are torrential in character and may bring with their flood drift trash and bowlders. The use of mason ry- stepped aprons must therefore be considered, under the conditions presented by most of these streams, as the only advisable way of bringing them from a high to a low level. The construction of these would necessarily be very heavy and therefore very expensive. As in the case of the dams, the sites of those aprons have not been carefully examined, and the estimate of cost can only be a rough approximation. It is the opinion of the Commission that the sum of $3, 500,000, assigned by the majority of the Board to the completion of the diversion channels, the construction of the dams and spillways, and the construction of these aprons, is inadequate, and should be increased by at least $6,500,000, which, with the usual 20 per cent added for contingencies, makes an increase of $7,800,000 to this item of the estimate.
If the foregoing increases be added to the $247,000,000 estimated by the majority of the Board, the cost of the sea-level canal will be found to be $272,000,00.
The time required to build the canal is estimated at twelve to thirteen years. The number of unknown factors which enter into this estimate is still greater than in the case of estimates of cost. There are two methods available for reaching a conclusion upon the subject. One is that followed by the Board, viz, to assume that the largest single piece of work-the Culebra Cut-will fix the time required, and that all other work can be completed while that is being executed, then to ascertain how many excavating miachines can be employed at one time in the Culebra cut, and then assign to each machine its daily or annual working capacity, under the conditions which prevail there. There is great uncertainty about all of these elements. The number of steam shovels which can work to advantage in Culebra cut is not known, lbut is pr obably much less than the number mentioned in the report, 100; and there is no experience to show what the output of a steam shovel will be under all the extremely varying conditions which obtain there. The other method is to examine the results obtained in the great operations of the old French company in this same work. It is not unusual to hear that company spoken of lightly, but it is to be remembered that it had at its head men who had recently built the Suez Canal, that it had the advice of the best engineering talent in Europe, and that its pecuniary resources for some years were practically unlimited. After devoting the years 1881 and 1882 to preliminary work, it began operations on a large scale in the early part of 1883, and continued them until the latter part of 1888, about six years or seventy-two months. It excavated altogether about 72,000,000 cubic yards of material, or about 1,000,000 per month if we attribute the work of 1881 and 1882 to the -later period, of which about one-third was the easy excavation with dredges in the coastal plains. In doing this it had every inducement that men could have to make haste. Its concession from Colombia for a limited period, its enormous interest charges, and the sanguine assurances of its promoters and managers, all urged the greatest possible speed. The wreckage
along the line of the canal to-day is a demonstration of the feverish energy with which every species of machinery was lavished upon the work. To get the work done was the primary consideration, its cost secondary. The circumstances are now different in several important respects. There have been great improvements in excavating machinery, and means have been found to
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL XI
remove the terror of yellow fever, both of which conditions favor an increase of output. On the other hand, there must be a much more careful adjustment of the means to the end. Extravagant duplication of machinery, or other reckless expenditure, can not be tolerated. It is hoped and believed that a considerable increase over the French rate of progress can be attained. What the percentage will bec is a matter of judgment, and is not capable of exact computation, but it would seem that the chances of error here are less than where all of the factors are unknown. Here at least the difference between spasmodic and long-contitinued effort, and the reduction of efficiency due to climate and distance from supplies are eliminated. In the opinion of the Commission it would not be unreasonable to hope for ain increase of 25 per cent; which would give an average output of 1,250,000 cubic yards per month. To excavate the 231,000,000 cubic yards of the sea-level canal at this rate would require one hundred and eightyfive months or fifteen and one-half years. There would be at least two and one-half years ait the beginning before this rate could be reached, and at least an equal amount of tim-te at the end, durino'whichi the contracted space at the bottom of the cut would compel a reduction of force. It is to be feared that the time required to construct a sea-level canal would be ighiteen or twenty years, rather than the twelve or thirteen years estimated by the majority, even supposing that the total amount of excavation will not exceed the 231,000,000 Cubic yards estimated. To reach that amount the majority of the Board has adopted steeper slopes in the Culebra cut than any previous board or commission has adjudged applicable. It mnay well happen that these Slopes must be reduced, and the amount of excavation thus increased. The majority of the Board has made no provision for the necessary turning-out places and widening at curvecs. It is not safe to estimate the time required for the construction of a sea-level canal at less than twenty years.
PLAN WITH LOCKS.
The plan, recommended by the minority of the Board is a canal with locks, f ollowing in general the same location as the other, but with slight variations therefromi in Limon and Panamna bays. Its controlling feature is a dan to close the valley of the Chagres at Gatun, thus creating an artificial lake of which the surface is to be 85 feet above the sea and which is to constitute thle summit level. The length of this dam will be 7,700 feet, and the height of its crest 135 feet, or 5( feet above the water surface. It will contain about 21,200,000 cubic yards of material, principally the spoil from the excavation of the canal prism. It is provided with ample spillways and regrulating works. A channel 500 feet wide at sea level leads from Uimon Bay to the Gatun dami, where is placed a double flight of three locks by means of which vessels are lifted into the artificial lake. The lake provides unrestricted navigation for a large part of its length, but becomes more contracted as the Continental Divide is approached until in the Culebra Cut the width at bottom is reduced to 200 feet. It finally terminates at Pedro Miguel, where the first lock on the Pacific side is placed, having a lift of 30 feet. By means of this lock vessels are lowered into another artificial lake created by a dam closing the valley of the Rio Grande, and by ttvo other damis closing other depressions, the level of the lake being 55 feet above the sea. The crests of these damns are 80 feet above the sea. Commtunication between the lake and Panama Bay is effected by a double flight of two locks placed near the shore on the high ground called Sosa hill. All locks are in duplicate and have a usable length 900 feet, width 95 feet, and depth over the miter sills 40 feet. The depth of the channel is everywhere at least 45 feet except in the locks and in Limon Bay*N, where it is 40 feet, the depth in Panamna Bay, however, being measured from mean tide and not from dead low water. In the lakes the depth is of termvery m iuch greater, being 75 feet near the Gatun dam, and nearly as much for nmany Tmiles. The width is nowhere less than 200 feet at bottom, and at most places is very much more. The length of the canal from deep water in Limon Bay to deep water in Panama Bay is 49.72 miles. Of 'this 19-i- miles is over 1,000 feet wide, 23 miles is o ver 800 feet wide, 35 miles is over 500 feet wide, and 42J miles is over 300 feet wide. That is, for about half the distance navigation is entirely unrestricted, while for more than two-thirds the distance the channels are 500 feet or more wide, and for only one-seventh the distance, including the locks, are they less than 300 feet wide.
--Xlli
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The cost of the canal under this plan is estimated by the minority of the Board at $139,705,200, and the time required to build it at nine years. We consider both of these estimates reasonable, subject to the remarks already made concerning unit prices.
The plan recommended by the minority of the board is of the same type as that recommended by the Commission of 1899-1901 and adopted by Congress, at least by inference, in the act approved June 28, 1902. It provides wider and deeper channels and larger locks than that plan and a different arrangement of dams, as well as a change in the Atlantic entrance, but the height of the summit level is the same, and the estimates of cost and of the time required for construction are very nearly the same. Some of the changes have been made necessary by new requirements for navigation, and others have been the result of further study by fresh minds. They are improvements, such as Congress could not possibly have intended to prohibit when it adopted the old plan. They are of importance, but they do not seem to us to be changes of such radical character as would require further action by Congress, as in the case of a canal at sea level.
The only features of this plan which do not fall within the limits of every-day practice are the height and size of the dams and the size of the locks. No question has been raised as to the stability of the Gatun dam, and, indeed, none can be raised while there are in successful operation in this country earth dams of less cross section retaining a greater head of water. The great quantity of material available has made it possible to give this dam dimensions which are much greater than are strictly necessary. The majority of the board, however, do question the effectiveness of that dam in retaining water, expressing the fear that the-subfoundation may be found so porous that seepage will be excessive. The minority point out that the material under the dam is exceptionably favorable, that for a depth of 200 feet it is practically impervious, and-that the more porous material which is found for a short distance below that depth is covered with this impervious blanket 200 feet thick for a long distance upstream. They express the opinion, in which we concur, that there would be no appreciable seepage under the dam. In the case of the Rio Grande dam, the majority goes further and states that the earth dam proposed for that locality is in danger of being pushed bodily out of place by the pressure due to the head of water in the reservoir," unless it be made very massive. In the opinion of the minority, in which we concur, the dam, as designed, is so massive that this is impossible. In this case, the greatest depth to rock is 64 feet, and all seepage can be cut off by sheet piling, if necessary; but the borings thus far indicate impervious material under the dam, and it is not expected that that device will be required.
The locks are larger than any which have heretofore been built, and the majority of the Board express the opinion that they are beyond the limit of prudent design. As a matter of fact, larger locks have been designed with the greatest prudence and with mathematical certainty. It can no more be said of lock building that it has reached the limit of judicious construction than of ship or bridge building or any other branch of engineering construction. A modern bridge of long span is a safer structure than the short span bridge of former days, because of better knowledge of the materials and improved methods of uniting them. So the proposed locks can be made safer than the Poe lock at the Sault, because they are designed after nine years of practical experience with that lock, an experience which shows it to be a safe place for a vessel.
It is our opinion that the entire feasibility of constructing the canal under the plan proposed by the minority of the Board can not be successfully questioned.
RELATIVE EFFICIENCY OF COMPLETED CANALS.
The majority of the Board express the opinion that the canal at sea level is the only one giving reasonable assurance of safe and uninterrupted navigation, and question the safety of large vessels in passing locks.
The most important ship canal in the world is that at the Sault Ste. Marie, at the outlet of Lake Superior. The tonnage which it carries per annum is about three tinies that carried by the Suez Canal, and is greater than the aggregate tonnage of the Suez, Manchester, Kiel, and
XIv
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. x
Amsterdam canals combined, although navigation is suspended several months each year by ice. One of its locks is the largest in existence, and during the season of navigation this lock alone carries three times the tonnage per month that the Suez Canal carries. It has been in successful operation since 1896, and has carried with ease and saf ety the largest vessels on the Great Lakes, some of them measuring 569 feet in length with .56 feet beam. The navigation interest has no fear of this lock. That interest is growing with marvelous rapidity, and is clamoring for deeper channels between the lakes, so that larger vessels miay be used and large r locks built. No engineer who is familiar with this lock has any mnisgiving~ about its safety, or about the entire feasibility. of building larger locks which shall be equally safe.
The majority of the Board have attempted to belittle this experience. They say it is not a "maritime canal." They explain that masters of vessels passing to and f ro every few weeks acquire familiarity with the canal and locks, which leads to a degree of skill and safety 'which could never be attained in the Panama Canal, which would be visited only at rare intervals, forgetting that this acquired skill simply makes unnecessary the services of a pilot, and can never be equal to the skill of the special pilots who would be employed at Panama. They attach importance to the fact that navigation at the Sault is closed by ice for several months each year, at which time the locks can be pumped out and repaired, not stopping to consider that at Panama there are two sets of locks, one of which can be pumped out and repaired at any part of the year. They point to the three accidents which have occurred to the locks within the last nine years, and make certain speculations as to how near these were to being serious and what would have happened if the lift had been as great as that proposed for Panamaa, omitting to note that during the same period the open channels below were completely blocked three times, besides being partially blocked at other times, by the sinking of vessels. During each of the complete blockades in the open channel navigation was entirely suspended from two and a half to five days, and during the partial blockades all vessels were delayed from five to twenty-four hours, this state of affairs lasting in one case ten days. It is true that locks are subject to accident, but so are narrow channels without locks. In addition to the evidence just given, mention may be made of the steamer chatkam-, by which the Suez Canal was wholly blockaded for ine days, and partially blockaded for about a month in September and October, 1905. We can not concur in the opinion that a canal at sea level 150 feet wide gives 'safe and uninterrupted navigation least of all if, as in this case, that canal is l ,iable to currents of 2.6 miles per hour. Moving in the same direction with such a current, it is doubtful whether one of the largest vessels now in, use could navigate the canal at all with her own power. Nor can we concur in the opinion that a lock properly constructed and managed is in any sense a iuienace to the safety of vessels. Practical experience has demonstrated the contrary beyond dispute.
The volume of. water contained in the proposed sea-level canal is about 100,664,000 Cubic yards; that contained in the proposed canal with locks, omitting all below 45 feet depth and all beyond 1, 000 f eet width, is abo ut 303, 614, 000 cubic yards. I t is a f air statem ent that on e w ate rway is three times the size of the other, and that but for the locks it affords three times the facilities for navigation.
In the canal at sea level there are many curves; in that with locks all the Courses are straight, changes of direction being made at the intersection of tangents, where additional width is given. These straight courses can~ be marked with ran ges, which greatly f ailitate navigation, particularly at night.
In the canal at sea level there is often a considerale current, which at times becomes obstructive. In the canal with locks there is no such obstruction.
The time required to pass through a canal of either type differs with the size of the vessels and the number of vessels. Following the method described in the report of the Isthmian Canal Commission of_ 1901, the minority of the Board find that for a small ship the canal at sea level has the advantage by about thirty-six minutes, provided the number of ships does not exceed 10 per day. If the number of ships exceed 30 per day, the canal with locks has the advantage by about three hours. For large ships the canal with locks has the advantage whatever be
xv
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
the number per day. If the number be 10, the advantage is about thirty-six minutes; if it be 30, the advantage is over three and one-half hours. We believe these results to be approximately correct, assuming that there is no current in the canal. Should there be a current of 2.6 miles per hour, such as the sea-level canal is subject to, the time of passage through that canal might be greatly increased. It is assumed also that numerous turning-out places are provided in the sea-level canal, although for these no provision is made in the plan or the estimate.
The majority of the Board claim that locks limit the traffic capacity of the canal, that lockages perhaps can not exceed 10 'per day for each lock, or 20 per day for the pair. The minority point to the experience at the Sault, which shows that this estimate is not in accord with American practice, and they show that with the double flight of locks proposed, a traffic of at least 80,000,000 tons per annum can be accommodated. Additional locks ma be built hereafter if needed.
The majority in one place express the opinion that the canal at sea level "will endure for all time," page 64, and in another give weight to the comparative ease and economy of enlarging the prism of the sea-level canal to accommodate any additional demands of the future," page 64. We estimate that to widen the sea-level canal 100 feet without deepening it will cost at least $87,000,000. To deepen it involves excavation under water throughout its length. The canal with locks may be deepened easily and cheaply by simply raising the crests of the spillways and the height of the locks.
The majority express the opinion that the cost of operating and maintaining a sea-level canal will be very much less than that for a canal with locks; and using the figures of the Commission of 1899-1901, they give the cost of operating and maintaining the locks at about $525,000 per annum. That estimate is probably as near an approximation to the truth as can now be given. The canal at sea level will require more dredging than the other, and it has one lock to be maintained. It must also be furnished with turn-out places and attendance there. A reasonable allowance for these expenses is $225,000, leaving $300,000 per annum as the apparent advantage in operating expenses of the sea-level canal. Against this is to be placed the interest on the additional investment. If the canal at sea level will cost $132,000,000 more than the canal with locks, as we believe it will, the interest on that sum is an additional fixed charge, and at 2 per cent amounts to $2,640,000 per annum; that is, the annual fixed charges of the canal at sea level will be $2,340,000 more than those of a canal with locks.
The majority of the Board point to the ease with which an enemy might in time of war disable the locks with a few sticks of dynamite and lay much stress upon the disastrous results which would ensue to the United States should the passage be interrupted. The difficulty of defending the canal was clearly pointed out by the Commission of 1899-1901, who closed their discussion as follows, viz: "It is the opinion of the Commission that a neutral canal, operated and controlled by American citizens, would materially add to the military strength of the United States; that a canal, whether neutral or not, controlled by foreigners, would be a source of weakness to the United States, rather than of strength; and that a canal not neutral, to be defended by the United States, whether by fortifications on land or by the Navy at sea, would be a source of weakness." In that opinion we concur. It applies equally to a canal at sea level and to a canal with locks. In the former, the great dam at Gamboa and the other great dams, the steep slopes at Culebra, and the tide lock at Sosa all present points of attack, less favorable, no doubt, than the locks, but sufficiently so to make the canal entirely vulnerable. The canal at sea level can be blocked by sinking a vessel at any part of its length, while the canal with locks, for a large part of its length, can not be blocked in that manner at all. Should the United States depart from its true policy of making the canal neutral, it will not gain anything in a military point of view by adopting the canal at sea level in preference to the one with locks.
There is one valid argument, and one only, which can be brought against the canal with locks, and that is the difficulty of fixing the dimensions of the lock chambers to provide for the possible enlarged vessels of the future. The majority of the bzoai-d propose a length of 1,000 feet, a width of 100 feet, and depth over the miter sills of 40 feet; while the minority propose a
XVI
REPORT OF' BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. XI
length of 900 f eet, a width of 95 f eet, and 40 f eet over the miter sills. In the f ollowing table is a list giving the dimensions of 12 of the largest ships in the world and the ratio of their length and beam to their draft:
Maxi
Name of steamer. Steamship line. When LengthBem mum Ratio of draft to huilt. over all. em loaded beam and length.
draf t.
Feet. Feet. Feet.
Kaiser Wilhelm der Grosse ...North German Lloyd.....1897 648.4 66.0 28.5 1 :2.311:22.75
Kaiser Wilhelm II............ ..... do .................... 1902 706. 5 72.0 30. 5 1 : 2.6 :2. 16
Kronprinz XWilhelm .......... ..... do ................... 1901 66. 3 66. 0 30.0 1 : 2. 20 :22.11
Oceanic...................... White Star ................ 1899 705. 6 68. 4 35. 7 1 :1. 91 : 19. 76
Celtic ....................... ..... do .................... 1901 697.5 75.4 6.8 1 :2.04:18.95
Cedric ...................... ..... do ..................... 1901 697.5 75.4 6.9 1:2.04:18.90
Baltic....................... ..... do ................... 1901 725.9 75.4 37.3 1:2.02:19.46
Dleutschland.................. llambnrg-Amricani.....1900 687. 5 67. 3 31. 0 1 :2. 17 :22. 17
Caronia...................... Cunard................... 1904 680. 0 72. 6 35. 0 1 :2. 07 .-19.42
Carmania ................... ..... do.................... 1904 680. 0 72. 6 5. 0 1 :2. 07 :19.42
Two new ships, unnamed .......... do .................... 1905-6 800. 0 88.0 8.0 1 :2. 31 :21. 05
Average ratio...................................1 :2. 14:20. 65
From this table it appears that the proportions suggested by the minority are more in accord with late practice than those suggested by the majority. If the locks are to be 1,000 feet long and 100 feet wide, apparently there should be greater depth over the miter sills. The minority Point out that the dimensions proposed by them will provide for ships having 25 per cent more tonnage than the new Cunarders, and will permit the passage of battle ships having 13 feet greater beam than any ship now in the United States Navy. Inasmuch as the new Cunarders are not yet completed, are very much larger than any other vessels in existence, and must still be regarded as experimental, it seems to us that this is looking as far into the future as is expedient. If ships too large for these locks should hereafter be developed, it will be possible to add new and 'Larger locks to accommodate them. The total estimated cost of all the locks and approach walls in the present project, including the contingency item of 20 per cent, is $44,425,000. They can therefore be entirely renewed for about half what it would cost to widen the sea-level canal 100 feet.
The water supply for the canal with locks as projected is sufficient to accommodate a traffic of about 50,000,000 tons annually. Should that traffic be exceeded in the future, the addition of a dam at Albajuela will provide a supply sufficient for 100,000,000 tons. Should it be found necessary in the future to provide for the passage of a still larger tonnage, the Chagres River and its tributaries will furnish additional water.
The lBoard of Consulting Engineers is unanimous in the opinion, in which we concur, that if a sea-level canal is ever to be constructed it should be constructed as such from the first.
A report from the chief engineer, Mr. John F. Stevens, giving his views upon the subject under consideration, is hereto appended.
CONCLUSIONS AND RECOMMENDATIONS.
From the foregoing it appears that the canal proposed by the minority of the Board of Consulting Engineers can be built in half the time and a little more than half the cost of the canal proposed by the majority of the board, and that when completed it will be a better canal for the following reasons:
(1) It provides greater safety for ships and less danger Of interruption to traffic by reason of its wider and deeper channels.
(2) It provides quicker passage across thle Isthmus for large ships or a large trafic.
(3) It is in much less danger of damage to' itself or of delays to ships from the flood waters of the Chagres and other streams.
S. Doe. 231, 59-1-...3*
xvil
XVIII REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
(4) Its cost of operation and maintenance, including fixed charges, will be less by some $2,000,000 or more per annum.
(5) It can be enlarged hereafter much more easily and cheaply than can a sea-level canal.
(6) Its military defense can be effected with as little or, perhaps, less difficulty than the sealevel canal.
It is our opinion that the plan proposed by the minority of the Board of Consulting Engineers is a most satisfactory solution of the problem of an isthmian canal, and, therefore, we recommend that the plan of the minority be adopted, subject, of course, to such changes as may be found desirable during construction and with the understanding that the works in Limon Bay are to be deferred for the present. The entrance now in use at that place must, for the present, be used in any event, in order to secure harbor room for the landing of supplies immediately needed. The question whether or not it should be changed and what changes should be made can better be determined hereafter.
Respectfully submitted.
T. P. SHONTS, Chairmnan.
CHARLE s E. MAGOON.
PETER C. HAINs,
Brigadier-CGeneral, U. S. Armny, Retired.
0. HI. ERNST,
Colonel of Engineers.
B. M. HARROD.
Hon. Wm. IH. TAFT,
Secretary of Wdar, Washington, D. C
MINORITY REPORT.
The undersigned does not concur in the preference for a lock canal, expressed by the Commission, but regards a sea-level canal, as proposed by the majority of the Board of Consulting Engineers, a better canal for commercial and military purposes.
First. Because, whilst for exceptionally large vessels, such as built for Atlantic liners, the time of transit might be as long as or longer than in the lock canal, the average time of transit of the class of vessels which will use the canal for a long term of years will be less than in the lock canal.
Second. Because the risks of interruption to traffic from accident are deemed greater in a high-level canal with six locks than in a sea-level canal with a tidal lock, notwithstanding the greater distance in the latter canal, which might be obstructed by a sunken vessel.
Third. Because the cost of maintenance and operation of the sea-level canal will be less.
Fourth. Because in the enlargements to accommodate increase in traffic the relative advantages of the sea-level canal will increase
It is the history of important canals that very soon after completion, when traffic becomes established, the increasing demands of commerce call for enlarged provisions, and when the location is upon established lines of trade or where commerce finds a more direct route than those previously obtaining, such increase makes rapid strides. It seems quite certain that such will be the history of the canal across the Isthmus of Panama. Either of the projects under consideration will admit of enlargement, but in that for a sea-level canal, which will consist of enlargement of its cross section and the addition of tidal locks, its progressive improvement will be in the direction of greater and greater freedom of transit, a lessening of such risks as may be inherent in a canal of its type, and an approach to what must be admitted as an ideal canal; whilst the enlargement Of the high lock level canal, although decreasing the restrictions in its narrower portions, will multiply and perpetuate the locks and leave in existence all the obstructions, delays, and risks attending their use.
Fifth. Because it is a better, safer, and more capacious canal from a military standpoint.
xviii
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
I regard the sea-level canal, according to the project of the majority of the consulting board, as affording greater immunity from hostile injury in time of war than a canal of high level with several locks.
The danger of a vessel being sunk in the canal is inherent in both; in a less degree in the lock canal because of a portion of its length being lake navigation, but a derangement of the operating mechanism of the locks or the direct crippling of a few of the gates is much more easily accomplished, and would ordinarily prove a far greater calamity and one far less quickly and easily remedied.
In both projects locks occur at the side of Sosa Hill, near the shores of Panama Bay, a flight of two locks in the high-level plans and one tidal lock in the sea-level plans. Both are equally subject to destruction by a hostile fleet, but such destruction, in the case of the high-level canal, would be extremely disastrous, in that it would ruin the canal for military or commercial purposes for several years; whilst in the case of the sea-level canal the dbris could be dynamited and removed in a few days and the canal remain navigable, since for at least one-half of each twenty-four hours the tidal lock always stands open for the passage of vessels without locking, and during neap tides, which extend over one-half of the month, when the rise and fall are least, it would allow of the continous transit of vessels in an emergency without the offices of a lock.
Again, the transit of a fleet of naval vessels, or an expeditionary force of army transports under convoy of a fleet, would be able to move with much more expedition than if compelled to pass through a lock canal. A war vessel acting singly could pass through the canal and proceed at once upon its way, but the movements of a fleet would probably be in unison, and in the case of a fleet of transports under convoy such would almost inevitably be the case, and the departure of the whole force would be delayed until the last vessel had made its exit from the canal. In the case of the lock canal this would cover a delay extending from the time the first vessel passed the last lock until the fiftieth, or some other last vessel corresponding to the numerical size of the fleet; whilst in the case of a sea-level canal for one half the hours of the twenty-four during one-half of the month, and for all the hours of the twenty-four during the other half the vessels would file through in rapid succession without locking. A transit which in the lock canal would take several days might, in the sea-level canal, be a matter of hours id less than a single day.
In military affairs tremendous consequences often hang about the question of time; and when to the inevitable delays to a fleet passing through a lock canal is added the danger of the latter being entirely disabled for a long- period, the great advantage of a sea-level canal over a lock canal from a military view is strongly emphasized.
There is no question that a sea-level canal is per se far superior in all respects to a lock canal, and where feasible and the cost not prohibitive it should be constructed. One is entirely feasible at the Isthmus of Panama and the cost estimated by the board of consulting engineers or by the Commission is not prohibitive.
The time necessary for the construction of a sea-level canal is esfimated at twelve to thirteen years by the majority of the Consulting Board and not less than fifteen by the minority, in which latter estimate I concur, and which I do not regard as militating against the advisability of adopting such type.
The great cost to transform a high-level lock canal into a sea-level canal as estimated by the Consulting Board--about $209,000,000-and the difficulties of the same render it impracticable. A sea-level canal reached by this method would cost at least $340,000,000.
An 85-foot summit lock canal once constructed means a lock canal always. If a sea-level canal is desired, it must be built directly without first building a lock canal.
Believing that a sea-level canal substantially according to the project of the Consulting Board would best serve the present and future commerce of the world and the military necessities of this nation, I have the honor to recommend its adoption.
Respectfully submitted. MORDECAI T. ENDICOTT.
XIX
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
WASHINGTON, D. C., January 26, 1906.
SIR: In reply to your request for a statement of my views on the question of a sea-level or a high-level canal, as *applicable to Panama, .and my conclusions as to the relative value of each type, as discussed in the reports of the Consulting Board of EngineersAs indicated in my letter of December 19, 1905, which was written prior to the receipt or inspection by myself of any report from the Consulting Board, my judgment was and is yet in favor of a high-level canal, and it has only been strengthened by the very able presentation of the facts and deductions made therefrom in the minority report.
I can therefore conscientiously and fully approve the adoption of the high-level type, and strongly recommend that the Commission give its official voice in favor of such a type as is described in the minority report, and there seems to be nothing that I can add to such report, in view of its clearness and completeness, more than that I am heartily in favor of its adoption.
As between a sea-level canal and any canal with a summit elevation of 30 feet or above, I decidedly prefer the high level, and believe the one with a summit level of 85 feet more fully meets the conditions and requirements than one at any lower level.
In my letter of December 19, 1 disapproved of the suggestion to change the present alignment of the canal at either ocean terminal. In relation to the northern terminal, at Colon, I am free to say that I now believe that either plan as recommended by the Consulting Board of Engineers in covering this question is preferable to the present alignment, and that the abandonment of the proposed seawall from Colon to English Point and the adoption of a plan for breakwaters parallel, or nearly so, to the proposed entrance channel (if such breakwaters are found necessary) much simplifies the situation.
I believe, however, that the construction of a large basin or inland harbor at or near Mindi, or at a convenient location which exists below the Gatun dam, such basin to be supplied with coaling.and other proper outfitting facilities, will be found advisable, the material excavated in the construction of such a basin to be used in the construction of the Gatun dam.
As regards the plan and alignment of the canal at the Pacific end, I am still inclined to my former expressed opinion that, on account of the military and sanitary features, the location of all the locks at Miraflors and Pedro Miguel, instead of part of them at La Boca, with the necessary dam at the same place, will be found more satisfactory; but as the latter plan will cost about $6,000,000 less to construct than the former one, I am ready to waive my views in favor of the latter plan, although simply on account of the difference in the estimated cost.
The minority report of the consulting board has discussed so fully the relative merit of the two types that it would seem entirely unnecessary for me to endeavor to extend the arguments.
I will, however, express my belief that some of the estimates as to the length of time and cost, as set forth by the report in favor of the sea-level type, are hardly justified. I believe that the estimated cost of the auxiliary works, such as diversion channels, dams, and spillways, may very readily exceed by several times the amount allowed, and that the danger to the canal by the existence of such works would be much greater than apparently appreciated.
It is perhaps possible that the unit price per yard allowed for the removal of material in the prism of a sea-level canal below +10 (40 feet of it being all rock and below sea level) is ample; but I seriously doubt it. This unit cost might easily be double the estimate as allowed, and such an increase alone would add $20,000,000 to the cost of the sea-level canal.
A difference alone of $100,000,000 in the cost of the canal means, at 2 per cent interest, an addition of $2,000,000 per year to fixed charges, which sum, of course, must be added to the cost of carrying charges and operation in estimating the relative value of the two types of canal. I believe the excess cost of the sea-level type, instead of being $107,000,000, as indicated in the reports, would be at least $135,000,000, and it might be very much more.
I also believe that the difference in the time required for the construction, as between the two types, will be much greater than reported, and I would not care to set a less time than eighteen or twenty years for the building of a sea-level canal, while I am firmly of the belief that the time, as shown in the minority report, for the construction of the high or 85-foot summit level is ample.
XX
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The sum of my conclusions is, therefore, that, all things considered, the lock or high-level canal is preferable to the sea-level type, so called, for the following reasons:
It will provide as safe and a quicker passage for ships, and therefore will be of greater capacity.
It will provide, beyond question, the best solution of the vital problem of how safely to care for the flood waters of the Chagres and other streams.
Provision is made for enlarging its capacity to almost any extent at very much less expense of time and money than can be provided for by any sea-level plan.
Its cost of operation, maintenance, and fixed charges will be very much less than any sealevel canal.
The time and cost of its construction will be not more than one-half that of a canal of the sea-level type.
The element of time might become, in case of war, actual or threatened, one of such importance that measured, not by years but by months, or even days, the entire cost of the canal would seem trivial in comparison.
Finally, even at the same cost in time and money for each type, I would favor the adoption of the high-level lock canal plan in preference to that of the proposed sea-level canal.
I therefore recommend the adoption of the plan for an 85-foot summit-level lock canal, as set forth in the minority report of the Consulting Board of Engineers.
Very respectfully,
JNO. F. STEVENS, Chief Engineer.
Mr. T. P. SHONTS,
Ohairman Isthlnian Canal Conmnmission,
Washington, D. U.
XXI
%
9
e
a
e
s
4
REPORT
OF THE
BOARD OF CONSULTING ENGINEERS
FOR THE
PANAMA CANAL
1
s
a
"e
i
1
- --- -
a s 4. r"
4
4
a
&
s
lb
MEMBERS OF THE BOARD OF CONSULTING ENGINEERS FOR THE PANAMA CANAL.
GEORGE W. I)AVIS, Major-General, U. S. Army, Retired, Chawirman. ALFRED NOBLE, Chief Engineer East River Div. P., N. Y. & L. I. R. R. Wm. BARCLAY PARSONS, Chief Engineer New York Subway. WILLIAM H. BURR, Consulting Engineer Board of Water Supply, New York City;
Professor of Civil Engineering, Columbia University; Engin~eering Expert,
Aqueduct Commissioners, New York City.
HENin L. ABBOT, Brigadier-General, U. S. Army, Retired. FREDERIC P. STEARNS, Chief Engineer Metropolitan Water and Sewerage Board,
.Boston.
JOSEPH RIPLEY, General Superintendent St. Marys Falls Canal. ISHAm RANDOLPH, Chief Engineer Sanitary District of Chicago. WILLIAM HENRY HUNTER, Mem.- Inst. C. E., Chief Engineer Manchester Ship
Canal; Commissioneri, Upper Mersey Navigation, England.
EUGEN TINCAUZER, K~niglich Preussischer Regierungs- und Baurat, Mitglied der
Regierung zu K~nigsberg i. Pr., Germany.
ADOLPHE GUERARD, Inspecteur-G eneral des Ponts et Chauss ces, France. E. QUELLENNEC, Inge'nieur en Chef des Ponts et Chausse-es; Inge~nieur Conseil de
la Cie. du Canal de Suez, France.
J. W. WELCKER, Hoof dingenieur Directeur van den Ryks Waterstaat, The
Netherlands.
JOHN C. OAKES, Captain, Corps of Engineers, General Staff, U. S. Army, Secretary.
3
0
CONTENTS.
Page.
Executive order.......----------------------------------------------------------------------------------9
Summary of proceedings......---------------------------------------------------------------------------9
Physical characteristics of the Panama route.. ...--------------------------------------------------.. ------15
Climate.... .. ...----------------------------------------------------------------------------------------16
Sanitation and hygiene. ......---------------------------------------------------------------------------18
Work done and present conditions.... ..------------------------------------------------------------------22
New field work........----------------------------------------------------------------------------------25
Projects of Mr. Lindon W. Bates. . .. ..-------------------------------------------------------------------26
Plan of Mr. P. Bunau-Varilla ... ...----------------------------------------------------------------------30
Plan of the Isthmian Canal Commission, 1901.. ...--------------------------------------------------------33
Plan of Maj. Cassius E. Gillette, Corps of Engineers, U. S. Army..----------------------------------------34
The 60-foot summit-level project adopted for comparison with the sea-level project-------------------------35
Safety and protection. ......-----------------------------------------------------------------------------36
Transformation of a lock canal into a sea-level canal...----------------------------------------------------38
Capacity of canal for traffic.......------------------------------------------------------------------------39
The control of the Chagres and other streams.. ..---------------------------------------------------------42
Dams.------------------------------------------------------------...-----------------------------45
The sea-level pIan recommended by the Board.....--------------------------------------------------------47
(a) Alignment and description.....--------------------------------------------------------.. ---------47
(b) Harbors----- .. ..-------------------------------------------------------------.. . ------.. . ---.. --.51
(c) Cross sections of the canal prism. .. ..--------------------------------------------------.. ----------56
(d) Estimate of cost-----------------.. . . ...---------------------------------------------------------58
(e) Estimate of time.......-------------------------------------------------------------------.. .----- 59
(f) Important considerations. . .. ..------------------------------------------------------------------61
Minority report.... ....---------------------------------------------------------------------------------67
The lock-canal project recommended... ..------------------------------------------------------------67
(a) The Colon entrance----------------------------------------.... .---------------------------67
(b) The Gatun dam --------.. ....---------------------------------------------------------------68
Stability of an earth dam. . ..-------------------------------------.----------------------70
Plan of the dam . . . ..-------------------------------------------------------------.-.- 72
Regulating works......------------------------------------------------------------------72
R eduction in cost.................-- ......- ............. ................. -...-...-............ 73
(c) Water supply of the canal. .....--------------------------------------------------------------74
(d) The summit level---------- . .. ...-----------------------------------------------------------76
(e) Lake Sosa-------------..--------- . . ..--------------------------------------------------...--.77
(f) Channel in Panama Bay-----. .-----------...------------------------------------------------.. ... 78
(g) Dim-ensions and cost----------------------.......---------------------------------------------78
Comparison with the Board's lock-canal project...---------------------------------------------------79
Comparison with the Board's sea-level canal project. ...-----------------------------------------------80
Relative time for completion of sea-level and 85-foot projects-------------.---.------------------------83
Relative time of transit.... ...-----------------------------------------------------------------------85
Capacity for traffic of the two projects. .. ..-----------------------------------------------------86
Safety of locks and other structures. .....-------------------------------------------------------------89
Relative safety of ships in the two types of canal...--------------------------------------------------92
Land damages... . ....-------------------------------------------------------------------------------93
Relocation of the Panama Railroad-------------------------------------------....-----..-------..-.. ---. .94
Estimated cost for project recommended...---------------------------------------- .-----------------95
Cost of maintenance and operation.....--------------------------------------------------------------96
Safety of dams. ... ....------------------------------------------------------------------------------98
Conclusions and recommendation. ..-----------------------------------.----------------------------99
5
6 CONTENTS.
Appendixes: Page A. Minutes of the proceedings of the Board.....--------------------------------------------------.. ----105
B. A geological study of the Isthmus of Panama.. . ..--------------------------------------------------149
C. Dimensions of largest ships and improvements in channels and harbors.---------------------------165
D. Principal canals of the world:
Manchester Ship Canal. . ....----------------------------------------------------------------171
Kaiser Wilhelm Canal (Kiel Sea Canal). ....--------------------------------------------------173
North Sea Canal. . . ...----------------------------------------------------------------------174
Suez Canal. . . ..---------------------------------------------------- .----------------------175
St. Marys Falls Canal......------------------------------------------------------------------180
Corinth Canal. ... ...------------------------------------------------------------------------182
Dimensions of the canals of Europe. .. ...------------------------------------------------------184
E. Hydraulics of the Panama Canal:
(a) Some of the hydraulic problems of a sea-level Panama Canal.------------------------------185
(b) Water supply of the canal for three variants, assuming a lake at Gatun raised to elevations 85
feet, 60 feet, and 30 feet, the latter combined with a lake at Bohio raised to elevation 60 feet. 192
F. Project of Mr. P. Bunau-Varilla. . .. ..-------------------------------------------------------------199
G. Statement of Mr. Lindon W. Bates before the Board September 19, 1905, and data submitted subsequently. . . ...-------------------------------------------------------------------------------247
H. Depths of harbors. . . ...------------------------------------------------------------------------267
I. The Gatun dam, by Mr. C. D. Ward. ... ..---------------------------------------------------------279
J. Hearings before the Board and notes of Mr. John F. Wallace:
Statement of Mr. John F. Stevens. . ..-------------------------------------------------------283
Statement of Mr. F. B. Maltby.....----------------------------------------------------------296
Statement of Mr. H. F. Dose----------------------------.-.-.--.-.-.-.-.-.-.-.-.-.-.-.-.---------------307
Statement of Mr. Charles Bertoncini. ...-----------------------------------------.. .------------315
Statement of Mr. W. E. Dauchy. .. ..--------------------------------------------------------321
Statement of Mr. John F. Wallace, October 27, 1905.----------------------------------------346
Notes on the Panama Canal submitted by Mr. John F. Wallace.-------------------------------350
Memorandum by Mr. John F. Wallace accompanying diagrams illustrating tentative method of
Culebra excavation.. .....------------------------------------------------------------------372
Statement by Mr. John F. Wallace, November 3, 1905..---------------------------------------375
K. Summary of excavation at Culebra from July 1, 1904, to October 1,1905.----------------------------395
L. Traffic capacity of a lock canal with summit level at elevation 85..---------------------------------397
M. Time required to pass a flight of locks at Bohio or at Gatun on the Panama Canal.-------------------403
N. Equipment recommended for canal excavation, with capacity of each unit.-------------------------..405
0. Vital statistics. . ....---------------------------------------------------------------------------407
P. Transformation of a lock canal into a sea-level canal....--------------------------------------------411
Q. Historical sketch of the Panama Canal. . ..-------------------------------------------------------415
R. Unit prices. . . ...------------------------------------------------------------------------------419
S. Artificial waterways, their improvement and navigation..-----------------------------------------421
T. Estimates of cost of lock canal. . .. ..-------------------------------------------------------------425
MAPS AND DIAGRAMS.
PLATE I. Map showing line of proposed sea-level canal.
II. Profile of the same.
III. Cross sections of the same.
IV. Profile of proposed lock canal with summit elevation at 60 feet, approved by the Board for comparison
with sea-level canal project.
V. Map showing location of proposed Gamboa dam.
VI. Profile of the same showing depths to rock.
VII. Map and profiles showing the locat-ion of borings in the vicinity of La Boca.
VIII. Map showing line of proposed lock canal, summit elevation 85 feet.
IX. Profile of the same.
X. Cross sections of the same.
XI. Map of vicinity of Gatun showing location of proposed dam and locks.
XII. Profiles showing new borings at Gatun.
XIII. Plan of regulating works at Gatun dam.
XIV. Comparison of existing and proposed dams.
XV. Diagram showing movement of vessels through Poe lock and approaches, St. Maryc Falls Canal, Michigan: Vessels moving through lock singly.
XVI. Same: Vessels moving through lock together.
XVII. Same: Vessels moving in canal above lock.
XVIII. Diagram showing course of vessels rounding curves, St. Marys River, Michigan: No. 1. XIX. Same: No. 2.
XX. Same: No. 3.
XXI. Same: No. 4.
XXII. Same: No. 5. XXIII. Same: No. 6. XXIV. Same: No. 7. XXV. Same: No. 8. XXVI. Same: No. 9. XXVII. Same: No. 10. XXVIII. Same: No. 11. XXIX. Diagram of speeds. XXX. Summary of dimensions and speed of vessels.
XXXI. Graphical illustration of practicable yearly excavation which would complete the Culebra cut in less than ten years.
7
a*
WASHINGTON, D. C., January 10, 1906. The ISTHI-,1AN CANAL COMMISSION.
GENTLEMEN: The Board'of Consulting Engineers for the Panama Canal, having completed the consideration of the question submitted to it in pursuance of the order of the President dated June 24, 1905, has the honor to submit its report.
The President's order is as follows:
EXECUTIVE ORDER.
It is hereby orde red that a Board of Consulting Engineers, consisting ofGeneral George W. Davis,
Mr. Alfred Noble,
Mr. William Barclay Parsons,
Mr. William H. Burr,
General Henry L. Abbot,
Mr. Frederic P. Stearns,
Mr. Joseph Ripley,
Mr. Herman Schussler,
Mr. Isham Randolph,
Mr. Win. Henry Hunter, nominated by the British Government, Herr Eugen Tincauizer, nominated by the German Government,
M. Gu6rard, nominated by the French Government,
M. Quellenuec, consulting engineer, Suez Canal, and one engineer to be designated by the Government of
the Netherlands,
shall convene in the City of Washington, at the rooms of the Isthmian Canal Commission, on the st day of September, 1905, for the purpose of considering the various plans proposed to and by the Isthimian Canal Commission for the construction of a canal across the Isthmus of Panama between Cristobal and La Boca; and that the deliberations of the Board of Consulting Engineers shall continue as long as they may deem it necessary and wise before they make their report to the Commission.
The Isthmiau Canal Commission is directed to have al the proposed plans in such detailed form, with maps, surveys, and other documents sufficient to enable the Consulting Engineers to consider and (decide the questions presented to them. Should it be deemed necessary by the members of the Consulting Board, they may visit the Isthmus before making their final report. If there is a difference of opinion between the members of the Consulting Board, minority reports are requested.
General George W. Davis is hereby designated as chairman of the Board of Consulting Engineers. Instructions more detailed will be given in time to be pre sented to the Board when it first convenes on the st of September.
The chairman is charged with the duty of communicating to the other members of the Board this order and the other details that may be necessary.
TnEoinoRE ROOSEVELT.
THE WHITE HOUSE, June 24, 1905.
SUMMARY OF PROCEEDINGS.
The Board met in the office of the Isthmian Canal Commission, Washington, D). C., on September 1, 1905, all the gentlemen named in the order being present with the following exceptions:
Mr. Herman Schussler, who notified the chairman of the Board that on account of pr-evious engagements and undertakings that could not be changed he felt obliged to delinie the appointment.
Mr. J. B. Berry, chief engineer, Union Pacific Railr-oad, who had been named by the President as a member in place of Mr. Schussler, declined the appointment on account of his responsibility to the railroad company, which required all of his time.
9
10 REPORT OF' BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
Prof. Jacon Kraus, chief of waterstaat, Netherlands Government., who had been named as the representative of Holland on the Board, was shortly thereafter called to a position in the ministry of the Government, and he therefore was obliged to decline the appointment.
To fill the place thus made vacant, Mr. J. W. Weleker, chief engineer of waterstaat, was nominated by the Government of the Netherlands. Mr. Weleker sat with the Board as the Dutch member.
After organization and the reading of the order of the President, the Chairman announced that Capt. John C. Oakes, Corps of Engineer,,, General Staff, U. S. Army, had been detailed by the War Department to act as secretary to the Board, and he has so acted.
The Board received the following communication from the Chairman of the Isthmian Canal Commission:
ISTHMIAN CANAL COMMISSION,
W'Vashington, D. (., September 1, 1905.
The BOARD oF, ENGINEERS ADVISORY UPON PLANS FOR THE PANAMA CANAL, WVashington, D. C.
GENTLEMEN: In accordance with the directions of the President, dated April 1, 1905, the Isthmian Canal Commission has the honor to lay before you physical data concerning the Isthmus of Panama, and to solicit your opinion as to the best plan to be followed in the completion of the Panama Canal within reasonable limits of cost and time.
As you are aware, this question has been the subject of prolonged and elaborate studies for many years by numerous able engineers. A vast amount of labor has been expended in the collection of information concerning the physics of the Isthmus, and in digesting it and formulating it into plans for the canal. The resu ts of all these labors, both in the field and in the office, down to a recent date are given in the reports of two distinguished commissions, viz, the Comit6 Technique, of which the report is dated at Paris, November 16, 1898, and the American Commission of 1899-1901, of which the report is dated at Washington, November 16, 1901. A careful perusal of these reports, and examination of the maps and documents which accompany them, will afford as satisfactory a view of the entire su bject, at the dates when they were written, as can now be given. They have been reprinted, each in a separate pamphlet, and in that form are now handed to you marked Part I,", and Part II," respectively.
During the last year additional surveys and observations have been made upon the Isthmus, the results of which are laid before you. It may be stated here in general terms that the information which they furnish does not involve any radical change in the plans previously favored. Among the observations alluded to may be included the experience of the last year in excavating the Culebra cut, from which some of our engineers have drawn unwarranted conclusions as to the probable cost of the work. There is nothing in this experience to justify the belief that the unit prices used in previous estimates were too high, or that the estimate of the time required for completing the work was too liberal. Nevertheless, this experience has been used as an argument in favor of a sea-leval canal, which plan had been condemned by the two commissions mentioned above. It becomes necessary to consider once more the sea-level scheme. The principal information available for a decision as to the merits of that project has been printed i n the form of a third pamphlet, which is now handed to you, marked Part III," and in which will be found the more important results of the recent surveys.
These three pamphlets are commended to your careful consideration. With the large map, scale 1:5,000, of which a copy is also handed to you, it is hoped that a fair idea may be obtained of the conditions on the Isthmus, and of the relative merits of the three plans proposed. There are on file here many other mnaps, reports, and drawings, any or all of which will be placed at your disposal should there be any point which requires further elucidation.
The plan described in the first pamphlet is the one which was adopted by Congress, at least by inference, in the act approved June 28, 1902. It is the plan under which the work is now progressing, and under which all work of construction has been done since the United States acquired the property. It closely resembles the plan of the Comit6 Technique, described in the second pamphlet, in niany essential particulars, but differs from it in the height of the Bohio dam and the important results which flow therefrom. The advantages which its authors expected to derive from this change were:
1. To take fuller advantage of the topography of the country, by which it was possible to make the Gigante spillway automatic, instead of mechanical, and adequate for the discharge of the greatest floods, with only one channel to the sea instead of two.
2. To increase the distance of lake navigation from seven to nearly thirteen miles.
3. To reduce the estimated cost of the canal by about $15,000,000.
The disadvantages of the change are the somewhat greater (diffi culties in constructing the higher dani and the locks of greater lift-difliculties, however, which are by no means insuperable.
A disadvantage which the two plans have in common is that the rapid developments of naval architecture make it difficult to determine the proper dimensions of the lock chambers. It is to be considered, however, that up to the present time such development has not been greatly hampered by deficient depth in the harbors of the world, and that development hereafter will have that obstruction to contend with. Moreover, it is not possible to dispense with locks entirely. Even with the sea-level canal a tide lock will be required at the Panama end.
10
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
In addition to the plans above mentioned, a pamphlet has been prepared by Mr. Lindon W. Bates, which gives in outline a sketch of a plan proposed by him, which is interesting on account of its novelty, and is, therefore, laid before you. It does not give detail enough for a close analysis, nor for estimates of cost. To obtain this, extensive additional surveys, to occupy at least a year's time, would be necessary.
A paper has been submitted to the President by Mr. P. Bunau-Varilla which explains a method by which a canal constructed at first with locks may be subsequently altered to a sea-level canal. This paper also is submitted for your consideration.
These last two documents are described in a fourth pamphlet, marked "Part IV," which is now handed to you.
It is to be noted that the law by which Congress ordered the construction of an Isthmian Canal contained the following proviso, viz:
"The President shall then, through the Isthmian Canal Commission hereinafter authorized, cause to be excavated, constructed, and completed, utilizing to that end, as far as practicable, the work heretofore done by the New Panama Canal Company, of France, and its predecessor company, a ship canal from the Caribbean Sea to the Pacific Ocean. Such canal shall be of sufficient capacity and depth as shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use, and such as may be reasonably anticipated, and shall be supplied with all necessary locks and other appliances to meet the necessities of vessels passing through the same from ocean to ocean; and he shall also cause to be constructed such safe and commodious harbors at the termini of said canal and make such provisions for defense as may be necessary for the safety and protection of said canal and harbors."
The Commission expects to visit the Isthmus of Panama, sailing from New York during the last week in September, the exact date to be fixed hereafter. You are cordially invited to accompany them.
This method of presenting the subject to you, by offering several well-digested plans, has been adopted because it seemed to be the method by which all essential information could be conveyed in the most condensed possible form. It is needless to say that the Commission desires your opinion not only upon these plans, but upon any variation of them, or upon any entirely different plan which may suggest itself to you. It requests your views as to what plan it is most expedient, all things considered, for the United States to follow in the completion of the Panama Canal.
Yours, very respectfully,
T. P. SHONTS, Chairman.
The order of the President required that there be submitted to the Board for its consideration and discussion "the various plans proposed to and by the Isthmian Canal Commission." The Commission transmitted to the Board:
1. A plan prepared by the old commission on isthmian routes, created in pursuance of the act of Congress approved March 3, 1899.
2. A plan proposed to the New Panama Canal Company November 16, 1898, by, the Comit6 Technique assembled by that company.
3. Three projects prepared by Mr. Lindon W. Bates, of New York.
4. The more important results of recent surveys, containing the principal information available for a decision respecting a canal at tide level.
There was also submitted a paper prepared by Mr. P. Bunau-Varilla, explaining a method of construction of a lock canal to be subsequently transformed to one at sea level.
At a subsequent meeting there was received from the Commission a paper entitled "The Panama Canal: Some serious objections to the sea-level plan," prepared by Maj. Cassius E. Gillette, Corps of Engineers, U. S. Army, and another entitled "The Gatun Dam," prepared by Mr. C. D. Ward, C. E.
On the other hand, the Board received no plans originating with the Commission. Therefore, and because the requirements of the act of Congress respecting the dimensions and capacity of the canal, together with the new information collected by surveys and examinations conducted during the last two years prevented the adoption of plans of former commissions, the Board was obliged to prepare plans and estimates based on such information and on other data collected at its request, and to act as a creative body as well as a consulting board.
In order to conduct its bUs'iness systematically the Board determined to hold regular stated meetings at such titles as the work required, and thirty of such meetings have been held. The proceedings of these meetings were recorded and the minutes will be found as Appendix A to this report. Although these meetings were executive in character, the members of the Isthmian Canal Commission were invited to be present at any or all of them, an invitation which was frequently accepted. To facilitate the work of the Board there were appointed:
An executive committee, consisting of the Chairman, General Abbot, and Mr. Hunter.
0
11
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
A committee on the preparation of plans for a sea-level canal, consisting of the Chairman, Messrs. Gudrard, Hunter, and Burr, to which Messrs. Parsons and Quellennec were subsequently added.
A committee on the preparation of plans for a lock canal, consisting of the Chairman, Messrs. Stearns, Tincauzer, and Ripley, to which General Abbot and Mr. -Noble were subsequently added.
A committee on unit prices for purposes of estimate, consisting of Messrs. Parsons, Welcker, and Randolph.
On September 11 the President received the Board at Oyster Bay, and addressed them as follows:
What I am about to say must be considered in the light of suggestion merely, not as direction. I have named you because in my judgment you are especially fit to serve as advisers in planning the greatest engineering work the world has yet seen; and I expect you to advise me, not what you think I want to hear but what you think I ought to hear.
There are two or three considerations which I trust you will steadily keep before your minds in coming to a conclusion as to the proper type of canal. I hope that ultimately it will prove possible to build a sea-level canal. Such a canal would undoubtedly be best in the end, if feasible, and I feel that one of the chief advantages of the Panama route is that ultimately a sea-level canal wilr be a possibility. But while paying due heed to the ideal perfectibility of the scheme from an engineer's standpoint, remember the need of having a plan which shall provide for the immediate building of a canal on the safest terms and in the shortest possible time.
If to build a sea-level canal will but slightly increase the risk, and will take but a little longer than a multilock higher-level canal, then of course it is preferable. But if to adopt the plan of a sea-level canal means to incur great hazard and to insure indefinite delay, then it is not preferable. If the advantages and disadvantages are closely balanced, I expect you to say so. I desire also to know whether, if you recommend a high-level multilock canal, it will be possible after it is completed to turn it into or to substitute for it, in time, a sea-level canal without interrupting the traffic upon it. Two of the prime considerations to be kept steadily in mind are(1) The utmost practicable speed of construction;
(2) Practical certainty that the plan proposed will be feasible-that it can be carried out with the minimum risk.
The quantity of work and the amount of work should be minimized so far as is possible.
There may be good reason why the delay incident to the adoption of a plan for an ideal canal should be incurred; but if there is not, then I hope to see the canal constructed on a system which will bring to the nearest possible date in the future the time when it is practicable to take the first ship across the Isthmus; that is, which will in the shortest time possible secure a Panama waterway between the oceans of such a character as to guarantee permanent and ample communication for the greatest ships of our Navy and for the largest steamers on either the Atlantic or the Pacific. The delay in transit of the vessels owing to additional locks would be of small consequence when compared with shortening the time for the construction of the canal or diminishing the risks in the construction.
In short, I desire your best judgment on all the various questions to be considered in choosing among the various plans for a comparatively high-level multilock canal, for a lower-level canal with fewer locks, and for a sea-level canal. Finally, I urge upon you the necessity of as great expedition in coming to a decision as is compatible with thoroughness in considering the conditions.
On September 27 the Board visited the^Wachusett dam and other works in Massachusetts constructed by the Metropolitan Water and Sewerage Board, and on September 28 sailed for the Isthmus, where the work already done and in progress was thoroughly inspected and the conditions affecting the type of canal and future construction examined and considered.
Messrs. P. Bunau-Varilla and Lindon W. Bates, who, through the Isthmian Canal Commission, had submitted projects for canals, appeared before the Board and further illustrated their projects by oral explanations. The explanations, subsequently revised by the authors, appear in an appropriate place in the appendix to this report. (Appendixes F and G.)
The Board invited Mr. John F. Wallace, who had acted as chief engineer to the Commission from June 9, 1904, to June 30, 1905, to appear before the Board and give it the benefit of his experience and study. This invitation was accepted by Mr. Wallace, and his communications, both written and oral, are given in full in Appendix J. These communications are of great value as embodying the results of the longest continuous study by one man since the taking over of the work by the Government, and consideration of them is therefore invited.
While on the Isthmus the Board invited Mr. John F. Stevens, the present chief engineer to the Commission,'to appear before the Board and aid it with such information as he had or such
12
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
suggestions as he might care to offer. His testimony is given in full in Appendix J, wherein it is stated that since he had been connected with the work only two months, during which time his whole attention had been given to matters of organization, he had given no consideration to the cost or type of canal, and therefore had no advice to offer. Mr. Stevens gave all the information he had at hand.
There also appeared before the Board while on the Isthmus, or subsequently at Washington, Messrs. Dauchy, Maltby, and Dose, division engineers, and Mr. Bertoncini, expert draftsman in charge of the French engineering records on the Isthmus, and their remarks are attached hereto (Appendix J). Col. W. C. Gorgas, U. S. Army, chief sanitary officer, gave the members of the Board the benefit of his great experience with tropical diseases, especially those most to be feared at Panama.
After the return from the Isthmus and the receipt of the additional information asked for by the Board, the question of the type of canal to be recommended, the character and size of the channels, locks, harbors, and other works, and the cost of the same, both in time and money, were considered by the Board.
As a basis for all plans the Board resolved by eleven affirmative and two negative votes that locks should have as minimum usable dimensions a length of 1,000 feet, a width of 100 feet, and a depth of 40 feet. The two members voting in the negative were Messrs. Noble and Ripley. The Board also decided unanimously that in order to make its estimates comparable in respect to totals with the estimates of previous commissions there should be added to the estimated cost of construction an allowance of 20 per cent to cover administration, engineering, and contingencies; but exclusive of interest during construction, sanitation, expense of Zone government, and collateral costs. The Board also decided not to attempt to make any estimate of cost of the lands to be flooded by the canal or lakes in connection therewith, on account of the impossibility of procuring any reliable data upon which to base such estimates. The Board wishes to point out, however, the possibility of such cost assuming large proportions, especially if lands near the terminal cities or lands including the larger interior villages should be required.
The Committee on Sea-Level Canal submitted a project for a canal, a description of which is given in full in another part of this report, from which it will be seen that in accordance with the instructions of Congress that the canal shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use and such as may be reasonably anticipated," the committee recommend a canal whose dimensions, both as to width and depth and consequent cost, exceed similar dimensions heretofore recommended by other commissions.
The Committee on Lock Canal submitted four projects to the Board:
Project No. 1 contemplates a summit level at elevation 85 feet, to be maintained by a flight of three locks at Gatun on the Atlantic side, and with one lock at Pedro Miguel and two locks in flight at Sosa Hill adjoining La Boca pier on the Pacific side, the estimated cost of which is $141,236,000.
Project No. 2 is the same as No. 1, except that on the Pacific side there are two locks in flight at Pedro Miguel and one at Miraflores rather than at Sosa. The estimated cost of this project is $148,272,000.
Project No. 3 is based on an elevation at summit level of 60 feet, maintained on the Atlantic side by a flight of two locks at Gatun and on the Pacific side with a single lock at Pedro Miguel and another at Miraflores. For the purpose of control of the Chagres River and to furnish a water supply there is included a dam at Gamboa. The total estimated cost of this project is $171,190,000.
Project No. 4 proposes a summit level at elevation 60 feet, to be maintained by a dami with single locks at Gatun and Bohio on the Atlantic side, and with single locks at Pedro Miguel and Miraflores on the Pacific side, with a damn at Alhajuela, at a total estimated cost of $1.75,929,720.
All elevations are stated with reference to mean sea level.
These four estimates include 20 per cent for contingencies.
It is well to note that in each of the above projects the proposed terminus of the canal near Panama differs from the terminus proposed in the sea-level plan, and is in each case less convenient.
a
13
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
In the above estimates no allowance is made for the value of lands overflowed by the lakes to be formed by the proposed dams at Gatun, Bohio, La Boca, Gamboa, or Alhajuela. On the other hand the estimates do include duplicate locks at all places, whether single or in flights of two or three. In submitting these projects to the Board the committee stated that it made no recommendations, the committee having been divided in its preferences. In a separate report, given elsewhere in detail (Appendix P), the committee agree as to the impracticability of converting a lock canal to one at sea level, in the immediate future, on account of the difficulty and danger of the operation and of the excessive cost. This view was concurred in by the Board.
After considering the four types of lock plans submitted by the committee, the Board determined, by a vote of eight to five, to adopt, for comparison with a sea-level canal, a canal the summit level of which should be at elevation 60 feet, the vote in the affirmative being Messrs. Hunter, Welcker, Gurard, Tincauzer, Abbot, Burr, Parsons, and Davis, and in the negative Messrs. Ripley, Randolph, Stearns, Quellennec, and Noble. The Board decided that on the Pacific side there should be one lock at Sosa and one at .Pedro Miguel; on the Atlantic side that there should be one lock at Gatun and one at Bohio, all in duplicate; and that there should be a dam for the regulation of the Chagres at Gamboa identical with that proposed for a sea-level canal. This plan is attached to and described in another portion of this report (p. 35). It is to be noted, however, that this plan, like the plans submitted by the Lock-Canal Committee, is not the most feasible which could be devised for subsequent conversion to sea level, the Board believing that such conversion would probably not be carried out. A motion to adopt such a type of lock canal by placing the locks immediately next to the continental divide, probably near Obispo on the Atlantic side and at Miraflores on the Pacific, with the canal constructed at sea level between such locks and the oceans, was defeated.
In regard to the question of time required to construct these two proposed canals, the Board resolved by a vote of seven (Messrs. Hunter, Welcker, Gurard, Tincauzer, Burr, Parsons, and Davis) to six (Messrs. Ripley, Randolph, Stearns, Quellennec, Abbot, and Noble)That the Board declare in its report that the time of finishing the sea-level canal depends on many contingencies that can not be definitely estimated in time; that under efficient management and not seriously affected by extraordinary and unforeseen difficulties, political obstructions, or bad sanitation it may be regarded as feasible to complete the work in about twelve or thirteen years; that adverse conditions may lengthen that period, while favorable circumstances and continuous first-class direction may make it possible to shorten that period by one or two years.
It was unanimously resolved in language similar to the resolution in connection with the sea-level canal that the canal with locks on the plan prepared by the Board may be constructed in the period of ten to eleven years.
The Board having adopted a type of sea-level canal and a type of canal with locks as seemed most suitable under all conditions involved, and having decided that it was not expedient to adopt any of the plans which had been submitted or proposed to the Board, the following resolution was moved and adopted by a vote of eight to five, those voting in the affirmative being Messrs. Davis, Parsons, Burr, Hunter, Gurard, Quellennec, Tincauzer, and Welcker, and those in the negative being Messrs. Abbot, Noble, Stearns, Randolph, and Ripley:
Whereas in the judgment of this Board, a sea-level canal is feasible, following a line with dimensions and such arrangements that the transit between the two oceans shall be secured in a permanent manner for all time under the best conditions for navigation and safety, for vessels of the largest tonnage and greatest draft now in use, or such a' may be reasonably anticipated: Therefore
Resolved, That the Board adopt and recommend to the President of the United States the plan of a sea-level canal with a depth of 40 feet, a width in rock of 200 feet, a minimum bottom width in earth of 150 feet, with a double tidal lock at Ancon whose usable dimensions shall be 1,000 feet in length and 100 feet in width, and with a dam at Gamboa for the control of the Chagres River.
The remarks by members explaining their votes on this resolution are given in the minutes of proceedings. (See Appendix A, twenty-fifth meeting.)
In accordance with the sense of this decision, the Board submits herewith a general plan for a sea-level canal and recommends the same for adoption.
0
14
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
PHYSICAL CHARACTERISTICS OF THE PANAMA ROUTE.
The combination of a very narrow isthmus with low summit is found at Panama. The route practicable for a canal there is not half as long as the Suez Canal. The portion of this route that is higher than the highest cutting at Suez is about seven miles in extent.
The drainage of the Isthmus throughout about three-fourths of its width is effected through the ChagresRiver and its tributaries to the Caribbean, and of the. remaining one-fourth through the Rio Grande to the Pacific. The proposed Pacific terminus is about 20 miles farther east than the Caribbean terminus, for at the Panama Isthmus the trend of the two coasts, there approximately parallel, is about east and west.
The drainage to the Pacific is now effected through the Rio Grande, a small stream discharging into Panama Bay to the west of Sosa Hill and about two miles west of the city of Panama.
The tidal oscillation in Limon Bay, the initial point of the canal route, is about two feet, while at Panama it is about 20 feet. The harbors are not naturally good, but they have been made to suffice for the limited traffic seeking this route.
The geologic features of the Isthmus are very well described by two eminent French scientists, a translation of whose report on this subject, together with the deductions from the existing facts as affecting proposed engineering operations, and especially the stability of the banks of the channel and slopes, are very lucidly set forth in a paper which will be found in Appendix B, while climatic conditions are treated in the section of this report which is devoted to this important subject.
As before stated, the drainage toward the Atlantic is naturally effected through the Chagres, the canal line by all plans being located in the immediate valley of that stream for about 21 miles. One of its tributaries, the Obispo, drains the extension of the canal line for about five miles toward the Culebra summit. The Chagres is a torrential stream, and drains a basin of an estimated total area of about 1,200 square miles, about half of which is above the point where the proposed canal line leaves the river. Its sources are in the San Blas Mountains to the northeast. The course of the Chagres is, in a general way, parallel to the Caribbean coast as far as the mouth of the Obispo, where it turns to the northward and follows a somewhat tortuous but on the whole fairly direct course to the Atlantic rim of its upper basin at Bohio, about 13 miles below the mouth of the Obispo. At Gatun, about 10 miles below Bohio, following the general course of the valley, the direct distance to the Atlantic at the head of Limon Bay is only three miles, but the river deviates to the westward, and after a further course of about seven miles, passing to the west of Limon Bay, discharges into the sea at the old. village of Chagres, about five miles west of Point Toro.
Above Bohio the Chagres Valley is undulating or hilly,.the declivities becoming steeper toward the sources of the river, where the country is mountainous. 'At Alhajuela, about eight miles in a direct line above the mouth of the Obispo, the low-water surface of the river is about 95 feet above sea level, and at the mouth of the Obispo 45 feet; but at Bohio, 13 miles farther down, it is practically at sea level. From Bohio to the sea the surface of the ground for considerable areas in the vicinity of the river is but little above sea level. In this low region the Chagres receives several tributaries, of which the Gatun from the eastward and the Trinidad from the westward are of considerable size.
There are several notable topographic features of the.Chagres Valley which have a very important bearing upon the canal problem. In the upper courses of the stream and its tributaries the bottom in the waterway is the original rock formation, and the channel is strewn with bowlders, pebbles, and sand which have been loosened by erosion. Borings have been made in this valley at several points from Alhajuela to Gatun, with a view of determining the character of the earth and depth to rock. It is found that at Aihajuela there is a depth of about 29 feet of gravel overlying the rock in midstream. The rock outcroppings in the bluff appears to be of a firm and homogeneous structure, of volcanic origin. At this point the hills on either side contract the valley in a marked degree. At Gamboa, which is just above the junction of the Obispo, the
15
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
gravel covering of the rock bed is about 50 feet in depth. At San Pablo the bed of gravel, sand, etc., is about 90 feet in thickness; at Buena Vista it is over 139 feet below sea level to rock, and a little farther downstream, 142 feet; at Bohio the rock is 168 feet below tide level, and the drills penetrated wood at various depths to 150 feet. At Gatun, the depth to what in this report is sometimes classed as rock-an indurated sandy clay-is 258 feet in the deepest place, and at another, on the same section, the depth of the sand, clay, gravel, etc., is about 240 feet. Here also buried wood was brought up by the drills.
It seems, therefore, to be certain that what may be called the geological valley of the Chagres-that is to say, the rock bottom of that stream-is represented by a deep groove or channel, now entirely or partly filled by the products of erosion and drift. If there has been a regional subsidence of the Isthmus, which the geologists suggest as possible, it may be that the ancient Chagres discharged into the sea through an ancient valley, which, with the land adjacent thereto, was some 300 feet higher in relation to the ocean than the present valley. The rock penetrated at Bohio and above, also that showing in the river banks and outcropping in neighboring hillsides, is all volcanic and much denser than the so-called rock at Gatun.
The Obispo flows over a rocky bed in a part of its lower course and at one point there is a natural cascade of a few meters over a rock shelf. The general surface on the upper course of the Obispo is more nearly level, with hills rising in its drainage basin and on its margins to the height of from 100 to 1,000 feet above the general surface. The general aspect of the central isthmus is one of great irregularity-the hills are numerous and have very steep slopes, while the valleys are narrow. Culebra is one of these hills, its summit being some 700 feet above the sea. The geologists suggest that the drainage area of the upper Obispo was once a lake of considerable size, for within this area are found a few sedimentary rocks containing fossils, also calcareous and carboniferous deposits, but the greater part of the material is of volcanic origin, the central masses of the hills containing hard volcanic rock and dikes of basalt.
Between, above, and below these hard-rock masses are softer rock and dark, indurated clay, while the upper covering of the supericies is composed of the same volcanic material, but much changed by exposure to the weather, and where cut through, as it is by the canal excavation all the way for seven miles through the dividing ridge, the covering is seen as a red clay, occasionally containing bowlders, having a varying thickness to 30 feet and at one place to more than 40 feet, but generally its thickness is but 10 to 20 feet. It is in this top layer of reddish clay that all the larger slides have taken place.
Toward the Pacific the slope is, for half the distance to the bay, much more rapid than in the Chagres Valley, but the physical characteristics are similar. The Rio Grande Valley, through nearly half its length, is a tidal estuary filled and emptied twice daily by the tides. The same or a similar rock to that showing in the upper Chagres Valley is the prevailing rock in the Rio Grande region, with but a few feet of earth covering. At Pedro Miguel and Miraflores the rock is near the surface. Near Panama are two isolated hills of considerable height showing volcanic rock outcrops of a very much denser character than any other on the Isthmus.
The facts being as stated, it follows that the streams draining the isthmian region have a much more permanent regimen in their upper courses than nearer the sea. The rock near the surface a few miles from the oceans is conveniently situated for foundations for locks, dams, etc., and is sufficiently dense to make good concrete material, while sand suitable for use in masonry structures is found in great abundance on the beaches of Panama Bay, and probably that found in some of the gravel beds in the Charges will also be suitable for the same purposes.
The hill and mountain slopes are covered with a tropical jungle, but there is no good timber for construction purposes found on the Isthmus near the railway.
CLIMATE.
The climate of any locality is determined by certain influences, the principal of which are latitude, altitude, proximity of oceans, high mountain ranges, humidity, and rainfall.
A detailed description of the climate of the.American Isthmus is quite unnecessary, for it is well known, but its adaptability as a residence for human beings employed in manual labor or
16
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
in a supervisory capacity is not generally very well understood. The state of the atmosphere respecting heat and moisture and meteorological conditions generally has a very important influence upon the health and contentment of the inhabitants.
That this question of climate has a very important bearing on the canal problem is acknowledged by all who have carried on engineering works in tropical countries and by those who are familiar with the history of such operations.
Temperatures at the Isthmus as low as 72o or as high as 98 are unusual. It is correct to say that the average daily range of the thermometer is from 75 to 84. The highest recorded temperature in the Chagres Valley is 970 and the lowest 64. The number of days in the year when the heat at night is less than 750 and greater by day than 84 are very few. In other words, the daily range in temperature is only about 10, with little variation between summer and winter, wet and dry seasons. But the atmosphere is generally quite damp, ranging in relative humidity from 80 per cent in the dry season to 87 per cent in the rainy season. With a temperature of approximately 80 and a relatively high humidity the air is damp and muggy, and therefore exhausting and oppressive to the white race unaccustomed to tropical conditions. These conditions are common to many tropical regions near the sea level.
The rainfall on the Isthmus is greater than in some parts of the tropics and much less than in others, the annual precipitation varying from about 140 inches at Colon and the lower Chagres Valley to 95 inches in the interior and to about 70 inches on the Pacific side. But the precipitation is very unequally distributed throughout the year. During the four diy nmonths--january, February, March, and April-and the eight wet months the average monthly rainfall and the average yearly total are as follows:
Atlantic Pm,
side and Interior. Nao, an
chagres La Boca.
valley.
Inches. Inches. Inches.
Dryseason------------------------3.7 1.56 1.74
Rainy season........................15.3 11.08 7.89
Total for year----------............. 137.2 94.87 64.70
These data are the result of observations covering a period of 33 years at Colon, 21 years at Gamboa, and from 3 to 10 years at the points on Panama Bay. The heaviest rainfall in any one month was 20.9 inches at Colon.
The number of days given in each year from 1889 to 1904 during which there was some fall of rain was, at Colon, 196; Bohio, 246; Alhajuela, 198; Gamboa, 190; La Boca, 141; but on many of these days the fall at all points was very slight.
It is well known that high winds having the character of hurricanes are very rare at the Panama Isthmus. Northers occur at rare intervals in the Caribbean. One or two of considerable violence have at times been felt in a year at Colon. Sometimes a whole year passes without a wind of greater velocity than a strong breeze; on the other hand, northers have occurred in which the wind velocity has reached 50 miles an hour, but there have been no accurate measurements made of these storms. These blows are never felt in the interior or on the Pacific side.
The observed monthly mean velocity of the wind at Colon from October, 1898, to May, 1899, varied from five to eight miles per hour, the maximum monthly mean observed being eight anid one-half miles, while the strongest observed on any day in eight months was 24 miles. There is generally a pleasant breeze every day from a northerly quarter, and this applies throughout the Isthmus. At Panama there is no record of a severe storm of any kind, and the winds are generally from the north and offshore.
A member of the Board, who since 1898 has resided nearly six years in the tropics, one year of which was spent at Panama, stated that he had observed no marked difference between the climate of Panama and that of other tropical countries.
465A-06-2
I7
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
SANITATION AND HYGIENE.
The Isthmus of Panama was not well known to the inhabitants of the United States until it became a favorite route of travel for the California immigration after the discovery of gold in the Sacramento Valley in 1848. Since then this route has been much used, not only by Americans but by Europeans and the inhabitants of the west coast of Central and South America.
After the gold discovery lines of steamers and sailing vessels on both oceans conveyed travelers to and from the Isthmus, the transit at first being effected by canoes on the Chagres River in connection with riding and pack animals between that stream and Panama Bay. The transfer from the Caribbean to the Pacific occupied from five to ten days, and very often much exposure and suffering resulted. In the light of present knowledge respecting the cause of yellow and malarial fevers it is not surprising that sickness and mortality were experienced among those who traversed the Isthmus in those early days. What has been called Chagres fever is now recognized as a malignant type of intermittent fever, otherwise known as malaria, which, as well as yellow fever, is believed by sanitarians to be communicated to man only by certain species of mosquitoes.
What the extent of the mortality among those early travelers was we do not know, but judging from what history records respecting the frightful losses among the French and English troops serving in the West Indies during the eighteenth and first half of the nineteenth centuries, particularly in Santo Domingo, Cuba, Nicaragua, and the Lesser Antilles, we can very well believe that the suffering on the Isthmus in the early days was very great, for the emigrants hurrying to California were but ill provided against hardships, were ignorant of the conditions, and were not controlled or governed by any constituted authority.
The construction of the Panama Railroad was undertaken in 1850, but the promoters of that enterprise understood local health conditions no better 'than did those who had preceded them. Workmen from the United States who were entirely unacclimatized were employed in large numbers and many succumbed-to the local fevers, others to exposure and diseases due to intemperance and disorderly living. The road was open throughout its 45 miles in 1S55, and thereafter the California immigration was spared the difficult canoe navigation of the Chagres and the land journey between Cruces and Panama.
It has been often stated that the mortality among the railroad workmen reached an aggregate which equaled in numbers the cross-ties used in the railway roadbed-that is to say, 150,000-but the chief engineer of that road, the late Col. George M. Totten, stated repeatedly that the total number of persons employed in building the road never exceeded 7,000 at any one time, and that the number of laborers and workmen who died in the whole five years did not exceed 1,200 in all.
To what extent yellow fever figured in those statistics is not known, but as this disease was then prevalent throughout the American tropics and warmer temperate latitudes there is little doubt that it was one of the principal causes of sickness. There is no doubt whatever that malarial fevers of all types-intermittent, malignant, and pernicious-were prevalent.
From 1855, the date of opening the all-rail route across the Isthmus, to 1881, when work was begun on the Panama Canal, the transit was used for transferring travelers, freight, mails, etc., between the Atlantic and Pacific oceans, and nearly all the superior employees of the corporation were Americans, but the annals of the Isthmus give us very little information respecting health conditions. We know that during this quarter of a century some hundreds of thousands of travelers used the transit, and many hundreds of citizens of the United States were employed by the company in operating its road. Some of these men remained on the Isthmus ten or twenty or more years and enjoyed good health. At the time the United States took over the Panama Canal there was a very considerable number of Americans employed on that road, who continued strong and vigorous when they observed ordinary sanitary rules. Of course they were well sheltered, their food was adequate and suitable, and medical attention and hospital treatment, with medicines, were available.
~18
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
Work on the canal was begun in 1881. In 1882 the force employed was 1,910, and in 1884 the average number for the year was 17,615, although the maximum was 19,243, in October. The aggregate of the numbers of those reported yearly as employed in the whole period is 86,812, or an average of 10,881 per year. By computation it is found that the total number treated for sickness during the eight years was 52,814. It is also found by reference to Tables 1 and 2, recently compiled (see Appendix 0), that the number of deaths of employees in the same period was 5,627, showing a rate of mortality among the sick of 10.62 per cent, and among the employed of 6.48 per cent. These important data, together with the recently compiled statistics for the city of Panama never yet published, are a very valuable contribution to our knowledge of the health conditions as they formerly existed on the Isthmus, not only during the activity of the old company but also for the years which have since elapsed, for the system of recording vital statistics instituted in 1881 has been continued to date.
The methods adopted by the health authorities on the Isthmus twenty years ago for coinbating tropical diseases which caused great sickness and mortality were such as were deemed most effective by the sanitarians of the period. The French company erected fine hospitals of large capacity, with up-to-date equipment, and their physicians and nursing force were competent and efficient, but modern methods for preventing sickness were then unknown. The old company, a private corporation, had no power to compel observance of health ordinances by the resident population, or by their own employees. The local authorities and permanent residents of the Isthmus were immune to yellow fever, and the people and municipal authorities were indifferent. Yellow fever was believed to be due to a poison, ever present, to which a certain proportion of newcomers, especially Europeans, was expected to succumb, as they had always done. It was believed that the disease was contagious and that the malady was transmitted by personal contact with the sick or their excreta, and the preventive measures employed to protect the new arrivals consisted of attempts at isolation of the sick, as is now done with those afflicted with smallpox.
Malaria was believed to be caused by a miasma exhaled from the soil or by decaying vegetation, and it was accepted that newly upturned soil caused the disease to spread. As the name implies, the disease was believed to be due to bad air. But discoveries of the very greatest importance to the human race have put an end to these misconceptions, and malaria and yellow fever are no longer a mystery to science. The mosquito theory of the transmission of these two diseases is now generally accepted as the solution of the mystery by all the leading sanitarians and physicians.
The knowledge of the discoveries of Reed, Lavaran, and Ross has been given world-wide publicity, and gradually has been accepted and acted upon in many parts of the world.
The yellow-fever record.on the Isthmus since the United States took over the canal works is as follows: In May, 1904, there was 1 case; in June, 1; in July, 2; August, none; September, 1; October, 1; November, 3; December, 6; January, 1905, 18; February, 14; March, 11; April, 9; May, 33; June, 62; July, 42; August, 27; September, 7; October, 3; November, 5, one of which was. from a point 30 miles distant, making a total in the nineteen months of 246 cases. Of these, 84 terminated fatally, or about 34 per cent.
Commenting upon these figures, Col. W. C. Gorgas, U. S. Army, the chief sanitary officer of the canal works at Panama, remarks in his October report as follows:
I consider this (the October record) as indicating the near approach of the disappearance of the disease. * Panama has often in its past history been free from yellow fever, but the only disappearance was when there were no nonimmunes to contract it. At all times in its past history when there were nonimmunes here they had yellow fever as long as the nonimmunes remained. We had during October all the natural conditions favorable to this disease, a larger number of nonimmunes probably than had ever before been present on the Isthmus-in the neighborhood of 5,000-with a wet and hot month.
Apparently, from the records, the season in Panama does not have much influence upon yellow fever. The weather in January is as favorable to the breeding of the Stegomyia as July, and the past records seem to show that if we have nonimmunes in Panama in December we will have as much fever as we would in July. It has altogether in the past depended upon the supply of nonimmune human beings. The only yellow-fever period when there was anything near to approximating as many nonimmunes on the Isthmus as we have at present was at the time during
19
20 REPORT OF BOARD OF CONSULTING ENGINEER8, PANAM A CANAL.
the French regime when they had their maximum force. This occurred in October, 1884, when they had 19,243 men on their rolls, of whom 2,706 were nonimmumnes. Among these they had 21 deaths from yellow fever in that month and approximately 84 cases. During October of this year our force has also reached its maximum, about 22,000,a of which number about 4,000 are nonilumunes. Among these 4,000 employees we had not a ingle (death from yellow fever and only a single case. Of the three cases occurring onl the Isthmus, two were people not employees of the Commission.
Here we are comparing two periods in which there was a large number of nonimmjunes present-the same season of the year and the same climatic conditions generally-the only difference being that in the year 1905 modern tropical sanitary methods were enforced all over the Isthmus byT some 2,200 men. Twenty years ago these methods were unknown, malaria and yellow fever were a mystery to science, and our predecessors were unable to do anything for their control.
The results obtained, I1 maintain, are solely and entirely due to the sanitary measures put in force. And he it remembered at the same time that we have at present with us fully one-third more people subject to yellow fever (nonimmunes) than the French had in October, 1884.
You can pick out in the history of Panama Octobers when there were no deaths from yellow fever, such as October, 1901, or October, 1895, or October, 1896; but during these Octobers there was nobody in Panama who could have yellow fever. Take any other October when there was present any considerable number of nonim-munes and they always had yellow fever to a considerable extent. In this October when we have more people liable to the disease than ever before we had only three cases.
The showing with respect to the sick rate of employees generally is very good. Among 22,000 men we have a daily average of about 450 in hospital. This gives us a constant sick rate of 21 per thousand. We could not hope to show a lower rate than this if our canal were being dug between Washington and Baltimore. The French in October, 1884, with their 19,243 employees, had 101 deaths, making a rate for that year of 100 per thousand. We, with a force of about 22,000, have had 61 deaths, which would give us for the year a death rate of 32 per thousand. I have no doubt that when the sanitary improvements at present going on, such as street paving in Panama and Colon, waterworks in these cities and along the line and comfortabl e screened buildings for employees at all points, shall have been completed the health conditions will be still further improved; but I am inclined to think that the sanitary question of Panama has been settled, as we have shown that a force of laborers as large as we are likely to have and as unfavorably situated as they ever will be canl work on the Isthmus without suiff ering from yellow fever, and that the general health of this same force can be kept as good as if they were digging a canal in a healthy part of Maryland.
In the city of Panama it is a requirement oi law that all burials shall take place in the city cemetery, and that the records of burials shall show the name, age, sex, nativity, cause of death, and the name of the physician certify ing to cause in every case. These records have been- carefully kept since 1882, and the chief sanitary officer of the Canal Zone has recently had every individual record of. burial f or the city of Panama examined, tabulating the result so far as it relates to those who succumbed to yellow and malarial fevers. The result of this inspection appears in Table 3, Appendix 0, wherein is set forth the mortality for those twentytwo years caused by the two fevers, the figures being given for each month of the whole elapsed period.
The stated population of the city is the closest approximation which can be obtained from the public officers of the Republic of Panama, for since 1871 there has been but one census, that of 1904 made by the sanitary staff of the Canal Zone.
During this period of twenty-two years there were three or four occasions when there was an influx to the Isthmus of a large nonimmune population. The first was in 1881-82 and continued to 1889. The next was in 1895 when a regiment of troops from the interior highlands of Colombia arrived for service on the Isthmus. The next year there was, another increase of military force from the same locality, those men also nonimmunes. The last was in 1901 when there was a further large increase consisting of a body of Colombian troops sent to Panama to operate against insurgents. On each of these occasions there was a large increase in the mortality from yellow and malarial fevers, ais may be seen by the table. During the intervening m-onthis or years there were very f ew cases. The rule held true continuously until full eff et was had f roin the sanitary measures taken by the United States health authorities in the Canal Zone, but it required a year and a half to secure full beneficial effect of the preventive means adopted. The records of the Panama cemetery are cited by the United States health authorities as fhirnishing evidence
a Including those employed on the Panama Railroad.
20
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 2
of the accuracy of their declaration that it is not only possible but feasible to bansh yellow fever from the Isthmus and to maintain the whole force of employees in a good state of health.
A few years ago the abandonment, as a canal headquarters, of the city of Ismaylia, situated on the line of the Suez Canal, was seriously considered because of the general sickness of the European inhabitants and the canal officials. Tile population was 9,000, of which the European inhabitants wcre 2,000. Amiong, these there were 1,400 cases of malarial fever annually, of which many resulted in death. The mosquitoes (anopheles) were killed and their breeding places destroyed in 1902. The number of cases of malaria since has been, yearly, 214, 90, and in ten months of 1905, 46, with no deaths. Those who have had malaria subsequent to the samitating of the place are those who had been chronic sufferers from the disease previously.
Recent reports received by the Commission contain interesting data concerning general health conditions, from which much knowledge is gained respecting health and disease, and indicate that the maladies prevailing on the Isthmus are generally the same as are common in the temperate climates.
In the largest hospital in the Zone, that at Ancon, there were treated in October 1,118 persons. Included in this number there were eight cases of typhoid fever, a very small number considering the population of the Zone-a total of 63,084-and the squalor, indi gence, and indifference to sanitary rules of a large part of the inhabitants. In this hospital there were 19 cases of dysentery, 30 of beriberi, 17 of pneumonia, 6 of bronchitis, 4 of consumption, 15 of venereal diseases, 6 of measles, 19 of piles and hernias, 33 abscesses, 24 wounds, and 13 of general debility. There was no case of either smallpox or plague.
In the whole Zone, including the cities of Panama and Colon, there were deaths as follows: Ninety *ere f rom f eve rs of all kinds; beriberi claimed 26; dysentery, 9; cerebral hemorrhage, 6; convulsions (children), 6; tetanus, 4; consumption, pneumonia, and bronchitis, 92; gastric disorders, 33; liver diseases, 5; genito-urinary diseases, 13; childbirth, 6; accidents, 9; dropsy, 7; heart diseases, 5.
To the ordinary observer the appearance of the city of Colon is much worse than that of Panama, yet its record for disease is better. Yellow,-fever has been comparatively rare there. Its better record may be due to its situation on an island, the surface of which is awash with sea water throughout a considerable part of its superfices. We are told by the sanitary officers that the mosquitoes which cause yellow fever and malaria do not breed in salt water. This has significance and weight in determining the general drainage system for the canal works.
The inability of the French companies' officers to enforce sanitary rules has been referred to, but this inability was not an important matter, for the then best-known health measures, no matter how thoroughly enforced, would have accomplished little of real benefit in reducing the sick list, for no one in France or elsewhere then had any conception of the present theory respe cting the cause of these two maladies which decimated the newcomers at Panama. But for the United States the situation is different. The discovery of the probable cause of yellow f ever, and the knowledge of the measures adopted by sanitarians to control and prevent its ravages, have simplified the task of those who are to make the canal.
The United States not only has the right granted by treaty to enforce all necessary rules of sanitation and for the preservation of order, but the authorities of the Republic of Panama have shown the most ready willingness to cooperate and assist in the efforts taken to rid the Isthmus of disease and prevent its importation.
Notwithstanding the fact that near-by Pacific ports have for several years been infected with bubonic plague, the health officers of the Canal Zone have, by means of a rigid quarantine, so far prevented this pest from obtaining a foothold on the Isthmus, and there seems to be good reason for the confidence of these officers in their ability to exclude that disease permanently. We now know that men from temperate climates living in the tropics, including Panama, can and do escape the great danger which twenty-ive years ago could not be evaded, and that the danger does not appear to be, greater than exists in many parts of the United States.
21
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
WORK DONE AND PRESENT CONDITIONS.
The present state of the canal work is but little different from that in which the old Panama Canal Company left it in 1889. The liquidator, who had control of the assets of the company under the decree of the French court from 1889 to 1894, did no work on the Isthmus other than that of preserving the property under his care. When the New Panama Canal Company was incorporated in 1894 it recommenced the work of excavation at the divide on a small scale and maintained those operations, with a force varying from a maximum of 3,800 men to a minimum of a few hundred, until the property was taken over by the United States Government in May, 1904. That company performed no other work in furtherance of the actual construction of the canal than the continuation of excavation at the summit divide and the dredging of about 3,000,000 cubic yards at the La Boca pier and approach thereto, although it maintained a sufficient force to care for the mass of materials and plant stored along the line of the canal.
The total work actually performed upon the canal can best be appreciated by keeping in view the plans contemplated by the French companies. In accordance with the decision of the International Scientific Congress held at Paris in May, 1879, the old Panama Canal Company adopted a sea-level plan for the canal. When, however, it became apparent that it would be financially impossible to carry out the work on that plan, a number of projects with locks and with various summit elevations were carefully considered. It was the purpose at that time to devise a project which would permit lock-canal navigation to be opened at the earliest possible date, and by the subsequent removal of the locks to ultimately realize the original conception of a canal at sea level. While these modified projects were under consideration the collapse of the old company occurred and all work ceased.
All subsequent studies conducted both by the liquidator and the New Panama Canal Company were also directed to the determination of lock plans. Both the Commission d'Etudes, created by the liquidator, and the Comit6 Technique, appointed by the New Panama Canal Company, rejected the sea-level plan and devoted their efforts to the development of a lock plan best adapted to the limiting financial conditions under which the new company would have to complete the work. The Comit6 Technique finally recommended a plan for a canal with a maximum summit elevation at nearly 101 feet above the sea, the bottom width of the canal being 98.4 feet in earth and 111.5 feet in rock, and with a minimum depth of water of 29.5 feet. This plan required a double flight of two locks at Bohio and another similar arrangement of locks at Obispo on the Caribbean side of the continental divide. On the Pacific slope there were contemplated duplicate single locks at Paraiso southerly of and close to the great Culebra cut, a double flight of two locks at Pedro Miguel, and duplicate single locks at Mirafiores, the latter being partially tidal locks, in order to control in the canal the varying heights of the tide in the bay of Panama. In connection with these locks the plan included a Caribbean sea-level section 14.84 miles long; an intermediate level between Bohio and Obispo 13.37 miles long, in which the water surface would vary in elevation from 52.49 feet to 65.62 feet above the sea; a summit level 6.22 miles in length from Obispo to Paraiso with a maximum elevation of 100.89 feet; an intermediate level 1.32 miles long from Paraiso to Pedro Miguel with a water surface at a maximum elevation of 76.28 feet; another intermediate level 1.32 miles long from Pedro Miguel to Miraflores with a maximum elevation 20.51 feet above mean tide, and a Pacific sea-level section 7.38 miles in length, the lengths of the various levels being given exclusive of the lengths of locks. The excavation made by the New Panama Canal Company at the summit was continued, to serve the execution of this plan, although it was thought possible that a lower summit level at 65.5 feet above the sea might ultimately be adopted, so as to eliminate the locks at Obispo and Paraiso.
There was also contemplated by the New Panama Canal Company the creation of a large reservoir for feeding the summit level of its adopted plan by constructing a masonry dam across the Chagres River at Alhajuela, about 11 miles by the feeder line from Obispo. A feeding canal, or aqueduct, with suitable appurtenances, was to be formed on this line in brder to connect this reservoir with the summit level above Obispo. No work, however, was ever performed either
22
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
in the construction of the dam or on the line of the feeder, but surveys and investigations were made and the necessary works were all completely planned.
The old Panama Canal Company made extensive surveys and soundings, and erected many buildings, shops, hospitals, etc., but confined its 'operations along the canal line wholly to the work of excavation, except for the construction of a small dry dock near the Colon terminus, and some docks or piers in the same vicinity required for the discharge of materials and machinery shipped to the Isthmus for the purposes of the work.
The country along the canal line from Colon to Obispo is nearly all low, in places marshy, and the material can generally be removed by dredging. The old company availed itself of this physical condition and, with the exception of Culebra, the greatest volume excavated in a limited distance was confined to this portion of the line. Between Cristobal Point (behind which the old company planned its canal entrance) and the mouth of the Mindi; a distance of about three miles, there is a small quantity of coral rock and a much larger quantity of hard sandy clay, which may be classed as soft rock, still remaining in place.
The depth of the excavation near Mindi and at one or two other points was about 29 feet below sea level; but the average depth for about one-half the distance from Colon to Bohio was not more than two-thirds of that amount below mean tide, while the depth of excavation for the remainder of the distance under consideration did not vary much from 25 to 27 feet. On account of the rising surface of the ground the depth below sea level was but a few feet at a distance of two miles from Bohio and decreased to nothing'at that point. This stretch of canal, about 11 miles long, with an original bottom width of about 72 feet, is still open, although some sediment has been deposited, and can be navigated throughout its entire length, save at one point, by vessels drawing from eight to ten feet, and much more in that portion of it between Mindi and Gatun.
In consequence of the fact that this portion of the canal line intersects the Chagres River at a number of points, thus forming a direct course, and for the further reason that diversion channels and small dams have been constructed, the water of the Chagres River flows through this excavated channel from a point about two miles below Bohio to Gatun, a distance of about seven miles. From Gatun its flow divides, a part of it, estimated as one-third at ordinary stages of the river, passing to the sea in the old channel and the remainder flowing into Limon Bay through the canal channel and the mouth of the Mindi. The portion of the old company's canal work between Colon and Bohio and the work of excavation in the Culebra cut are the two largest and most impressive features of the accomplished work in its present condition.
At Bohio an extensive mass of volcanic rock outcrops. This rock has been used for structural purposes at Colon and along the railroad line, and in a portion of this outcrop the old canal company made an excavation of considerable magnitude for the locks which it proposed to locate there after it was compelled to abandon the sea-level plan. This excavation, like many other portions of the company's work, may be utilized in subsequent construction.
Between Bohio, 15 miles from the Colon terminus of the canal, and Miraflores, about 41 miles from the same point, the ground is relatively high, rising gradually on the Caribbean side to the continental divide at Culebra, then falling rapidly to 15 or 20 feet above sea level at the Rio Grande between Pedro Miguel and Miraflores. Throughout this distance, with the exception~of that portion between Obispo and Culebra, a distance of about seven miles, the excavation made by the old company consists of a shallow but nearly continuous cutting. At several relatively high points the cuttings are deeper, but the amount in the aggregate is relatively small. From Bohio nearly to Obispo the canal line frequently intersects the course of the Chagres; but at a point a little less than a mile from Obispo the Chagres Valley trends abruptly to the northeast, almost at right angles to the line of the canal, which here follows approximately up the course of the Obispo in a southeasterly direction toward Panama. At Gamboa, less than a mile from Obispo, a short distance upstream from the point where the canal line leaves the river, both the old and the new companies at different times projected the construction of a dam for the purpose of controlling the Chagres floods and feeding the summit-level locks, but finally abandoned the idea of a dam at that site.
23
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The present condition of the seven-mile cut through the continental divide shows that a large amount of material has been excavated in that locality, principally by the old company, but to he extent of about 7,000,000 cubic yards by the new company and nearly 1,000,000 cubic yards by the Isthmian Canal Commission during 1904-5: The maximum depth of this cutting below the original surface-333 feet above sea level-is about 165 feet. The excavated material has been deposited mainly in the Lirio marsh, about a mile northeast from the deepest part of the cut, and to a less extent in the Rio Grande Valley near Cucaracha, immediately south of the southerly end of the cutting.
The alignment adopted by the old and the new companies for the Pacific sea-level section of the canal followed approximately the course of the Rio Grande from Miraflores to La Boca. It intersected the course of the river a number of times and required small diversion channels at either side, but the Pacific terminus of the canal was practically identical with the mouth of the river. The valley of the lower Rio Grande is a salt marsh or swamp, although if the canal should be excavated to a depth of 40 feet below the sea level some rock will be encountered in the channel. The old company excavated the canal for a distance of about two miles from La Boca to an average depth of about 20 feet from the original surface, which is at nearly extreme high water. As the extreme range of tide at the Pacific terminus of the canal is from about 10 feet above mean sea level to 10 feet below, the old company planned to make the Pacific sealevel section of the canal from Miraflores to deep water 39.4 feet deep below mean tide. Less than one-third of the total requisite excavation was made between La Boca and Miraflores, nor was a channel to full depth completed by that company from La Boca to the deep water of Panama Bay. This latter work would have required the excavation of a considerable quantity of hard rock.
The old company not only excavated for the channel of the canal proper, but it also excavated diversion channels parallel with the axis of the canal on both sides of it and distributed throughout nearly its entire course, to the aggregate length of 20.2 miles on the easterly side of the canal and 13.16 miles on the westerly side. These diversion channels were constructed for the purpose generally of intercepting the flow of the streams which would otherwise discharge into the canal, and they were to be permanent features of the work. A few short lengths were designed to serve a similar purpose only during construction. The largest of these diversion channels are mostly found between Obispo and Colon, as it was necessary under the French plans to divert the entire flow of the Chagres throughout some portions of that distance. Among these is the Gatun diversion. The excavation already done in it amounts to nearly 2,700,000 cubic yards. Its length is 6.13 miles. It was designed to discharge 17,600 cubic feet per second.
The diversion channels on the easterly side of the canal line were designed with bottom widths varying from about 52.5 to 131 feet, with side slopes having in general an inclination of about 450. The maximum depth of water contemplated in these channels was nearly 15 feet. On the westerly side of the canal line some of the diversion channels are of smaller section, varying in bottom width from about 20 feet to the same maximum of 131 feet as on the easterly side. At one point, near Obispo, a tunnel 1,203 feet in length and about 16 feet wide and of equal height was nearly finished for diversion of the Obispo, which in flood now flows through it. A few of these diversion channels were finished, but the greater number were only partially completed. Some of them have received the waters for which they were intended and have been scoured to an increased depth, while others have been partly filled with sand or silt moved by freshets.
A total amount of about 80,000,000 cubic yards of all classes of materials has been excavated throughout the entire line of the canal, making almost continuous work from one end to the other. By far the greater portion of this excavation was soft material or earth largely removed by dredges, but a comparatively small portion of it may be classed as rock. This means that the principal portion of the remaining material to be taken out must be considered rock, and much of it as hard rock. A substantial portion of this 80,000,000 cubic yards of excavation has been so deposited along the proposed line of canal that it will have to be again moved in the work of construction, because of the greatly increased cross section of prism now required.
24
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 25
It is difficult if not impossible to state what portion of this excavation will be available in future construction. The entire excavation made at the divide is of this useful character, but it is probable that the aggregate of all the useful portions of the work done will not exceed 40,000,000 cubic yards.
The aggregate volume of excavation in the diversion channels will probably not exceed 5,000,000 cubic yards, but it is practically all available for the construction of a sea-level canal. The portion of the same aggregate which would be useful in the construction of a lock canal would depend upon the plan adopted.
The general location and alignment of the canal is, on the whole, satisfactory. There are places, like that in the summit cut extending from Emperador to a point near Cucaracha, where the alignment may be improved without much change of location, but necessitating increased cutting both in the hill at Eiperador and that at Culebra, and an equal saving in other places. The curvature generally is sufficiently easy, the minimum radius being 8,202 feet. There is some objectionable curvature at the termini, especially near Colon, which the plan proposed by the Board will remove.
In addition to this work of excavation there were immense quantities of material, machinery, and appliances required for the prosecution of the work of construction received and distributed along the entire line. The book value of this great quantity of construction material, nearly all of which still remains upon the Isthmus in various degrees of repair, is about $29,000,000. Much of it is housed and in good order, although now nearly useless in consequence of its obsolete character, while other and larger portions of it are found exposed along nearly the entire canal in all conditions of disuse and decay.
Over 2,000 buildings-mostly houses for the employees of the old company, excellent hospitals, and some storehouses or shops--still remain, some in good condition and others in need of much repair. These buildings are generally capable of being put into service.
There are also six machine shops, some of considerable capacity, the principal of which are at La Boca, at Matachin, and at Colon. These shops contain a considerable quantity of usable machinery. They were put into service during the summer and autumn of 1904, and have since been somewhat enlarged and developed. They constitute a valuable asset, and will be of great service in repairin-g machinery, rolling stock, and other appliances required in the work of construction of the canal, and they have sufficient capacity for the purpose of building some of the simpler forms of plant required in the work.
NEW FIELD WORK.
The Board has had access to all the data on file in the office of the Isthmian Canal Commission. Very accurate cross sections of the canal prism included between Obispo and Paraiso, seven miles and a half, were obtained. These cross sections were taken at very close intervals where the slopes are changing; in those portions where the grade is nearly uniform and the topography unmarked by notable features the cross sections are considerably farther apart. These cross sections are used in the estimates of the Board.
It early became apparent that additional information was desirable relating particularly to the possible dam and lock sites at Mindi, Gatun, and in the vicinity of La Boca. The Board requested the Isthmian Canal Commission to have further examinations made, as follows:
1. On the Mindi line the examination to be topographic with respect to the ridgo line to the east of the Mimdi through to Jaramillo Hill, thence to the shores of Limon Bay, in order to develop any low passes communicating with the Chagres River, and over the Jaramillo Hill near the high ridge line to the Chagres River and across the same, connecting with the high land to the west of the Chagres. This examination to be carried up to elevation 50.
2. Borings and topography at Gatun, south and west from Gatun Hill, over the hill opposite, across the diversion channel, and to high land beyond. Also to develop lock foundations in the hill east of Gatun.
3. A survey showing the necessary relocation of the Panama Railroad in case of a terminal lake formed by a high dam at Gatun.
0
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
4. A line of soundings across the Rio Grande Valley from Sosa Hill, passing by La Boca pier, to the high land above the mouth of the Farfan River.
5. A survey and soundings on the shortest line from Ancon Hill across the high land to the east, to show the physical conditions that would influence the construction of a dam to raise the water in the Rio Grande Lake to elevation of about 65.
6. Borings to rock on saddle between Ancon and Sosa hills, and across the Rio Grande from Sosa Hill to the nearest high land, to develop the practicability of a lock between Ancon and Sosa and a dam for raising water .30 feet above sea level. Also borings along a line for the proposed Pacific section of the canal, this line leaving the old route about kilometer 63, passing straight to the saddle between Ancon and Sosa hills, thence in a straight-line to deep water in the bay to or near the entrance channel now in use.
With reference to the Mindi location Mr. F. B. Maltby, division engineer, reported:
On the west side of the canal the high ground is continuous from the Jaramillo Hill to the Chagres River. * From a personal examination I am quite sure that a point can be found in this vicinity where the distance across the Chagres Valley to an elevation of at least 50 feet is not more than 3,000 feet. I think it more than probable that surveys would develop a possible crossing of a shorter length. On the east side of the diversion at Mindi the hills are simply isolated knolls for a distance of half a mile east from the diversion channel. From these there is a continuous ridge which is very much broken in elevation, but in which there is no point which has an elevation of less than about 40 feet. * It therefore seems possible that, should such a project be contemplated, a dam might be built from the Jaramillo Hill across the canal connecting the various hills as far as the east diversion opposite Mindi. From there for a distance of half a mile it is probable that a dam having a base at an elevation of only five or six feet above the sea would require construction for half the distance. In addition to this there would be a dam across the Chagres River of about 3,000 feet in length.
In response to the request of the Board, some topographic work was done in the vicinity of Gatun, outside of the limits of the French maps. Borings were taken across the valleys along the lines indicated, and this information was forwarded for consideration of the Board. The topography and the location of the borings are shown on Plate XI, and the section as determined by these borings on Plate XI. These borings were completed across the entire valley and taken at intervals along the surface of the ground up to an elevation of about 85 feet at each end. It is noted that the elevation of the indurated clay follows very closely the irregularities in the surface of the ground. The borings were also made on the hill to the east-of the Chagres for the purpose of determining a site for a lock, and this same condition generally holds, the clay being found between 15 and 20 feet below the surface of the ground.
Mr. Stevens reports, with reference to the Gatun site:
Extreme depth, to so-called rock or indurated clay, was found in the valley at 258 feet below mean tide level and on the bank of the west diversion. Apparently there are two deep and distinct valleys or gorges in this material, with the indurated clay rising a considerable distance above the mean low tide between them. A flow of water was reached in several of these holes. Most notable ones were at station 54+51 and at station 52+67. The flow of water at the former was quite a strong one, and indicated emphatically the imperviousness of the soil overlying the gravel.
See section, Plate XII.
The borings in the vicinity of La Boca and Ancon Hill, as well as those of the marine section, are given on Plate VII. They show the practicability of a lock in the Ancon-Sosa saddle and also at the westerly foot of Sosa Hill.
The geological sections also show depths to rock at several points that have been suggested as suitable for dams required in maintaining a terminal lake in the Rio Grande Valley.
The Commission and its engineering staff responded with great promptness to every request made upon it for additional physical data.
PROJECTS OF MR. LINDON W. BATES.
Mr. Bates presents three projects, designated A, B, and B'. He does not appear to attach great importance to the elevations of the lake surfaces shown in those projects, as the latter, including the elevation of the summit levels and terminal lake levels, where those features are found, are modified to almost any extent under his general presentation.
26
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The feature of terminal lakes is not new, indeed it is as old as the International Scientific Congress at Paris in 1879, one of the many plans proposed at that time suggesting a dam at Gatun. Again, in 1880 Mr. C. D. Ward, member of the American Society of Civil Engineers, advocated the creation of a reservoir formed by a dam at Gatun for the purpose of securing interior lake navigation. Nearly two years ago be again agitated the same question in communications to members of the then Isthmian Canal Commission, and published a paper upon the same subject in the Transactions of the American Society of Civil Engineers for May, 1904. (See Appendix I.)
Mr. Bates appears to express a preference for project B, which contemplates two terminal lakes, one on the Caribbean side formed by a dam at Mindi called Lake Chagres having a maximum elevation of water surface of 33.5 feet above mean tide, another at the Panama end formed by a dam connecting Ancon and Sosa hills with each other, and a second dam from Sosa Hill to the high ground on the westerly side of the Rio Grande-estuary. A third dam would also be needed to prevent escape of water over low land east of Panama, the waters thus impounded to be called Lake Panama, with a maximum elevation of water surface of 27 feet above mean tide. He also has an intermediate lake formed by a dam across the Chagres at Bohio called Lake Bohio, with the summit level at a maximum elevation of 62 feet extending through the continental divide to Pedro Miguel.
This plan provides four lockages-one at Mindi, one at Bohio, one at Pedro Miguel, and another between Ancon and Sosa hills. A variant of the plan contemplates the removal from Bohio to Gatun of the dam forming the intermediate lake or summit level.
This project also includes two terminal harbors, one called Balboa, a small protected area formed behind a proposed breakwater from the easterly side of the southerly portion of Limon Bay consisting of two parts, the opening between forming the entrance for the deep approach channel from deep water outside to the entrance of the canal proper, which he locates at the mouth of the Mindi.
Another possible variant of this plan is indicated by placing a breakwater in two parts directly across Limon Bay from Manzanillo Point to Toro Point, with an entrance between them about 1,000 feet wide, b4g in the hearing before the Board Mr. Bates stated that he did not consider this breakwater necessary, and its cost is not included in his estimate of cost. (Project B.) For the reasons already stated in the section on harbors in this report it is the judgment of this Board that the outer harbor, through which the dredged approach channel lies, must be protected practically from the point of its beginning in deep water to the southerly limit of Limon Bay. This may in a measure be done by the outer breakwater shown on Mr. Bates's plan, in which case the inner- one could be omitted. In making up the estimate of cost of this project the additional cost of this breakwater should therefore be included.
The general project of the harbor of Panama, forming the Pacific terminus, is much more elaborate than the harbor of Balboa. The former is to be inclosed by two great breakwaters, one starting at Guinea Point and running in a southeasterly direction to the island of Naos, and the other starting at Paitilla Point, extending first nearly due south, then southwesterly to the island of Perico. He proposes to dredge an entrance channel to the canal between the islands of Perico and Naos and running straight to the lock in the dam between Sosa and Ancon hills, the canal line nearly to Miraflores constituting a straight extension of the center line of the approach channel. This harbor is an ambitious one and includes a naval station on the north side of Ancon Hill. An entirely new site, formed by filling with the excavated material from the canal, is proposed for an extension of the city of Panama many times in extent the area occupied by the present city. He proposes some minor modifications of these projects for new harbors, but they do not affect materially the character of his harbor plans. These proposed terminal harbors are common to his three canal projects.
Project A has a summit level of 27 feet only above mean tide, maintained by two dams, one at Mindi and one connecting Ancon and Sosa hills with the high ground above Farfan Point, both of these being identical with the terminal dams of project B in location, but the former is of less height. The peculiarity of this plan is the low summit level, 27 feet above mean tide,
27
28 REPORT OF BOARD OF CONSULTING ENGINEERS) PANAMA CANAL.
extending from Mindi through to the Panama terminus, a single'lift lock being placed at Mndi and another in the Ancon-Sosa saddle.
The remaining project, B', bears approximately the same relation to project B that B does to project A. As B is derived from A by inserting an intermediate lock and summit level between the terminal lakes, so B' may be said to be derived from B by raising the summit level, introducing an intermediate lake between the Caribbean terminal lake and this level, and providing a second lock at Pedro Miguel. This project, therefore, contemplates two terminal lake levels formed by dams at Mindi and at Sosa Hill, already described in project A, with the elevation of water surface behind those dams 27 feet above mean tide; a dam at Gatun. behind which the elevation of water surface is brought up to 62, and finally a summit lake held by a dam at Bohio forming the summit elevation at 97 feet above mean tide, retained at the Pacific end by a dam and flight of two locks at Pedro Miguel. There are thus found six locks in this project, one at Mmndi, one at Gatun, one at Bohio, a flight of two at Pedro Miguel, and one at the AnconSosa saddle, it being understood that duplicate locks are contemplated throughout.
After a comprehensive examination and study of these various projects the Board was unanimously of the opinion that if project A alone were to be considered it could not be preferred to a sea-level plan. The low elevation of its summit brings the volume of excavation so near to that necessary for a sea-level plan that the work required, combined with that involved in the construction of the two dams and the locks, possesses no economical advantages over that required for the canal at sea level. The Board, therefore, unanimously disapproves project A.
This disapproval leaves projects B and B' only to be considered. As Mr. Bates himself indicates a preference for project B, the Board has centered on it the greater part of the consideration given to these two plans. The Board is unanimously of the opinion that the summit level of 97 feet above mean tide of project B' should not receive approval.
The papers, including plans and other information first submitted by Mr. Bates, i o
include a detailed statement of the amounts of work required to be done or of the items of cost of the different classes of work included. Upon 'request of the Board, however, Mr. Bates submitted supplementary profiles and sections of prism of the three projects or parts of those projects, with a tabulation of approximate quantities of excavation required under the three different plans. These approximate quantities were not given in sufficient detail to enable the totals to be satisfactorily checked or confirmed, nor were those approximate quantities so classified as to exhibit the amounts of hard and soft material required to be excavated or the amounts of the different classes of work to be performed for the appurtenant structures such as locks, dams, and other main features. It has, therefore, been impracticable to verify the lump or partially detailed estimates of cost set forth in the papers and plans submitted by Mr. Bates. Under such circumstances it is impossible to deduce close approximate quantities of work required to be performed in the execution of the plans, or a reasonably close estimate of cost of the entire work or of its various parts. The Board has made as close a comparison as possible between the total itemized quantities of excavation submitted by Mr. Bates and the more or less corresponding quantities computed by the Board for its own purposes. It has further coordi, nated for use in estimating the cost of the work under plan B its own estimates of costs for such appurtenant works as locks, dams, breakwaters, and other similar main features of the canal p roj ect.
The items of excavation given in his supplementary Graphic diagram of approximate quantities" appear to be less than those which the Board would estimate for the same purpose, but if the unit prices adopted by the Board be applied to the quantities for project B as given by Mr. Bates, the total cost of excavation alone, after deducting the useful French work, will be $85,289,500. To this sumn is to be added the estimated costs of the dams and locks at Mmndi, Gatun or Bohio, Pedro Miguel, near Panama, Ancon-Sosa, La Boca, and other large features of the plan, besides the breakwaters and other works at the two terminal harbors, and the regulating dams at Gamboa and other points on the Chagres, as indicated in his plans. His allowances for these various main portions of the work other than excavation seem to be insufficient. If these
28
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
works be allowed for on the same basis as corresponding works in the Board's plans the total cost of the entire project B, without adding any percentage for contingencies or other allowances, will approximate about $160,000,000. To this must be added a large but indeterminate sum for the great extent of country flooded by the terminal lakes, particularly Lake Chagres or Lake Bohio if Gatun rather than Bohio be adopted for the location of the dam creating the summitlevel lake. This inundated land includes a large portion of the most valuable lands in the Canal Zone and its near vicinity. It would include many villages along the line of the railroad between Mindi and La Boca, besides lands devoted to grazing and dairy purposes as well as.many banana plantations. It is quite impossible at this time to estimate the damages which the United States Government would have to pay for these submerged lands, but if past experiences in this field are any guide in making this estimate the sum would be very large. This question is also complicated by the doubtful validity of titles of many parcels of land claimed to be owned by private parties.
The land damages alluded to do not cover the lands which would be required for the regulating lakes at Gamboa and above that point on the Chagres River. While compensation would have to be made for these damages, that district is comparatively uninhabited and the amount of compensation would be relatively small; but this is an outlay practically common to all projects in which the control of the Chagres is to be effected at Gamboa or at points above.
The extended examination which the Board has given to Mr. Bates's project B fails to indicate that the work embraced by it can be completed for a sum much less than an amount nearly 50 per cent in excess of his estimate of $134,000,000, including the additional cost for the outer breakwater in Limon Bay and the same 20 per cent for contingencies, sanitation, and policing used in the other estimates of this Board. There can, therefore, be no material economy in the adoption of this plan.
At Obispo, where the Chagres cuts the canal line, Mr. Bates introduces a feature which he calls the Obispo triangle, designed to divide the flood waters of the Chagres entering the canal into two equal portions, one to flow through the canal prism toward Panama and the other toward Colon. .The accomplishment of this result is practically an impossibility.
The assumption is unwarrantable that a large volume of water introduced at the middle point of a channel over 20 miles long, which in the dry season is an ordinary canal and which in the rainy season receives lateral contributions varying with the locus of local downpour, will automatically divide itself into two equal volumes flowing in opposite directions.
Water levels will determine the flow at the central point, and local deposits with erosions caused by the excessive discharges will completely destroy the conditions necessary for the equal and opposite flows which he assumes.
That some of the waters, the quantity to be determined by experience, would seek exit to the south through the canal prism is probable, and the sea-level plan contemplates such a southern diversion, but it is not claimed that it would be automatic and equal. As the distance to the Pacific is less than to the Caribbean the hydraulic gradient will be steeper, and the flow in the sea-level canal would be controlled by the regulating sluices proposed; but the diversion of any part of the Chagres flow to the Pacific is not an essential feature of said plan.
Furthermore the Board believes that the proposed method of control of the Chagres, by a number of small reservoirs at Gamboa and above that point on the river, will be less effective and more expensive to maintain than that resulting from the construction of a single larger reservoir with a suitable dam at Gamboa. It is the further judgment of the Board that the proposed designs for the dams, dikes, or barrages proposed to be constructed at La Boca, Mindi, Gatun, or Bohio do not show the incorporation of such features of construction as will give reasonable assurance of their stability or efficiency for the purposes contemplated, and that a proper provision for those features would greatly swell the costs indicated by Mr. Bates.
Again, Mr. Bates has outlined no method and has apparently given no consideration to such procedures as would be required to transform the work executed under his project B to a sea-level canal, nor has he made any estimates of cost whatever for such transformation. It is
29
30 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
obvious, however, that the work of transformation would be very costly and that the expense of that work would swell to an excessive or even prohibitory amount the ultimate cost of the sea-level canal so attained.
This project is less well adapted for transformation to a sea-level Canal than the lock plan with a summit elevation of 60 feet above mean tide adopted by the Board for comparison, although the difference between the two is not great. Such difference as exists is found chiefly in the more costly structures of Mr. Bates's project, such as the dam and spillway at Pedro Miguel and tjie works at the Obispo triangle, and in the less effective system of control of the Chagres floods. Much more elaborate harbor constructions and the more costly character of their appurtenant works chiefly account for the excess of the estimated cost of Mr.. Bates's project B over that of the 60-foot summit level lock plan of the Board, to which allusion has already been made.
Finally, this Board believes that on the grounds of both first and ultimate economy, for safety in construction and operation, and in adaptability for transformation to a sea-level plan, the lock plan above referred to, adopted by the Board for purposes of comparison, is to be preferred to Mr. Bates's project B.
It has been urged by Mr. Bates that the health conditions would be much improved if the plan he proposes should be adopted of submerging the valleys of the Chagres and Rio Grande and converting those broad areas into fresh-water lakes. It is now the generally accepted theory of sanitarians that the mosquito which causes yellow fever breeds only in vessels and pools of fresh water in the houses and in their immediate proximity. If this is accepted as fact we should not expect that the existence or nonexistence of broad expanses of fresh water would have any influence upon the occurrence and spread of yellow fever. In the margins of lakes and ponds the malaria mosquito would breed, and on the other hand' the submergence of the sites of present villages would deeply flood and destroy the present habitat of the anopheles, but they would find new breeding places in the shallow margins of the lakes; since these lakes could not be f ormed until the canal is completed, the health conditions as affected by the malaria mosquito would not be changed during construction. If the sea-level plan be acepted, the ultimate drainage will be far below the earth's surface nearly throughout, and the desiccation of stagnant pools and marshy surf aces near the canal will be easy. There will be no lake margins near, and the canal will at all times be the ultimate receptacle of all surface drainage and will contain only clear water flowing through a channel with steep sides, which water will, near the termini, be salt or brackish and in the dry season salt throughout. All things considered, it is not probable that the conditions as respects malaria would be materially diff erent whichever be the plan adopted; but if there is a difference, the sea-level waterway will be more favorable to health conditions.
That the Isthmus would continue to be pest ridden unless the transit be effected through submerged valleys is rejected by the Board as without any basis of sound argument or fact. The present transit of the Isthmus, which, with voluntary and necessary detentions usually occupies at least a day, has not, so far as disclosed, for a quarter of a century been attended with jeopardy to health, and under no conceivable conditions of. transit by ocean steamers is it- believed that serious dangers would be incurred by the passengers and crews of the vessels. The health of the marine battalion that has been serving on the Isthmus for two years has been uniformly good. TINo member of the command has contracted yellow fever and there has been no death from malaria.
For all the above reasons the Board disapproves the adoption of project B of Mr. Bates's system for the construction of the Panama Canal.
PLAN OF MR. P. BUNAU-VARILLA.
Mr. Bunan-Yar illa proposes to construct a lock canal with a high summit level, and after its completion to proceed with its transformation into a sea-level canal. He estimates the time required to complete the lock canal at four years, with a summit level at elevation 130. The
30
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 3
transformation will require a widening as well as a deepening of all channels above sea level. The widening above water is to be done first by the ordinary methods for excavation in the dry, but all excavation below water is to be by dredging. By using water power to develop electricity for the dredges and other machinery he estimates that the work can be done at a very low cost.
In a succeeding section the Board has indicated its judgment that any lock canal may be transformed in some manner into a sea-level canal, so that, if time, cost, and danger be left out of consideration, the change can be made without sensible interference with traffic. If the latter condition were observed rigidly the time and cost would be greatly increased, and it is probable in order to avoid such extraordinary increase, that some interference with traffic would be tolerated in the process of transf ormation, as in many canals or navigated waterways the depth s and widths of which have been increased.
Mr. Bunau-Varilla has outlined to the Board a very ingenious procedure to be followed in effecting such a transformattion, with special reference to the difficulties of eliminating the locks successively and of disposing of the excavated materials. If the locks were of single lifts (as would be the case in the lock-canal project with summit level at elevation 60), he would modify their construction by placing the gate sills for the upper ends of locks at the level of the canal bottom below instead of above the lock, the latter being the usual practice. This would result in adding greatly to the weight of these gates, making them a little less convenient to operate. With locks so arranged the canal above the lock could be deepened in mnoderate stages, of five to ten feet for example, during which process the full depth of 40 feet of water would be maintained in the canal and no excavation would be required in depths exceeding 45 or 50 feet. After this amount of deepening throughout the summit level the water would be lowered by the same amount and the process repeated sufficiently to depress this level to those adjacent, when all the gates in the upper level could be thrown open. Before any further lowering could be commenced it would be necessary to remove the floors of the duplicate locks, one lock at a time, while open navigation would be maintained through the other.
If the locks were in -flights of two or more, the modification in the original construction would not be so simple; in each lock below the upper one an additional pair of gates would be placed near the upper end, so that when the gates and floor of the upper lock were all removed and the site deepened the additional pair could be used as upper gates. Until the completion of the change the provision of additional gates would lengthen the locks about 100 feet, arid thus increase the time required for filling and emptying and encroach on the water supply. The process of transforming the canal would be the same as for a canal with single locks up to the point when the gates of the upper lock are thrown open after the level above has been lowered by an amount equal to the lift of that lock. The transformation would then become more difficult, because if one lock were closed to remove the floor there would be lock navigation instead of open navigation through the other one, and if the traffic were heavy it might be necessary to build a third flight so as to have two in constant use; and the provision of a third flighniight be demanded for the security of the navigation so that duplicates might always be in readiness, except during short periods when one was being repaired or the machinery refitted. It seems probable that it would be judicious to provide the third flight of locks before beginning the transformation, and if this were done any desired change could be made in the same by successively closing them to navigation until the changes were made, and with such third fight the modifications suggested by Mr. Bunan-Varilla, which would be objectionable in a lock canal, would be dispensed with.
For disposing of materials excavated during the transformation Mr. Buna-Varilla proposes to construct a flight of locks which would connect the elevation of sea level with the surface of Lake Gamboa, and use this lake as a dumping ground for materials dredged from the canal. Such of these locks as were below the surface of the summit level of the lock canal would have to be built before any raising of the water in the Chagres, and all would have to be built before beginning the transformation. The lower locks would be submerged, and would not be used until they emerged with the successive lowering of the summit level. With this communication
1131
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
with Lake Gamboa it would not be necessary at any time to pass barges loaded with excavated materials through the canal locks, and interference at the locks with navigation would be entirely avoided.
This method of disposing of dredged material is feasible but not inexpensive, and although the disposal of a large volume in Lake Gamboa would reduce to some extent its efficiency for floodscontrol and for catching silt, the volume of the lake would be so great that this reduction would not be important. If a lock-canal project with a small terminal lake on the Atlantic side should be adopted, alternatives to the plan of disposal submitted by Mr. Bunau-Varilla would be to pass the barges with excavated material through the canal locks to sea, from which some interference with navigation might result, or to rehandle the greater part of the dredged material at various points along the canal and deposit it on the areas above water level, which would be expensive. With summit level at elevation 85, extending northward to Gatun, a vast amount of excavated material could be dumped in the low areas in Lake Gatun above Bohio until the summit level were lowered to about elevation 60, and between Bohio and Gatun until the summit level were lowered to about elevation 30. Of the relatively small amount of material then remaining, the portion suitable for suction dredging could be pumped to higher elevations and the remainder could be passed through the canal locks to sea without very serious or prolonged interference with navigation; or, if this limited interference were found inadmissible, it could be transferred from barges to cars and disposed of at some suitable dumping ground. Although the unit cost of such rehandling would be considerable, the volume would be small compared with the amount to be disposed of in a similar manner if the 60-foot level were adopted for the summit and the 30-foot level for the stretch between Bohio and Gatun.
The claim made by Mr. Bunau-Varilla that the excavation required for the transformation can be done at low cost rests mainly on the expectation that by the use of electric power, developed at the Gamboa dam and distributed along the line, the expense for fuel for generating steam will be eliminated and the cost of all mechanical operations reduced by what appears to the Board to be a much exaggerated estimate of the economies thus effected, and on the further expectation that excavation can be made at very much less cost by dredging than in the dry. This reduced cost of dredging is probably true for sand, clay, or other materials that can be moved without being shattered by some preliminary process, but nearly all the materials to be dredged for the transformation are classified in the Board's estimates as rock, and will have to be loosened by blasting under water, by breaking or pulverizing, as in the Lobnitz method, or by such other methods as may be devised. Moreover, it must be remembered that the greater part of the dredging is to be done under 40 to 50 feet of water, which will add much to the cost. The unit prices adopted by the Board represent its best judgment in regard to the cost of excavating the several classes of materials which the transformation would require with the best methods and appliances now in use. Comparison of the cost of first constructing a lock canal and then lowering it to sea level with the cost of making the latter canal at once, on the basis of adopted unit prices, shows that the removal of nearly all the material under water by subaqueous blasting or otherwise shattering, and then dredging, would cost much more than if taken out in the dry; and hence, as is shown in a following section of this report, the final cost of a sea-level canal ultimately secured by the process of transformation, and of the channel dimensions adopted, would be about $100,000,000 greater than by immediate construction, without taking into account the loss of the costly locks and other structures abandoned or demolished after reduction to sea level.
The advantages claimed to be secured by Mr. Bunau-Varilla by his method of excavation of successive strata without occupation of the navigation channel would be realized only when the side slopes are not steep, the advantages increasing with gentle slopes and disappearing as the slopes become more nearly vertical. Inasmuch as by far the greater part of the under-water excavation in his process of transformation would be made in material classed as rock, large portions of the side slopes might be as steep as four vertical on one horizontal, and a very small portion, if any of them, will be less steep than three vertical on two horizontal. It is therefore probable that little would be gained through this special feature of Mr. Bunau-Varilla's plan.
32
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 3
W hile it is possible that the actual cost might be lessened by improvements in means and methods yet to be developed, it would not be prudent to assume this and reduce the estimate given above.
Mr. Bunau-Varilla estimates the time required to build a high-level lock canal at four years. Although smaller locks than those proposed by the Board or those required by the act of Congress under which the canal construction has been- commenced might be defended for a canal built for temporary purposes, they would have to accommodate war ships of the largest size as well as large commercial ships, and could not be made as small as those proposed by the New Panama Canal Company, which were to be 82 feet wide with a useful length of 738 feet. The Comit6' Technique estimated that the construction of the Bohio locks would require four years after the excavation was practically completed, and no shorter period has been suggested by any later commission. Mr. Bunau-Varilla's project not only provides more locks aong the canal line than any other plan, but also requires the cons tructi on, as part of the original work, of those locks of the flight leading f romn sea level to Lake Gamboa which are f ounded below the summit level of his plan. Making due allowance of time to provide suitable excavating plant and to make the excavations at the several lock sites, the term of four years is far too short for the work to be done,
After a full and careful consideration of all the features of Mr. Buna-Varila's plan, the Board is of the opinion that it should not be adopted for the Panamia Canal for the following reasons, which have already been indicated:
1. The construction of the large locks required under the present law and necessary for the accommodation of the traffic seeking the canal after its completion makes it quite impossible to complete the preliminary lock canal even nearly within the period stated.
2. The excessive cost of transformation added to the loss of costly locks and other appurtenant structures required by the preliminary lock canal.
3. If the lock canal is likely to be retained for many years it should be made for the most efficient service and not be encumbered with modifications in loc k construction which would prove inconvenient in use.
PLAN OF ItHE ISTHMIAN CANAL COMMISSION, 1901.
This plan was submitted to the Board and has received careful consideration. The plan as described in detail in the reports of the 'Commission is here referred to only as respects certain features.
The depth proposed for the excavated channel was 35 feet and the bottom width 150 feet, except in Colon Harbor where 500 feet was proposed, in Panama Bay 200 feet, and in submerged excavated channels in Lake Bohio 200 feet. The summit level was to be at a maximum of 90 feet, attained by two locks on the Atlantic side at Bohio, and on the Pacific side byone at Mirafiores and two at Pedro Miguel. The locks were to have a clear length of 740 feet and width of 84 feet. An earth dam with masonry core wall at Bohio was to form a lake in the Chagres Valley above that point, with elevation of surface varying from 82) to 90 f et. The alignment was the same as that of the French lock plan. The entrance to the canal at Colon required a double curvature, the radius of one of the curves being 38,281 -feet. The total cube of excavation was estimated at 94, 863,703 cubic yards; the cost, with 20 per cent for contingencies, was fixed at $144,233,358, and the time of completion ten years.
As stated in another part of this report, the Spooner Act authorized the construction of an isthmiian canal and fixed certain conditions respecting dimensions and capacity which were not within the cognizance of those who recommended the plan of 1901. If the canal then contemnpltdwere now in existence itwol notafrpsagtoelgst ships flow il course of construction.
The plan contemplated five lift locks-works which the Board believes:should not be used if' a convenient and safe passage is to be provided for the largest existing and expected vessels at a cost in tim-e and money which is reasonable; the plan under consideration would not fulfill present and future requirements.
465A--06--3
33
34 REPORT OF BOARD OF CONSULTING ENGINEERS) PANAMA CANAL.
The Board has therefore found itself unable to recommend the sthmiian Commission's plan of 1901 for adoption by the Government, nor does it believe that any modification of that plan involving the use of lift locks should be adopted for the Panama Canal.
PLAN OF MAJ. CASSIUS E. GILLETTE, U. S. ARMY.
Among the papers submitted to the Board was un article by Maj. Cassius E. Gillette, Corps of Engineers, U. S. Army, which had been printed in the Engineering News of July 2, 1905. The article is entitled "The Panama Canal: Some serious objections to the sea-level plan." Under this heading occurs a general description of the various canal plans, ending with a description and recommendation by the author of a plan for a 100-foot summit level canal.
He states that the engineering work is best which accomplishes the desired object at the least expense, and also that the cost of a canal is made up of the first cost, with that of operation and maintenance, and the cost of enlargement, the latter being a very important matter, as is shown by the history of all existing canals. Mention is made of the work being done on existing canals at the present time, and, in the opinion of the author, the best canal would be one that could be most easily enlarged. He thinks that the lock canal can be more easily changed and its capacity increased.
He points out the advantages to be obtained by a canal with a high dam at Gatun, with reference to the elements of cost, time of construction, serviceableness, and ease of enlargement.
In his opinion the question of sediment has not been heretofore sufficiently considered, and a description of the topographical features of the country as affecting sediment in the streams is given. The problem of disposing of sediment with a sea-level canal is, in the author's opinion, a serious one.
It is alleged that large ships would have difficulty in navigating the present Atlantic entrance in the high winds which prevail in that vicinity, on account Of the sharp reverse curve necessary to enter the canal. He recommends practically a straight line for the canal from Gatun to deep water in Limon Bay, almost exactly the line which has been recommended by the Board in the sea-level plan.
Objection is made to a high earth dam with a mi-asonry core at Gamboa. He suggests that a masonry core really converts a dam from an earth and rock structure into an inefficient masonry work, and that by the stoppage of all seepage water the rock and clay above the dam become thoroughly saturated, and the large proportion of soluble clay in its composition would make it, so far as pressure is concerned, heavier than water and increase the thrust.
Major Gillette advocates a 100-foot summit level canal with a dam at Gatun. This will provide, in his opinion, a lake having an area of at least 100 square miles, subject to very slight fluctuations, and capable of settling for ages all the mud that the streams would bring into it; it would also supply all the water necessary for lockages and 'Would give a straigt channel between Bohio and Gatun.
The proposed dam at Gatun is of earth, with a core of impervious material. To prevent seepage under the dam a method is suggested of using steel sheet piles driven to a depth of about (30 feet, and then to drive, in sections to bed rock immediately alongside of this sheeting, three-inch pipes, five to six feet apart, through which is to be forced cement grout.
The project under discussion assumes a flight of three locks whose usable dimensions are 900 feet in length by (90 -feet in width, with lifts of 35, 35, and 30 feet. The author thinks the prejudice against locks of greater lifts than 35 feet, based upon difficulties inherent to gates with mniter sills, may be overcome by the use of floating caisson gates. The estimate for the flight of locks at Gatuin is $1,900,000. It is evident that this is for a single flight of locks.
Many of the criticisms of the various suggested canal plans are the same which have been made in the sessions of thelBoard, whose plan is the logical development as a correction of the defects of previot~s pllans. The Board has adopted a line for the canal from Gatun to deep water which is practicallyv the one recommended by Major Gillette.
His criticism of a high earth dam Nwith a masory core at Gamboa is worthy of attentionm. This matter has been considered by the Board, and in its plans the proposed estimate
34
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
of the Gamboa dam has been made large enough for the construction of a dam of masonry throughout.
The dimensions of the Gatun dam are very similar to those recommended by several members of the Board in its discussion, for example, of the 85-foot summit level plan. His estimate of cost, however, appears to be too small. The Lock-Canal Committee of the Board estimated for a dam at Gatun for a lake level of this height, with its spillway and regulating works but without any arrangements to stop seepage under the dlam, a total of $8,000,000. Major Gillette, for his 100-foot summit level, estimates $2,800,000. It is probable that one cause of this discrepancy is the fact that the Board has had the advantage of recent surveys, which show that the maps from which Major Gillette worked were inaccurate.
The objection to a dam at this site has already been set forth in the discussion on dams.
The Board is unable to approve the suggested method of preventing seepage under this dam on account of its cost and doubt as to its effectiveness as applied to that site.
The Lock-Canal Committee of the Board, in its estimate for the 85-foot summit level with flights of three locks each, having less lift but somewhat greater length and width, viz, 1,000 by 100 feet, arrived at the sum of $7,410,000 for each flight. It is very evident to the Board that the estimates of cost given by Major Gillette throughout his paper are very much too small.
THE 60-FOOT SUMMIT LEVEL PROJECT ADOPTED FOR COMPARISON WITH THE SEA-LEVEL PROJECT.
This plan provides for a summit level of moderate height and for corresponding dams. Such a canal could be built in somewhat less time than one at sea level. It would have duplicate locks throughout of one lift only between adjacent levels, and could be transformed into a sea-level canal with less difficulty than one with a higher summit level. For these reasons it is preferred by the Board to any other lock-canal project before it.
The proposed harbor on the Atlantic side is to be the same as described in the sea-level plan. The canal between Mindi and Gatun is to be 500 feet wide, as in the harbor, giving a broad waterway and furnishing material for an earth dam at Gatun of sufficient height to sustain a head of 30 feet. The lift at Gatun will be made with one lock. From Gatun to Bohio the channel is to be 300 feet wide, the banks generally submerged. At Bohio another dam and a lock of the same lift as at Gatun would raise the level to elevation 60. Sluices for the discharge of surplus water are provided in connection with both dams.
For the control of the floods of the Chagres and the storage of water for canal supply a dam is proposed at Gamboa identical with that for the sea-level canal. From Bohio to San Pablo, about eight and four-fifths miles, the canal is to be 500 feet wide, with channel banks generally submerged; from San Pablo to Obispo, nearly seven miles, it is to be 300 feet wide, and at the latter place reduced to 200 feet, which is to be continued for a distance of seven and one-half miles through the Culebra cut to Pedro Miguel.
The descent to the Pacific is to be made by two locks, one being at Pedro Miguel, the other six miles beyond, on the west side of Sosa Hill, near the shore of Panama Bay. The canal is to be 300 feet wide between these locks with water surface at elevation 27, the lift at Pedro Miguel being 33 feet, that at Sosa varying with the tide, being about 34 feet at ordinary low water. A spillway to discharge surplus water is proposed at the Ancon-Sosa saddle. The level between Pedro Miguel and Sosa is to be maintained by an earth embankment of considerable dimensions across the Rio Grande opposite Sosa Hill, and smaller ones in the Ancon-Sosa saddle and between the Ancon Hill and high ground to the eastward. These embankments, as well as the Gatun and Bohio dams, are to have unusual width and height above water.
In Panama Bay a short distance beyond the Sosa lock the line joins the line of the French company, and the width of 300 feet is maintained from the Sosa lock to the seven-fathoum contour. The location of the canal is the same as that of the sea-level canal except a small variation at Gatun and the greater one from Pedro Miguel to the terminus in Panamna Bay resulting from locating the tidal lock on the west side of Sosa instead of in the Ancon-Sosa saddle. In the narrow channel through the Culebra cut the sides of the wet section are to be vertical or nearly so; elsewhere they have slopes suitable for the material passed through. The widths above
35
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
given are bottom widths. Excluding the locks, only one-sixth of the canal is to have a bottom width of less than 300 feet. (See Plate IV, Maps and Diagrams.) It is estimated by the Board that the cost of the canal thus described, including 20 per cent for contingencies, would be $176,000,000.
SAFETY AND PROTECTION.
The general question of defense of the Isthmian transit will be in no way affected by the type of the canal.
Dismissing, then, any consideration of the question of general military defense, the Board is of the opinion that the safety and protection of the canal will be sensibly influenced and affected by its type; in estimating these influences the following considerations should be noted:
As having very important bearing upon the type of canal to be recommended for adoption, it is assumed to be of primal importance in the design of the waterway that the military necessity of the United States demands a passage between the two oceans, whereby the navy in the Pacific might be quickly transferred to the Atlantic, and vice versa; which necessity, in 1898, became so important that it had a controlling influence upon public opinion respecting the canal and had a decided influence in crystallizing ideas and in hastening final action by Congress on the whole project for interoceanic communication.
In the Spooner Act of June 28, 1902, already quoted in part, is found the only Congressional legislative requirement respecting the dimensions and protection of the canal. In that act it is provided that the canal must afford a passage for the largest existing vessels as well as for those which may be reasonably anticipated, and that this passage must be a "convenient" one, so that all "necessities" of shipping may be met. Necessary measures must be taken to insure safety and protection. The harbors to be provided must be "safe and commodious" for said existing largest vessels and for those to be expected in the future. It therefore behooves the Board to show that the type of canal recommended for adoption possesses the features best subserving adequacy in capacity, convenience and safety in use, and capability for protection.
According to Sir W. Laird Clowes's Naval Pocket Book for 1904, the largest war vessel afloat in March, 1904, had a length of 454 feet. The greatest beam noted is of 80 feet, and the deepest draft 27 feet 2 inches. However, several battle ships and cruisers are building of from 14,000 to 20,000 gross tons, and at least one of 22,000 tons, but the authority consulted does not give particulars as to size of this last, although war ships of such tonnage may well have dimensions closely approximating those of the largest existing commercial vessels. The largest war vessel building of which particulars are available has a beam of 83 feet 6 inches, but as yet there is no indication that the commercial and passenger steamers will not continue to lead in size, and therefore it results that if the channels, anchorages, and locks are adequate for the largest ocean liners and freighters, then the largest naval vessels will find adequate dimensions for convenient passage.
The beam of modern seagoing vessels furnishes a fair indication of tonnage and other dimensions. By reference to Lloyd's Register of Shipping, 1905-6, and the before-cited Naval Docket Book, it is seen that as respects beam the large commercial and war vessels may be classed as follows:
Beam of large ocean steamers.
Commer- War ships
Beam. cial ships in use or Total.
in use. projected.
40 to 45 feet........................2,101 201 2,302
45 to 50feet........................ 1,993 139 2,132
50 to 55 feet......................... 692 110 802
55to 60feet......................... 177 83 260
60 to 65 feet........................ .53 44 97
65 to 70 feet......... .... .....26 123 149
70 to75 feet......................... 6 85 91
75 to 80feet.......................... 3 81 84
80 to 85 feet.................................... 8 8
Total........... ............... 5,051 874 5,925
36
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The largest commercial steamers recently put in service are generally of less breadth than the newest naval vessels, but the former are of greater length. However, the Cunard Company has now under construction two steamers 800 feet in length and 88 feet in beam.
It has been urged in some quarters that the express passenger steamers will not make commercial use of the canal. If this contention be admitted as true, it does not follow that the capacity of the canal should be restricted as to dimensions, so shutting out this class of the ocean marine. It is understood that the requirement imposed by the statute that the canal must conveniently accommodate the largest existing and expected ships contemplated, in the opinion of the law-making power, the existence of a necessity for such dimensions which would arise in the event that the military needs of the United States may require the transfer from one ocean to the other of large bodies of troops with their equipment and supplies. In such contingency the largest express steamers obtainable would certainly be employed as transports. Military exigency requires, and it therefore results, that the dimensions of the canal and its appurtenances must be adequate for the largest vessels upon the oceans.
Between 1867 and 1906 the Cunard Steamship Company constructed 16 large ships. It is interesting and instructive to note the increasing measurements of this fleet. The ships placed in service between the years 1862 and 1874 showed 29 per cent increase in length over those in use before, and. 4, per cent increase in beam. In the next decade the new ships were 12 per cent longer and 30 per cent broader than in 1874. The increases in the third decade were 20 and 14 per cent. The new ships launched up to 1905 were 8 per cent longer and nearly 11 per cent broader than the largest of 1893, while those laid down in 1905 were 23 per cent longer and of 21L per cent more beam than those in use the year before. There seems to be no recognizable tendency to discontinue this expansion of dimensions of deep-sea vessels.
The voyages from the North Atlantic ports to those of Australasia and the Orient will be the longest existing between great terminal ports and commercial marts, and if larger vessels are generally more profitable than small ones, or if very large freight and passenger vessels are used anywhere, it would seem to be certain that they will ultimately, and probably as soon as the canal is available, seek the interoceanic transit at Panama. That the convenient passage there will, within a quarter of a century, be used by ships 900 feet long and 90 feet beam seems not at all improbable.
The modern lock for ocean-going vessels is a work which an enemy, through stratagem, could with no great difficulty put ot4 of use in an hour or in even a few minutes. If a small detachment from the enemy's fleet, armed with high explosives, landing secretly by night at some nearby shore or inlet, hiding in the neighboring jungle, should surprise the canal guards, or if a few malicious individuals in disguise should succeed in exploding against a lock gate under high water pressure as much explosive as they could carry, they could disable the lock, and could probably cause damage of such colossal magnitude as would put the canal out of use for months. This danger is one that very strict watch and guard might prevent in great measure, but it is well-nigh impossible to provide effectually and always against such peril. Sovereign rulers, bridges, railway trains, buildings, and ships, all under very strict watch, have been destroyed by lawless individuals. Guards would, of course, be always on duty at the danger points and every protective measure possible would be adopted, but if a few desperate characters should set out to disable the canal, and persist in the attempt, regardless of consequences to themselves, the peril would be very great.
As respects vulnerability of the canal or its works to injury and interruption of traffic by a few lawless individuals, the means and results are not difficult to foresee and estimate.
(a) The wrecking by explosives of the lock gates while under unequal water pressure, or of the valve chambers where the lock filling and emptying mechanism is situated: The remedy in the one case would consist in the removal of the wreckage and the replacement of the gates; in the other, in possibly very extensive .repairs requiring much time. If the controlling gates of an upper lock should be destroyed the summit level would be drained, and if the gates were wrecked so as to afford a free outlet to the water the locks below and the canal itself would be ruined or at the least greatly damaged. In case the gates or controlling mechanism of a lock
37
38 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
were ruin ed, and free exit for the upper waters was permitted through the chamber, the lock alongside would also be emptied and put out of' commission until its neighbor was repaired.
(7)) The blowing up in a lock of a vessel offered for transit, but designedly laden with high explosives for ignition at the proper moment: In that event the lock would be destroyed, and if it was a lift lock a year or more would be required for repairs.
(e) The detonation of some high explosive against or under some portion of a dam built to maintain a summit level: This would be a much more difficult undertaking and one less likely to be attempted. The wrecking by explosives of the controlling and discharging sluices in dams would be easier, but a good many men and considerable time f or a successful operation would be necessary. This might be a serious jeopardy at one point for a sea-level canal, but provisional repairs with timber could always be quickly effected.
(d) The sinking of a large vessel in the canal prism by any means: Recently the steamship Glialkamn, of 2,500 tons displacement, laden in part with blasting gelatin, met with an accident in the Suez Canal and later was sunk. It had to be blown up an-d removed before transit could be resumed. The time during which the canal was closed to vessels was ten days. In case of a similar incident at Panama, whether resulting from an accident as at Suez or from design, the consequences, so ~a as interruption of transit is concerned, might be expected to have a similar result.
The plan proposed by the Board for the isthmian transit will have twin tidal locks near the Pacific terminus which, if disabled, one or both, as tinder (a), would still be usable (after removal of wreckage) for a part of each day (the period of spring tides) in each lunar month, and probably throughout the whole twenty-four hours during the remainder of the lunar month (neap tides).
The-.plan also contemplates a damn at Gamboa for Chagres control, provided with regulating sluices. There are to be three small dams for the control of minor streams, but there are to be no lift locks, for these, it is claimed, both single and especially in flight, are much more vulnerable than any other essential accessory that has been proposed to be used hin any type of canal that has been considered by the Board, and this jeopardy is considered to be a very grave one.
Respecting the liability of the canal to injury and the importance of its defense, the Isthmian Canal Commission in its report dated November 16, 1901, said:
It is always to be borne in mind that during the excitement of war the canal will not he a safe place for the man-of-war of any nation, no matter who is nominally in control. A small prty of resolute men, armed with a few sticks of dynamite, could temporarily disable it without very great difficulty.
The Board believes that this jeopardy will exist at all times during the stress of war.
If an interruption to traffic from any cause should occur while military and naval operations by the United States were in progress, calamitous results would inevitably ensue. If the two belligerents did not include the United States-the custodian of the canal-the closing of the passage might be attempted by one or both the contending powers, and while it would not be done openly, their secret agents would probabl y conspire to its accomplishment. S uch an attempt was feared at Suez while the Russian fleet was passing through that canal en- route to the East, and special precautions to guard against the danger were taken by the canal officials and the Egyptian Governmnent. That the risks would be very much greater for a canal in which lift locks are an essential feature is self-evident, anid in the opinion of the Board such devices should be rigorously excluded from the design of the canal.
TRANSFORMATION OF A LOCK CANAL INTO A SEA-LEVEL CANAL.
The instructions of the President to the Consulting Board under date of September 11, 1905, contain the following inquiry:
I desire also to know whether, if you recommend a high-level mltilock canal, it will be posible after it is completed to turn it into, or to substitute for it, in time, a sea-level canal without interrupting the traffic upon it.
The Board is of opinion that is is possible to transform a lock canal into a sea-level canal without material interruption of traffic and without serious delays to navigation, although the
38
.4
9AJi4?t L40k,4 04/c~ _op
Aa
r 4,4-74 Av
,41 As rA-3 ctt t 7
4
4
4
a '4
4
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
operation would not be an easy one, nor can a trustworthy estimate o.f its cost be made at the present time. The work evidently involves the excavation of immense quantities of rock and earth, much of it at depths considerably exceeding 40 feet below the surface of the water. The Board, having in view the removal of rock at depths less than 40 feet, has adopted as the price for excavating rock under water $2.50 per cubic yard, while for rock excavated "in the dry" it has adopted $1 and $1.15 per cubic yard, except in the Culebra divide cut, where for all classes of materials above elevation 10 a price of 80 cents per cubic yard has been adopted, and for all classes of materials below elevation 10 a price of $1.25 per cubic yard. For the dredging of earth from the canal a price of 25 cents per cubic yard was adopted as against 40 cents per cubic yard for earth in the dry.
As rock is the predominating material to be excavated in depressing the canal from a lock level, it is obvious from the unit prices adopted that a sea-level canal obtained by first building a lock canal would cost very much more than a sea-level canal constructed by a direct process.
An approximate estimate of cost of reducing a lock canal with a terminal lake on the Atlantic side formed by a dam at Gatun, with three locks on the Atlaltic side and three on the Pacific, and with a summit level 85 feet above mean tide, to a sea-level canal with the dimensions of prism adopted for the sea-level plan, may be made as follows: 64,500,000 cubic yards earth, kilometer 8 to kilometer 46, at $0.25. ..--------------------------------$16, 125, 000
13,400,000 cubic yards rock under water, kilometer 8 to kilometer 46, at $2.50-----------------------..33, 500, 000
14,200,000 cubic yards excavation above water in Culebra section, at $0.80..--------------------------11, 360, 000
6,500,000 cubic yards rock excavation in Culebra section from surface of water to 25 feet below, at $1.50. 9, 750, 000 35,300,000 cubic-yards rock excavation in Culebra section more than 25 feet below water surface, at $2.50. 88, 250, 000 Add for dams and diversion channels and for transforming section of canal between Pedro Miguel and Miraflores, say. . . . ..-------------------------------------------------------------------------25, 000, 000
Add for removing the locks at Gatun and Pedro Miguel, for modifying the lock at Miraflores, and for removing the regulating works at the Gatun dam and at Miraflores, say.--------------------------..25, 000, 000
Total cost of transforming lock canal to sea level, on basis of canal sections of Sea-Level Canal
Committee, without allowance for contingencies .. ...---------------------------------------208, 985, 000
After a full and careful consideration of all phases of this question the Board has reached the following conclusions:
1. That it is possible to turn any lock canal which it has considered into a sea-level canal without interrupting the traffic upon it.
2. That it is practicable from an engineering standpoint to transform any lock canal which it has considered into a sea-level canal; but that the cost and difficulty of such transformation would be so great as to render such a change impracticable from a financial standpoint until the traffic should have so increased as to tax the capacity of the lock canal, or until other good and sufficient reasons existed for such a change.
3. That if a sea-level canal is to be constructed in the near future it should be built directly without first building a lock canal.
4. That the date for developing a sea-level from an existing lock canal would be so remote, and that there would be so little difference in the time and cost of the transformation for different types of lock canals with a common summit level, that the design of a lock canal should not be controlled by the view that it is subsequently to be so transformed.
5. That the Board is unable to express any definite opinion as to the time required to effect such a transformation into a sea-level canal.
CAPACITY OF CANAL FOR TRAFFIC.
The Board considered that the provisions of the law of Congress by which the construction of an isthmian canal was authorized required that this law should furnish the basis upon which all deliberations should proceed and upon which every conclusion should be established.
The terms of the particular portion of the law which affected the conclusions arrived at by the Board in respect to the dimensions which should be given to the canal locks and prism were conveyed to the Board in the letter signed by Mr. Shonts and printed on pages 10 and 11
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
of this report, in which the Isthmian Canal Commission laid before the members certain projects for the construction of the canal which had already been submitted to the Commission. The terms relate to the excavation, construction, and completion of a "ship canal from the Caribbean Sea to the Pacific Ocean," and proceed "such canal shall be of sufficient capacity and depth as shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use, and such as may be reasonably anticipated, and shall be supplied with all necessary locks and other appliances to meet the necessities of vessels passing through the same from ocean to ocean."
Having these terms as well as "the rapid developments of naval architecture" referred to by the Commission in the letter of its Chairman in view; having noted that steamers of a length of 740 fet over all and a breadth of 75 feet are at present engaged in ocean navigation, while vessels of a length of 800 feet by 88 feet in breadth are now actually being built, and having the assured opinion that naval development has by no means come to an end, the Board arrived at the following conclusions:
1. That the locks on a canal of any type should be of such usable dimensions as will afford a length of 1,000 feet, a breadth of 100 feet, and a depth of 40 feet.
2. That the prism of the canal for the length to be excavated through the divide (i. e., the length usually known as Culebra cut) should have a depth of 40 feet, a bottom width of 200 feet, and sides with slopes of about ten vertical to one horizontal.
It is considered that with such dimensions the Panama Canal will meet the necessities of the traffic which will use it and the requirements of the law which authorized its construction. It is further considered that if the canal were formed with smaller dimensions than these, experience would prove it to be regrettably deficient in capacity,
The following particulars of existing maritime canals may be useful for the purpose of comparison when regard is had to the fact that not one of these canals is capable of accommodating steamers of the largest draft now employed in the world's trade:
Suez Canal, Egypt.-The Suez Canal presents the nearest analogy to the case of the Panama Canal. It is a sea-level canal without locks, and has a depth of 31 feet.2 inches, which is now being increased to 34.feet 5 inches. The bottom width in the canal proper varies from 108 feet, where the side slopes are very flat, to 118 feet, where the side slopes are steeper, with garages or passing places at intervals for vessels of very large size, as vessels are not allowed to pass each other while both are in motion. In order to avoid this difficulty widening operations are in progress, by which the passing places will be united and the bottom width of the canal increased to a minimum of 147 feet 6 inches.
The largest commercial vessels which navigate the Suez Canal are about 600 feet in length over all by 67 feet 3 inches in beam, with a draft of 27 feet. War vessels of 76 feet beam have passed.
Amnsterdam Canal, Lolland.-The Amsterdam Canal has only one pair of locks, at Ymuiden, which form the entrance to the canal from the North Sea. The dimensions of the largest lock are 738 feet by 82 feet by 31 feet 2 inches.
The bottom width of the canal is at present 115 feet, which is being increased to 164 feet, and the depth is 27.9 feet, which is being increased to 32 feet 2 inches. The total length of the canal is 15.4 miles.
JJanc/ester Ship Canal, England.-The entrance to the Manchester Ship Canal is controlled by tidal locks, of which the largest is 600 feet long by 80 feet wide. The locks in the length of the canal beyond the influence of the tide are 600 feet in length and 65 feet wide. The falls at the locks (i. e., the differences between the respective high and low levels) vary from 15 feet to 13 feet.
The ruling width of the bottom of the canal is 120 feet, which is gradually being increased to 180 feet, and the depth at low water is 26 feet, which is now being increased to 28 feet.
The length of the tidal portion of the canal is 21 miles and of the portion beyond the influence of the tide, 14 miles, making a total length of 35 miles.
40
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The largest vessels which now navigate the Manchester Ship Canal are 490 feet in length over all by 58 feet 2 inches beam.
Kaiser Wlilieln -Canal, Germany.-The Kaiser Wilhelm Canal is furnished with tidal locks at each terminus. The dimensions of the locks are 492 feet by 82 feet by 32-feet.
The bottom width of the canal is 72 feet, with frequent passing places, and the depth is 29 feet 6 inches at mean water level.
The length of the canal, which, as will be seen, affords a single-way navigation, is about 60 miles.
St. lfarys Falls Canal, United States.-The St. Mrys Falls Canal is not a maritime highway. It connects Lake Superior with Lake Huron and thus forms a link in the great lake navigation system of North America.
It was opened to navigation for vessels of 12 feet draft in 1855. There were then two locks in flight, each 350 feet long and 70 feet wide. Enlargements to meet the growing needs were begun in 1870, and in 1881 the canal was completed, so enlarged in dimensions as to pass vessels of 16 feet draft, and a lock was constructed 515 feet long and 80 feet wide. The capacity of the new waterway was soon seen to be insufficient, and in-1887 the first locks were removed and in 1896 a new one was put into commission 800 feet long, 80 feet wide, and 22 feet over the miter sill, the canal approaches being deepened to 25 feet.
In 1895 a canal on the Canadian side of the boundary was opened with a lock 900 feet long, 60 feet wide, and 22 feet over the miter sill. But the passage has again become inadequate, and a lock with a length of 1,400 feet, a width of 80 feet, and a depth of 25 feet is about to be constructed on the American side, for which purpose the 515-foot lock is to be removed, the new one to occupy its site.
The canal proper is only one and three-fifths miles in length, but the improvement in the lake channels extends over a length of 34 miles. The width of the canal varies from 108 feet at the narrowest place to 1,000 feet at the lower entrance. The widths of the river channels vary from 300 to 600 and 1,500 feet. The depth of the canal is 25 feet and that in the channels is 21 feet. The largest vessels which now use the St. Marys Falls Canal are 569 by 56 feet, with a draft of 20 feet.
It will be observed that in the case of each of the foregoing canals (except the Kaiser Wilhelm Canal) operations are in progress for the widening and deepening of the waterways, experience having shown that growth in the dimensions of ships has advanced far more rapidly than was conceived to be possible when the canals were projected, and therefore that their original dimensions were insufficient for the exigencies of modern traffic. There is, so far as the Board is aware, no example on record of the promoters and designers of a maritime highway having had occasion to regret that they had given too great dimensions to the highway, but there are many cases in which they have found that dimensions originally regarded as ample have been proved to be far too meager.
As this report is being written the public press announces that orders have been given by the Imperial Government of Germany for the preparation of plans for the enlargement of the Kaiser Wilhelm Canal.
A just estimate of the growth of traffic on the Panama Canal can not be formed from the statistics of the growth of trade on any existing waterway. The unprecedented increase in the population of the world which has taken place as civilization has advanced-it is generally agreed that the civilized population of the world-was doubled in the course of the nineteenth centuryand the movement of the surplus population westward, i. e., from Europe to North and South America, must of necessity not only proceed but proceed at an accelerated rate, so that the growth of trade on the interoceanic highway will not be, as in the case of the Suez Canal, merely due to the expansion.of the volume of commerce which takes place year by year as facilities are presented for the movement of commodities, but to that expansion multiplied by the increasing requirements of a constantly expanding industrial population.
It is therefore essential that the Panama Canal should furnish a double road for traffic throughout, and we consider that the locks should be built in pairs; that twin locks should lie side
41
42 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
by side, and that the different lengths of the canal should be of such dimensions as to permit two of the ordinarily large-sized commercial steamers to pass each other at any part of the journey.
When the canal is used for the transit of large line-of-battle ships or commercial vessels of largest size, all other vessels should be moored to one side so as to leave those great vessels as clear a course as practicable.
THE CONTROL OF THE CHAGRES AND OTHER STREAMS.
The Chagres has been considered to be an element of great difficulty in the construction of the Panama Canal from the earliest stages of discussion of the project. Its general character above lBohio is that of a clear mountain stream, although that observation~ is more applicable above Gamboa than below that point, its watershed being much more mountainous in its upper portions than between Gamboa and Bohio. The entire area drained by this stream has never been determined, even with approximate accuracy, but it has been considered under various estimates to range from 700 to 875 square miles above Bohio, or from 450 to 625 square miles aboVe Gamnboa. The adoption of the latter as the site for the dam of the great controlling reservoir makes it necessary to consider, in connetion with the problem of control of the Chagres, only the watershe d above the dam, but provision has been made for the control or diversion of all the streams contributary to the Chagres from Gamboa to the Colon terminus.
The entire watershed of the river above Gamboa is bold and quick, so that a heavy downfall of rain within its limits results in a rapid rise of the river. Inasmuch as the total annual precipitation in the Chagres watershed may reach from 100 to 125 inches, it is obvious that under existing conditions of run-off severe floods may be expected, although the river is not a large one. Nearly the entire watershed under consideration is heavily wooded, with a density of vegetation characteristic of a tropical country, and the steep clayey and rocky slopes afford all the conditions required for a rapidly varying stage of river in the rainy season.
At the site of the Gamboa dam, 30 miles from Colon, the river bed has an elevation of about 50 feet above mean sea level, but the deepest rock is at practically sea level, making it necessary to sink the foundations of a dam to a maximum depth of only 53 or 54 feet below water at the low stages of the river before finding material on which to formn a suitable foundation bed. At the proposed site of the dam the high hills approach each other within 2,020 feet at an elevation of 180 feet and within 1,170 feet at the bottom of the valley. The earth overlying the rock is of moderate depth, so that the conditions are favorable for the construction of any type of dam which may be adopted.
Fortunately for the solution of the problem of control of the river, more data regarding rainfall and river flow have been collected by observations at (Jamboa than at any other point in the river's course. The locat ion is also well adapted for the construction of a dam to serve the purposes of controlling floods or feeding the canal, and for the development of a power plant to drive electrical machinery for lighting, operating the Panama Railroad, and for other purposes, as it is the point at which the river in its flow toward the sea first cuts the line of the canal. If, therefore, the control of floods is satisfactorily accomplished at Gamboa, there remains to be considered only the discharge of contributary streams below that point, which in the aggregate is relatively so small that its control is a matter of little difficulty or expense.
Observations, more or less complete, of the discharge of the Chagres River at Gamnboa have been maintained from 1882 to the present time. Its flow in the dry season may fall to less than 300 cubic feet per second, while in the flood of 1879 it is supposed to have risen for a short period to nearly 80,000 cubic feet per second. During the past fifty years there have been six severe floods, all of which have occurred in the moths of November or December-that is, toward the end of the rainy season. The following table gives some of the main elements of these various floods as they have occurred at Gamboa:
42
REPORT OF BOARD OF CONSUl
Date of flood.
LTING ENGINEERS, PANAMA CANAL. 48
Cubic feet per second. Period when disHeight charge
above low was above
Maximum water at 20,000 cuMaximum. average in Gamboa. bic feet
48 hours. per second.
November- Feet. Hours.
1879.............................. 78,614(?) 65, 000(?) 36.65(?) ............
1885.............................. 64,488 43,404 31.50 46
December1885.............................. 44,923 32,421 24.11 43
1888.............................. 58,132 48,278 31.37 58
1890............................ 65,371 34,752 31.82 35
1893.............................. 43,086 27,971 25.33 32
The data relating to the floods between 1885 and 1893 have been deduced from accurate observations; but such is not the case with that of 1879, the greatest of all. No hydrographic observations along the river were made at that time, but certain high-water marks were approximately determined subsequent to the flood, largely from such information as could be obtained from the memory of ordinary observers. These have been compared with high-water marks of floods since 1879, whence maximum discharges at Bohio have been estimated and corresponding maximum discharges at Gamboa inferred from them. The approximate results given in the above table for the 1879 flood are those which have been found in this manner by the careful work of Gen. Henry L. Abbot, member of the Board.
Certain general results of value in connection with the problem of the Chagres River at Gamboa follow from an inspection of the preceding tabulation. It is seen at once that the maximum discharge of any flood of record during the past fifty years has not exceeded about 65,000 cubic feet per second, but that the approximate maximum discharge of the 1879 flood reached nearly 79,000 cubic feet per second. Inasmuch as there have been but six severe floods in half a century, it is obvious that they areof infrequent occurrence.
The next important conclusion established by this long record is the fact that these floods are of short duration. A discharge in excess of 20,000 cubic feet per second has never been observed to last more than 58 hours, although that limit may have been exceeded in 1879. It is convenient, in view of this fact, to deduce the maximum average discharge for a period of 48 hours in each case, as the resulting aggregate volume will represent what may practically be considered the total flood flow of the river. The third column of the table shows that the maximum average 48-hour discharge in the six severe floods has ranged from about 28,000 cubic feet per second to an estimated maximum average of 65,000 cubic feet per second for the flood of 1879. Finally, the greatest high-water elevation above low water during these floods is seen in the fourth column of the table to vary from about 25 feet to the estimated elevation of 36.65 feet for, 1879. The preceding data are sufficient for the determination of complete reservoir control of the Chagres floods by a dam at Gamboa.
A reservoir created by the proposed damn may have two important functions-that of control only, in the case of a sea-level canal, and those of control and water supply in the case of a lock canal. It will be seen that if the reservoir is of sufficient capacity to control satisfactorily the floods of the Chagres, there will be abundant storage capacity for supplying the summit level of any lock plan.
In providing reservoir capacity for the control of the Chagres floods, it is to be borne il mind that two floods may follow each other with only a short intervening period, and that such a succession of floods may be both preceded and followed by comparatively high water in the river, although not sufficiently high to be considered a flood flow. It is obviously impracticable to estimate the severest combined effects of such conditions for the future, but the observed records of flow during the past twenty years are sufficient to make an entirely safe provision for any' exigency of combined high water and flood flow, especially in view of the fact that two
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
severe floods, like either of those of November, 1885 or 1888, in close succession have never been observed in such a connection, not to cite the phenomenal flood of 1879.
If a dam be constructed at Gamboa with an elevation of its top at 180 feet above mean sea level, or 130 feet above the river bed, and if the highest flow line of that reservoir be taken at 170 feet, the area included within that flow line will be 29.47 square miles. With the minimum depth of water of 40 feet provided for the sea-level canal, the minimum wetted cross section would have an area of over 8,000 square feet, so that if 15,000 cubic feet of flood water per second from the Chagres be permitted to enter the canal prism at Gamboa, the resulting current, if the entire quantity admitted flows in one direction, will be but one and one-fourth miles per hour, a negligible quantity so far as its effects upon navigation are concerned; but the plans for a sea-level canal contemplate a provision which would permit the discharge through the canal prism and regulating sluices near the tidal lock on the Pacific side of approximately one-third of this Gamboa discharge, and to that extent, at least, dividing the flow between the two oceans and consequently reducing the current velocity. For the purposes of estimation inconnection with this problem of flood control the Board has therefore assumed that the controlling sluices to be provided in the Gamboa dam may admit the flood waters of the Chagres to the canal prism at the uniform maximum rate of 15,000 cubic feet per second.
If a flood should occur with a discharge equal to that estimated for 1879, viz, 65,000 cubic feet per second at Gamboa for a period of forty-eight hours, and if a uniform outflow of 15,000 cubic feet per second be permitted during the same time, there would be accumulated in Gamboa Lake 8,640,000,000 cubic feet of water, which is that portion of the volume of the lake included between water surfaces at elevations of 159 feet and 170 feet above sea level. Furthermore, a uniform outflow from the lake at the rate of 15,000 cubic feet per second would discharge the entire maximum average 48-hour flow of the 1879 flood in 8.7 days. It is seen, therefore, that there would be no practical difficulty in depressing the surface of the water in Gamboa Lake between two severe floods sufficiently toreceive the entire maximum average 48-hour flow of such a phenomenal flood as that of 1879.
The capacity of flood control provided in sucha lake as that under consideration is further illustrated by the fact that its volume between water surfaces at 108 and 170 feet above mean sea level is sufficient to take the aggregate discharge of three times the maximum average 48-hour flow of the 1879 flood without any water escaping through the regulating sluices of the dam; or the volume between elevations 128 feet and 170 feet will hold three times the flow of such a flood if a uniform discharge of 15,000 cubic feet per second be permitted concurrently through the regulating sluices.
These computations demonstrate conclusively that the controlling capacity of the Gamboa Lake as proposed by the Board is ample for all the exigencies of flood flow which can ever occur in the Chagres River without any other regulating or controlling aid, especially when it is observed that the highest mean monthly discharge for the rainy months of any year since 1890 (for 1892) is a little less than 5,300 cubic feet per second. There would only be required a simple grade of supervision, under which the water surface would always be depressed immediately after any flood low enough to receive any subsequent sudden flood flow which might possibly occur. This grade of supervision requires no special estimation or provision of future events, but is quite within the ordinary administration of this feature of canal maintenance and operation.
The elevation of water surface assumed at 170 feet is sufficient to permit the use of an open channel between the Chagres watershed and the headwaters of the Gatun River for the discharge of surplus flood waters in that direction, should it ever be required. The controlling capacity of the Gamboa Lake, however, is so complete and satisfactory that the Board does not believe that it will ever become desirable to construct this open channel across the divide between the Chagres and Gatun watersheds.
The Gamboa Lake affords complete regulation and control of the Chagres River above Gamboa. It has already been stated that there are small streams now discharging into the Chagres River below Gamboa which must be taken care of during the construction of the canal. Ample provision has been made for the control of these smaller streams, either by utilizing the
44
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMVA CANAL. 45
diversion channels planned by the old French company and now partially constructed or by constructing dams across their courses high enough to compel them to reverse their flow and discharge thrqugh the divides at the heads of their watersheds. Among the latter class are the Caflo Quebrado and the Gigantito, the reverse flow of which would be discharged into the headwaters of the Trinidlad and the Gigante, whose reverse flow would be turned into the basin of the Pefi-a Blanca marsh and pass on to the sea through the Chagres channel and its existing diversion. The Gatunl River (sometimes called the Gatuncillo) would discharge its waters and those of the Mmndi through the Gatun diversion, nearly completed by -the old company, into that part of Manzanillo Bay known as Puerto Escondido. After the completion of the canal the aggregate observed flood discharge of all the streams entering it below Gainboa-the Caflo Quebrado, Gigante; and Gigantito being diverted as hitherto observed-would amount to less than 4,000 cubic feet per second (see p. 240, Report of the Isthmnian Canal Com-mission, 1901), a quantity that would exercise no material influence upon currents in the canal channel.
A similar observation will apply to the aggregate flood flow of the small streams between the Culebra cut and the Panama terminus, which may be taken into the canal _prism at the completion of the work, but which would be controlled by diversion channels now largely exavated and by other temporary works of a simple and inexpensive character during construction.
The difference between the flood discharge of the Chagres at Boio and at Gamboa, which discharge is partly observed and partly estimated, is stated by General Abbot to be 34,000 cubic feet per second, while the gauged flow of the contributing streams between Gamboa and Bohio is given by him as 26,335 second-feet.
Taking the flood flow of these streams at 32,000 second-feet, it is found that the maximum current velocity in the canal-which would be at Bohio due to the -fow of said streams which are not diverted, together with 15,000 second-f eet coming from the upper Chagres through the sluices contemplated-will be but 2.64 miles per hour, a velocity which will not interrupt navigation. As a part of the upper Chagres discharge will flow to the Pacific, and -as the highest mean monthly discharge of this river in the rainy season at Gamiboa is but 5,300 second-feet, as General Abbot points out, the currents in the canal will usually not exceed one mile per hour, and at extreme low water in the river there will scarcely be a perceptible current. At such times the water in the canal prism will be brackish, without currents save as influenced by the insignificant Caribbean tide.
The tributary streams, whose beds at point of junction with the canal are considerably above the prism of the latter, will be discharged over mnasonry-stepped aprons or through metallic discharge pipes, or these beds will be sloped and lowered so as to prevent objectionable currents at junction points. The means for the accomplishment of these results are such as are in common use on nearly all important canals.
During three-fourths of the time these streams discharge an insignificant amount of clear water. When they are in flood they will bring down some silt, and it is recognized that the maintenance of the navigable canal channel will require a small amount of dredging.
DAMS.
The consideration of the projects presented by Mr. Bates, Major Gillette, and~ others has raised cer tain questions regarding the types of damns, which the Board believes can better be treated as an independent subject than in connection with the plans presented by Mr. Bates or others, especially as some of these considerations bear also upon the desi gn of the dam at Gamboa recommended for construction in the sea-level plan.
in these projects or plans it has been proposed]to) retain terumiunil or other lakes by earth damis resting upon the natural soil, consisting of sand, gravel, or sandy clay; or, as at La Boca,
at he anaa ed o th caalupon mud and silt between San Juan Point and the easterly shore of the Rio Grande estuary near Sosa Hill, also between Sosa and Ancon hills. ne ,some of these dams or dikes the plans or proposals indicate that shallow sheet piling might be used in some. cases, and in other cases that feature is absent. There are grave reasons for
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
doubting the stability of these types of structures under such circumstances. The earth dams which have already been built for the retention of large bodies of water, some of them exceeding 100 feet in height, show that this type of structure may give satisfactory results when properly designed and constructed, but the character of the foundation-material on which such dams are built and the means for preventing dangerous seepage underneath or through such foundations must always be carefully considered. The earth dams which have been proposed for terminal lakes at the Caribbean and Panama ends of the canal are proposed to be placed directly upon the natural soil at Mindi or Gatun, near Colon, or on the silt, mud, and clayey material at La Boca, near Panama. It has not been proposed to dredge out the soft and yielding material at either place other than possibly a shallow strip of the natural surface, nor has it been proposed to sink a curtain either of masonry or of timber, such as deep sheet piling or of any other material, to cut off percolation or seepage underneath the structure.
These are disquieting considerations in the design of dams to retain water of depths varying from 30 to possibly 85 feet or more. The subsurface material at Mindi and at Gatun, extending down to the hard indurated sandy clay or soft rock, attaining a maximum depth of 258 feet, is in large part of a comparatively fine character, consisting of sand and clay in varying portions and in various degrees of admixture, but the borings have also shown coarse sand and gravel with water flowing through it and out of some of the pipes used in making the examinations. As a presumption or speculation it may be stated as probable that most of this material under the weight of an earth dam would be so nearly impervious that only a small or negligible quantity of water would find its way through, even with the increased head of the reservoir; but that is simply conjecture.
It is more than possible, it is highly probable if not certain, that at various points the material is sufficiently loose in texture to permit seepage or percolation in dangerous quantities. Nothing is more common in the sandy deposits of river valleys and in all sandy material than small passages or channels through which water moves, varying in size from thread-like openings to those sufficient to yield flowing wells of large discharge. Extended experience in dealing with the underground flow of subsurface waters in many places in the United States, and wherever investigations in that field of hydraulics have been made, shows this to be the case.
Vast volumes of water are daily taken from subsurface sands, and have been for years, for the public water supply of many cities in the United States, prominent among which is the borough of Brooklyn of the city of New York. All such experience indicates conclusively the danger of depending upon stopping, or even materially diminishing, such a flow by the weight alone of any superincumbent mass of earth.
The assumption of negligible seepage or percolation below these earth dams must necessarily be based upon the practically uniform quality 'or distribution of the material claimed to be essentially impervious. It is safe to state that this is never the natural condition over any considerable portion of a profile at the site of a great dam. The fine or coarse sandy or even gravelly material found in such locations has been deposited under radically varying conditions of floods and resulting currents separated by low-water intervals, so that it is physically impossible that even practical uniformity either as to kind of material or rate of deposition should result. The inevitable consequence is the great variation in strata, more widely different at some locations than others, but in all cases there is a wide departure from uniformity. It is one of the early and marked experiences in the construction of filter beds that the most scrupulous care must be taken in placing the sand or other filtering material so as to avoid variation in its character or its density of texture. If there is a lack of uniformity or a place at which a surface of separation betwveen two portions of material of different character or variation in compactness exists, the water invariably finds such passages of decreased resistance to flow, and forms for itself small channels through which it escapes with readiness without being filtered. Indeed, the degree of care which is required to accomplish the uniformity of texture or compactness necessary for a proper flow without these small channels is shown by the fact that mien are frequently forbidden to walk over the surface of a new sand filter, so as to avoid the
46
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
separating surfaces between the increased compactness under the foot and the looser material surrounding the footprint.
A careful consideration of these conditions of actual experience will show that any computations apparently indicating that the seepage or percolation taking place through a great geological profile like that at the sites of the proposed dams at Mindi, Gatun, Bohio, Gamboa, or at.any similar location, are based upon assumptions without any warrant in engineering experience and involving the grave danger of excessive percolation under an earth dam.
The dam at La Boca between San Juan Point and Sosa Hill, unless carried down to bed rock at that location, would be placed upon a far worse foundation even than that proposed at Gatun or Mindi. The La Boca site is one covered by an ooze of mud and silt, with some sandy material overlying the rock. It is practicable to construct here an earth dam, with a heavy masonry core running down to bed rock, whose stability would be beyond question. Such a structure would be far more costly than a great mound of earth placed upon the mud and silt forming the natural bottom of the Rio Grande estuary. Unless some feature equivalent to that of a heavy masonry core characterizes the design of the dam at this point, or unless resort be made to dredging down to bed rock or near to it and refilling with suitable material, or an earth dam at this location be made very massive, it would be in grave danger of being pushed bodily out of place by the pressure due to the head of water in the reservoir.
The nearest approach to the earth dams which have been advocated in these localities is the great north dike or embankment of the Wachusett reservoir, a part of the new Boston watersupply system very recently constructed by Mr. F. P. Stearns, a member of the Board. In that case, deep and heavy sheet piling or deep excavation of the natural soil with refilling of suitable material was employed to prevent seepage or percolation wherever it was apprehended that the nature of the substrata was such as to permit it. It is the judgment of the Board that such safeguarding features as core walls, sheet piling, or the removal of unsuitable material should not be omitted in similar structures on this work of extraordinary magnitude and supreme importance.
The United States Government is proposing to expend many millions of dollars for the construction of this great waterway, which is to serve the commerce of the world for all time and the very existence of which would depend upon the permanent stability and unquestioned safety of its dams. The Board is therefore of opinion that the existence of such costly facilities for the world's commerce should not depend upon great reservoirs held by earth embankments resting literally upon mud foundations or those of even sand and gravel. The Board is unqualifiedly of opinion that no such vast and doubtful experiment should be indulged in, but on the contrary that every work of whatever nature should be so designed and built as to include only those features which experience has demonstrated to be positively safe and efficient.
The considerations of these and other reasons have prompted the Board to recommend lt Gamboa either an earth dam with a heavy masonry core carried down to bed rock, or an allmasonry structure founded at the same depth and upon the same material.
THE SEA-LEVEL PLAN RECOMMENDED BY THE BOARD.
(A) ALIGNMENT AND DESCRIUPTION.
The width of the Isthmus at Panama is less than at any other point where it is feasible to construct a canal open throughout between the oceans. The width, less than 36 miles in a straight line, is only five miles greater than at the narrowest place, San Blas, but an open cut is impracticable there. The summit on the Panama route, which was 333 feet above the sea originally, is lower than at any other known point between the Arctic Ocean and the Straits of Magellan, Nicaragua only excepted, while at the latter place, by reason of the greater distance between the oceans, the volume of material to be removed to form a lock canal is much greater than at Panama, and a sea-level canal is obviously impossible. At Panama alone is a sea-level canal in open cutting feasible, and the Board has no doubt of the practicability of such a canal.
47
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The general direction of the Isthmus in this vicinity is nearly northeast and southwest and the general route for the canal nearly northwest and southeast. The summit at Culebra lies about nine miles from Panama Bay, and the distance between the point on the northern approach to this summit where the present elevation on the proposed canal axis is 100 feet above sea level to the point on the southern approach to Culebra at the same height is nearly nine miles. Within this distance will be found nearly one-half the total excavation required to make an open channel at the sea level adequate in dimensions and capacity to pass not only the largest existing commercial and naval vessels, but the largest which may be expected to require transfer between the Atlantic and Pacific oceans.
The line adopted by the Board for the sea-level canal which it recommends for construction is in general that which was adopted by both the old and the new Panama Canal companies for their projects. While the Board approves this alignment for the purposes of ultimate construction, it believes that further examination should be made for the reduction of curvature and for other improvements of the line in detail, particularly at the deepest portion of the Culebra cut. It is believed that a judicious relocation between Emperador and Cucaracha will reduce the excavation considerably with only a comparatively small change of alignment. In this manner, at this particular portion of the line, excessive excavation on the easterly side of the deep part of the Culebra cut may be avoided, at the same time utilizing Lhe entire volume of existing excavation between Emperador and Cucaracha.
At the Colon and La Boca terminals, however, it is the judgment of the Board that material changes should be made both in the plans of these terminals and in the alignment to eliminate considerable curvature. The terminal plans recommended by the Board are described under the section of "Harbors."
The initial point of the axis of the canal is located in Limon Bay, about one mile northwest of Manzanillo light, at the beginning of the dredged entrance channel, where the depth of water is at least 40 feet at low tide. From that point the axis of the dredged approach channel runs straight to near the southern limit of Limon Bay, where, near Mindi, a curve unites it with the center line of the canal, as partially completed by the old company. From Mindi the proposed line follows the partially excavated canal through the low marshy ground nearly to Bohio, a distance of 12 miles. The canal line first cuts the course of the Chagres River at Gatun, seven miles from Colon, and then repeatedly cuts it from that point to Bohio. The excavation throughout this entire distance from the sea channel to Bohio can be made by the simple operation of dredging, but there is some hard clay to be removed.
After passing Bohio the ground rises gradually toward Panama and radically changes in character. A considerable quantity of rock must be removed at Bohio, and the same material is found in considerable quantities throughout almost the entire remaining distance to the shore of Panama Bay. The canal line from Bohio follows practically the general line of the Chagres River, cutting or coinciding with the bed of the river at many points, to Obispo, 14 miles from Bohio. The bed of the river at Bohio is practically at sea level, and about 50 feet above sea level at Gamboa near Obispo. While the surface of the ground is varied and broken, the ascent is gradual and nearly uniform to Obispo. The material to be excavated is clayey and sandy in large part, although rock in substantial quantities is found projecting above sea level at some points, mostly in the lower part of the proposed excavation. The excavations made by the old company along this portion of the route were generally shallow, although deeper at some points where hills exist, but constituting a nearly continuous surface cutting. That company excavated very little rock in this vicinity.
The general course of the canal from Colon to Obispo is southeast, and in part due south. Although there are several curves they are all of large radii, the shortest arc being one and fourtenths miles in length.
The vicinity of Obispo, about three-fourths of a mile only from Gamboa on the Chagres River, is a marked one in the alignment of the canal. At this point the valley of the Chagres, passing upstream, trends sharply to the northeast nearly at right angles to its course below
48
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
49
Gamboa, but the canal line continues toward the southeast, i. e., toward Panama. The great reservoir for controlling the floods of the Chagres, to be created by a dam at Gamboa, is described in another section of this report. The waters escaping from that reservoir through regulating sluices will enter the canal prism about three-fourths of a mile north of, or below, Obispo.
Continuing toward Panama the ground rises at a more rapid rate. At Obispo the great summit cut may be said to begin, as there is at that point a more abrupt rise in the surface of the ground and a correspondingly rapid increase in the depth of excavation. There is much rock to be removed from the canal prism at Obispo, and that material continues to form by far the greater part of the excavation through the divide to a point beyond Pedro Miguel, on the Pacific slope of the Cordillera. The deepest part of the summit cut at Culebra is about five and one-half miles from Obispo. The maximum depth of excavation required for a sea-level canal will be about 373 feet below the original surface where the axis cuts the saddle. The deepest part of the present cut, however, is about 160 feet below the original surface, or about 213 feet above the bottom of the excavated channel required by the sea-level plan. The length of the main part of the great summit cut is about nine miles, from Obispo to Pedro Miguel. The material to be removed is partly of indurated clay so hard as to be classed as soft rock, and partly of hard rock with a surface covering of clay.
The heaviest work of excavation done by the old and the new French companies is shown by this cut between Emperador and the southerly slope of Culebra Hill, where the canal line intersects the course of the Rio Grande River.
As has already been indicated in this report, it is believed that a slight relocation can be advantageously made along this portion of the line between Emperador and the little village of Cucaracha, on the Pacific slope of the divide. A careful study should be made to ascertain whether it may not be feasible to throw the center line of the canal a little to the westward of its present position in the deepest part of the Culebra excavation, so as to avoid further cutting of the high portion of the hill on the easterly side of the line. This would enable the further cut ting to be made in the lower hill on the westerly side. It is possible also that improvement in the alignment at Emperador may be made, although at the expense of cutting more deeply into the hill at that point.
The canal line reaches low marshy ground nearly at sea level at a point about two miles below Pedro Miguel. From that point to deep water in Panama Bay the Board has adopted a different alignment from that of the French companies. The latter followed as closely as possible the course of the Rio Grande to its mouth at La Boca in order to avoid rock excavation, but that alignment included two curves which are avoided in the new location. The location recommended by the Board is practically a straight line from a point a short distance from Miraflores through the Rio Grande swamp; but opposite Corozal a low ridge or spur from the eastern highland is crossed, in which ridge the borings show rock. Advantage is to be taken of this conformation to locate on the rock foundation a wide spillway with regulating sluices primarily for discharging into the Rio Grande and so into the Pacific a part of the Chagres flow at Gamboa coming through the Culebra, but the sluices may also be used to regulate and reduce the currents in the canal while the tidal lock is open.
'the canal continues in a straight line through the swamp to and through the saddle between Ancon and Sosa hills, where the tidal lock is to be placed, and thence to deep water off Isle Flamenco. From Miraflores to the lock the canal will be leveed, so as to prevent the tidal flow from entering it.
The French plan required a tidal lock at Miraflores some five miles from the bay shore, whereas in the new location it will be in the low Ancon-Sosa saddle, thus bringing it almost to the margin of the shore and avoiding the long approach channel wherein tidal currents would be generated if the locks for their control were at Miraflores, far inland.
Experience in the navigation of maritime canals shows that the area of the wet section of the prism must be at least four times that of the immersed section of the ship passing through it at a speed of six miles per hour. The smallest area of cross section of the canal prism, in rock
465A-06---4
50 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
excavation, exceeds 8,000 square feet. The dimensions adopted by the Board, therefore, will permit a speed of six miles per hour for the largest existing vessels using it, and of not less than eight miles per hour for the average ship. For a ship of 90 feet beam and 38 feet draft a speed of four or five miles per hour might be considered sufficient.
These speeds will enable ships of the largest size to pass through the canal in seven hours if the gates of the tidal lock at Panama are open, as they will be for more than half the time, or in eight hours during high spring tides, when the tidal locks will be in use. The time of passage of the average ship will probably be between five and six hours with the gates of the tidal lock open, or one hour longer when the tidal lock is in use. For a ship of the exceptional size given the time of transit might reach ten hours.
After the completion of the canal the tracks of the Panama Railroad can judiciously be placed on one of the berms of the canal, at least between Bohio and Mirafiores, as the railroad will then lose its present character and serve local and passenger traffic only, besides being a tender to the canal for its maintenance and for other similar purposes. Power for operating it would be developed at the Gamboa dam.
Some dredging will be required in the harbor channels as well as in the canal proper, but this will be nearly the same for either type of canal.
The entire length of the line between shore lines is a little over 40 miles, while the total distance including harbor channels is 49.35 miles.
The total length of curves is 19.17 miles, leaving 30.18 miles of tangents or straight portions.
Summarized, the sea-level canal as recommended by this Board is a channel commencing at the 41-foot contour in Limon Bay, about 5,000 feet northerly of a line between Toro and Manzanillo lights, protected by two diverging jetties with a width of opening of 1,000 feet; thence with a straight channel 500 feet in width at the bottom and a depth of 40 feet, protected by a parallel jetty on the west and by Manzanillo Island on the east, to Mindi, whence the land canal begins.
This canal is designed with a depth of 40 feet and a bottom width of 150 feet in earth, with side slopes adjusted to the nature of the ground so as to give a surface width of from 302 feet to 437 feet. In rock the section is to be altered so as to have a bottom width of 200 feet and a surface width of 208 feet. At the Pacific end the canal is to be protected by a tidal lock located between Ancon and Sosa hills. Beyond this tidal lock there is to be a straight channel projected into Panama Bay, with a bottom width of 300 feet and extending for a distance of three and threefourths miles to the 45-foot contour.a
The width adopted for the canal will be sufficient to permit steamers to maintain a speed of six to eight knots per hour, and to allow two ordinary merchant steamers to pass each other on the line of the canal without stopping.
At Gamboa there is to be located a dam, either of masonry or of earth and masonry combined, for the control of the Chagres, and at Corozal, sluices by which, during half the tide period when the level in the Pacific is lower than that in the Atlantic, water can be discharged from the canal into Panama Bay.
The following tabulation gives the total excavation as very carefully computed from the data supplied by the Isthmian Canal Commission, supplemented by data collected at the instance of the Board:
Estimate of excavation of a sea-level canal 40 feet deep.
[December 22, 1905.]
Stations. Classification. Cubic yards. Uit Amount.
price.
41-foot contour to shore line of Limon Bay, 0 to Earth....................... 2,781,668 $0.15 $417, 250.00
mile 3.92. Indurated clay............. 5,566 .70 3,896.20
Coral ....................... 135,500 1. 50 203,250.00
2,922,734 $624,396.20
Shore line to Mindi, mile 3.92 to mile 5.49-....... Earth........................ 7,695,885 .25 1, 923, 971.25
Indurated clay.............2,351,588 70 1, 646,111. 60
10,047,473 3,570,082.85
a Contours refer to mean sea level.
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
Estimate of excavation of a sea-level canal 40 feet deep-Continued.
Stations.
Mindi to Bohio, mile 5.49 to mile 17.22 ..........
Classification.
Earth. ....................
Rock above sea level Rock below sea level.
Bohio to Obispo, mile 17.22 to mile 30.96.......... Earth --------..........-...-
Obispo to Pedro Miguel, mile 30.96 to mile 39.04.
Rock above sea level-....... Rock below sea level..... All material above + 10.... All material below + 10 ....
Pedro Miguel to Miraflores, mile 39.04 to mile Earth above sea level. 4O0771
Miraflores to south end of Sosa lock, mile 40.77 to mile 45.57.
Earth below sea level-.--Rock above sea level....... Rock below sea level....... Earth-.....................
Rock nearly all below sea level.
South end Sosa lock to 45-foot *contour in Pa- Earth.......................
cific, mile 45.37 to mile 49.35. Rock-....................
Total-.-............
Cubic ya
21,730,653
628, 088 2,198, 643
48,787,149
4, 490, 926 7, 396, 362 93, 697, 408 16, 194, 302 13 11 2,)136, 125
300, 000 518,881
2, 474,138 6,106,828 5, 223, 700
3,508, 945 2, 663,922
ards. Unit
rd. price.
$0.25 1.00 2.50 24,557,584
.40 1.15 2.50 60,674,437
.80
1.25 09, 891, 710
.40 .25 1.15
2.50 5, 429,144
.40 2.50
11,330,528 .1
.15 2.50
6,172,0-67 231 026,477
Amount.
$5, 432,663.25
628,088.00 5,497,107.50 19,__4,-- $11,557,858.75 19,514,859. 60 5,164, 564.90 18,491, 905.00
- 43)1719329.5074,957,926.40 20,242,877. 50
45 95,200,803.90
854, 450. 00 75, 000. 00 596,713.15 6,185, 345. 00
7,711,508.15
2,444, 731.20 12,659,250.00
-15, 103, 981. 10
536, 341. 75 5,659,805.00
6,196,146.75
183,136,107.30
Contours refer to mean sea level.
(B) HARBORS.
The harbor of Colon.-A first-class nAtural harbor is not found at either terminal of the canal, but good harbor accommodations can be created without unusual difficulty or extraordinary expense.
Limon Bay, on the easterly side of which is the city of Colon, must be the Caribbean terminal of the canal. It is a rectangular indentation of the low-lying coast, with a width of two and three-fourths miles and a length approximately in a north and south direction of a little more than four miles. It is shallow, freely open to the sea from the north, and but little less exposed to the northeast and northwest. The extreme range of tide seldom exceeds two feet six inches except under the influence of high winds. The mean range is about one foot six inches.
The depth of water at the entrance to the bay in its central portion is from 30 to 38 feet opposite the water front of Colon. The southern half of the bay is so shallow as to be of no value for harbor purposes. The depth of water varies from 28 feet opposite Cristobal Point, and gradually shoals to the gently sloping'sandy beach at the extreme southerly end.
The currents in the bay have little velocity. One, called the Rio Magdalena current, comes from the east and is at times felt along the eastern and western shores, but chiefly along the latter. The discharge of a large portion of the Chagres River through the partially excavated canal prism between Gatun and Mindi, and through the latter into the head of the bay, produces a gentle outward current which opposes that described above. These currents are neither constant nor strong, and -are often influenced by the wind. The tides are so small and the tidal section so large that they have little influence upon the currents.
The greater part of the bottom of Limon Bay is soft. A large number of observations have been made under the direction of the Isthmian Canal Commission by sounding with railroad rails, weighted where necessary by the hammer of a floating pile driver. The silt or other sediment forming the bottom is of such character that these railroad rails used as sounding rods usually sank from 10 or 15 feet to as much as 30 feet by their own weight. This material, therefore, is readily moved when the water is shallow by storm waves or by currents induced by the wind or other agencies.
There is undoubtedly a decided movement of the material of the soft bottom in the easterly portions of the bay south of Cristobal Point by storm waves, although the rarity of the storms prevents the aggregate of movement being very large. Since surveys were made by the old Panama Canal Company there a sensible advance of the shore line at the southeastern limit of the bay has been observed, particularly in the vicinity of the mouth of the Mindi River, where the
51
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
sediment carried by such of the flood waters of the Chagres as is here discharged is deposited. That portion of the harbor outside of the five-fathom line has been but little affected by the deposition of sediment, but there has apparently been some slight advance of this contour. With the diversion of the Mindi there should be no further decrease of depths in the bay. These physical characteristics have been carefully considered in the design of a terminal harbor at Colon.
In spite of this soft material and the depth of the bay, the anchorage is good enough for such conditions of weather as ordinarily prevail at Colon. The best anchorage is about one-half mile to a mile off the water front. Ships have no trouble in holding in this location except in the rare instances of very high winds. The swells that roll into the harbor at times from remote storms in the Caribbean do not give any serious trouble to vessels at anchor.
Limon Bay is open to the north, and northers blow directly into it. These northers are severe windstorms, usually accompanied by rain, generally from slightly west of north, but occasionally a little easterly of that point. They occur, on the average, not more than three or four days in the year and during some years not at all. During these storms the wind blows with high velocity, driving storm waves of great magnitude and force directly into the bay. At such times ships can not lie at anchor nor be berthed alongside the piers on the water front without grave danger. Indeed, vessels unable to get away in time to escape such storms have been wrecked on the water front of Colon as well as at other points in the bay. So many ships have lost their ground tackle while at anchor off Manzanillo Island that not infrequently anchors and chains are brought up by ships while raising their own anchors. During the very severe norther of November, 1879, a brig drawing 18 feet at anchor in five fathoms touched bottom in the trough of the sea and lost her sternpost and rudder. When northers begin to blow, all the steam vessels invariably get to sea as soon as possible. Many vessels then seek the naturally protected adjacent harbor of Porto Bello.
A prominent feature of Limon Bay is the artificial point or jetty head known as Cristobal Point. This was built by the old Panama Canal Company of material excavated from the canal or taken from other points, with its surface brought to about five feet above sea level. It is founded largely upon a coral bank which originally stood at about sea level. Its margin is protected by a rough revetment of fragments of the country rock of small size and concrete blocks a meter (3.28 ft.) cube. This artificial point projects about 1,300 feet into the bay from its easterly side. Recent surveys show that the bottom of all that part of the bay west and north of Cristobal Point is formed largely of mud from 15 or 20 to possibly 30 or more feet deep, the depth of water in the bay opposite being about 28 feet.
The fact that the old Panama Canal Company made the course of the approach channel a tortuous one, with curves of short radius to the entrance of the canal immediately south of and under the protection of the point, indicates the necessity of protecting the entrance of the canal from storm waves. The peculiar formation of the bed of the bay west and north of the jetty indicates that waves and sea currents may, unless checked, produce undesirable or even serious changes in the bottom at a depth of 30 feet and less.
As ships may wish to enter the canal at any time, the terminal harbor must offer safe entrance to it any day in the year and under all conditions of weather. In view of the experience with northers ever since the harbor of Colon has been frequented by shipping it is imperative that this terminal harbor should be so designed and constructed as to protect the dredged approach channel, both against the storm waves and the resulting currents which would otherwise tend to fill the channel. Without such ample protection it is practically certain that the dredged approach channel in the bay of Limon would be filled by sediment during one such norther as that of January, 1905, which was witnessed by three members of the Board. There should also be afforded ample anchorage ground within the protected harbor, with the requisite room for maneuvering.
To enable vessels to enter or leave the harbor at all times, even during severe northers, the channel should have the same direction as the winds during such storms, which are almost always from a point slightly west of north. A vessel entering or leaving this channel in a storm would therefore have the wind ahead or astern and without any wind abeam to complicate the navigation
52
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
of the channel. It is for this reason that the Board has proposed a straight entrance channel nearly parallel to the Colon shore and united at its southerly end by a curve of large radius with the axis of the canal near Mindi, as laid down by the French company.
If a line be drawn due west across Limon Bay from Cristobal Point, behind which is found the inner harbor leading to the canal near the mouth of the Mindi, the depth of 28 feet will be found on this line at mean low water throughout the greater part of its length, and it will be seen that the water loses depth at nearly a uniform rate from that point to the shallow mud beach at the southerly extremity of the bay. To the seaward of this line the depth increases quite uniformly to 40 feet about one mile north of Manzanillo Point light.
After much consideration of all the conditions bearing upon the construction of a safe and commodious harbor, the Board provisionally adopted two converging breakwaters, one extending from the beach to the easterly of the light-house in a northwesterly direction one mile, to a point where the low-water depth is at least 40 feet and a short distance westerly of a small reef; the other starting from a point about 3,750 feet west of Manzanillo light, running also one mile to a point where the depth at mean low water is at least 40 feet, so placed as to afford an entrance between the extremities of these breakwaters 1,000 feet in width, the southerly extremity of the latter breakwater to be connected with Great Reef, off Mindi Point, by a breakwater or stone dike two and one-half miles in length. The nearest point of this breakwater to Cristobal Point would also be about 3,750 feet. These breakwaters, therefore, would inclose a harbor area nearly 9,000 feet long from the entrance and nearly 4,000 feet wide for a distance of at least eight-tenths of a mile, within which the depth at low water would vary from 30 to 35 feet. Within the protected harbor a dredged entrance channel 500 feet wide on the bottom and 40 feet deep at low water would lead straight from the entrance between jetties to the canal entrance near the mouth of the Mindi.
At the same time, the inner harbor immediately south of Cristobal Point, and projected as the canal entrance by both the French companies, should be so completed as to afford on its easterly side the necessary coaling facilities, administration offices, and other buildings required by the canal traffic. Vessels entering the outer or main harbor will anchor, if they desire to do so, arrange for payment of dues and their passage through the canal, secure such supplies and make such other communications with the port as may be necessary, then pass to the coaling station, if desired, or proceed directly into the canal.
The breakwaters may be constructed as mounds composed of suitable fragments of hard rock for their superstructures, or blocks of concrete, as may be considered most economical or desirable, but resting upon rubble substructures, which may be of softer material taken from the excavations or from other sources, as the actual construction of the work may make most convenient or economical. The type and cross section of these breakwaters and the general character of the structures would be similar to others which have been constructed on the Atlantic, Pacific, and Gulf coasts of the United States, as at Delaware Bay, San Pedro, on the coast of southern California, and Galveston, Tex.
This harbor as designed, including the ports of Cristobal and Colon, will furnish sufficient accommodations for an indefinite period in the future for the greatest traffic which can now be anticipated for the canal. The Board does not set forth this plan as that which it would necessarily hold to in all details after a more prolonged study and consideration of all the circumstances affecting the construction of such a harbor, but it believes that the accommodations which it would afford will be ample for the purpose and that the amount estimated as its cost is sufficient to cover the construction of a suitable harbor for the Caribbean terminus of the canal should the plan herein described be modified or displaced by another.
Tke harbor of Ancon.-The harbor conditions at the Pacific terminus are radically different from those found at the Caribbean end, in that no storms ever occur of sufficient magnitude to disturb vessels anchored in the roadstead northerly of the islands of Perico and Naos, the usual anchorage, which is three miles by the present dredged channel to the entrance of the canal at La Boca. Owing to littoral currents from the west this channel requires the practically constant service of dredges in order to maintain a depth of 20 to 22 feet. At the present entrance of the
53
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
canal, which is also the mouth of the Rio Grande estuary, there has been built a wharf or pier of steel 1,000 feet long, carrying two railroad tracks and a platform for the exchange of cargo between ships lying alongside the pier and freight cars on the railroad tracks. The foundation structures of this pier, known as the La lBoca pier, are steel cylinders sunk to bed rock by the pneumatic process and illed with concrete. Mud and rock have been dredged not only alongside the pier, but over an area in front of it to make a turning basin suffcient for the present needs. The depth of water alongside and in the basin varies f rom 22 to 25 feet at low water, but, like the entrance channel, must be frequently dredged to maintain this depth.
The bottom of the bay of Panama, at the anchorage off the islands of Perico and Naos, consists of mud mixed with sand, shells, and other materials, and forms excellent holding ground. There are no swells to disturb ships at anchor. There is, however, little depth of water near the shore, and the 30-foot contour lies to the westward and southward of those islands. Deep-water channels approach the islands or this anchorage from three directions, that -immediately eastward of the island of Flamenco being probably the best adapted for the approach to the dredged channel leading into the canal.
.The tides in Panama Bay are of far greater range than those at Colon, although mean sea level is the same in both harbors. They are very regular. During spring tides the water surface may oscillate between 10 feet above mean sea level to 10 below. During neap tides the range from. high to low may not exceed 7.9 feet. Tidal observations have been made at the manigraph station on the island of Naos for many years and they supply data for the statement of the tidal range given above.
The flood tide passes between Naos and Guinea Point, in a direction north-northwest, with a maximum current exceeding two miles per hour. The tide ascends the Rio Grande to a point nearly f our miles above La B~oca pier and inundates, up to Miraflores, the manglares or low marshes through which the river flows. The period of inflow is short, and after it the water recedes from the swamp with an outgoing current increased by that in the river between two and four hours after high tide. This maximum current is estimated at a little over three miles per hour during the spring tides in. that part of the rainy season in which high freshets occur. Under ordinary conditions the current in the Rio Grande during the dry season, or in those portions of the wet season when the rainfall is small, is too slight to have any effect upon the ebb flow of the tide. Between La Boca and the anchorage ground the ebb follows essetially the direction of the dredged channel, with gradually decreasing current, and then turns to the south and southeast beyond Flamenco.
The direction of the present dredged change is about N. 600 W. It was originally intended by the old Panama Canal Company to give the channel a depth of 301 feet at low water and a bottom width of about 170 feet, with side slopes of one vertical on three horizontal. The present channel was dredged to a depth of 30 feet below mean tide, and was opened to navigation in December, 1900, since which time it has been in constant service, but this depth has not been maintained. The material taken out in this dredging consisted of mud and silt, some material of vegetable origin, sand, gravel, and, in the vicinity of La Boca pier, a small quantity of rock.
It has already been observed that a littoral current moves from west to east across the dredged channel, causing considerable sediment to deposit. As a consequence of this condition nearly continuous dredging is required to maintain a depth in the qhbannel of 21 to 22 feet at low water. The volume dredged in this manner is about 150,000 cubic yards annually, and sometimes rises to 20,000 or more cubic yards per month. This dredged material is not, except in comparatively small quantities, brought down by the Rio Grande River, but is moved into the channel by the littoral current. The course of that river is short and the volume of its flow far too small to bear a sensible quantity of sediment, nor does the latter appear to be of the character found along the banks of the Rio Grande or in its bed.
There are also other small currents existing in the bay in the vicinity of the entrance channel, and under certain conditions of tide and wind there may be even a little westerly current, but all other movements than that from the west are small and probably negligible in their effects upon the maintenance of the entrance, whether in its present location or on a new line between Ancon and Sosa naills.
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
55
If the present location of the Pacific end of the canal from Miratlores to La Boca should be retained it would be necessary to widen and deepen the channel sufficiently to meet the requireihents of the ship canal now projected. Remembering that extremely low water may be as much as 10- feet below mean tide it is obvious that a much deeper excavation will be required to afford the prescribed minimum depth of 40 feet in the harbor approach channel than will suffice at the Caribbean terminus of the canal. The location of the tidal lock will determine the distance inland to which this maximum depth of excavation must be carried. If, as in the former French plans, that lock should be located at Miraflores, a little over four miles from La Boca, the maximum depth of excavation would be carried to that point, but, on the other hand, should the new location for the tidal lock nearer the shore line be adopted the deep-channel excavation would be carried only to that lock.
The French location extending from Miraflores to the anchorage ground in deep water requires much more curvature than is desirable for a canal entrance, and the Board believes that a straight entrance possesses sufficient additional advantages over the old one to justify substantial increase in expenditure to obtain it. A new alignment, therefore, for the Pacific end of the canal and the dredged channel has been adopted, extending from a point between Corozal and Miraflores in a straight course to the new site of the tidal lock between Sosa and Ancon hills, thence with a slight change in direction near the lock directly to deep water off the island of Flamenco. Rock outcrops between Ancon and Sosa hills and that vicinity afford a perfectly satisfactory foundation for this structure. Although the tidal currents might be small in a sealevel section extending from the shore line to a tidal lock at Miraflores, and might only be a source of temporary inconvenience, yet they are undesirable for the navigation of large steamers, and would be entirely avoided by the location for the lock adopted by the Board.
This relocation of the terminal portion of the canal line necessitates the excavation of a materially increased amount of hard rock, which has been included in the estimate of total cost, although as much submarine rock excavation in the vicinity of the islands has been avoided as possible. While there may be a difference of opinion as to the justification for such additional cost in securing a better entrance, there can be no doubt that the alignment adopted by the Board will result in easier and safer navigation for vessels entering the canal from the Pacific, and in much less cost for dredging to maintain it.
The bottom width of the entrance channel leading from deep water off the island of Flamenco to the tidal lock near Sosa Hill will be 300 feet, but the side slopes will depend upon the character of the material to be excavated. Inasmuch as extreme low water of spring tides will occur but rarely, the depth of excavation in this dredged channel is recommended to be but 45 feet below mean sea level. This excavation is sufficient to give at least 40 feet at low water for all but those spring tides having a range of more than 10 feet. As the mean tidal range in Panama Bay does not exceed about 14 feet it is considered that the depth of excavated channel to be provided will never be a source of any inconvenience or any delay whatever for the great bulk of the traffic of the canal, the measure of the maximum inconvenience for ships of greatest draft seeking the canal, if they should be ready to enter it at extreme low water or at about that time, being a total of only two or three hours.
It is evident that the approach channel on this new location may be subject to shoaling by sand moved by the eastward littoral current, as is the present channel. The rock excavated from the new entrance should be deposited along its westerly side so as to form a low dike, completely isolating it from the Rio Grande estuary. This will in no way change the regimen of the latter or of the roadstead near the islands, but it will afford complete protection against the easterly drift of the sediment and thus prevent deposition in the channel. It is possible, though not anticipated, that it may be advisable to form a similar low dike on the easterly side of the channel, and there will be sufficient rock from the channel excavation for that purpose should it be desired. The precise character and amount of these measures of protection for the entrance channel can only be determined in the last instance by observations which may be made during the progress of its construction. It is important to observe that there is no reason whatever to believe that this proposed entrance work will change in any way the character of 'the anchorage ground north of the islands of Naos, Perico, and Flamenco, which has always been of
56 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
so much value to the harbor of Panama and which will in the future be of equal value to the Pacific terminal harbor of the canal.
The principal, reason for the existence of the La Boca pier will vanish with the opening of the canal, ibut even with the new location of the Pacific terminal, uses of value will probably be found for that structure. No better location for shops, small shipways, and other similar and necessary plant can be found near the Pacific terminal than that now occupied at La Boca for those purposes. The req(uisite depth of water required for the service of these plants in their present positions can always be maintained at small cost, so that their usefulness will in no way be impaired.
The question of the necessity of a tidal lock at the Panama end of the canal has been raised by engineers of repute, but' the limited time available to the Board has bot permitted the full consideration of this question which is desirable. It is probable that in the absence of a tidal lock the tidal currents during extreme spring oscillations would reach five miles per hour. While it might be possible to devise facilities which would permit ships of large size to enter or leave the canal during the existence of such currents, the Board has considered it advisable to contemplate and estimate for twin tidal locks located near Sosa Hill, even though the period during which they would be needed would probably be confined to a part of each spring tide.
IThe highest recently recorded range Of spring tides which the Board has seen (Septemiber, 1905), was 19 feet 9 inches between extreme low and extreme high water, while from 1882 to 1887 the highest amplitude reported was 20.93 feet. With such tides for a brief period at dead low water there would be a differential head of about 10 f eet-that is to say, the water in the canal would be 10 feet above that in the bay, while at extreme high water for a correspondingly short period the level of the water in the bay would be 10 f eet higher than that in the canal.
At the period of mean tide there would be no difference of level between the bay and the canal, so that during that period of the tide all the gates of the tidal lock could be open, leaving' an unobstructed passage for vessels untilI the approach of the flood tide rendered it necessary f or the gates to be closed until slack water would again be reached, and so on for each succeeding spring tide. During neap tides the range is so small that it will not be found necessary to bring the gates of the lock into use. Consequently, throughout the neap period of each tidal cycle a continuously open arid unobstructed passage for traffic will be provided through the tidal locks.
If the matter be put into figures for the sake of comparison, it -will appear (1) tnat in the project for the sea-level canal one lock may be required at times at the Panama end of the waterway. For one-half of each tidal cycle of fourteen days the gates may be operated to control a difference of head of an average height or depth of about eight feet for short periods on each tide, while for the remainder the difference of level between canal and ocean will be negligible. For the remaining half of each tidal cycle the gates will be out of operation and the locks will present an open and unobstructed channel, and (2) that in the project for the lock canal six locks or even niore will be required for a canal with a summit level 80 to 90 feet above the mean level of the sea; that these locks will have differences of level ranging from about 27 to 35 feet; that their operation will be perennial, they will always be required, and consequently that the menace which they wiii present to the safe navigation of the canal by large steamers can not be avoided and wii be cumulative, i. e., must be multiplied by the number of lockages to which such vessels will be subjected during their passage through the canal.
(C) CR055 SECTIONS OF THE CANAL PRISM."G
The cross sections .of the prisms will vary with the character of the material excavated. Furthermore, the cross section of the deeply dredged channels at the terminal harbors m-ust obviously be different from those in the canal proper between the shore lines of the Isthmus.
In the judgment of the Board the depth of water in the canal prism and in both of the approach channels of the terminal harbors should not be less than 40 feet, except in the case of the channel in the bay of Panama, where at intervals that depth would not be f ound during short periods at extremely low spring tides. The depth of 40 feet was therefore adopted by the Board as the standard minimuni depth in the canal.
a See Plate III for diagram.
56
a
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 57
The standard bottom width in firm earth, including the dredged portions in soft material between the shore line of Limon Bay and Bohio, was fixed at 150 feet, the side slopes in the same material being taken at one vertical on two horizontal.
In rock the bottom width was taken at 200 feet with side slopes in the channel of ten vertical on one horizontal, i. e., practically vertical. The side slopes above water, as well as below, in firm earth between Bohio and Obispo and south of Paraiso were taken at the inclination of two vertical on three horizontal.
Some modifications of these standard sections were made by the Board in its estimates of quantities of material to be excavated in combined rock and earth sections between Bohio and Pedro Miguel, but not including the Culebra section. At many places throughout this distance the lower portions of those parts of the cuts above the water surface in the canal will be rock overlaid by earth or softer material. In the great summit cut the surface material overlying the rock for a considerable distance in the vicinity of Culebra Hill is clay, which, like all clay, slips easily when wet. When, however, this clay is drained, or otherwise protected from becoming saturated, it stands with satisfactory firmness and gives no trouble. Throughout these combined rock and earth slopes the rock is given a face slope in the estimates of ten vertical on one horizontal and the clay or other material above it one vertical on two horizontal. In the great Culebra cut, which really means the summit divide from Obispo to Pedro Miguel, a distance of seven and onefourth miles, a special form of section has been taken, although it includes the same elements of slope adopted for other portions of the cuts taken out in the dry. The same rock section for the prism of 200 feet bottom width and with side slopes of ten vertical on one horizontal is carried up to an elevation of 10 feet above mean tide, at which elevation there is provided a horizontal berm 50 feet in width on each side of the canal prism. From the exterior limits of these berms benches are assumed for the purpose of estimate, each 30 feet high, with a face slope of four vertical on one horizontal, the width of the bench at top being 12k feet. These benches are carried to the upper limit of the rock portion of the cut. This makes the average or mean slope of the rock three vertical on two horizontal. The clay or other soft material overlying the rock is given the same slope of one vertical on two horizontal already described.
It is believed by the Board that the estimated volume based upon these side slopes is ample. It is probable that large portions of this summit cut, composed of harder rock than the indurated clay which forms the material classified as soft rock, will permit of faces having a slope of four vertical on one horizontal to be taken out much higher than 30 feet. It is further believed that there will be little sliding of these benches, assumed in the computations of quantities, so that the volume taken out of the great summit cut is much more likely to be less than that estimated than in excess of it, especially as a contingent margin has been added to all items of cost.
The materials classified as soft and hard rock have been exposed with surfaces fully as steep as four vertical on one horizontal ever since the old company ceased work in 1889, a period of sixteen years. Furthermore, these slopes and others equally steep produced by the excavation made by the new French company have been under the personal observation of two members of the Board throughout the past six years, and under the daily observation of another member for over a year. During this time the effects of weathering have been small, soft rock as well as the hard having stood without sensible slipping or other deterioration. In fact, it is the result of extended experience with these steep faces both in Central America and on the Isthmus that the steeper the faces stand without crushing at their lower portions the less weathering and wash from the tropical rains will occur. It is therefore highly desirable to finish these slopes in as high benches and with face slopes as steep as practicable.
Very few slips of rock have occurred in the deepest portions of the Culebra cut since it was first opened. They are small and have been of such rare occurrence as not to affect the correctness of the preceding observations. The cross sections of the approach channels to be dredged in the harbors of Colon and Panama have been described under "Harbors."
It is believed by the Board that the cross sections of the prism for all parts of the canal from deep water to deep water are well adapted to meet the requirements of the law under which work
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
on the canal is now prosecuted, and that they are sufficient to accommodate ships of the deepest draft now afloat and which may be reasonably expected for the future. It is further believed that the conditions assumed, especially for the great divide cut, are such as to make the estimated total quantities larger than the quantities which will be actually excavated.
(D) ESTIMATE OF .COST.
The unit prices to be applied to the various items of work entering the completion of a sealevel canal have been formulated by the Board after most careful deliberation upon all the conditions affecting the actual prosecution of the work, including climatic effects, inefficiency of available labor, the distance of centers of supplies, the present condition of the various incomplete excavations, the general experience of the Isthmian Canal Commission since its creation, and other influences peculiar to the circumstances which will surround the execution of work in the field to its completion. It has been the intention of the Board to make these prices liberal, so as to remove as far as possible any probability of the ultimate cost of the work being greater than that estimated, and it is believed that they are sufficiently liberal to accomplish that purpose.
It will be observed that they pertain to methods and material which have been well tried in engineering construction and do not rest upon anything of an experimental character, as it is the judgment of the Board that nothing should be included in the proposed plan other than that which has been justified by engineering experience with work as nearly similar to that contemplated in this project as possible. A complete schedule of these unit prices will be found in Appendix R.
The Board has taken account of and given due weight to the fact that vast improvements in' mechanical excavating devices have, in the past few years, been made and their effectiveness demonstrated. The Board also believes that other improvements specially applicable at Panama will be developed and used as the work progresses, as was the case during the making of the Suez and the Chicago Drainage canals, and that these improvements will result in large economies and show that the unit prices are much too large; but in fixing these units account has been taken of nothing which has not been tested and justified in actual practice.
Applying the unit prices adopted to the quantities-a tabulation of the main items with a grouping of the smaller items-the following estimate of.cost results: Jetties in Limon Bay---------------... ....------------------------------------------------------- $5,000,000
Excavation and dredging in earth, rock, etc., throughout the canal.-------------------------------.. . 183,136,000
Completion of river diversions, formation of dams across tributary streams, regulation of rivers which
flow into the canal, etc-------------------------.. .. ..-----------------------------------------3, 500, 000
Dam across Chagres Valley at Gamboa, with flood sluices, etc..--------------------------------------6, 000, 000
Spillway, with flood sluices, near La Boca ...-------------------------------------------------------920, 000
Twin tidal locks in the Ancon-Sosa saddle-.------------------------------------------------------6, 000, 000
Leading jetties above and below locks...-----------------------------------------------------------795, 000
Relaying track of Panama Railroad ..--------------------------------------------------------------500,000
205, 851, 000
20 per cent for contingencies, administration, and engineering------------------------------------41, 170, 200
Total.. ........----------------------------------------------------------------------------247, 021, 200
The Board is confident that the Panama Canal can be constructed and completed under the plans set forth and recommended in this report within the preceding total sum of $247,021,200.
There are certain items of cost, such as construction of military defenses, naval stations, government of the Canal Zone, sanitation, light-houses, buoying, lighting, and the provision of tugs, lighters, derricks, dredges, scows, etc., which have not been included. They are common to any type of canal. It was not understood to be the desire of the President that the Board should take into account anything that did not relate to the engineering features of the canal construetion, but there is no doubt, in the opinion of the Board, that the expense of maintenance of a sealevel canal will be very much less than for a canal requiring lift locks.
Assuming that the total cost of the Panama Canal, including construction, payments to the French company for the property and franebise, to the Panama Republic for the rights conveyed,
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
the cost of the Zone government until the canal is open, and other collateral costs, the total possibly reaching $333,000,000, the interest charge on this sum at three per cent would reach $10,000,000. That such an investment would be a safe one from a commercial standpoint is indicated by the fact that the interest and dividends paid to the owners of the Suez Canal last year reached the total of $17,000,000, after paying all expenses of maintenance and operation, also the cost of the extensive enlargements and deepenings which are continually in progress.
(E) ESTIMATE OF TIME.
The time required for the construction of a ship canal across the Isthmus is one of the main elements of the whole subject. If the execution of the work in accordance with any one plan could be completed within a reasonable time while the execution of the work under another plan of equal merit could be realized within a less time, it is clear that the latter plan should be adopted. If, however, there are two plans, both feasible and each involving an amount of work which can be accomplished within a reasonable period, it is clear that the execution of that plan requiring the longer period may be justifiable if the advantages thereby gained are sufficient, or more than sufficient, to compensate for the delay. If the work required under the less desirable plan can be finished within ten or eleven years while that under the more desirable plan would require but two years longer, the small delay in the passage of the first vessel through the waterway might easily be neglected in comparison with the advantages secured under the better plan. It is necessary, therefore, to weigh carefully the significance of the time elements in reaching a conclusion as to the plan of canal to be adopted. In weighing these elements it is further necessary to consider that in the execution of the many locks and dams required for the lock canal, accidents during construction which would defer the opening of the waterway are more likely to take place than in the simpler works of the sea-level canal.
The time required to complete the construction of one or more of the main features of the plan controls the time required for the completion of the entire work, for the obvious reason that the various smaller features may be attacked and completed in detail in less time than would be required for the main or controlling ones. Under well-balanced administration of the work, therefore, the entire canal should be completed when the part requiring longest time is finished. As affecting the question of time for completion, and in marked degree that of cost also, there are two features of the sea-level plan which are of great moment: One is the excavation of the channel through the great divide, amounting to about 110,000,000 cubic yards in a length of about seven miles, and the other the construction of the tidal lock near Ancon-Sosa, having a usable length of 1,000 feet and width of 100 feet, with a maximum lift above mean sea level of 10 feet, this structure requiring over 600,000 cubic yards of concrete and other masonry. These two features have received an extended and careful study.
Inasmuch as hard rock outcrops in the immediate vicinity of the tidal lock site near Sosa Hill the amount of excavation required to secure a suitable foundation is not large and it can be expeditiously completed. The most serious part of this particular problem is to secure and assemble at the site the requisite cement, sand, gravel, or broken and other stone, and the plant required to mix and put in place the great mass of concrete and granite for the masonry portion of the lock. The gates as planned would be of steel, and each leaf would weigh about 275 tons. Their construction, shipment to the Isthmus, and erection in the locks would probably require a period of nearly two years. The Board has estimated that the time required for placement of the concrete and stonework would be four years after the excavation had been completed. It is therefore reasonable to estimate that the entire twin-lock construction, including excavation, concreting, erecting gates, and installing machinery, will require a period of not more than eight years. In estimating the time required it must be remembered that inasmuch as the change of level may bein both directions, up or down, to accommodate extreme high and low stages of tide, two sets of gates will be required in each of the twin locks. The total length of the structure will be not far from 1,300 feet exclusive of the approach works. While these locks are great structures the lifts are comparatively small.
59
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
It may be suggested that the Gamboa dam, built to the height of 180 feet above the rock in the deepest place, is also a great controlling factor as respects time, but the Board does not indorse such an opinion. If the dam be entirely of masonry, and allowing amply for interruptions by freshets or floods, the structure can easily be completed in less time than the tidal locks.
The excavation of 110,000,000 cubic yards probably can not be completed in the seven miles of summit cutting within the period of eight years which are estimated to be requisite for the construction of the tidal locks. The excavation at the summit may therefore be considered as the controlling element in the time required to build a sea-level canal. The work in this cut is unprecedented. Great excavations for similar purposes have been made in the Chicago Drainage Canal, at the Corinth Canal in Greece, and in the Manchester Ship Canal. The maximum annual excavations, however, in these works have been 12,500,000, 2,500,000, and 12,000,000 cubic yards, respectively, but in no case was it all steam-shovel work, as it probably will be in the divide cut at Panama. The maximum depth at the Culebra cut from the original surface to the bottom of the canal will be 373 feet and from the present surface 208 feet. The maximum depth of cut in the Corinth Canal was 286 feet, but no other excavation in recent years approaches in depth that proposed at Panama.
The time required to remove this great mass of material, by far the greater part being soft and hard rock, will depend greatly upon the efficiency of the method of operation and the organization of force and plant, all of which must be ultimately the result of most careful consideration of all the elements, including those of climate and character of labor available. It is clear that for the best results the greatest possible amount of work must be done by mechanical appliances and the least possible by manual labor. It is equally clear that the methods of conducting the work, including the control of the plant and force, must be such as will be subject to a minimum of climatic interference and effects of rainfall in the rainy seasons. All parts of the cut must be completely drained, so that the effects of rainfall and springs on the material to be moved may be reduced to the lowest limit.
In considering this part of the Board's work it has taken full evidence regarding this great excavation from not only the present and former chief engineers of the Isthmian Canal Commission, but also from the division and resident engineers who have had the direct charge of the work. The records and plans of the French engineers and committees have been diligently studied. It appears safe to estimate from this evidence that from 80 to 100 steam shovels of the most effective type now in use on the Isthmus can be efficiently employed continually on this work after complete organization. It will require from two to two and a half years to install and put in operation this excavating plant. The independent' studies by the Board of the arrangement of railroad tracks and of complete systems of attack at both ends of this summit cut completely confirm the conservatism of the evidence given before it. It is as clearly demonstrable as any estimate of rate of progress and time for the completion of any great engineering work can be that after the full installation of plant not less than 100 steam shovels may be continuously engaged between Obispo and Pedro Miguel until the amount of work remaining to be done becomes too small to afford space for the operation of the whole plant.
The Board recognizes that the removal of the material in the summit cut is in reality a problem of transportation. It is a comparatively simple matter to excavate the material within a much shorter time than that allowed for the work, even on the supposition that all of it except the clay near the surface must be shattered by preliminary blasting. The whole difficulty attending this part of the construction of the canal is attached to the removal of the material from the shovels or other excavators to the spoil banks. This problem of transportation is in reality the substance of the problem of building the transisthmian canal and, in treating this part of the project, the Board realizes and has considered the large amount of railroad track and the extensive transportation organization required for the disposition of the waste material. It is probable, as has been estimated, that not less than three miles of standard track 'will be required for each shovel employed, making a total of 300 miles of trackage for 100 shovels.
If it be assumed that 100 shovels are available for continuous work, there being a sufficient surplus above that number undergoing repairs whenever necessary to maintain the working
60
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
complement, it can be demonstrated that as much as 20,000,000 cubic yards of material classed as rock may be annually removed from the summit cut. This estimate is based upon an average number of working days of not more than 20 per month throughout the year, which is an underestimate on the b-asis of the experience of the French companies and of that which has accrued since American occupation began, in May, 1904. In this estimate the capacity of one shovel is taken as materially less than would be justified by the actual operations of steam shovels in the Culebra cut during the past year, both in wet and dry seasons. Furthermore, it has been supposed that the working day is to be but eight hours long and that one shift only of laborers would be employed per day, whereas it is perfectly feasible to work two shifts in twenty-four hours during the greater part of the year and possibly during the entire year. Using these estimates for the period of what may be assumed to be the maximum annual output in the Culebra cut, and allowing at least two and a half years to attain this maximum rate at the beginning of the work and a period of not less than three years for a decreasing output in the more contracted space in the lower portions of the cut during the closing period of operations, it is found that the entire quantity of 110,000,000 cubic yards of material in the divide can be removed within ten years. (For time curve illustrating practicable excavation of Culebra cut, see Plate XXXI.)
Although the preceding estimate of time has been based upon ample allowances for the effect of the rainy seasons, for the low grade of labor available on the Isthmus, and for climatic conditions in general, the Board has added about 25 per cent to it for other contingent causes of delay, either similar to those already provided for or of any other character. It is therefore the judgment of the Board that a ship canal on the sea-level plan outlined in this report can be completed within a period of time not exceeding twelve or thirteen years.
(F) IMPORTANT CONSIDERATIONS.
A map of the world or, still better, an ordinary terrestrial globe presents at a glance the reason for the construction of the Panama Canal, such map or globe being of itself sufficient to indicate what the status kf' the waterway will be, and to show that the canal will provide the one great maritime highway of the West-not between seas, but between oceans; not for countries, but for continents.
The vastness ofte interests to be served by the canal, many of which interests now wait for their development on e construction of the waterway, demands that the canal shall, when opened for traffic, be of the type which will most perfectly fulfill the purposes which the waterway is intended to accomplish.
First and foremost it is essential that the Panama Canal shall present not merely a means of interoceanic navigation-it may be said that any type of canal would enable vessels to pass from ocean to ocean-but a means of safe and uninterrupted navigation, on which no special hazards will be encountered by and no vexatious delays will be occasioned to the vessels which will traverse it. It is therefore evident that the canal ought to be formed in such manner that the course thereof shall be free from all unnecessary obstructions, and that no obstacles should be interposed in that course, whether temporary or permanent, which would by their very nature be an occasion of peril and of detention to passing vessels, and more particularly to vessels of the great size which the Panama Canal is (in accordance with the provisions of the law of Congress) designed to accommodate.
The Board is of opinion that this consideration should be of determinative force in respect to the type of canal to be adopted, and that it should lead to rejection of all proposed plans in which lift locks, whether few or many, form the principal or dominating features, and consequently to the acceptance of the sea-level plan as the only one giving reasonable assurance of safe and uninterrupted navigation.
It is not suggested that a maritime canal with locks forming the essential feature is an inherently unsafe system of navigation, for experience has not only demonstrated the contrary, but also that the matter is one of degree. A navigation with locks of small size capable of passing the ordinary commercial steamers may be made reasonably safe, while a maritime waterway with locks of the dimensions which the Board has considered to be necessary in order to
01
62 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
meet the requirements of the Spooner Act 'Might be and is- thought to be so unsafe f or the passage of the great seagoing vessels contemplated by that act as to be altogether beyond the limit of prudent design for safe operation and administrative efficiency.
In the course of the proceedings of the Board it transpired that during the last nine years three accidents arising from collisions between steamers in transit and the lock gates, and resulting in each case in dangerous damage to these gates, occurred in the St. Marys Falls Canal; and also that three accidents arising from the same cause and having the same result occurred in the Manchester Ship Canal in England.
Several of these accidents were so serious that disastrous consequences were escaped by a narrow margin only. It is practically certain that if the locks upon which these accidents took place had been of the dimensions and had controlled the great differences of level contemplated for the locks of the Panama Canal, not merely serious accidents but disasters would have followed in perhaps all these cases, throwing the whole canal out of operation for a period which can not be estimated, and also wrecking the vessels in the path of the resulting flood, while the cost required to repair the damages is not within the limits of reasonable computation.
The three accidents at St. Marys Falls Canal occurred within a period of nine years, where there is only one lockage of about 20 feet. If six locks should be adopted in a plan for the Panama Canal, each having a lift of 30 feet or more, as has been proposed in several projects, it would not be unreasonable, with an equal number of vessels, to look for six times the number of accidents in the same period of time, which would be at the rate of two per year. If groups of locks should be arranged in flights, as has also been proposed in some projects, the imminence of disastrous accidents would be greatly enhanced, as would be the amount of damage to the structures and to the vessels involved. Indeed, it is highly probable that the grave disaster of a great ocean steamship breaking through the gates of the upper lock and plunging down through those below might be realized.
It is the unqualified judgment of the Board that the United States Government should not construct an interoceanic waterway to acconlmnodate the commerce of the world exposed to hazards of this sort. These conditions become even more serious when it is contemplated that this canal is to be used for strategic purposes, and theref ore for the interoceanic transit of vessels of war of the United States Navy.
Consideration of the growth in size and weight of battle ships during the last ten years-and of the fact that this growth is still progressing-leads to the inevitable conclusion that in the no4 distant future armor-clad vessels of a beam of 90 feet and with a displacement of 25,000 tons may be expected. The dimensions adopted by the Board for the canal prism and for the lock chambers would admit of the passage of these vessels.
Argument does not seem to be required to emphasize the necessity of avoiding the process of locking these ponderous and unwieldy ironclads up or down in the Panama Canal. The difficulty of handling them in the most favorable circumstances is notorious, while in the operations required for raising them in one series of locks and for dropping them down in another series the difficulty would come so perilously near impracticability that in the opinion of the Board no scheme involving it should be accepted.
As there is no maritime canal in the United States or about its borders it is natural to regard the navigation of the St. Marys Falls Canal as exhibiting conditions practically parallel to those which would exist in the Panama Canal, but inferences drawn upon such a basis may be greatly misleading. The lock in that canal has been SO SUCCesfully operated and its administration has exhibited such gratifying results that there is danger of f orgetting that it is located in an environment of a highly special character. It is now a marked feature of the navigation route of the Great Lakes. The masters of the vessels passing this canal and lock are therefore familiar not only with every detail of the short canal in which the lock is located and of the lock itself, bt also of every circumstance of its operation. They pass to and fro with their ships every two or three weeks during the period of navigation, so that the vessels which the lock serves are almost fixed features of a dai ly routine from which there is little or no variation. Entrance to and exit from the lock becomes by constant familiarity a routine performance in which constant repeti-
62
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.(3
tion leads to a degree of skill and safety which can never be attained in a maritime waterway like that of the Panama Canal, serving the commerce of the world, carried in vessels whose masters would come in contact with the physical conditions surrounding the locks and the regulations governing their operation at rare intervals only, and whose crews would be absolutely strange to every feature of this canal service. Under such circumstances any variation f rom the simplest and plainest conditions of navigation would necessarily be a source of grave danger and likely to lead to serious accident. Again, the canal navigation at Sault Ste. Marie is closed by ice for three or four months each year. Then the locks are or can be pumped out, the gates and all other mechanism examined and repaired or replaced; but there will be ifo such annual period of idleness for similar overhauling at Panama.
It has already been shown in this report how seriously the existence or nonexistence of locks may affect the safety of this canal navigation. Those considerations will not be repeated here, but it should be observed that the ease with which vicious enemies of all classes may destroy locks by small quantities of high explosives, or even ram lock gates with a passing ship in an apparently innocent manner, or produce other similar damage to -locks, might actually put the control of a canal with lift locks in the hands of such an enemy at a juncture when its m-aintenance of operation for the passage of naval vessels or for other strategic purposes might be of the utmost necessity to the United States Government.
It is true that a sea-level canal or any restricted waterway may be closed by accident, as by a vessel stranding or sinking. Such an obstruction would he temporary only, as it could be removed in a few days, even if the wreck had to be blown up, as recently occurred in the Suez Canal, an incident mentioned elsewhere in this report. Such an accident is not to be compared with those greater and more far-reaching, resulting in the destruction of the-lock gates, the drawing off of the water from the summit level, and the possible serious damage to the canal prism.
It may be argued that the objections to which we have referred as existing to the employment of Hist locks apply also to the sea-level plan in which the construction of tidal locks at or near the Pacific terminus is a feature. In reply it may be conceded that the argument is at first sight a fair one and that due weight should be given to it; but while it is clear in any case that one obstruction in the course of a maritime highway would be preferable to six or eight, the difference between the functions of any lift lock in the lock-canal proposal and those of the tidal locks in the sea-level plan should be clear to any impartial critic.
The tidal lock is for regulating purposes only, and the reason for its introduction is due to the natural circumstances which exist, there being practically no tidal range in the bay of Limon, at the Atlantic end of the canal, while in the bay of Panama, at the Pacific terminus, the range at high spring tides is more than 20 feet.
Much has been said in the projects submitted to the Board about the advantages of lake navigation in the great reservoirs or lakes which it has been proposed, to create by dams across the Chagres on the one side of the Isthmus and across the estuary of the Rio Grande on the other. Extended experience in the navigation of maritime canals on the continent of Europe and in Great Britain has shown that this advantage is. largely imaginary, for it has been found in such canals, with prisms of much less dimensions than those recommended for this route, that steamers of the largest size which they can accommodate uiay steam through them at speeds of about six miles per hour without any real difficulty or danger. Such is the case in the Suez Canal and the Manchester Ship Canal. As a matter of fact, throughout the greater part of the Panama Canal traversing the proposed lakes the actual channels would have submerged banks, necessitating buoys, and within which the speed of vessels 'Would not greatly exceed that possible in the sea-level canal.
It must also be observed in making a comparative consideration of the lock and sea-level types of canal that the locks in the former constitute a restriction or limit to the capacity for traffic of the waterway in which they are found,' i. e., they are in a substantial measure obstructions to navigation. There is a limit to the number of lopkages per day which may be made, perhaps not exceeding ten per lock or twenty per pair in any of the lock plans hitherto
63
64 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
considered. The maintenance and operation of locks is also costly. If of such great dimensions as those considered necessary by the Board under the Spooner Act, they require the installation, maintenance, and operation of an extensive power plant for the working of the gates. It is not easy to estimate what the annual cost of maintenance, including renewals and operation, of these would be, but, using the estimates of the Isthmian Canal Commission of 1899-1901, it is probable that the annual cost of operation of the six locks contemplated in the projects brought before the Board would be about $525,000. This annual charge capitalized at three per cent would make a sum of $17,500,000 to be added to the cost of the lock canal. The corresponding item in the sea-level plan would be the capitalized annual cost of operating the tidal locks near Panama.
The comparative ease and economy of enlarging the prism of the sea-level canal to accommodate any additional demands of the future must be given the weight which properly belongs to it. The operations which have already been conducted so extensively in enlarging the prisms of the Suez and Manchester Ship canals, and which are now about to be undertaken at the Kaiser Wilhelm Canal at Kiel, show that such operations may be required. The facility with which work of that character may be done in a sea-level waterway where there are no lock structures constitutes a material advantage.
It has already been stated as the opinion of the Board that the time required for the construction of the Panama Canal with a summit level at 60 feet above mean sea level will at best be only two years less than required for the construction of the sea-level canal. But as affecting this question of time, it should be observed that accidents during construction leading to an extension of the time required to complete the canal would be more likely to occur in the more numerous structures involved in the building of the lock canal than in the works for the sealevel canal. It has f urther been shown that the difference in cost between the two plans will not exceed about $71,000,000 in favor of the former, which must be reduced by the capitalized cost of the maintenance and operation of locks and by the cost of the overflowed lands, as before stated.
It is seen, therefore, that the lock design has inconsiderable advantage either in time of realization or ultimate cost over the one recommended by the Board for adoption by the United States Government, which possesses all the advantages of practically indefinite capacity for traffic, besides a degree of safety and uninterrupted operation which can not be approached by any lock plan.
Did a canal now exist of the widths proposed, but limited in depth to 35 feet, it would accommodate all existing shipping. By restricting the depths in the prisms (but not in the locks), as suggested but not recommended, the channel could probably be opened in a year or two less than if constructed at first to full depth, and the saving in cost would amount to about $17,000,000. When it should be decided to take out the other five feet in order to accommodate vessels of a greater depth, that could readily be done at some increase of cost over what would have been incurred if made originally at the fll depth of 40 feet.
The Board desires to emphasize the fact that in its knowledge no great enterprise in connection with transportation, whether it be a canal, a railway, a harbor or docks, or similar work, has ever Yet been completed of such size or proportions that subsequent enlargement did not become necessary. The Board is therefore of the opinion that in this particular case the United States Government should construct this great artificial waterway of such type and dimensions as to give it at the outset the maximum capacity that seems likely to be required, guaranteeing the greatest facility of operation, and leaving the canal as constructed with ample provision for a reasonable future increase of traffic and in condition for most speedy and economical enlargement in response to the future demands of commerce, without the undoing of any construction.
It is the belief of the Board that the essential and the indispensable features of a convenient and safe ship canal at the American Isthmus are now known; that such a canal can be constructed in twelve or thirteen years' time; that the cost will be less than $250,000,000; that it will endure for all time.
64
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
The Board does not believe that a provisional treatment of this great question would yield results which would be satisfactory to the American nation or advantageous to American commerce, or that such treatment would be in consonance with the increase of population, of trade, and of wealth which will surely take place during the next half century in the Western Hemisphere.
For all these reasons the Board recommends that the sea-level plan be adopted for the Panama Canal.
Mr. Quellennec's indorsement' of this report is to be considered in connection with his statements qualifying his vote as recorded in the minutes of the nineteenth and twenty-fifth meetings.
Respectfully submitted.
GEO. W. DAvIs. Wm. BARCLAY PARSONS. Wm. H. BURR. Wm. HENRY HUNTER. AD. GUE'RARD. EUGEN TINCAUZER. J. W. WELCKER. E. QUELLENNEC.
465A-06-5
65
0
MINORITY REPORT.
The undersigned, a minority of the Board, concurring with much of the preceding report, dissent from the preference expressed for a sea-level canal.
We believe a lock canal the better one for the United States to construct, for the following reasons:
1. Greater capacity for traffic than afforded by the narrow waterway proposed by the Board.
2. Greater safety for ships and less danger of interruption to traffic by reason of the wider and deeper channels which the lock canal makes possible at small cost.
3. Quicker passage across the Isthmus for large ships or a large traffic.
4. Materially less time required for construction.
5. Materially less cost.
The studies of a lock canal by the Board, and for the Board by its committees, embraced a number of projects with summit levels varying from 30 to 90 feet above mean tide (which will be hereinafter referred to as elevation 30, elevation 90, etc.), with duplicate locks having usable widths of 95 and 100 feet, and usable lengths of 900 and 1,000 feet, located at various places, and with the summit level maintained on the Atlantic side by dams at Mindi, Gatun, Bohio, or Obispo. The projects of Mr. Bates, with summit levels up to elevation 97, of Major Gillette, with summit level at elevation 100, and of Mr. Bunau-Varilla, with summit level at elevation 130, were also considered. The Board selected for comparison with the sea-level project a lock canal with summit level at elevation 60 and with locks having a width of 100 feet and usable length of 1,000 feet, which is described in the report of the Board.
The undersigned are of opinion that there are several variants for lock canals which should have preference over the sea-level project, consideration being given to facility and safety of transit, and time and cost of construction; and that, for reasons which follow, locks of the smaller dimensions noted above will adequately meet all probable demands for a long term of years. We present for comparison with the project preferred by the Board, to be considered later, a project wifh summit level at elevation 85 maintained by a dam and duplicate flights of three locks at Gatun. This is recommended for adoption, General Abbot preferring a lower dam with duplicate flights of two locks at Gatun, supplemented by a dam and duplicate single locks at Bohio, raising the summit level to elevation 85, as before.
THE LOCK-CANAL PROJECT RECOMMENDED.
This project is a modification of the one adopted by the Isthmian Canal Commission of 1899-1901, the modifications being due in part to the requirement for greater dimensions imposed by the act of Congress approved June 28, 1902, called the Spooner Act, and in part to data collected within the last two years, which make it feasible to design a much better canal without increased cost. The elevation of the summit level is practically the same as in the earlier project. Unfavorable developments at the site of the proposed Bohio dam and the existence of more favorable conditions at a site nearer the Atlantic, together with important incidental advantages, have led us to recommend the latter. On the Pacific side the terminal lock is placed at Sosa, instead of at Miraflores, for reasons which will appear further oi.
(A) THE COLON ENTRANCE.
Commencing the description at the Atlantic end, the plan of the Board for a breakwater in Limon Bay is, with only a slight change, adopted for purposes of estimate. The change consists in swinging the long westerly line out from the shore at Mindi Point far enough to permit the 67
68 REPORT OF BOARD OF CONSULTING E NGINEERS, PANAMA CANAL.
channel (500 feet wide and 41 feet deep at mean tide) to be made through the easily dredged earth outside the point, instead of inside the point where there would be much expensive rock excavation. The breakwater and channel as modified will be extended to the head of the bay. It seems possible that the breakwater may be dispensed with wholly, or in part, and the channel widened to 1,000 feet or more, to the advantage of navigation and with a reduction of cost.
The Board's plan of harbor and canal entrance, however, is much superior to that of the French company, as it provides a safe and easy entrance at all times. The distance from the head of the breakwater to the shore line near the mouth of the river Mmndi is 4.55 miles. From this point the 500-foot channel is to be continued 2.6 miles farther, to the locks at Gatun.
(B) THE GATUN -DAM.
The controlling feature ef the project with summit level at elevation 85 is the earth dam across the Chagres at Gatun. The object of this dam is to form a great reservoir, or inland lake, in which~ the floods of the Chagres will be received and from which the surplus water will be discharged through sluices and the height of water in the reservoir regulated. Lake Gatun will be about 110 square miles in area and will form the summit level of the canal. The lake will also serve to impound water for lockage and other purposes during the dry season and to give free, open navigation in a broad waterway all the way from Gatun to Obispo.
Every lock plan heretofore recommended for a Panama Canal has included a dam across the Chagres, thereby providing for lake navigation for a portion of the distance across the Isthmus. All of the official reports have recommended that the dam be placed at Boio, where the valley is narrow, but Gatun has also been mentioned as a site which would be advantageous if the feasibility of building a dam and locks at this place at a reasonable cost were established.
Since the United States has taken charge at the Isthmus, the Isthmnian Canal Commission has had many borings made at and near these two sites. Those at Bohio, which are especially complete, show a greater proportion of water-bearing porous material than had previously been found. The maximum depth to the rock on the most feasible line for a dam at this place is 165 feet below sea level.
The borings made prior _to September, 1905, at and near Gatun showed nearly everywhere an admixture of sand with clay and impervious material with a maximum depth to rock of 204 feet below sea level. Many of the borings, even those at considerable depths, encountered shells, wood, and vegetable matter, all tending to show that the material had been deposited in currents too sluggish to transport gravel and other coarse material.
The borings were water jet" or wash drill'" borings, made by first driving, when necessary, an iron pipe (known as a casing) having an inside diameter of two or two and one-half inches, and then inserting a smaller pipe through which a jet of water was forced, washing the material in the larger pipe through the annular space between the two pipes to the surface of the ground. It was characteristic of these borings, and also significant, that in Wany cases it was not necessary to drive any casing; or, if one was driven, it was not necessary to drive it to the full depth, as the material contained enough clay to sustain the sides of the hole without the casing.
Of 27' borings made before September with reference to the location of a dam at or near Gatun, no casing was used in thirteen holes; in three other holes the length of casing did not exceed 20 feet, while in the remainder the length of casing ranged from 28 to 101 feet, but in no instance was the casing driven much more than halfway down to the bottom of the hole.
The depth to rock was shown to be so great, both at Bohio and at Gatun, that it would be costly and diffioualt in either case, if not impracticable, to excavate to the rock or to provide any efficient cut-off or stop- water extending from the surface of the ground to the rock; and if a dam were to be built without such cut-off the borings showed clearly that there would be less seepage beneath a dam built at Gatun than at Bohio.
In addition to the borings, the Commission had caused topographic surveys to be made at the site of the dam, which showed what was apparently an excellent site for locks on the high ground back of Gatun, and a suitable site for a diversion channel for conveying the water of the
68
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
Chagres during the construction of the earth dam and for regulating works to control the discharge of surplus water from the lake to be formed by the dam.
Few borings had been made at the exact site selected for the dam, and none had been made at the sites selected on the high lands for the locks and the regulating works. The Commission was therefore requested by the Board to have some additional borings made, both on the high lands and in the valleys, and also some additional tQpographic surveys.
The location of all borings is shown on the map of the Gatun dam site, Plate XI, and the borings on a line across the valley at the dam site are shown on Plate XII.
It will be noticed on Plate XII that there are two deep depressions or gorges in the rock, which have been filled with alluvial material. The deepest boring penetrated this material 258 feet before striking rock. The lower 50 to 60 feet of the material in the deepest gorge was found to be for the most part porous sand and gravel, which was undoubtedly deposited at a time when the currents through the gorge were swifter than existed when the upper 200 feet of the alluvial material was deposited. In the upper 200 feet some of the later borings show fine sand, while other borings near by show clay at the same depths, indicating, as do previous borings, that the upper 200 feet is practically impervious material. There wasan outflow from several of the borings which penetrated the gravelly material in the bottom of the deep gorge, although the tops of the casings were above the surface of the river. This showed conclusively that there was no near connection with the bed of the river; in other words, that the material covering the sand and gravel was impervious for a long distance.
A sample of the material washed from the ground during the boring operations, which had been collected in a pail without allowing any of the fine material to escape, was shown to the Board during its visit to the Isthmus. This sample showed material of sizes varying from sand to the very fine particles of clay which settled last and formed an impervious film over the surface of the coarser material deposited in the bottom of the pail.
The samples of sand which had been obtained up to the time of the visit of the Board were fine, much more so than samples from borings at the Bohio site.
We believe as a result of the borings which have been made that if a large earth dam were to be built at Gatun, as indicated upon the drawings, there would be no appreciable seepage under the dam, owing to the practically impervious nature of the material on which it would rest and to the fact that the more pervious material found at the bottom of one of the gorges in the lower 50 feet is covered by a blanket of practically impervious material 200 feet thick.
The borings on the high ground,-at the site of the locks, the regulating works, and elsewhere, showed generally soft clay to a depth of 20 to 30 feet below the surface, where indurated clay-a soft but compact rock-was found.
In making the design of an earth dam at Gatun, it was thought best to provide a dam which could not be destroyed by any of the forces of nature, and which could only be destroyed by making excavations which would require a large force working for a long time.
The cross section of the dam has been given the unprecedentedly large dimensions shown on Plate XIV. Its top is 50 feet above the water level in the lake and 100 feet wide; at the water level the distance through the dam is 374 feet, and at sea level the corresponding distance is 2,625 feet, or one-half mile.
It is intended that the downstream toe of the dam for about 200 feet shall be composed of rock obtained from excavation in the canal prism, so that if there should be any seepage of water through the dam there will be material at the toe which can not be washed away. The lower part of the dam, up to elevation 50, or even to elevation 80, is to be made from material dredged from the canal between the Gatun locks and Limon Bay, pumped by a suction dredge into the dam, the process being similar to the sluicing process employed in the construction of some important dams in the western part of the United States. By this process it is feasible when using a material like the alluvial material at Gatun, which contains both coarse and fine material, to separate the two and to deposit the coarser material toward the downstream slopes, forcing the finer material to the extent desired into the upstream portion of the dam. An embankment built in this vay will be water-tight.
69
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
For the upstream slope, rock obtained from canal excavations will be dumped as riprap, care being taken to provide an ample thickness at and near the level where the dam will be exposed to wave action.
The portion of the dam above elevation 80 will be built of impervious material to a few feet above the water level, and at higher levels may be made of either earth or rock, as most convenient. It is expected that for the upper part of the dam, spoil from the Culebra cut will be used.
While earth dams are in common use, and in many cases support greater heads of water than would exist at the proposed Gatun dam, it will still be argued by many that in a great work like the Panama Canal nothing should be trusted but the most massive masonry dam on a solid rock foundation. At Gatun the rock lies at so great a depth that a masonry dam thus founded is impracticable, and without such foundation a masonry dam would be most unsuitable. It seems desirable, therefore, to enter to some extent into the discussion of the stability of the proposed earth dam.
STABILITY OF AN EARTH DAM.
It is obvious that if a dam of this kind is to fail, some part of its length must be pushed away bodily, or the earth of which it is composed must be carried away by currents of water. There are no other natural forces which can materially affect the stability of the dam.
The horizontal pressure of the water in the lake per linear foot of dam is less than one sixty-third of the weight of the dam per linear foot, a pressure so small that it is obvious that it can not move the whole mass, and there is left, therefore, as the only way in which a dam of this kind may fail, the carrying away of its parts by a current of water.
The currents of water requiring consideration are those resulting from the action of the waves, from the rainfall, or from seepage through the dam.
The feasibility of protecting the face of the dam from the action of waves will hardly be questioned. The effect of the rainfall can easily be provided for, particularly on the main downstream slope, which falls but one foot in twenty-five.
It is impossible for water to flow over the top of a dam that is raised 50 feet above the water level, and if the dam and the underlying material were strictly impervious there would be no' water from the lake passing through it. On the other hand, if the material in or under the dam is somewhat pervious, there will be some water passing through which will appear at the surface, either immediately below the dam or toward the lower portion of the downstream slope.
The amount of water which will pass through somewhat pervious material in or under a damdepends upon the relation between the total head and the distance through the dam, and not, as is sometimes assumed, upon the total head against the dam.
If two dams are built under similar conditions, except that one has a thickness five times as great as the other, then there will be at the dam having the greater thickness only one-fifth as much seepage as at the other; that is to say, other things being equal, the seepage through a dam will be substantially in proportion to the depth of water against the dam, divided by the distance through the dam, giving what may be called the hydraulic gradient or slope of the line of saturation, which in this case does not exceed four per cent.
There have been many experiments on the vertical and horizontal filtration of water through various kinds of materials and with various hydraulic gradients. Some of these were made at the Lawrence Experiment Station of the Massachusetts Board of Health and others were made at the Vachusett reservoir of the Metropolitan Water Works, in Massachusetts, in connection with the construction of a dam similar to that proposed at Gatun. These experiments were made with materials of uniform character, through which more water would filter than through materials containing fine and coarse particles of the same average degree of coarseness, such as those found at the site of the Gatun dam, and they furnished results which confirm the statement already made that there would be no appreciable seepage under this dam.
If, however, a condition which does not exist be assumed, and all of the alluvial material beneath the embankment of the dam were considered to be a clean and reasonably uniform sand of
70
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
medium size, the total amount of filtration would then be for the whole length of the dam only about 10 cubic feet per second. Even this amount, which is much larger than would actually exist, is insignificant, and is less than one-half of one per cent of the water supply available in the driest season.
Few engineers who have been connected with the filtration of city water supplies would hesitate to provide works which would permit the amount of water above stated to rise to the surface without carrying with it any of the earth, because they have a much more difficult problem in connection with the downward filtration of water, where the works must be so built that the sand will not be carried down with the water.
The method followed in water filtration is to place coarse stones at the bottom of the filter and to cover these stones with finer and finer stones, and then with coarse sand, in order to retain the finer sand used for filtration. It is a simple operation to build the reverse of such a filter, which will permit the water to rise from the ground without carrying the earth with it.
It is not expected that there will be enough seepage through the Gatun dam to require any special treatment, but if there should be it could readily be taken care of by the method indicated, which has already been used with success in connection with a dam built-of sand on a sand and mud foundation at Jeypore, India.
Upward filtration occurs frequently in nature, where water comes from springs near the base of hills, often in sandy or gravelly material, without carrying with it any appreciable quantity of earth.
Many small earth dams and levees have failed, owing to a passage being made through them by some burrowing animal, or by the water following some pipe or other structure built through the dam, but in the present case it is not proposed to lay any pipe or other structure through the dam, and a burrowing animal could not burrow through where the shortest distance at the water line is 374 feet.
It seems to be impossible that any of the particles of earth buried in the body of the dam could be moved by a slow seepage of water, except such particles as were soluble, which might, in the course of ages, be dissolved and carried off by the seepage water.
Some of 'the views held in respect to the movement of material in the body of earth dams are based upon observations of very small dams, and often of those negligently constructed or of a very narrow section, and have no place in connection with a properly constructed large earth dam.
A dam such as the one proposed is very heavy, the weight upon its foundation being about one ton per square foot for each 20 feet in height of embankment. Under the highest part of the embankment the pressure would be six and one-half tons per square foot. It is obviously impossible that with such a pressure upon the material any particles could be moved by the extremely gradual seepage of water through the interstices due to a difference of water level of less than four feet in 100.
Such a dam as is here proposed if not absolutely earthquake proof is probably more nearly so than any other type of dam.
A comparison between the section of the Gatun dam and that of a few existing earth dams is shown on Plate XIV. The San Leandro dam of the Contra Costa Water Company, 120 feet high, which supplies water to Oakland, Cal., is the highest earth dam in the world, and it was constructed in part by sluicing. The Pilarcitos dam, 95 feet high, built in 1866 by the Spring Valley Water Company, which supplies water to San Francisco, is also one of the larger dams, although there are several others of about the same size, which have been successful.
The Jeypore dam is introduced on the diagram because it was built of sand on a foundation of sand, mud, and soil, and at a place where the material is very pervious, so that considerable water filters under and through the dam. It has, however, proved to be stable under these conditions.
The United States Reclamation Service has recently planned an earth dam to sustain a head of 100 feet with a width at the water line less than one-fourth that proposed for the Gatun dam and with a proportionately narrow base.
II
REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.
It will be noted that, these dams have a small section in proportion to the depth of water behind them when compared with the Gatun dam.
Earth dams are in such common use, are so generally indorsed by engineers, many of whom prefer them to other forms, that this extended discussion has been given only because the proposed use of earth dams has been unduly criticised in the report of the Board.
The nearest precedent in general design for the Gatun dam is the north dike of the Wachusett reservoir of the Metropolitan Water Works, of Massachusetts, which is two miles long and at the deepest place will have 65 feet of water against it. The highest portion of this dike was built on exactly the plan proposed for the Gatun dam, namely, the fine material of which the dike is composed was deposited on the fine underlying material without the use of either masonry or sheet piling to prevent the filtration of water. Under portions of this dike the depth to the rock is as great as at the Gatun dam.
PLAN OF THE DAM.
Plate XI shows a plan of the dam. Its total length from the locks to the westerly end is 7,700 feet. About midway in the length of the dam there is rising ground in which it is proposed to excavate, as already indicated, a diversion channel through which the Chagres will flow during the construction of the earth dam.
The regulating works, to be subsequently described, will be built mainly of concrete and will be located in part in the diversion channel and on each side of it. On each side of the rising ground referred to, and extending from it westerly to the high ground and easterly to the locks back of Gatun, there will be great earth embankments of the cross section already described, which will together contain 21,200,000 cubic yards of material. The westerly embankment will cross a French diversion channel. The easterly embankment will cross the French canal and the Chagres.
It will be feasible to begin at once the construction of one of the earth embankments, permitting the water to flow through the channel or channels at the site of the other embankment. It will also be feasible to begin at once the construction of the diversion channel, utilizing the material excavated in the embankments of the dam.
In the construction of the dam it is proposed to remove all trees, stumps, and roots from its site and to excavate the surface material to such an extent that the impervious material of the embankment will come in direct contact with the impervious clayey material which is found nearly everywhere in this region; also to do any other work required to cut off the flow through any pervious material which further investigations may disclose. For such work an allowance of $400,000 for all dams has been made in the estimate of cost.
The diversion channel is to have a minimum width of 150 feet and is to be excavated to sea level, or somewhat below it; although the lower part of the channel will be through indurated clay, it is proposed to place in it concrete where required for the protection of the channel or for the regulating works up to sea level, and to build in the channel to an elevation about four feet above sea level the foundations of certain piers and walls, which will remain for a time at this elevation, so that they will form only a slight obstruction to the discharge of flood waters.
After the earthwork of the dam reaches a suffiCient height to be beyond all danger of overflow, the piers and walls, which will be above water at low stages of the river, and which will have in them grooves for stop planks, will be built to higher elevations to furnish a ready means of turning the river through half of the diversion channel while the other half is pumped dry to permit the placing of the concrete of the regulating works, and by turning the river alternately from one side to the other the regulating works may be built without special difficulty.
REGULATING WORKS.
The general design of the regulating works is shown on Plate XIII. The central 150 feet of their length, which will be built up from the bottom of the diversion channel, is to be a solid mass of concrete, having its crest at elevation 69. The crest is to be made wide with the downstream slope two horizontal to one vertical, making an unusually strong section.
72
|
