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FLORIDA STATE BOARD OF CONSERVATION
J. T. Hurst, Supervisor

FLORIDA GEOLOGICAL SURVEY
Herman Gunter, Director









REPORT OF INVESTIGATIONS
No. 6





GEOLOGY AND GROUND LATER OF THE FORT LAUDERDALE AREA, FLORIDA

By

ROBERT C. VORHIS


PREPARED BY THE
GEOLOGICAL SURVEY
UNITED STATES DEPARTMENT OF THE INTERIOR
IN COOPERATION WITH THE
FLORIDA GEOLOGICAL SURVEY



1948












AGAI.

LiBRARY






CONTENTS


INTRODUCTION . . .
GEOGRAPHY. . . .
Location and area .. .. .
Topography and drainage . .
Climate ... .. ..
Population and development. .. ..* .
Development of municipal water supplies at Fort Lauderdale. ..
GEOLOGIC FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS. ....
TERTIARY SYSTEM. . . .
Mitcene series, ,
Hawthorn formation .. .
Pliocene series .
Tamiami ermation . . .
Caloosahatchee marl . .
QUATERNARY SYSTEM . .. .
Pleistocene and Recent series. . .
PFot Thompson formation . .
Miami oolite,. . .
Pamlico sand . .
Lake Flirt marl . . .
Recent organic soils. . .
PRESENT INVESTIGATIONS . . .
TEST-WELL STUDIES. . . .
Value and useb of test wells.. ,. . o
Test-well drilling. . ..
Results and interpretations . .
WATER-LEVEL STUDIES. . . ..
Water-stage recorders . .
Observation well drilling program . .
The leveling program. . . .
Results and interpretations . . .
TRANSMISSIBILITY . .
SALT-WATER ENCROACHMENT. . . .
SUMMARY AND CONCLUSIONS, . . .
BIBLIOGRAPHY . . . .


ILLUSTRATIONS


Plate
1 Map of southern Florida showing area of this report .
2 Average daily pumpage, Fort Lauderdale well field, ..
3 Geologic cross-section, . ...
4 A-Miami oolite north of Fort Lauderdale.. B--Water-stage
recorder on well G 221 near Fort Lauderdale water plant .
5 A--Drilling well G 513. B--Water-stage recorder on
well S 329. ... . . .
6 Hydrograph of well S 329. .. .
7 Water-table contour map of Fort Lauderdale area for
March 1, 1947 . . .
8 Water-table contour map of Fort Lauderdale area for
May 24, 1947 . .
9 Water-table contour map of Fort Lauderdale area for
June 13, 1947 ... .
10 Time-drawdown graph for well G 221. .
11 Chloride graphs . .
12 Map of Fort Lauderdale well field and adjacent areas .


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32







GEOLOGY AND GROUND WATER


of the

FORT LAUDERDALE AREA, FLORIDA I/

By

ROBERT C. VORHIS


INTRODUCTION

The City of Fort Lauderdale, being faced with the problem of a greatly

'increased demand for water, has had need for geologic and ground-water data on

which to base engineering decisions concerning the adequacy of the present well

field and possible locations for an additional well field. In order that the data

might be collected, the City of Fort Lauderdale, in October 1946, requested an

investigation by the U. S. Geological Survey and the study was started immediately.

Some of the work has been done as a part of the southern Florida water-resources

investigations that are being made by the U. S. Geological Survey in cooperation

with the Florida Geological Survey, but.most of the cost has been borne by the

City of Fort Lauderdale.

Little detailed work relating to ground-water conditions had been done

previously in the Fort Lauderdale area. An annotated bibliography of articles

with material relating specifically to geology and ground water of this area is

included at the end of this report.

The investigation was directed toward assembling, organizing, and

interpreting geologic and hydrologic data concerning the following:

(1) Areal extent and vertical distribution of water-bearing formations

(aquifers).

(2) Hydrologic and lithologic characteristics of these aquifers.


l/ Published with the permission of the Directors of the U. S. and Florida
Geological Surveys.

1













i----------i

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'FORT
LAUDERDALE


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10 0 10


IN MILES
20 30 40 50


MAP OF


SOUTHERN FLORIDA SHOWING


AREA OF THIS REPORT


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(3) Quality of water at various depths in aquifers.

(4) Present extent of and probable future salt-water encroachment.

(5) Elevation and shape of the water table in the well-field area

at various times of the year.

(6) Effect on the water table of pumping from wells, as shown by

the mapped cone of depression around the well field.

(7) Effect on the water table of drainage ditches and other developments.

(8) Average height of water table at various places in the area.

The office and field work was done under the general administration and

supervision of A. N. Sayre, Geologist in Charge of the Ground Water Division,

U. S. Geological Survey, Washington, D. C., and Herman Gunter, Director, Florida

Geological Survey, Tallahassee, Florida. Immediate supervision of the investi-

gation and of the writing of this report was by Garald G. Parker, District

Geologist, Miami, Florida. Additional help and advice was given by Nevin D. Hoy,

Geologist, M. A. Warren, Hydraulic Engineer, both of the Miami office, and

H. H. Cooper, Jr., District Engineer of the Tallahassee office. Water analyses

were made by Berton Law, Chemist, in the Miami laboratory of the U. S. Geological

Survey and by Mrs. Patricia Sherwood, who was then City Chemist of Fort

Lauderdale. The leveling was done under the direction of Kenneth L. Jackson,

Engineering Aide, Illustrations were drafted by Ross A. Ellwood, Engineering

Draftsman, and the typing was done by M. Marvine Melton and Laura G. Pollard.

Mr. J. H. Philpott, former City Manager of Fort Lauderdale, Mr. Charles

L. Fiveash, Superintendent of the Department of Water and Sewers, Dr. A. P.

Black, Consulting Chemist, Gainesville, Florida, and Messrs. L. C. Coe and

Guy Tanner, Miami, Florida, well-drilling contractors, have been especially

helpful and deserve much credit for the prosecution of the studies. In addition,

grateful acknowledgment is made for cooperation and assistance given by officials

and many citizens of the City of Fort Lauderdale,







GEOGRAPHY


Location and area


Fort Lauderdale is on the Atlantic Coastal Ridge, 25 miles north of Miami.

This ridge lies between the muck lands of the Everglades on the west and the

narrow mangrove swamps along the Atlantic Ocean on the east.

Most of the field work in connection with this report was done in the region

to the west of Fort Lauderdale as shown on plate 1. The area of intensive field

work is centered about the grounds of tha Fort Lauderdale Golf and Country Club,

in which the city well field is located (see pl. 12).



Topography and drainage


The Atlantic Coastal Ridge near Fort Lauderdale is approximately 5 miles

wide and has very little relief, averaging only 8 feet above mean sea level, the

highest elevation rising to about 20 feet.

Oolitic limestone, sand, muck, and marl are the geologic materials out-

cropping in the Fort Lauderdale Area. The sand and oolitic sands are very

permeable and permit rain water to penetrate downward rapidly. Drainage is largely

underground, thus accounting for the scarcity of surficial drainage channels. The

principal one is New River (see pl. 12) a shallow forked stream which heads about

6j miles inland and cuts through the coastal ridge to the Atlantic Ocean.

North Fork of New River is relatively unimproved and uncontrolled. Its

tidal portion extends upstream to a point approximately 21 miles northeast of the

well field, and salt water is free to advance upstream as far as the tides and the

fresh-water flow in the fork permit. The bed of North Fork is rather heavily

silted in its upper reaches and is therefore relatively impermeable; thus, the

salt water that occasionally extends to these reaches does not greatly contaminate

the surrounding ground water,







South Fork of New River is maintained as a navigable stream. Portions of

the channel have been dredged and numerous boat basins have been constructed,

the largest of which is shown near the bend in Riverland Road on plate 12.

Middle River, a sluggish, shallow forked stream about 2 miles long, empties

about 3 miles north of the mouth of New River into a salt-water lagoon in which

the Intra-coastal Waterway has been developed.

Between 1907 and 1918 most of the major drainage canals of the Everglades

were dredged, One of those, the North New River Canal, empties into the South

Fork of New River; and another, the South New River Canal, discharges both into

the South Fork of New River and into the Dania Cut-off Canal.


Climate


The climate of Fort Lauderdale is semitropical. The average annual rainfall

during a 31-year period of record is 65.19 inches, and the heaviest rainfall

occurs between May and November. The prevailing wind is from the southeast and

has an approximate average velocity of 13 miles per hour. Transpiration, evapo-

ration, and humidity are high the year around.

The average annual temperature is 75.2 degrees Fahrenheit. The average

monthly minimum and maximum temperatures are 68.5 and 82.0 degrees F. and occur

in January and August, respectively. The temperature of most samples of ground

water collected from depths below 30 or 40 feet is very close to the mean

temperature, or 76 degrees, The temperature of samples from shallower depths

varies with the seasons, ranging from about 70 to 82 degrees.



Population and development

The population of Fort Lauderdale has increased markedly in recent years.

The census of 1920 listed 2,065 inhabitants; in 1930 the population was 8,666;








in 1940 it was 17,996; and a.census in the summer of 1945 placed the total per-

manent population at 26,185. The population is greatly increased each winter by

the influx of tourists and by many home-owners who live there only during the

winter months. The Fort Lauderdale Chamber of Commerce estimates that the total

of winter residents in 1946 was between 60,000 and 65,000.

The rapid growth in population that has already occurred has taxed the capac-

ity of the present water treatment plant, and has made necessary the construction

of an addition, This will more than double the original capacity of the plant and

will permit greater consumption by present users as well as permitting water to be

supplied to those parts of the city to which mains have not yet been extended.



Development of municipal water supplies at Fort Lauderdale


For many years the water supply for Fort Lauderdale was drawn from two wells,

6 inches in diameter and approximately 60 feet deep, located to the northwest of

the intersection of Andrews Avenue and 2nd Street S. W. Mr. Charles Fiveash,

Superintendent of The Department of Water and Sewers, reports that these wells

would yield considerably more at high tide than at low tide suggesting that river

water might be able to enter the wells. Inasmuch as New River was polluted with

considerable amounts of untreated sewage, it was decided to develop a new well

field and locate it sufficiently far to the west to be free from the possibility

of pollution. Accordingly, the two original wells were abandoned in June 1926.

As an interim supply during the construction of the present water plant, two wells

(S 894 and S 895 on plate 12), one 10 and the other 12 inches in diameter, were

drilled to depths of 90 and 104 feet, respectively, at Broward Boulevard and 14th

Avenue. These wells served as the source of supply from June 1926 until December

1927, when the present well field and plant, to the west of Fort Lauderdale, were

put in operation. The 12-inch well (S 895) is still maintained as a standby for

emergency use,







The present water plant wasl:ompleted late in 1927 and has been treating

all water since supplied to the city. Additional treatment facilities now under

construction will raise the capacity of the plant from 6 to 14 million gallons

a day.

The city supply wells of Fort Lauderdale are in two different but adjacent

groups and are therefore generally thought of as composing one well-field area.

The first group consists of nine wells on the grounds of the Fort Lauderdale

golf course, The golf course is near the western shoulder of the Atlantic Coastal

Ridge, approximately 7 miles from the ocean and 14 miles north of the North New

River Canal, The second group is composed of two wells at the municipal water

plant on the crest of the Atlantic Coastal Ridge, approximately 1 mile southeast

of the first group. Land-surface elevations in the well-field area average about

9 feet above mean sea level.

The 11 wells are gravel-packed and are pumped at a total maximum rate of

approximately 6,600 gallons per minute. This is by no means the maximum capacity

of the wells, a figure that has never been determined, but the present pumpage

certainly is only a fraction of what these wells would yield if pumped to capacity.

The City Water Department has not deemed it wise to pump these wells at greater

rates for fear of causing salt-water encroachment.

Eight wells, Nos. 1, 2, 3, 4, 5, 6, 11, and 12, were drilled in 1927; Nos.

7 and 8 were drilled in 1940; and Nos. 9 and 10 were drilled in 1945. Well 1

does not contribute to the City supply but is used exclusively for watering the

golf course. It was drilled and developed in the same manner as the other wells.

Wells 11 and 12 are the two that are located a hundred feet east of the water

plant (see pl. 12).

All except No. 11 are 12-inch wells, and all except Nos. 8, 11, and 12 were

finished with casing set approximately 80 feet below land surface. All had 10

feet of open hole unscreenedd) below the bottom of the casing. Well 12 was cased







to a depth of 92 feet below land surface. Mr. Fiveash reports that at the time

the wells were completed the water table averaged about 3 feet below land surface

or 6 feet above sea level,

In 1940, two new gravel-packed wells 12 inches in diameter, (Nos. 7 and 8),

were completed, the casing being seated 80 feet below land surface in No. 7 and 62

feet below land surface in No. 8. A 6-inch diameter screen, 35 feet long, was

installed below the casing of each well.,

During 1940 the older wells (all other than 7 and 8) were deepened 45 feet,

which allowed the insertion of 35 feet of screen with 10 feet of blank pipe below

the screen. All the wells were then gravel-packed.

The daily pumpage from these wells has ranged in the period from January

1930 to the present from a low of 234,000 gallons per day to a maximum of

6,615,000 gallons per day. The average daily pumpage has gradually increased over

the years, as shown in plate 2, a graph of the average daily pumpage from the Fort

Lauderdale municipal wells during the period 1930-1947. Records are not available

for pumpage prior to 1930.












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3







GEOLOGIC FORMATIONS

AND THEIR

WATER-BEARING CHARACTERISTICS



The surface materials of southeastern Broward County in the vicinity of Fort

Lauderdale are formed largely by a mantle of several feet of sand (Pamlico sand)

of late Pleistocene age. On the western edge of the Atlantic Coastal Ridge muck

is found, especially in the vicinity of natural drainage channels. The mantling

nature of these materials plus the low relief and lack of any deep cuts in the

rock make it impossible to determine the geologic nature of the region from rock

exposures. Examination of shallow exposures in the banks and spoil of the Ever-

glades drainage canals and study of well-log data are the only reliable sources of

geologic information. An east-west cross section along the North New River Canal

from Fort Lauderdale to 20-Mile Bend is shown in plate 3.

In southeastern Florida strata older than the Hawthorn formation are of no

importance as a source of potable water because the water in older strata is

highly mineralized, The water is under artesian pressure but its quality is such

that no use has been found for it, except for limited row-irrigation of garden

vegetables and lawn sprinkling. It corrodes pipe so rapidly that it has been

found to be not economically profitable to make use of the artesian pressure,. All

the known pre-Hawthorn strata have these same water-bearing characteristics.

Inasmuch as their water is unusable for public supply these formations are not

discussed in this paper.


TERTIARY SYSTEM

Miocene series

Hawthorn formation

In southern Florida the Hawthorn formation is composed predominantly of

greenish-colored sediments that were laid down in a shallow, warm transgressing






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Tc
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Th .Tc
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QUATERNARY
QO = RECENT ORGANIC SOILS
QI = LAKE FLIRT MARL


Qp =


PAMLICO SAND


Qm = MIAMI OOLITE
Qf = FORTTHOMPSON FORMATION
TERTIARY
TC = CALOOSAHATCHEE MARL
Tt I TAMIAMI FORMATION
Th HAWTHORN FORMATION


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SCALE IN MILES
0 I 2 3 4 5


PLATE 3 EAST-WEST


CROSS-SECTION


ALONG NORTH NEW


RIVER CANAL FROM


20 MILE BEND TO FORT LAUDERDALE


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-100


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-200


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sea which flooded an eroded land surface. Thus, the lower contact is unconformable.

These marine deposits may be blue-green clay, gray-green marl, or varying shades

of greenish sand. The change to greenish-colored sediments gives a sharp contrast

with the predominantly buff to gray color of the overlying beds and makes for easy

identification of the upper contact.

In the coastal area the Hawthorn formation is about 400 to 601 feet thick.

Because it is composed largely of clay and marl, the formation is relatively

impermeable and therefore acts as an aquiclude (non-water-bearing bed) between the
water
highly mineralized artesian/of the underlying Eocene and related limestones and

the fresh water in the overlying formations of Pliocene and Pleistocene age.

Locally, wells may be developed in the Hawthorn but the water yielded is generally

too highly mineralized for most purposes and occurs in rather limited quantities.

The water from the Hawthorn formation is significantly different from water

of the overlying formations. It has more dissolved solids, especially of magnesium,

sodium, potassium, and sulfate. The water is generally too highly mineralized to

be potable but is suitable for other purposes, such as use by stock and for

irrigation.


Pliocene series

Tamiami formation

The Tamiami formation is named for deposits "composed principally of white

to cream-colored calcareous sandstone, sandy limestone, and beds and pockets of

quartz sand" (Parker 1944, p. 64).

Near Fort Lauderdale the Tamiami formation interfingers with the contem-

poraneous Caloosahatchee marl (see description of Caloosahatohee marl below).

Inasmuch as the Tamiami has no fauna distinct from faunas of the other Pliocene

formations of southern Florida, it is impossible to distinguish the Tamiami except

by lithologio characteristics. For this reason the cavernous sandy limestones

and caloareous sandstones of Pliocene age a'e considered to be Tamiami,






At Miami the Tamiami formation averages about 100 feet thick. It has been

found to be one of the most productive water-bearing formations ever investigated

by the U. S. Geological Survey, ranking with coarse, clean, well-sorted gravel in

its capacity of transmitting water (Parker and Cooke, 1944, p. 65). In Broward

County this formation is cavernous and permeable but the interfingering with the

sand of the Caloosahatchee marl makes for a lower yield than in Dade County, where

there is little such interfingering.

Water from this aquifer is generally very good in quality except in zones

where salt-water contamination has occurred.


Caloosahatchee marl

The Caloosahatchee marl underlies most of the Everglades and is found in the

subsurface eastward under the Atlantic Coastal Ridge. According to Parker and

Ccoke (.1944, p. 59) "The Caloosahatchee marl is a littoral (beach) and neritic

shallowo, off-shore zone) deposit composed of sand, silt, clay, shells, and often

enough calcareous material to make it a true marl. It contains many local beds or

lenses of pure sand or clay, but the usual condition is just what one would expect

of a deposit where constantly shifting currents acted upon a shallow sea bottom

and shores adjacent to a low land mass that contributed only fine sediments." The

large number of perfectly preserved shells is an indication that the water was

deep enough to prevent breakage due to violent agitation by waves (Cooke, 1945, p.

214).

In the Fort Lauderdale area the Caloosahatchee marl occurs as gray to green

marl, fine to medium-grained quartz sand, shelly sand, sandy marl, and a greenish

clay. It interfingers with the contemporaneous Tamiami formation as shown in

plate 3. In the logs of the test wells, the soft, relatively impermeable sandy,

shelly, and marly sediments of Pliocene age are considered to be the Caloosahatchee,

and the limy sandstones and sandy limestones to be the Tamiami. Separation by

paleontological means is not possible, as the faunas of both are so similar.
10













T


-.4
It t


A. MIAMI OOLITE EEBPOSED IN A ROCK PIT NCRTH OF FORT LAUDERDALE.
NOTE CROSS-BEDDING AND SOLUTION HOLES IN THE OOLITE. PAMLICO
SAND IS SHOWN AS CONES AT THE BASE OF THE SOLUTION HOLES AND
AS A MANTLING LAYER OVER THE OOLITE. THE 6-YEAR OLD BOY GIVES
SCALE.


T


4 urt$ \~ *
"'rIr
'I(


B. WATER-STAGE RECORDER ON WELL G
WATER PLANT.


221 NEAR FORT LAUDERDALE


PLATE 4






Florida have been built.

The Miami oolite probably was largely deposited during the Sangamon inter-

glacial stage. The melting of the continental glaciers formed during the preceding

Illinoian stage was so extensive that the ocean level rose 100 feet above its

present level. Later, as the glaciers began to re-form, the sea level dropped

first to 70 feet and then to 42 feet (above present sea level), At all three

levels marine terraces were formed, and it was largely during these high stages

of sea level that the Miami oolite and related formations were deposited. The end

of deposition was brought about by a fall in ocean level caused by the advance of

glacial ice during the early part of the Wisconsin stage.

The Miami oolite is a fair source of water but the formation is so thin and

near the surface that comparatively few wells are developed in it. The large

numbers of vertical solution holes make for greater vertical than horizontal per-

meability, but even so the formation is generally so permeable that water can be

pumped quite easily from it in most places. Water found in the oolite is hard--a

typical calcium-bicarbonate water. Unless contaminated it usually contains from

6 to 20 parts per million of chloride; locally there may be considerable color of

organic origin.


Pamlico sand

The Pamlico sand consists largely of quartz sand and is of late Pleistocene

age. Over large areas in southeastern Florida it overlies the Miami oolite and

fills natural channels and solution holes in it. In color the sand ranges from

dazzling white through shades of yellow and brown to red or black. The yellowish

to red colors are due to iron oxide but the gray to black color is generally due

to organic materials that adhere to the surfaces ofthe sand grains or fill the

interstices between them.

The Pamlico sand was probably laid down at the time of the latest Pleisto-

cene high-level sea, when the shore line was 25 feet above the present one. The

'12






sand was derived; from previous deposits farther north; and was washed southward

by ocean currents and waves. Its principal original source is probably from the

rocks of the Piedmont in Georgia and Carolinas.

The ocean level presumably stood very low during the several glacial stages

that preceded the late Pleistocene 25-foot rise, because the transverse glade

valleys, having depths as great as 100 feet, were then formed by streams origina-

ting in the Lake Okeechobee-Everglades area. Thqse stream valleys indicate consid-

erable erosion. Pamlico sand now fills these valleys and mantles the surface of

the oolite.

The Pamlico sand in the transverse glades generally is a source of potable

ground water. The sand is not permeable enough to yield as much water as can be

obtained from the cavernous rocks of the Tamiami formation, but it is a source of

adequate supplies where nnly small quantities are needed. The water is fresh,

where not contaminated by encroaching salty water, but it may have an objectionable

coler due to organic materials, and locally it may have the characteristics of

"swamp water", with considerable color and a smell of hydrogen sulfide.

Plate 4A shows Pamlico sand mantling the Miami oolite and filling solution

holes.


Lake Flirt marl

The Lake Flirt marl was deposited in the Everglades and parts of the coastal

marshes of southern Florida in areas of shallow, open water, In places it over-

lies the Pamlico sand, the Fort Thompson formation, and the Miami oolite, It has

a thickness of about 1 foot in western Broward County (see pl. 3).


Recent organic soils

Peat and muck deposits accumulated in perennially flooded areas of the Ever-

glades in both late Pleistocene and Recent time. These deposits are comparatively

thin in the Fort Lauderdale area of the Everglades, and overlap the western edge

of the Atlantic Coastal Ridge.






PRESENT INVESTIGATIONS


The present investigations have continued and expanded the work previously

done in the course of the southeastern Florida water-resources investigations,

which were financed until 1944 by theiU. S. Geological Survey in joint cooperation

with Dade County and the cities of Miami, Miami Beach, and Coral Gables, Since

that time the U. S. Geological Survey and the Florida Geological Survey have

continued observational and research work in Broward County as a part of the joint

State-wide investigation of geology and ground water.

The City of Fort Lauderdale has largely financed the additional work, which

included (1) the drilling of five test wells averaging about 200 feet in depth

(G 512 G 516, incl.); (2) re-installation of the water-level recorder on well

S 329, located on the northeastern edge of the Fort Lauderdale golf course; (3)
installation of another such recorder on well G 221, located on the east side of

State Highway 7 about 400 feet northwest of the municipal water plant; (4) drilling

of 52 shallow observation wells; (5) obtaining and recording data on 90 private

wells; (6) periodic measurement of water levels; (7) collecting and analyzing for

chloride content water samples from 116 wells; (8) establishment of a net of levels

about 27 miles long based on the U. S. Coast and Geodetic Survey mean sea level

datum plane; (9) tying in all measuring points to this datum; and (10) preparation

of charts, diagrams, and maps to illustrate these data. The preparation of a base

map was one of the earliest and most time-consuming jobs, for it was found that

no accurate large-scale map of this area existed prior to this investigation.
The above steps have been taken to obtain information about current ground-

water conditions. In addition it is planned to continue, in cooperation with the

City of Fort Lauderdale and the Florida Geological Survey, observations to deter-

mine long-time trends. Thirty-six key wells located in or adjacent to zones of

salt-water encroachment are to be sampled monthly for chloride content. It is also

proposed that water-table maps of the well-field area be prepared at monthly





intervals. Three such maps for selected times during late winter and spring of

1947 are included in this report (pls. 7-9).


TEST-WELL STUDIES


Value and uses of test wells


Test-well drilling has been the chief source of information on the geology

and ground-water hydrology of the Fort Lauderdale area. The nature of the under-

lying rocks has been ascertained, and ground-water samples from numerous intervals

in depth have been collected and analyzed. The usefulness of the wells was not

ended as soon as their drilling was completed; measurements of water level are

made periodically and samples of water are collected at monthly intervals to de-

termine whether salt-water encroachment is occurring.



Test-well drilling


The five test wells (G 512 through G 516) drilled during the course of the

current investigations were put down by the jet-percussion method. Plate 5A shows

the rig used in drilling these wells. At the start of the drilling a 20-foot

length of 2-inch casing was driven down. The material forced into the casing was

then jetted out, using a 1-inch jetting line, and the jetting was continued to a

depth approximately 10 feet below the end of the casing. The jetting line was

then removed, a pump was connected and, if possible, a water sample was obtained.

Pumping continued for a long enough period to make certain that the sample would

not be contaminated or diluted by water introduced into the bed during the jetting,

After the sample had been collected, a section of casing 10 feet long was added

and driven down to land surface; then jetting was resumed. Occasionally no water

samples could be collected, owing either to low permeability or to very fine sand

"heaving" in the casing and making pumping impossible. This type of "running
.15



































A. DRILLING WELL G 513


B. WATER-STAGE RECORDER ON WELL S 329 NEAR CITY WELL 3 ON
FOIT LAUDERDALE GOLF COURSE.


PLATE 5


c






sand", more properly termed quicksand, is rather common in some parts of the area,

In many instances it was necessary te drive a sand-point into the sandy materials

below the bottom of the casing in order to obtain water samples. Every effort

was made to obtain representative water samples at regular intervals as the test

wells were deepened.

Results and interpretations


Interpretations of the well logs show that during Pliocene time deposits

of fine-grained quartz sand were laid down alternately with deposits of calcareous

sediments ranging from sandy limestone to rather pure marl. The sand is typical

of littoral (beach) and neritic (near-shore) deposits derived from a nearby low-

lying land mass composed largely of sandy materials. It is considered to be an

eastward extension of the Caloosahatchee marl. The limy sediments are typical

of shallow-water deposits of the open ocean, laid down far enough from land to

have included little detrital material. These limestones are considered a

northern and eastern extension of the Tamiami formation, which is typically

developed in Dade and Collier counties. Using these lithologic characteristics

as a basis of formation identification, it is apparent that there is considerable

interfingering between the two formations. This interfingering is probably a

product of alternating landward and seaward migration of the shore line due to

minor changes in sea level during the Pliocene.

Until the five test wells were drilled it was believed that limestone of

the Tamiami formation would be found to be the principal component of the aquifer

in the area, and that the permeability would be somewhat lower than that found in

Miami, However, results of test drilling and pumping show that the sand and silt

of the Caloosahatchee marl are abundant and, with minor quantities of admixed

clay, markedly reduce the transmissibility and yield of the aquifer as a whole.

A bed of fine white quartz sand, possibly of Caloosahatchee age, is found






to underlie the Miami oolite in nearly all the wells of the Fort Lauderdale area.

It is uncertain whether the individual beds or layers underlying this sand layer

have any considerable horizontal continuity. The geologic section included here-

with (pl. 3) shows the various beds correlated by means of lithology, but because

of lack of sufficient test wells it may be somewhat in error, Many of the beds

were deposited as shallow marine and littoral sediments in an environment where

currents and waves sharply limited the area in which any one type of sediment

could be deposited; therefore, exact correlation of such beds is well-nigh

impossible.





WATER-LEVEL STUDIES


Water-stage recorders

Two continuous automatic water-stage recorders are installed on observation

wells in the Fort Lauderdale area. These provide the basis for a record, called

a hydrograph, which shows the rise and fall of water levels plotted against time.

These two recorders are shown in plates 4B and 5B and a hydrograph for well S 329

is shown in plate 6.


Observation well drilling program

In order to prepare a water-table map it is necessary to have a number of

wells in which depth-to-water measurements can be taken. At the start of the in-

vestigation only 15 wells suitable for this purpose were available; therefore it

was found necessary to drill an additional 52 shallow observation wells to furnish

needed control.

The locations were chosen in several ways. In order to determine the effect

of the pumping of the city wells, observation wells were installed 10 feet from

each city supply well, although in some places this distance ranged up to 100 feet.

Shallow wells were also drilled approximately 1,000 feet from each two adjacent

city supply wells, and additional shallow wells were drilled at approximately half-

mile intervals eastward into Fort Lauderdale, northward to Plantation Road, and

westward to Peter's Canal (see pl. 12),

The observation wells range in depth from 11 to 28 feet and are nearly all

equipped with sand points. After being drilled each well was pumped sufficiently

to be certain that it would respond quickly to water-table fluctuations.

In addition to the above wells, 10 observation points were established for

water-level measurements on streams, canals, and drainage ditches. These give

additional information and control for preparing water-table maps.

The leveling program

The datum plane used by the U. S,.Geological Survey in preparing water-table

maps in southern Florida is U. S. Coast and Geodetic Survey mean sea level (1929
18

















































I !!


- t-i .L


PLATE 6


HYDROGRAPH OF WELL S-329


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adjustment). ,This datum plane is used by the Everglades Drainage District, by
many municipalities, and is the most satisfactory datum plane for use in ground-

and surface-water studies.

In order to determine accurately the water-table height with respect to

mean sea level, it is necessary to know the elevation of the measuring point on

each observation well. This was obtained by running a net of levels from a

second-order level line established by the U. S. Coast and Geodetic Survey. The

line runs along State Highway 7 through the area of this report. The U. S.

Geological Survey level net in the well-field area includes more than 27 miles of

lines that were run and tied in to the above-mentioned U. S. Coast and Geodetic

Survey line.

The points from which measurements are made and to which elevations are

accurately established are usually the tops of the well casings. Inasmuch as the

depth to water can be determined to a hundredth of a foot (the limit of accuracy

to which a wetted steel tape can be read easily), it was necessary that the eleva-

tions be established to a corresponding accuracy and 27 miles of closed level

lines were run to accord with such a standard.

The well elevations are shown on plate 12 in italics. The measuring point

in each case is the top of the well casing, the well cap being removed.


Results and interpretations

Three maps of the water table in the Fort Lauderdale area are included with

this report. Plate 7 shows the water table as of March 1, 1947, and is typical

of the conditions found in late winter of 1947. Plate 8 shows the water table on

May 24, 1947, very close to the end of a dry spring period. Plate 9 depicts the

water table as of June 13, 1947, after a week in which there were a number of

very heavy rains.

The contours, which are drawn with an interval of 0.25 of a foot, show that

pumpage from the well-field area has only a slight effect on the water table. No

deep cone of depression is ever apparent, and the usual situation found is that
19






































































S8700


LEGEND
2.75-- WATER TALEt CONTOURS 10.25 FOOT INTERVALS)
o MON"-LOWING WELL
O PUBLIC SUPPLY WELL
A WELL WITr AUTOMATIC WATER STAGE RECORDER
S9 4A WELLS. COLOIDE ODATA AVAILABLE
-* OBSERVATION POINT OR STAlf GAGf


DATUM: MEAN SEA LEVEL, U.S.C. 0O.S.


MAP OF
FORT LAUDERDALE
WELL FIELD AREA


MARCH 1. 1947
MARCH 1947






































































S TOg


LEGEND
2.7- WATER TAsLIC CONTOURS o10.5 FOOT INTEIIVASL
0 NON-PLOWING WELL
O PUBLIC SUPPLY WELL
A WELL WITH AUTOMATIC WATER STAGE RECORDER
SS 4A WELLS, CHLOniDE DATA AVAILABLE
4. OBSERVATION POINT OR STAFF GAGE


DATUM- MEAN 4EA LEVEL. U.S.C. l 0.S.


MAP OF
FORT LAUDERDALE
WELL FIELD AREA
SCALE IN FEET

MAY 24, 1947





































































SS700


LEGEND
2.75- WATER TABLE CONTOURS (0.25 FOOT INTERVALS)
O NONP-LOWING WELL
0 PUBLIC SUPPLY WELL
A WELL WITH AUTOMATIC WATER STAGE RECORDER
QO 4 WELLS. CHLORIDE DATA AVAILABLE
OBSERVATION POINT OR STAFF GAGE


DATUM: MEAN SEA LCVt., U.S.C. B G.S.


MAP OF
FORT LAUDERDALE
WELL FIELD AREA


S JUNo E IS, 1O
JUNE 13, 1947






the contours,.instead of ;beihg'smoothly curved lines on the map (as they would be

if no pumpage occurred), are slightly deflected in the area of pumpage. Greatest

effect of pumpage on the shape'of the water table is shown on Plate 8 where a

closed contour (1.50 feet) occurs at the water plant with slight bending of ad-

jacent contours, and a small area is similarly affected on the golf grounds. Note

on this same plate the ground-water mound built up by irrigation at the west end

of Peters Road.

The contours indicate that ground-water flow is generally from northwest to

southeast, on a very gentle gradient averaging approximately 1 foot to the mile.

By drawing flow lines normal to the contour lines on the water table, the area

contributing water to the well field can be delineated. The ground water con-

tributing to the wells originates from rainfall on the well field itself and im-

mediately to the northwest; it is not derived from areas far out in the Everglades,

as many people have believed,

The water table maps indicate that no over-development of ground-water

supplies in the well-field area has taken place.



TRANSMISSIBILITY

The capacity of a formation to transmit water may be expressed by the

coefficient of transmissibility, which is the number of gallons of water that will

move in 1 day under a unit hydraulic gradient (1 foot per mile) through a vertical

strip of the aquifer 1 mile wide and having the full depth (or thickness) of the

aquifer.

The coefficient of transmissibility for the aquifer in the Fort Lauderdale

well-field area is approximately 1,200,000. This means that 1,200,000 gallons of

water will flow in 1 day through a vertical strip of the aquifer 1 mile wide under

a hydraulic gradient of 1 foot per mile, The graphical method (Cooper and Jacob)

used in arriving at this Value is shown in plate 10. Drawdown and time data were




a m %4 Co a N W Ii a CO *o.- P4 ca -" u D Go 6)

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PLATE 10






taken from water-stage recorder charts; rate of pumping is the quantity reported

for city supply wells 11 and 12. The falling off of the last two points on the

graph indicates a boundary effect, or reduced transmissibility as water levels

decline, or both. The value given for the coefficient of transmissibility is

tentative and indicates only the order of magnitude for the coefficient. In order

to obtain a value on which important engineering decisions may be based, a care-

fully controlled pumping test would be necessary.


SALT-WATER ENCROACHMENT


Samples of 'ground water were collected from all test wells at frequent

intervals during the drilling. In addition to the test-well samples, a large

number of water samples were collected from wells in areas of possible salt-water

encroachment, and from most of the observation wells.

Samples from wells not equipped with pumps were collected by means of a

portable. power pump or a common pitcher pump. In collecting samples from wells in

which the water had been standing unpumped for a relatively long period of time,

sufficient pumping was done to clear the well and obtain a representative sample

of water from the aquifer.

All analyses of these samples for chloride content were made in accordance

with the standards of the U. S. Geological Survey. The error is less than 1 per-

cent, regardless of the salt concentration.

In addition to using chemical analyses for chloride determination, the

electrical-resistivity method of geophysical prospecting was used to test for the

presence of salt water at depth. The locations of the test sites are shown on

plate 12. The final results obtained from these tests are not available as yet.

However, field computations indicate that the method is successful and that min-

eralized water underlies the entire area at differing depths. A subsequent report

will give the detailed results.







Chloride encroachment in the Fort Lauderdale area may be from any of four

sources" (1) from the ocean; (2) from ocean-water tongues in canals; (3) from

Everglades Drainage District canals into which salty Everglades ground water has

seeped; (4) from the salty connate.or residual water which underlies the area at

a depth of from 150 to 300 feet and more.

In the Fort Lauderdale area encroachment from the ocean directly into the

aquifer is believed to occur only within a mile or so of the shore. Owing to a

number of factors, the rate and extent of ocean-water encroachment at Fort Lauder-

dale has not been as fast nor as extensive as in Dade County near Miami. These

factors include (1) lower transmissibility; (2) layers or beds of sediments that

are relatively impermeable; (3) less pumpage; (4) higher water table.

In part of the Miami area encroachment from the ocean at depth in the aquifer

has been computed to be as great as 890 feet per year and to have averaged about

235 feet per year (Parker, 1945 b, p. 539). The rate of encroachment in the Fort

Lauderdale area has not been computed but it is probably much less, owing to the

above-mentioned factors. This type of encroachment is not found in any of the

area shown on plate 12.

The most serious threat of well-field contamination from ocean water exists

in the lateral movement of salt water from North New River canal. Plate 11 indi-

cates the high chloride content found from time to time in this canal as far in-

land as the control lock and dam. Test well G 514, located at 9th Street and 12th

Avenue Southwest in Fort Lauderdale, shows marked contamination from this source.

At a depth of 116 feet below land surface the chloride content was 178 parts per

million, but only 10 feet deeper, at 126 feet, it was 2,690 parts per million.

This chloride content is far too large to have been derived from the connate salt

water which underlies all of south Florida, for connate water at this elevation

has been flushed out in areas much farther to the west. Further, the chloride

concentration is too great to be explained by seepage of salty Everglades water







into the canal. The profiles of ocean-water encroachment published by Brown and

Parker (1945, figs. 11-13) indicate that, where there is direct encroachment of

ocean water, the chloride content increases with depth more rapidly than is the

case in well Q 514. Thus, by a process of elimination, the source of the contami-

nation is concluded to be ocean-water tongues that have intruded along the bed of

North New River.

Other wells along New River show contamination from this source. These in-

clude wells S 827 and 828 on the North Fork df New River and wells S 808 and S 820

on the left bank of the South Fork of New River. Pumping the above wells has

drawn in salty water from the canal. On the right bank of the river (see pl. 12)

wells S 862, S 866, S 864, S 868, S 870, S 872, and S 874 all show even greater

contamination. This is due to slow, sustained movement of the ground water from

northwest to southeast, carrying contaminated water with it contamination that

seeped both downward and laterally and was carried farthest in the most permeable

parts of the aquifer.

Chloride tests on water from test wells G 512 and G 513 illustrate this type

of encroachment. In well G 512 a zone of contamination in which the water con-

tained 180 parts per million was found at 42 feet. This was the highest salt

content for any horizon in the entire 175-foot depth of the well. In well G 513

zones of lateral intrusion were found 10 and 52 feet below land surface. In these

two zones the chloride content was 59 and 52 parts per million, respectively, The

beds enclosing these zones contained water of only 28 parts per million or less.

The encroachment was selective, occurring only in the more permeable zones.

This selective type of encroachment occurs especially during dry periods

when there is little or no seaward flow in the canals and rivers; instead, there

is an inland flow of ocean water. In dry weather wells are pumped most heavily

and this serves to accelerate the rate and amount of encroachment. This type of

intrusion can be prevented only by (1) continuous fresh-water flow sufficient to


23






keep the salt water swept out of the canals; or (2) installation of locks at some

downstream site,

Another area in which lateral encroachment has occurred is in the vicinity

of the Dania plant of the Florida Power and Light Company. The water in well

S 330 at this plant contained 213 parts per million of chloride when first sampled
by the U. S. Geological Survey in November 1940 (see pl. 11). This indicates

salt-water intrusion because in this area the normal chloride content of ground

water is only about 20 parts per million, and canal water from the Everglades has

not been observed to exceed 148 parts per million in the North New River Canal.

In subsequent samplings the amount of chloride in well S 330 decreased gradually

to 53 parts per million, with but few slight variations. Then the effects of

drought became noticeable and the chloride content rose to 615 parts per million

in October 1943. Fall rains of that year pushed the encroaching salty ground

water oceanward and gradually reduced the concentration to 458 parts per million

by April 1944. Since then, reduced flow in the South New River Canal and a

lowered water table have permitted several salt-water advances such as are shown

for the North New River Canal in plate 9. A maximum chloride content of 2,700

parts per million was reached in November 1945, and it has since declined to 640

parts per million (in July 1947).

Contamination from mineralized canal water where the saltiness is picked up

by inflow of salty ground water in the middle and upper Everglades operates in the

same fashion as the type described immediately above. The results, however, are

far less serious. The chloride content of the North New River Canal at the up-

stream side of the coastal lock and dam during the period from February 1941

through April 1947 has been observed to vary from a low of 49 parts per million

to a maximum of 148 parts per million (see pl. 11).

These amounts are not sufficient to render water unfit for drinking, but it
is important to recognize this type of intrustion for what it is and not confuse





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it with intrusion by way of ocean-water: tongues. Once this canal water seeps into

the ground there is little likelihood that its chloride content will be further

concentrated. Instead, its chloride content will be diluted by mixing with fresh

ground water.

The chloride content of uncontaminated ground water may range from approxi-

mately 4 to 30 parts per million. In areas adjacent to canals or rivers any con-

tent in excess of 30 parts per million but less than 150 parts per million, may

represent encroachment by contaminated canal water from the Everglades. Any con-

tent higher than approximately 150 parts per million is evidence that the contami-

nation originated from ocean water.

Salty water underlies all of southern Florida and is found in all areas if

drilling is carried deep enough. The observed range in depths to salty water in

the Fort Lauderdale well-field area is 150 to 225 feet. One test well in the area

(G 516, 200 feet deep) failed to show salt water, but it is probable that salt

water can be found even under this well, probably within the next 25 to 50 feet of

depth. This salty ground water, especially at great depth, may be of connate

origin (water deposited with the sediments in which it is found), but it is more

likely that it is modified sea water that penetrated downward during the late

Pleistocene when this area was submerged beneath the high-level seas of an inter-

glacial stage. Since then the ocean level has not declined enough or sufficient

time has not elapsed for this water to be completely drained or flushed out and

replaced by fresh water, but it has been altered by cation exchange and dilution.

In well G 515, near the center of the Fort Lauderdale golf course, a

chloride content of 300 parts per million was found at a depth of 165 feet below

land surface and this increased to 600 parts per million at 183 feet. It is

possible that heavy pumping would cause this salt water to be drawn upward, thus

acting as another source of contamination. In fact, this salty ground water

probably is the source of the higher chloride contents now found in the raw water







of the municipal supply, Records kept by Mr. Charles Fiveash, Superintendent of

the Department of Water and Sewers, indicate that the chloride content of raw

water from the Fort Lauderdale well field has increased gradually since the well

field was put in operation. These records show that the average chloride content

of the water in the well field when pumping first started in 1927 was about 10

parts per million. Records are available for average chloride content during

6-month periods from 1932 to the present. The average for the first 6 months in

1932 was 13 parts per million. During the last 6 months of 1932 the average was

12 parts per million.

The content has gradually increased, with some fluctuations, and for the

first 4-months of 1947 was 20 parts per million. The highest 6-month average

was 24 parts per million for January-June 1944. The lowest 6-month average was

for the last half of 1933, only 10 parts per million.


SUMMARY AND CONCLUSIONS


The lithology of the well-field area has been determined from study of the

cuttings obtained from six test wells, among which is G 515 in the grounds of the

Fort Lauderdale golf course. A large part of the upper section of the aquifer

has a low permeability, being composed of very fine-grained quartz sand mixed with

clay and marl. The most permeable zone at well G 515 is found between 104 and 123

feet below the land surface, and it is in this zone that future wells can best be

developed. This permeable zone is characterized by discontinuous layers of sandy

limestone or calcareous sandstone up to 6 feet thick, associated with permeable

shelly sands. The water from this horizon is in a semi-confined state, owing to

the relatively low permeability of the overlying beds. The water is under no

artesian pressure as such that is, it does not rise in wells above the level at

which it is struck but when water is removed by pumping the inflowing water

finds it easiest to travel in a more or less horizontal rather than a vertical

direction.,
.26





Lenses of permeable sand, which in some places have considerable

horizontal extent, interfinger with the beds having relatively low permeabili-

ty in the upper section of the aquifer, and it is in these permeable lenses that

salty water moves out of the tidal canals most easily.

Hydrologic studies indicate that ground-water flow is generally from north-

west to southeast, and that the source of the ground water is not far distant,

most of it being derived from.rain which has fallen on the Atlantic Coastal Ridge;

not from far in the Everglades. The floor of the middle and northern Everglades

is quite impermeable and the ground water is relatively highly mineralized even

near the surface. If there were any considerable ground-water flow through the

rocks underlying the Everglades, fresh water should long since have flushed out

the salty water.

The water-table contours indicate that the present drainage canals and

ditches in the well-field area do not draw off excessive quantities of ground

water. In fact, there is evidence that during dry seasons Peters Canal helps

considerably to maintain higher water levels closer to the North New River Canal

than would be found if Peters Canal were not in existence. Furthermore, irriga-

tion with pumped ground water around the farm buildings of the Peters' ranch has

created a ground-water mound to the west and southwest of the Fort Lauderdale

well field, and helps maintain the ground-water level of the well field during

dry periods (see pls. 7 and 8).

The quantity of water available for pumping is not known. No city supply

well in the area has ever been pumped to its maximum capacity, nor has a punting

test been run to determine the hydrologic coefficients of the aquifer. However,

it is obvious that the present well field is not over developed.

The average water levels seem to be adequate to protect the present wells

from salt-water encroachment, provided present rates of withdrawal are not ex-

ceeded. During dry seasons the well-field water levels average about 2.5 feet

above mean sea level, but rainfall raises the water level rapidly and the annual







average water level of approximately 4 feet is adequate to protect the wells from

any further ocean-water encroachment to a depth of approximately 160 feet.

With the establishment of the Broward Conservation District's new water

preserve it should be possible, during droughts, to divert water to the well-field

area by means of ditches, dikes, and pumps. A higher water table, averaging 5 or

6 feet above mean sea level, could then be maintained in the well-field area to

give adequate safety against salt-water encroachment. This highly colored surface

water might cause a slight rise in the color of the City's raw-water supply but

it probably would not be excessive.

The years 1940 46 during which water-level measurements have been recorded

include only one year, 1940, in which the rainfall exceeded the average annual

rainfall. From 1941-44 it ranged from 10 to 24 inches below normal. Weather

Bureau records for Fort Lauderdale are incomplete for the years 1944-46 but the

years 1944 and 1945 are among the driest years on record for southern Florida.

A slight increase in the chloride content of the City water supply has

occurred over the years, probably as a result of upward movement of the mineral-

ized water underlying the well field. The water from the city wells during the

first year of pumping averaged about 10 or 11 parts per million of chloride. This

has risen gradually, with slight fluctuations, to the present average of 21 parts

per million. The increase was probably caused to some extent by deepening the

wells in 1940. There is no immediate danger from this source, but pumping rates

should not be increased without further studies to determine the probable effects.

As for private supplies, many wells in the North New River Basin have been

factors in inducing chloride contamination of the aquifer by drawing salty ocean

water in from the canals. These contaminated zones are irregular in shape and

areal distribution. The chloride has come from ocean-water tongues which have

intruded North New River, its tributaries, and the lower reaches of its tributary

canals. This source of contamination can be checked only in two ways: 1) by







providing sufficient flow in the canals to keep ocean-water tongues washed out of

the rivers and canals, and 2) by building a dam or control works as far downstream

as possible to prevent salt-water tongues from advancing into critical areas.

On the basis of present information a number of conclusions can be drawn

relative to the well field. The present wells probably are adequate to supply

the quantities needed but without pumping test data the present pumping rates

cannot be materially increased without the danger of inducing chloride encroach-

ment from the underlying salt water. The present pumping does not intercept a

very large portion of the natural ground-water flow, most of which is wasted by

flow to the North New River Canal and thus to the ocean. This will always be the

case to some extent, but much of this wasted flow could be captured by extending

the well field to the northwest and increasing the pumpage.

Sufficient work has not been done during -he present investigation to de-

termine accurately the hydrologic coefficients of the aquifer and to obtain this

information it is recommended that as soon as possible a pumping test be made in

accordance with the methods used by the U. S. Geological Survey. During this test

a well discharging at least 1,000 gallons per minute should be used. Such a test

can determine whether an increased rate of pumping will promote encroachment from

the salty connate water underlying the well field. It can also furnish quantita-

tive information as to the coefficients of storage and transmissibility of the

aquifer and these data could then be used to determine the proper well spacing

for maximum production of water with minimum drawdown of the water table. Draw-

downs in observation wolls near the present city supply wells indicate a coef-

ficient of transmissibility of approximately 1,200,000 gallons per day per foot

but this should be verified by a comprehensive pumping test before being used

in well-spacing calculations or in predicting future drawdowns and extent of

cones of depression.

On account of continually changing conditions of weather, drainage, pumpage,







cultural developments, etc,., it is believed that the following investigative

ground-water program should be carried out in the future: (1) chloride determi-

nations should be made regularly until such time as definite trends can be estab-

lished; this can be accomplished if the sampling of the 36 wells now being done

monthly is continued and analyses are made regularly for a period of several

years; (2) monthly observations should be made of the water table in the well-

field area; and (3) at least two more water-stage recorders should be installed,

one to the northwest and the other to the north of the present well field, so that

information may be had for these source areas of the present Fort Lauderdale water

supply.







BIBLIOGRAPHY


Brown, R. H.,,and Parker, .. G.

1945., Salt water encroachment in limestone at Silver Bluff, Miami,

Florida: Econ.,Geology, vol. 40, pp. 235-262,

Discusses ocean-water encroachment at depth in the aquifer.

Cooke, C..W.

1945., Geology of Florida: Florida Geological Survey Bull. 29.

Mentions specifically many of the geologic formations found

in Broward County and includes a geologic map.

Cooper,. H., H., and Jacob, C. E,

1946. A generalized graphical method for evaluating formation

constants and summarizing well-field history. Am. Geophys.

Union Trans., vol. 27, pp. 526-534.

Matson, G. C., and Sanford, Samuel

1913. Geology and ground waters of Florida: U. S. Geological

Survey Water-Supply Paper 319.

Describes Miami oolite along New River; mentions reports of

fresh-water submarine springs near Fort Lauderdale; gives

well records and data for a few wells at Fort Lauderdale.

Parker, G. G., and Cooke, C. W,

1944. Late Cenozoic geology of southern Florida, with a discussion

of the ground water: Florida Geological Survey Bull. 27.

Describes character and explains origin of several geologic

features, including transverse glades south of Fort Lauderdale,

the "bottomless holes" of New River and the Atlantic Coastal

Ridge, Maps include a geologic map not showing the surficial







sands, a map of surficial deposits, a topographic-ecologic

map, and a hyposometric map.

Parker, G. G,

1945a. Memorandum on the Fort Lauderdale municipal ground water

supply: Unpublished manuscript in open files of U. S.

Geological Survey. Describes Fort Lauderdale well field

and discusses water levels and chloride encroachment in

the Fort Lauderdale area. Graphs included show chloride

content of well S 330 and hydrograph of average monthly

water level in well S 329.

1945b. Salt water encroachment in southern Florida: Am. Water

Works Assoc. Jour., vol. 37, pp. 526-542..

Includes the chloride graph of well S 330 at Dania Plant

of Florida Power and Light Company. The text describes

the causes of observed changes.







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PAGE 1

FLORIDA STATE BOARD OF CONSERVATION J. T. Hurst, Supervisor FLORIDA GEOLOGICAL SURVEY Herman Gunter, Director REPORT OF INVESTIGATIONS No. 6 GEOLOGY AND GROUND ;:ATER OF THE FORT LAUDERDALE AREA, FLORIDA By ROBERT C. VORHIS PREPARED BY THE GEOLOGICAL SURVEY UNITED STATES DEPARTMENT OF THE INTERIOR IN COOPERATION WITH THE FLORIDA GEOLOGICAL SURVEY 1948

PAGE 2

rqoo C. AGkl. LiBRARY

PAGE 3

CONTENTS Page INTRODUCTION ............................1 GEOGRAPHY. .. ............... .....3 Location and area ... .* ... ..........3 Topography and drainage... .... ......... .3 Climate ................ .............4 Population and development. .............4 Development of municipal water supplies at Fort Lauderdale. ....5 GEOLOGIC FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS. .....8 TERTIARY SYSTEM. .........................8 Miocene series ...................* 8 Hawthorn formation. ...... *, .......... 8 Pliocene series ..* i ..* ..... ..9 Tamiami frmation .......................9 Caloosahatchee marl .... ........10 QUATERNARY SYSTEM# ..............11 Pleistocene and Recent series. ....* ........11 PFrt Thompson formation ........ .......11 Miamlico d ........................1 Pamlico sands a 9 s a o 12 do~eFlirt marl 9 # 9 o 13 Lake Flirt marl .......................13 Recent organic soils. ........... ......13 PRESENT INVESTIGATIONS ..........., ....1 .....14 TEST-WELL STUDIES. .......................15 Value and uses of test wells. ..., ............15 Test-well drilling. ........................15 Results and interpretations .... ..... .......16 WATER-LEVEL STUDIES. .. ............... ... ..18 Water-stage recorders ...................... .18 Observation well drilling program ... .0 ........18 The leveling program. ..................18 Results and interpretations. .... .... .....19 TRANSMISSIBILITY ..........................20 SALT-WATER ENCROACHMIET. ............................ 21 SUMMARY AND CONCLUSIONS, ............... ....26 BIBLIOGRAPHY. ........................31 ILLUSTRATIONS Plate 1 Map of southern Florida showing area of this report ....following 1 2 Average daily pumpage, Fort Lauderdale well field ....following 7 3 Geologic cross-section, .a. ..............following 8 4 A-Miami oolite north of Fort Lauderdale.. B--Water-stage recorder on well G 221 near Fort Lauderdale water plant ..following 11 5 A--Drilling well G 513. B--Water-stage recorder on well S 329, .. ...................following 15 6 Hydrograph of well S 329. ................following 18 7 Water-table contour map of Fort Lauderdale area for March 1, 1947 ....................following 19 8 Water-table contour map of Fort Lauderdale area for May 24, 1947 ..•. ..................following 19 9 Water-table contour map of Fort Lauderdale area for June 13, 1947 ,. ...............following 19 10 Time-drawdown graph for well G 221. .........following 20 11 Chloride graphs J ........... .......following 24 12 Map of Fort Lauderdale well field and adjacent areas. ..following 32 1,

PAGE 4

GEOLOGY AND GROUND WATER of the FORT LAUDERDALE AREA, FLORIDA I/ By ROBERT C. VORHIS INTRODUCTION The City of Fort Lauderdale, being faced with the problem of a greatly 'increased demand for water, has had need for geologic and ground-water data on which to base engineering decisions concerning the adequacy of the present well field and possible locations for an additional well field. In order that the data might be collected, the City of Fort Lauderdale, in October 1946, requested an investigation by the U. S. Geological Survey and the study was started immediately. Some of the work has been done as a part of the southern Florida water-resources investigations that are being made by the U. S. Geological Survey in cooperation with the Florida Geological Survey, but.most of the cost has been borne by the City of Fort Lauderdale. Little detailed work relating to ground-water conditions had been done previously in the Fort Lauderdale area. An annotated bibliography of articles with material relating specifically to geology and ground water of this area is included at the end of this report. The investigation was directed toward assembling, organizing, and interpreting geologic and hydrologic data concerning the following: (1) Areal extent and vertical distribution of water-bearing formations (aquifers). (2) Hydrologic and lithologic characteristics of these aquifers. 1/ Published with the permission of the Directors of the U. S. and Florida Geological Surveys. 1 r

PAGE 5

---------~---l----f---^-'-L) LAKE s C) SOKEECHOBEE EI I I r/-E--A ---I--\ r \B R WARD S \ ^FORT I S.N R. LAUDERDALE C' I 0KEO -SCALE IN MILES V 10 0 10 20 30 40 50 PL. I MAP OF SOUTHERN FLORIDA SHOWING AREA OF THIS REPORT AREA OF THIS REPORT

PAGE 6

(3) Quality of water at various depths in aquifers. (4) Present extent of and probable future salt-water encroachment. (5) Elevation and shape of the water table in the well-field area at various times of the year. (6) Effect on the water table of pumping from wells, as shown by the mapped cone of depression around the well field. (7) Effect on the water table of drainage ditches and other developments. (8) Average height of water table at various places in the area. The office and field work was done under the general administration and supervision of A. N. Sayre, Geologist in Charge of the Ground Water Division, U. S. Geological Survey, Washington, D. C., and Herman Gunter, Director, Florida Geological Survey, Tallahassee, Florida. Immediate supervision of the investigation and of the writing of this report was by Garald G. Parker, District Geologist, Miami, Florida. Additional help and advice was given by Nevin D. Hoy, Geologist, M. A. Warren, Hydraulic Engineer, both of the Miami office, and H. H. Cooper, Jr., District Engineer of the Tallahassee office. Water analyses were made by Berton Law, Chemist, in the Miami laboratory of the U. S. Geological Survey and by Mrs. Patricia Sherwood, who was then City Chemist of Fort Lauderdale. The leveling was done under the direction of Kenneth L. Jackson, Engineering Aide, Illustrations were drafted by Ross A. Ellwood, Engineering Draftsman, and the typing was done by M. Marvine Melton and Laura G. Pollard. Mr. J. H. Philpott, former City Manager of Fort Lauderdale, Mr. Charles L. Fiveash, Superintendent of the Department of Water and Sewers, Dr. A. P. Black, Consulting Chemist, Gainesville, Florida, and Messrs. L. C. Coe and Guy Tanner, Miami, Florida, well-drilling contractors, have been especially helpful and deserve much credit for the prosecution of the studies. In addition, grateful acknowledgment is made for cooperation and assistance given by officials and many citizens of the City of Fort Lauderdale, 2

PAGE 7

GEOGRAPHY Location and area Fort Lauderdale is on the Atlantic Coastal Ridge, 25 miles north of Miami. This ridge lies between the muck lands of the Everglades on the west and the narrow mangrove swamps along the Atlantic Ocean on the east. Most of the field work in connection with this report was done in the region to the west of Fort Lauderdale as shown on plate 1. The area of intensive field work is centered about the grounds of the Fort Lauderdale Golf and Country Club, in which the city well field is located (see pl. 12). Topography and drainage The Atlantic Coastal Ridge near Fort Lauderdale is approximately 5 miles wide and has very little relief, averaging only 8 feet above mean sea level, the highest elevation rising to about 20 feet. Oolitic limestone, sand, muck, and marl are the geologic materials outcropping in the Fort Lauderdale Area. The sand and oolitic sands are very permeable and permit rain water to penetrate downward rapidly. Drainage is largely underground, thus accounting for the scarcity of surficial drainage channels. The principal one is New River (see pl. 12) a shallow forked stream which heads about 6j miles inland and cuts through the coastal ridge to the Atlantic Ocean. North Fork of New River is relatively unimproved and uncontrolled. Its tidal portion extends upstream to a point approximately 21 miles northeast of the well field, and salt water is free to advance upstream as far as the tides and the fresh-water flow in the fork permit. The bed of North Fork is rather heavily silted in its upper reaches and is therefore relatively impermeable; thus, the salt water that occasionally extends to these reaches does not greatly contaminate the surrounding ground water, 3

PAGE 8

South Fork of New River is maintained as a navigable stream. Portions of the channel have been dredged and numerous boat basins have been constructed, the largest of which is shown near the bend in Riverland Road on plate 12. Middle River, a sluggish, shallow forked stream about 2 miles long, empties about 3 miles north of the mouth of New River into a salt-water lagoon in which the Intra-coastal Waterway has been developed. Between 1907 and 1918 most of the major drainage canals of the Everglades were dredged. One of those, the North New River Canal, empties into the South Fork of New River; and another, the South New River Canal, discharges both into the South Fork of New River and into the Dania Cut-off Canal. Climate The climate of Fort Lauderdale is semitropical. The average annual rainfall during a 31-year period of record is 65.19 inches, and the heaviest rainfall occurs between May and November. The prevailing wind is from the southeast and has an approximate average velocity of 13 miles per hour. Transpiration, evaporation, and humidity are high the year around. The average annual temperature is 75.2 degrees Fahrenheit. The average monthly minimum and maximum temperatures are 68.5 and 82.0 degrees F. and occur in January and August, respectively. The temperature of most samples of ground water collected from depths below 30 or 40 feet is very close to the mean temperature, or 76 degrees, The temperature of samples from shallower depths varies with the seasons, ranging from about 70 to 82 degrees. Population and development The population of Fort Lauderdale has increased markedly in recent years. The census of 1920 listed 2,065 inhabitants; in 1930 the population was 8,666; 4

PAGE 9

in 1940 it was 17,996; and a.census in the summer of 1945 placed the total permanent population at 26,185. The population is greatly increased each winter by the influx of tourists and by many home-owners who live there only during the winter months. The Fort Lauderdale Chamber of Commerce estimates that the total of winter residents in 1946 was between 60,000 and 65,000. The rapid growth in population that has already occurred has taxed the capacity of the present water treatment plant, and has made necessary the construction of an addition, This will more than double the original capacity of the plant and will permit greater consumption by present users as well as permitting water to be supplied to those parts of the city to which mains have not yet been extended. Development of municipal water supplies at Fort Lauderdale For many years the water supply for Fort Lauderdale was drawn from two wells, 6 inches in diameter and approximately 60 feet deep, located to the northwest of the intersection of Andrews Avenue and 2nd Street S. W. Mr. Charles Fiveash, Superintendent of The Department of Water and Sewers, reports that these wells would yield considerably more at high tide than at low tide suggesting that river water might be able to enter the wells. Inasmuch as New River was polluted with considerable amounts of untreated sewage, it was decided to develop a new well field and locate it sufficiently far to the west to be free from the possibility of pollution. Accordingly, the two original wells were abandoned in June 1926. As an interim supply during the construction of the present water plant, two wells (S 894 and S 895 on plate 12), one 10 and the other 12 inches in diameter, were drilled to depths of 90 and 104 feet, respectively, at Broward Boulevard and 14th Avenue. These wells served as the source of supply from June 1926 until December 1927, when the present well field and plant, to the west of Fort Lauderdale, were put in operation. The 12-inch well (S 895) is still maintained as a standby for emergency use, 5

PAGE 10

The present water plant was ompleted late in 1927 and has been treating all water since supplied to the city. Additional treatment facilities now under construction will raise the capacity of the plant from 6 to 14 million gallons a day. The city supply wells of Fort Lauderdale are in two different but adjacent groups and are therefore generally thought of as composing one well-field area. The first group consists of nine wells on the grounds of the Fort Lauderdale golf course, The golf course is near the western shoulder of the Atlantic Coastal Ridge, approximately 7 miles from the ocean and 14 miles north of the North New River Canal. The second group is composed of two wells at the municipal water plant on the crest of the Atlantic Coastal Ridge, approximately 1 mile southeast of the first group. Land-surface elevations in the well-field area average about 9 feet above mean sea level. The 11 wells are gravel-packed and are pumped at a total maximum rate of approximately 6,600 gallons per minute. This is by no means the maximum capacity of the wells, a figure that has never been determined, but the present pumpage certainly is only a fraction of what these wells would yield if pumped to capacity. The City Water Department has not deemed it wise to pump these wells at greater rates for fear of causing salt-water encroachment. Eight wells, Nos. 1, 2, 3, 4, 5, 6, 11, and 12, were drilled in 1927; Nos. 7 and 8 were drilled in 1940; and Nos. 9 and 10 were drilled in 1945. Well 1 does not contribute to the City supply but is used exclusively for watering the golf course. It was drilled and developed in the same manner as the other wells. Wells 11 and 12 are the two that are located a hundred feet east of the water plant (see pl. 12). All except No. 11 are 12-inch wells, and all except Nos. 8, 11, and 12 were finished with casing set approximately 80 feet below land surface. All had 10 feet of open hole (unscreened) below the bottom of the casing. Well 12 was cased 6

PAGE 11

to a depth of 92 feet below land surface. Mr. Fiveash reports that at the time the wells were completed the water table averaged about 3 feet below land surface or 6 feet above sea level, In 1940, two new gravel-packed wells 12 inches in diameter, (Nos. 7 and 8), were completed, the casing being seated 80 feet below land surface in No. 7 and 62 feet below land surface in No. 8. A 6-inch diameter screen, 35 feet long, was installed below the casing of each well,. During 1940 the older wells (all other than 7 and 8) were deepened 45 feet, which allowed the insertion of 35 feet of screen with 10 feet of blank pipe below the screen. All the wells were then gravel-packed. The daily pumpage from these wells has ranged in the period from January 1930 to the present from a low of 234,000 gallons per day to a maximum of 6,615,000 gallons per day. The average daily pumpage has gradually increased over the years, as shown in plate 2, a graph of the average daily pumpage from the Fort Lauderdale municipal wells during the period 1930-1947. Records are not available for pumpage prior to 1930. 7

PAGE 12

! !t -" 4 4 "4 f-: 3 ---------E--E------5; -t -t 19AL-19 19AL 19 19_A3_._ 19A44.. 19A5-19.A ,6-_ 19A_4. 19 19. I .^ --lC -J---t-r ---" ""^"" I I 1 9F -I 1 91 ~ I -| I I I r I I IaIaF PLATE 2 ARAGE DAILY PUMPAGE FORT LAUDERDALE MUNICIPAL WELL FIELD -_ 19 3 1

PAGE 13

GEOLOGIC FORMATIONS AND THEIR WATER-BEARING CHARACTERISTICS The surface materials of southeastern Broward County in the vicinity of Fort Lauderdale are formed largely by a mantle of several feet of sand (Pamlico sand) of late Pleistocene age. On the western edge of the Atlantic Coastal Ridge muck is found, especially in the vicinity of natural drainage channels. The mantling nature of these materials plus the low relief and lack of any deep cuts in the rock make it impossible to determine the geologic nature of the region from rock exposures. Examination of shallow exposures in the banks and spoil of the Everglades drainage canals and study of well-log data are the only reliable sources of geologic information. An east-west cross section along the North New River Canal from Fort Lauderdale to 20-Mile Bend is shown in plate 3. In southeastern Florida strata older than the Hawthorn formation are of no importance as a source of potable water because the water in older strata is highly mineralized, The water is under artesian pressure but its quality is such that no use has been found for it, except for limited row-irrigation of garden vegetables and lawn sprinkling. It corrodes pipe so rapidly that it has been found to be not economically profitable to make use of the artesian pressure,. All the known pre-Hawthorn strata have these same water-bearing characteristics. Inasmuch as their water is unusable for public supply these formations are not discussed in this paper. TERTIARY SYSTEM Miocene series Hawthorn formation In southern Florida the Hawthorn formation is composed predominantly of greenish-colored sediments that were laid down in a shallow, warm transgressing

PAGE 14

V0 +50 A Ao.o-----=-----" --QP .0 ---Qm = --_ --fTt t Q p Qm Qm Q ml,--TQ Tc Tt T-... .Tt Tt so QUT RNR ?------t Tc ... Tc Tc Tc Tt ST c ... -100 -...---C SLEGEND Tt Tt QUATERNARY s Tt -150 Q = RECENT ORGANIC SOILS T Tc QI = LAKE FLIRT MARL SO Qp = PAMLICO SAND QO = MIAMI OOLITE Th -200 Qf = FORTTHOMPSON FORMATION TERTIARY sTC = CALOOSAHATCHEE MARL SCALE IN MILES TtI TAMIAMI FORMATION 0 1 2 3 4 5 -250 Th = HAWTHORN FORMATION PLATE 3 EAST-WEST CROSS-SECTION ALONG NORTH NEW RIVER CANAL FROM 20 MILE BEND TO FORT LAUDERDALE

PAGE 15

sea which flooded an eroded land surface. Thus, the lower contact is unconformable. These marine deposits may be blue-green clay, gray-green marl, or varying shades of greenish sand, The change to greenish-colored sediments gives a sharp contrast with the predominantly buff to gray color of the overlying beds and makes for easy identification of the upper contact. In the coastal area the Hawthorn formation is about 400 to 601 feet thick. Because it is composed largely of clay and marl, the formation is relatively impermeable and therefore acts as an aquiclude (non-water-bearing bed) between the water highly mineralized artesian/of the underlying Eocene and related limestones and the fresh water in the overlying formations of Pliocene and Pleistocene age. Locally, wells may be developed in the Hawthorn but the water yielded is generally too highly mineralized for most purposes and occurs in rather limited quantities. The water from the Hawthorn formation is significantly different from water of the overlying formations. It has more dissolved solids, especially of magnesium, sodium, potassium, and sulfate. The water is generally too highly mineralized to be potable but is suitable for other purposes, such as use by stock and for irrigation. Pliocene series Tamiami formation The Tamiami formation is named for deposits "composed principally of white to cream-colored calcareous sandstone, sandy limestone, and beds and pockets of quartz sand" (Parker 1944, p. 64). Near Fort Lauderdale the Tamiami formation interfingers with the contemporaneous Caloosahatchee marl (see description of Caloosahatchee marl below). Inasmuch as the Tamiami has no fauna distinct from faunas of the other Pliocene formations of southern Florida, it is 'impossible to distinguish the Tamiami except by lithologio characteristics. For this reason the cavernous sandy limestones and caloareous sandstores of Pliocene age a'e considered to be Tamiami, S9

PAGE 16

At Miami the Tamiami formation averages about 100 feet thick. It has been found to be one of the most productive water-bearing formations ever investigated by the U. S. Geological Survey, ranking with coarse, clean, well-sorted gravel in its capacity of transmitting water (Parker and Cooke, 1944, p. 65). In Broward County this formation is cavernous and permeable but the interfingering with the sand of the Caloosahatchee marl makes for a lower yield than in Dade County, where there is little such interfingering. Water from this aquifer is generally very good in quality except in zones where salt-water contamination has occurred. Caloosahatchee marl The Caloosahatchee marl underlies most of the Everglades and is found in the subsurface eastward under the Atlantic Coastal Ridge. According to Parker and Ccoke (.1944, p. 59) "The Caloosahatchee marl is a littoral (beach) and neritic (shall.ow, off-shore zone) deposit composed of sand, silt, clay, shells, and often enough calcareous material to make it a true marl. It contains many local beds or lenses of pure sand or clay, but the usual condition is just what one would expect of a deposit where constantly shifting currents acted upon a shallow sea bottom and shores adjacent to a low land mass that contributed only fine sediments." The large number of perfectly preserved shells is an indication that the water was deep enough to prevent breakage due to violent agitation by waves (Cooke, 1945, p. 214). In the Fort Lauderdale area the Caloosahatchee marl occurs as gray to green marl, fine to medium-grained quartz sand, shelly sand, sandy marl, and a greenish clay. It interfingers with the contemporaneous Tamiami formation as shown in plate 3. In the logs of the test wells, the soft, relatively impermeable sandy, shelly, and marly sediments of Pliocene age are considered to be the Caloosahatchee, and the limy sandstones and sandy limestones to be the Tamiami. Separation by paleontological means is not possible, as the faunas of both are so similar. 10

PAGE 17

A. MIAMI 00LITE EXPOSED IN A ROCK PIT NORTH OF FORT LAUDERDALE.NOTE CROSS-BEDDING AND SOLUTION HOLES IN THE OOLITE. PAMLICOSAND IS SHOWN AS CONES AT THE BASE OF THE SOLUTION HOLES ANDAS A MANTLING LAYER OVER THE OOLITE. THE 6-YEAR OLD BOY GIVESSCALE.B. WATER-STAGE RECORDER ON WELL G 221 NEAR FORT LAUDERDALEWAT ER PLANTPLATE 4

PAGE 18

Florida have been built. The Miami oolite probably was largely deposited during the Sangamon interglacial stage. The melting of the continental glaciers formed during the preceding Illinoian stage was so extensive that the ocean level rose 100 feet above its present level. Later, as the glaciers began to re-form, the sea level dropped first to 70 feet and then to 42 feet (above present sea level), At all three levels marine terraces were formed, and it was largely during these high stages of sea level that the Miami oolite and related formations were deposited. The end of deposition was brought about by a fall in ocean level caused by the advance of glacial ice during the early part of the Wisconsin stage. The Miami oolite is a fair source of water but the formation is so thin and near the surface that comparatively few wells are developed in it. The large numbers of vertical solution holes make for greater vertical than horizontal permeability, but even so the formation is generally so permeable that water can be pumped quite easily from it in most places. Water found in the oolite is hard--a typical calcium-bicarbonate water. Unless contaminated it usually contains from 6 to 20 parts per million of chloride; locally there may be considerable color of organic origin. Pamlico sand The Pamlico sand consists largely of quartz sand and is of late Pleistocene age. Over large areas in southeastern Florida it overlies the Miami oolite and fills natural channels and solution holes in it. In color the sand ranges from dazzling white through shades of yellow and brown to red or black. The yellowish to red colors are due to iron oxide but the gray to black color is generally due to organic materials that adhere to the surfaces of the sand grains or fill the interstices between them. The Pamlico sand was probably laid down at the time of the latest Pleistocene high-level sea, when the shore line was 25 feet above the present one. The '12

PAGE 19

sand was derived: from previous deposits farther north; and was washed southward by ocean currents and waves. Its principal original source is probably from the rocks of the Piedmont in Georgia and Carolinas. The ocean level presumably stood very low during the several glacial stages that preceded the late Pleistocene 25-foot rise, because the transverse glade valleys, having depths as great as 100 feet, were then formed by streams originating in the Lake Okeechobee-Everglades area. These stream valleys indicate considerable erosion. Pamlico sand now fills these valleys and mantles the surface of the oolite. The Pamlico sand in the transverse glades generally is a source of potable ground water. The sand is not permeable enough to yield as much water as can be obtained from the cavernous rocks of the Tamiami formation, but it is a source of adequate supplies where nnly small quantities are needed. The water is fresh, where not contaminated by encroaching salty water, but it may have an objectionable coler due to organic materials, and locally it may have the characteristics of "swamp water", with considerable color and a smell of hydrogen sulfide. Plate 4A shows Pamlico sand mantling the Miami oolite and filling solution holes. Lake Flirt marl The Lake Flirt marl was deposited in the Everglades and parts of the coastal marshes of southern Florida in areas of shallow, open water, In places it overlies the Pamlico sand, the Fort Thompson formation, and the Miami oolite, It has a thickness of about 1 foot in western Broward County (see pl. 3). Recent organic soils Peat and muck deposits accumulated in perennially flooded areas of the Everglades in both late Pleistocene and Recent time. These deposits are comparatively thin in the Fort Lauderdale area of the Everglades, and overlap the western edge of the Atlantic Coastal Ridge.

PAGE 20

PRESEMT INVESTIGATIONS The present investigations have continued and expanded the work previously done in the course of the southeastern Florida water-resources investigations, which were financed until 1944 by theiU. S. Geological Survey in joint cooperation with Dade County and the cities of Miami, Miami Beach, and Coral Gables, Since that time the U. S. Geological Survey and the Florida Geological Survey have continued observational and research work in Broward County as a part of the joint State-wide investigation of geology and ground water. The City of Fort Lauderdale has largely financed the additional work, which included (1) the drilling of five test wells averaging about 200 feet in depth (G 512 -G 516, incl.); (2) re-installation of the water-level recorder on well S 329, located on the northeastern edge of the Fort Lauderdale golf course; (3) installation of another such recorder on well G 221, located on the east side of State Highway 7 about 400 feet northwest of the municipal water plant; (4) drilling of 52 shallow observation wells; (5) obtaining and recording data on 90 private wells; (6) periodic measurement of water levels; (7) collecting and analyzing for chloride content water samples from 116 wells; (8) establishment of a net of levels about 27 miles long based on the U. S. Coast and Geodetic Survey mean sea level datum plane; (9) tying in all measuring points to this datum; and (10) preparation of charts, diagrams, and maps to illustrate these data. The preparation of a base map was one of the earliest and most time-consuming jobs, for it was found that no accurate large-scale map of this area existed prior to this investigation. The above steps have been taken to obtain information about current groundwater conditions. In addition it is planned to continue, in cooperation with the City of Fort Lauderdale and the Florida Geological Survey, observations to determine long-time trends. Thirty-six key wells located in or adjacent to zones of salt-water encroachment are to be sampled monthly for chloride content. It is also proposed that water-table maps of the well-field area be prepared at monthly 14

PAGE 21

intervals. Three such maps for selected times during late winter and spring of 1947 are included in this report (pls. 7-9). TEST-WELL STUDIES Value and uses of test wells Test-well drilling has been the chief source of information on the geology and ground-water hydrology of the Fort Lauderdale area. The nature of the underlying rocks has been ascertained, and ground-water samples from numerous intervals in depth have been collected and analyzed. The usefulness of the wells was not ended as soon as their drilling was completed; measurements of water level are made periodically and samples of water are collected at monthly intervals to determine whether salt-water encroachment is occurring. Test-well drilling The five test wells (G 512 through G 516) drilled during the course of the current investigations were put down by the jet-percussion method. Plate 5A shows the rig used in drilling these wells. At the start of the drilling a 20-foot length of 2-inch casing was driven down. The material forced into the casing was then jetted out, using a 1-inch jetting line, and the jetting was continued to a depth approximately 10 feet below the end of the casing. The jetting line was then removed, a pump was connected and, if possible, a water sample was obtained. Pumping continued for a long enough period to make certain that the sample would not be contaminated or diluted by water introduced into the bed during the jetting, After the sample had been collected, a section of casing 10 feet long was added and driven down to land surface; then jetting was resumed. Occasionally no water samples could be collected, owing either to low permeability or to very fine sand "heaving" in the casing and making pumping impossible. This type of "running 15

PAGE 22

A. DRILLING WELL G 513 ," B. WATER-STAGE RECORDER ON WELL S 329 NEAR CITY WELL 3 ON FOIT LAUDERDALE GOLF COURSE. PLATE 5

PAGE 23

sand", more properly termed quicksand, is rather common in some parts of the area, In many instances it was necessary te drive a sand-point into the sandy materials below the bottom of the casing in order to obtain water samples. Every effort was made to obtain representative water samples at regular intervals as the test wells were deepened. Results and interpretations Interpretations of the well logs show that during Pliocene time deposits of fine-grained quartz sand were laid down alternately with deposits of calcareous sediments ranging from sandy limestone to rather pure marl. The sand is typical of littoral (beach) and neritic (near-shore) deposits derived from a nearby lowlying land mass composed largely of sandy materials. It is considered to be an eastward extension of the Caloosahatchee marl. The limy sediments are typical of shallow-water deposits of the open ocean, laid down far enough from land to have included little detrital material. These limestones are considered a northern and eastern extension of the Tamiami format.ion, which is typically developed in Dade and Collier counties. Using these lithologic characteristics as a basis of formation identification, it is apparent that there is considerable interfingering between the two formations. This interfingering is probably a product of alternating landward and seaward migration of the shore line due to minor changes in sea level during the Pliocene. Until the five test wells were drilled it was believed that limestone of the Tamiami formation would be found to be the principal component of the aquifer in the area, and that the permeability would be somewhat lower than that found in Miami, However, results of test drilling and pumping show that the sand and silt of the Caloosahatchee marl are abundant and, with minor quantities of admixed clay, markedly reduce the transmissibility and yield of the aquifer as a whole. A bed of fine white quartz sand, possibly of Caloosahatchee age, is found 16

PAGE 24

to underlie the Miami oolite in nearly all the wells of the Fort Lauderdale area. It is uncertain whether the individual beds or layers underlying this sand layer have any considerable horizontal continuity. The geologic section included herewith (pl. 3) shows the various beds correlated by means of lithology, but because of lack of sufficient test wells it may be somewhat in error, Many of the beds were deposited as shallow marine and littoral sediments in an environment where currents and waves sharply limited the area in which any one type of sediment could be deposited; therefore, exact correlation of such beds is well-nigh impossible. 17

PAGE 25

WATER-LEVEL STUDIES Water-stage recorders Two continuous automatic water-stage recorders are installed on observation wells in the Fort Lauderdale area. These provide the basis for a record, called a hydrograph, which shows the rise and fall of water levels plotted against time. These two recorders are shown in plates 4B and 5B and a hydrograph for well S 329 is shown in plate 6. Observation well drilling program In order to prepare a water-table map it is necessary to have a number of wells in which depth-to-water measurements can be taken. At the start of the investigation only 15 wells suitable for this purpose were available; therefore it was found necessary to drill an additional 52 shallow observation wells to furnish needed control. The locations were chosen in several ways. In order to determine the effect of the pumping of the city wells, observation wells were installed 10 feet from each city supply well, although in some places this distance ranged up to 100 feet. Shallow wells were also drilled approximately 1,000 feet from each two adjacent city supply wells, and additional shallow wells were drilled at approximately halfmile intervals eastward into Fort Lauderdale, northward to Plantation Road, and westward to Peter's Canal (see pl. 12). The observation wells range in depth from 11 to 28 feet and are nearly all equipped with sand points. After being drilled each well was pumped sufficiently to be certain that it would respond quickly to water-table fluctuations. In addition to the above wells, 10 observation points were established for water-level measurements on streams, canals, and drainage ditches. These give additional information and control for preparing water-table maps. The leveling program The datum plane used by the U. S,.Geological Survey in preparing water-table maps in southern Florida is U. S. Coast and Geodetic Survey mean sea level (1929 18

PAGE 26

I.. I .|._ .i.T .r I i4 7 fl 4-----4 ---. -7 .7 -r ---a z -j632vit: (A 19AJ-19AL19A2 19A2L. 19AA19A519A-.. 19A3. PLATE 6 HYDROGRAPH OF WELL S-329

PAGE 27

adjustment). ,This datum plane is used by the Everglades Drainage District, by many municipalities, and is the most satisfactory datum plane for use in groundand surface-water studies. In order to determine accurately the water-table height with respect to mean sea level, it is necessary to know the elevation of the measuring point on each observation well. This was obtained by running a net of levels from a second-order level line established by the U. S. Coast and Geodetic Survey. The line runs along State Highway 7 through the area of this report. The U. S. Geological Survey level net in the well-field area includes more than 27 miles of lines that were run and tied in to the above-mentioned U. S. Coast and Geodetic Survey line. The points from which measurements are made and to which elevations are accurately established are usually the tops of the well casings. Inasmuch as the depth to water can be determined to a hundredth of a foot (the limit of accuracy to which a wetted steel tape can be read easily), it was necessary that the elevations be established to a corresponding accuracy and 27 miles of closed level lines were run to accord with such a standard. The well elevations are shown on plate 12 in italics. The measuring point in each case is the top of the well casing, the well cap being removed. Results and interpretations Three maps of the water table in the Fort Lauderdale area are included with this report. Plate 7 shows the water table as of March 1, 1947, and is typical of the conditions found in late winter of 1947. Plate 8 shows the water table on May 24, 1947, very close to the end of a dry spring period. Plate 9 depicts the water table as of June 13, 1947, after a week in which there were a number of very heavy rains. The contours, which are drawn with an interval of 0.25 of a foot, show that pumpage from the well-field area has only a slight effect on the water table. No deep cone of depression is ever apparent, and the usual situation found is that 19

PAGE 28

SA.S ,oON A. s .CHLORIDE DATA WEIL 6 WELL G6 WELL NO/ P A \ P. P ,I. IV • r 530 \ \Is IN 032 to 0 5335 0497 0554 26 2 tog 05J. 042 'r -. 5. W -0E TANLE 0 45R .234E L "; /
PAGE 29

PLANTATION R~ 41 CE K 42 E pso1 s^ Zo s
PAGE 30

-irR 41 El 49 9 im• -....M, • .,,... 212 a1o0, 0. 14a 1 6.00 zos A.a "I sses as • p a f A u,-5 / s/ --4 **** ersa 531 3 589 0 "sa so es r r00 "a 6 a sn 045 6 os o O#r LIU WELL r Lo 48 ' 0488 0 cc 410a 60* 9470 es*6so seen a ass do asse see /se /, co _--_ / ..l -.. 0 4 0* 1 s a l e 5 3 4s e a 04 53872 esa ,~~R 9 /wasdc, ~ ~ ~ ~ ~ ~ o o ,O,, 0 N -SN12 z o 'e.,. Au, ./ MAP OF Cu wmwrg u 049r 0-1 9 too-,-c: aUL, FORT LAUDER0ALE S A S A V I 04I~ L _~~ ) € ed i *Ls, tonor onA ava,"La WEsLL FIELD AREA DA~u: ON o Itwo, us.C a ~s.JUNE I1, 1947 ci 1 1on i a pp f s a es 4.A5 492 4.50 --C551 0 524 .I547 C546 S Y ii I 4.2A 3 $11so M YACT BASN ROA M3 S. ?, C51 05875 so s $948 sal og"o ---,5*5 LLEGENDcno~ 01 orI~~* I I ~ 4 58700 0 NON-FLO WING WELL P -tIRA PUBIC SPPLYWILLMAP OF WELL WITM AUTOMAIC WATER STAGE REICORDER FORT LAUDERDALE 0 4 WErLLS. CHLORIDEL DATA AVAILABLE WELL FIELD AREA OBSERVATION POINIT OR STAFF CADE SCALE IN FIERT V JUNE 13, 1947 DATUM: MEAN SEA 1.9109,., U.S.C 6 a.$ PLATE 9

PAGE 31

the contours,.instead of b;eihg'smoothly curved lines on the map (as they would be if no pumpage occurred), are slightly deflected in the area of pumpage. Greatest effect of pumpage on the shape'of the water table is shown on Plate 8 where a closed contour (1.50 feet) occurs at the water plant with slight bending of adjacent contours, and a small area is similarly affected on the golf grounds. Note on this same plate the ground-water mound built up by irrigation at the west end of Peters Road. The contours indicate that ground-water flow is generally from northwest to southeast, on a very gentle gradient averaging approximately 1 foot to the mile. By drawing flow lines normal to the contour lines on the water table, the area contributing water to the well field can be delineated. The ground water contributing to the wells originates from rainfall on the well field itself and immediately to the northwest; it is not derived from areas far out in the Everglades, as many people have believed, The water table maps indicate that no over-development of ground-water supplies in the well-field area has taken place. TRANSMISSIBILITY The capacity of a formation to transmit water may be expressed by the coefficient of transmissibility, which is the number of gallons of water that will move in 1 day under a unit hydraulic gradient (1 foot per mile) through a vertical strip of the aquifer 1 mile wide and having the full depth (or thickness) of the aquifer. The coefficient of transmissibility for the aquifer in the Fort Lauderdale well-field area is approximately 1,200,000. This means that 1,200,000 gallons of water will flow in 1 day through a vertical strip of the aquifer 1 mile wide under a hydraulic gradient of 1 foot per mile, The graphical method (Cooper and Jacob) used in arriving at this Value is shown in plate 10. Drawdown and time data were 20

PAGE 32

caW .CI @ u N W %4 Co. cc ~ P8 Car .b u a C jm N IN ca Go W' 4b ll 0. '* I II rF J I I 0-2 111111tfT l I:,; 'I 1 I IN H M IN I Ill 1I I iI1 1 11 U 1111111.11 1 : I I l1 f i1 1 1 1 1 1h illIIIIiI II I1 11.1 11111111 Ill I i i. Id M l lit Ill I~~~Z insIII* I P, I I fill till 113 111 11 1 lilt I H III II1 I I llllillllll 1L I 1 11111111111 1 I 1_ U L L IU II lilt lllllllll IiIH M! IIIIIIIII 1 I 0 ---11 !1 il I I T i I : I HIl I IIif I 0 .3 i ' I m :if t!I1 ill !i; d III Il Ill i i 0.4* Hil I! i .I P m i litilll llll~rlili 1! 1 11 1 i 1 1 11 1111111 1 11 1111 1;; 1 If I Ill: 1: I if II I Hilllll illl i11 11 11 1 11 11[111111~ I I f I I I IIiiI II l ll I il ili 11:! I M :I!I ;!I, X i I ; 'lilt il l 111 0..1 I iI II I l IIIJ MIR I I. 111;Il ill I .i t I ll ~ ::IIll I I I I II Ii I ill IT Ill lllllllll I I I fllli ill llll II I l I I I I I II 1 1111111 11111111 llllllll l I 1 I I I T T l i l lI n~lilllllI1l~lll rllll n i Il l: !I l Ill! 11:1 1 l i lt T U I, i! I I I II til l t Ill Ill Ii I ii 1:i .1: 1 .: I -~l l I, I! I lii I PLATE 10 I TMDRW W GRP FOR W i I l tf l i~l~ill it lit, Ifu HII ill 3 fil 1111111111 1 1 1 1 1 1 I i t I I I I f i l l Ill 11 ill Ill! I I I I I I I I I I I I I I t I l if l f i l l f il Ii I I iili ;!; ti l I; Tll !:ii 1 1 1 Ill. I I I i i I I f I I! l !l l i ll lll fill -1 H I f11 11 fill 11 1 i I I fill fillll lll I ll ln lni i I I f lli i if1 I llII!II Il I I ijiI; 0 .8 Ii~:i~ ll li, i I: lll H Hl I I I IiI I IiIN lll~ Ill illMi Iiii 11 1 1 1 1i 111 I!Ll!!l~il~i~lll, ;1 11 fll I HI 111111 1 r17 1 7 n rllllllll 7TT [liillili 11 1111 1111 Ili I I till HI I I f i l l iilliIll I I I I I I Ili! I IS LI I IIlli illllllllI A lli M; lit 11111111 iiIULilllli 11 ;!1 iidliLl I I fillrllliilll l i I Illllllll I I Il ili:lW I I I f I I I II U I~l ll ll l ill l II111111 11 -1111111 1 11 .11 1 N .I I I I IIII I! Ill i~~~ I f i l 1 I i ` 1 il I It Iiii I M f i l l l ll fill I i I I I I I 1 1 11 1 1 1 1,1 111

PAGE 33

taken from water-stage recorder charts; rate of pumping is the quantity reported for city supply wells 11 and 12. The falling off of the last two points on the graph indicates a boundary effect, or reduced transmissibility as water levels decline, or both. The value given for the coefficient of transmissibility is tentative and indicates only the order of magnitude for the coefficient. In order to obtain a value on which important engineering decisions may be based, a carefully controlled pumping test would be necessary. SALT-WATER ENCROACIMENT Samples of 'ground water were collected from all test wells at frequent intervals during the drilling. In addition to the test-well samples, a large number of water samples were collected from wells in areas of possible salt-water encroachment, and from most of the observation wells. Samples from wells not equipped with pumps were collected by means of a portable. power pump or a common pitcher pump. In collecting samples from wells in which the water had been standing unpumped for a relatively long period of time, sufficient pumping was done to clear the well and obtain a representative sample of water from the aquifer. All analyses of these samples for chloride content were made in accordance with the standards of the U. S. Geological Survey. The error is less than 1 percent, regardless of the salt concentration. In addition to using chemical analyses for chloride determination, the electrical-resistivity method of geophysical prospecting was used to test for the presence of salt water at depth. The locations of the test sites are shown on plate 12. The final results obtained from these tests are not available as yet. However, field computations indicate that the method is successful and that mineralized water underlies the entire area at differing depths. A subsequent report will give the detailed results. 21

PAGE 34

Chloride encroachment in the Fort Lauderdale area may be from any of four sources. (1) from the ocean; (2) from ocean.-water tongues in canals; (3) from Everglades Drainage District canals into which salty Everglades ground water has seeped; (4) from the salty connate.or residual water which underlies the area at a depth of from 150 to 300 feet and more. In the Fort Lauderdale area encroachment from the ocean directly into the aquifer is believed to occur only within a mile or so of the shore. Owing to a number of factors, the rate and extent of ocean-water encroachment at Fort Lauderdale has not been as fast nor as extensive as in Dade County near Miami. These factors include (1) lower transmissibility; (2) layers or beds of sediments that are relatively impermeable; (3) less pumpage; (4) higher water table. In part of the Miami area encroachment from the ocean at depth in the aquifer has been computed to be as great as 890 feet per year and to have averaged about 235 feet per year (Parker, 1945 b, p. 539). The rate of encroachment in the Fort Lauderdale area has not been computed but it is probably much less, owing to the above-mentioned factors. This type of encroachment is not found in any of the area shown on plate 12. The most serious threat of well-field contamination from ocean water exists in the lateral movement of salt water from North New River canal. Plate 11 indicates the high chloride content found from time to time in this canal as far inland as the control lock and dam. Test well G 514, located at 9th Street and 12th Avenue Southwest in Fort Lauderdale, shows marked contamination from this source. At a depth of 116 feet below land surface the chloride content was 178 parts per million, but only 10 feet deeper, at 126 feet, it was 2,690 parts per million. This chloride content is far too large to have been derived from the connate salt water which underlies all of south Florida, for connate water at this elevation has been flushed out in areas much farther to the west. Further, the chloride concentration is too great to be explained by seepage of salty Everglades water 22

PAGE 35

into the canal. The profiles of ocean-water encroachment published by Brown and Parker (1945, figs. 11-13) indicate that, where there is direct encroachment of ocean water, the chloride content increases with depth more rapidly than is the case in well Q 514. Thus, by a process of elimination, the source of the contamination is concluded to be ocean-water tongues that have intruded along the bed of North New River. Other wells along New River show contamination from this source. These include wells S 827 and 828 on the North Fork df New River and wells S 808 and S 820 on the left bank of the South Fork of New River. Pumping the above wells has drawn in salty water from the canal. On the right bank of the river (see pl. 12) wells S 862, S 866, S 864, S 868, S 870, S 872, and S 874 all show even greater contamination. This is due to slow, sustained movement of the ground water from northwest to southeast, carrying contaminated water with it -contamination that seeped both downward and laterally and was carried farthest in the most permeable parts of the aquifer. Chloride tests on water from test wells G 512 and G 513 illustrate this type of encroachment. In well G 512 a zone of contamination in which the water contained 180 parts per million was found at 42 feet. This was the highest salt content for any horizon in the entire 175-foot depth of the well. In well G 513 zones of lateral intrusion were found 10 and 52 feet below land surface. In these two zones the chloride content was 59 and 52 parts per million, respectively, The beds enclosing these zones contained water of only 28 parts per million or less. The encroachment was selective, occurring only in the more permeable zones. This selective type of encroachment occurs especially during dry periods when there is little or no seaward flow in the canals and rivers; instead, there is an inland flow of ocean water. In dry weather wells are pumped most heavily and this serves to accelerate the rate and amount of encroachment. This type of intrusion can be prevented only by (1) continuous fresh-water flow sufficient to 23

PAGE 36

keep the salt water swept out of the canals; or (2) installation of locks at some downstream site, Another area in which lateral encroachment has occurred is in the vicinity of the Dania plant of the Florida Power and Light Company. The water in well S 330 at this plant contained 213 parts per million of chloride when first sampled by the U. S. Geological Survey in November 1940 (see pl. 11). This indicates salt-water intrusion because in this area the normal chloride content of ground water is only about 20 parts per million, and canal water from the Everglades has not been observed to exceed 148 parts per million in the North New River Canal. In subsequent samplings the amount of chloride in well S 330 decreased gradually to 53 parts per million, with but few slight variations. Then the effects of drought became noticeable and the chloride content rose to 615 parts per million in October 1943. Fall rains of that year pushed the encroaching salty ground water oceanward and gradually reduced the concentration to 458 parts per million by April 1944. Since then, reduced flow in the South New River Canal and a lowered water table have permitted several salt-water advances such as are shown for the North New River Canal in plate 9. A maximum chloride content of 2,700 parts per million was reached in November 1945, and it has since declined to 640 parts per million (in July 1947). Contamination from mineralized canal water where the saltiness is picked up by inflow of salty ground water in the middle and upper Everglades operates in the same fashion as the type described immediately above. The results, however, are far less serious. The chloride content of the North New River Canal at the upstream side of the coastal lock and dam during the period from February 1941 through April 1947 has been observed to vary from a low of 49 parts per million to a maximum of 148 parts per million (see pl. 11). These amounts are not sufficient to render water unfit for drinking, but it is important to recognize this type of intrustion for what it is and not confuse 24

PAGE 37

3,000 1 A -#l-1 2, 000 1,000-0 .15,000 -E EEEE E 10,00 ---5,000 zE-^^ E filt---::r::r= 200 100 0 19AL 191 R942 19RaF19 4-4 | 19AT5E19AD619AZ-PLATE II CHLORIDE GRAPHS OF SURFACE WATER AND GROUND WATER

PAGE 38

it with intrusion by way of ocean-water: tongues. Once this canal water seeps into the ground there is little likelihood that its chloride content will be further concentrated. Instead, its chloride content will be diluted by mixing with fresh ground water. The chloride content of uncontaminated ground water may range from approximately 4 to 30 parts per million. In areas adjacent to canals or rivers any content in excess of 30 parts per million but less than 150 parts per million, may represent encroachment by contaminated canal water from the Everglades. Any content higher than approximately 150 parts per million is evidence that the contamination originated from ocean water. Salty water underlies all of southern Florida and is found in all areas if drilling is carried deep enough. The observed range in depths to salty water in the Fort Lauderdale well-field area is 150 to 225 feet. One test well in the area (G 516, 200 feet deep) failed to show salt water, but it is probable that salt water can be found even under this well, probably within the next 25 to 50 feet of depth. This salty ground water, especially at great depth, may be of connate origin (water deposited with the sediments in which it is found), but it is more likely that it is modified sea water that penetrated downward during the late Pleistocene when this area was submerged beneath the high-level seas of an interglacial stage. Since then the ocean level has not declined enough or sufficient time has not elapsed for this water to be completely drained or flushed out and replaced by fresh water, but it has been altered by cation exchange and dilution. In well G 515, near the center of the Fort Lauderdale golf course, a chloride content of 300 parts per million was found at a depth of 165 feet below land surface and this increased to 600 parts per million at 183 feet. It is possible that heavy pumping would cause this salt water to be drawn upward, thus acting as another source of contamination. In fact, this salty ground water probably is the source of the higher chloride contents now found in the raw water 25

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of the municipal supply, Records kept by Mr. Charles Fiveash, Superintendent of the Department of Water and Sewers, indicate that the chloride content of raw water from the Fort Lauderdale well field has increased gradually since the well field was put in operation. These records show that the average chloride content of the water in the well field when pumping first started in 1927 was about 10 parts per million. Records are available for average chloride content during 6-month periods from 1932 to the present. The average for the first 6 months in 1932 was 13 parts per million. During the last 6 months of 1932 the average was 12 parts per million. The content has gradually increased, with some fluctuations, and for the first 4-months of 1947 was 20 parts per million. The highest 6-month average was 24 parts per million for January-June 1944. The lowest 6-month average was for the last half of 1933, only 10 parts per million. SUMMARY AND CONCLUSIONS The lithology of the well-field area has been determined from study of the cuttings obtained from six test wells, among which is G 515 in the grounds of the Fort Lauderdale golf course. A large part of the upper section of the aquifer has a low permeability, being composed of very fine-grained quartz sand mixed with clay and marl. The most permeable zone at well G 515 is found between 104 and 123 feet below the land surface, and it is in this zone that future wells can best be developed. This permeable zone is characterized by discontinuous layers of sandy limestone or calcareous sandstone up to 6 feet thick, associated with permeable shelly sands. The water from this horizon is in a semi-confined state, owing to the relatively low permeability of the overlying beds. The water is under no artesian pressure as such -that is, it does not rise in wells above the level at which it is struck -but when water is removed by pumping the inflowing water finds it easiest to travel in a more or less horizontal rather than a vertical direotion., .26

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Lenses of permeable sand, which in some places have considerable horizontal extent, interfinger with the beds having relatively low permeability in the upper section of the aquifer, and it is in these permeable lenses that salty water moves out of the tidal canals most easily. Hydrologic studies indicate that ground-water flow is generally from northwest to southeast, and that the source of the ground water is not far distant, most of it being derived from.rain which has fallen on the Atlantic Coastal Ridge; not from far in the Everglades. The floor of the middle and northern Everglades is quite impermeable and the ground water is relatively highly mineralized even near the surface. If there were any considerable ground-water flow through the rocks underlying the Everglades, fresh water should long since have flushed out the salty water. The water-table contours indicate that the present drainage canals and ditches in the well-field area do not draw off excessive quantities of ground water. In fact, there is evidence that during dry seasons Peters Canal helps considerably to maintain higher water levels closer to the North New River Canal than would be found if Peters Canal were not in existence. Furthermore, irrigation with pumped ground water around the farm buildings of the Peters' ranch has created a ground-water mound to the west and southwest of the Fort Lauderdale well field, and helps maintain the ground-water level of the well field during dry periods (see pls. 7 and 8). The quantity of water available for pumping is not known. No city supply well in the area has ever been pumped to its maximum capacity, nor has a punping test been run to determine the hydrologic coefficients of the aquifer. However, it is obvious that the present well field is not over developed. The average water levels seem to be adequate to protect the present wells from salt-water encroachment, provided present rates of withdrawal are not exceeded. During dry seasons the well-field water levels average about 2.5 feet above mean sea level, but rainfall raises the water level rapidly and the annual 27

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average water level of approximately 4 feet is adequate to protect the wells from any further ocean-water encroachment to a depth of approximately 160 feet. With the establishment of the Broward Conservation District's new water preserve it should be possible, during droughts, to divert water to the well-field area by means of ditches, dikes, and pumps. A higher water table, averaging 5 or 6 feet above mean sea level, could then be maintained in the well-field area to give adequate safety against salt-water encroachment. This highly colored surface water might cause a slight rise in the color of the City's raw-water supply but it probably would not be excessive. The years 1940 -46 during which water-level measurements have been recorded include only one year, 1940, in which the rainfall exceeded the average annual rainfall. From 1941-44 it ranged from 10 to 24 inches below normal. Weather Bureau records for Fort Lauderdale are incomplete for the years 1944-46 but the years 1944 and 1945 are among the driest years on record for southern Florida. A slight increase in the chloride content of the City water supply has occurred over the years, probably as a result of upward movement of the mineralized water underlying the well field. The water from the city wells during the first year of pumping averaged about 10 or 11 parts per million of chloride. This has risen gradually, with slight fluctuations, to the present average of 21 parts per million. The increase was probably caused to some extent by deepening the wells in 1940. There is no immediate danger from this source, but pumping rates should not be increased without further studies to determine the probable effects. As for private supplies, many wells in the North New River Basin have been factors in inducing chloride contamination of the aquifer by drawing salty ocean water in from the canals. These contaminated zones are irregular in shape and areal distribution. The chloride has come from ocean-water tongues which have intruded North New River, its tributaries, and the lower reaches of its tributary canals. This source of contamination can be checked only in two ways: 1) by 28

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providing sufficient flow in the canals to keep ocean-water tongues washed out of the rivers and canals, and 2) by building a dam or control works as far downstream as possible to prevent salt-water tongues from advancing into critical areas. On the basis of present information a number of conclusions can be drawn relative to the well field. The present wells probably are adequate to supply the quantities needed but without pumping test data the present pumping rates cannot be materially increased without the danger of inducing chloride encroachment from the underlying salt water. The present pumping does not intercept a very large portion of the natural ground-water flow, most of which is wasted by flow to the North New River Canal and thus to the ocean. This will always be the case to some extent, but much of this wasted flow could be captured by extending the well field to the northwest and increasing the pumpage. Sufficient work has not been done during -he present investigation to determine accurately the hydrologic coefficients of the aquifer and to obtain this information it is recommended that as soon as possible a pumping test be made in accordance with the methods used by the U. S. Geological Survey. During this test a well discharging at least 1,000 gallons per minute should be used. Such a test can determine whether an increased rate of pumping will promote encroachment from the salty connate water underlying the well field. It can also furnish quantitative information as to the coefficients of storage and transmissibility of the aquifer and these data could then be used to determine the proper well spacing for maximum production of water with minimum drawdown of the water table. Drawdowns in observation wolls near the present city supply wells indicate a coefficient of transmissibility of approximately 1,200,000 gallons per day per foot but this should be verified by a comprehensive pumping test before being used in well-spacing calculations or in predicting future drawdowns and extent of cones of depression. On account of continually changing conditions of weather, drainage, pumpage, 29

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cultural developments, etc,., it is believed that the following investigative ground-water program should be carried out in the future: (1) chloride determinations should be made regularly until such time as definite trends can be established; this can be accomplished if the sampling of the 36 wells now being done monthly is continued and analyses are made regularly for a period of several years; (2) monthly observations should be made of the water table in the wellfield area; and (3) at least two more water-stage recorders should be installed, one to the northwest and the other to the north of the present well field, so that information may be had for these source areas of the present Fort Lauderdale water supply. 30

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BIBLIOGRAPHY Brown, R. H.,,and Parker,.G. Go. 1945., Salt water encroachment in limestone at Silver Bluff, Miami, Florida: Econ..Geology, vol. 40, pp. 235-262, Discusses ocean-water encroachment at depth in the aquifer. Cooke, C..W. 1945., Geology of Florida: Florida Geological Survey Bull. 29. Mentions specifically many of the geologic formations found in Broward County and includes a geologic map. Cooper,. H. H., and Jacob, C. E, 1946. A generalized graphical method for evaluating formation constants and summarizing well-field history. Am. Geophys. Union Trans., vol. 27, pp. 526-534. Matson, G. C., and Sanford, Samuel 1913. Geology and ground waters of Florida: U. S. Geological Survey Water-Supply Paper 319. Describes Miami oolite along New River; mentions reports of fresh-water submarine springs near Fort Lauderdale; gives well records and data for a few wells at Fort Lauderdale. Parker, G. G., and Cooke, C. W, 1944. Late Cenozoic geology of southern Florida, with a discussion of the ground water: Florida Geological Survey Bull. 27. Describes character and explains origin of several geologic features, including transverse glades south of Fort Lauderdale, the "bottomless holes" of New River and the Atlantic Coastal Ridge, Maps include a geologic map not showing the surficial 31

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sands, a map of surficial deposits, a topographic-ecologic map, and a hyposometric map. Parker, G. G, 1945a. Memorandum on the Fort Lauderdale municipal ground water supply: Unpublished manuscript in open files of U. S. Geological Survey. Describes Fort Lauderdale well field and discusses water levels and chloride encroachment in the Fort Lauderdale area. Graphs included show chloride content of well S 330 and hydrograph of average monthly water level in well S 329. 1945b. Salt water encroachment in southern Florida: Am. Water Works Assoc. Jour., vol. 37, pp. 526-542.. Includes the chloride graph of well S 330 at Dania Plant of Florida Power and Light Company. The text describes the causes of observed changes. 32

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.,R41E,42 E f. ) PLANTATIu;ON R 41 E O .42 Eo P114 1 4")0 483 S10. 03o) N0H OP II5 NW. BTH ST. 0522 G4 N.W.9 INCINERATOR ROAO ROWARD BOULEVARD 135GI Z50.S ) 3 OP116 9 .041 60523M 3 W1 815532 II S809 $G0s 5 480 t 045 ( NTRA BL516V 1 8 S5321 64 0 40 0 8 0 ,0.45 o 40 0 o44 r o 00 459 8 0 £7.5 FOOR LAOLACROAE WEL2L ELO TGOLF PpNo COUNTRY CLWAUB) E, 046 1 <.,, 4¢S1 4 9s32 2 456 42 141 NTRA a 0D530828 InO G 1.44) S 5 82 0G49, 0541d, 111.2010 ,.j) 0496. 5TH 5 0 t ).4s 1, 5(.o, 5860 60S u S$ 321 lO#DG455, G44 aS 8 IIILS 4ELEvATIOI AT SP oF £3. 431 D o i AILROA '1 WELLS EQUIP4ED WITH ARTSFOR R L, UDERDAL &0221 5842 O 7WELLS FOR WHICH CHLOIDE 'IS)..$DATA ARE AVAILABLE SOS19 ts wrus Io wme cuaI I .OI53 BaRI T 9A 5941 tL PoRCH B LIGH CO G AIIALYSES ARE AVAILABLE 11 NEW RIVER CANAL -584 PLATE F G C SURVERY6A IAI 1641) G )542 111 OS4 YACHTI BAJSIN ROAD T S 65.3 7 054 z T.1 SS 8 4 / 4 5 // 5 8 5 \8 j 5 8 7 3 S S4QUIPPED WITH PUM0 0 -SCALE IN FEET 40 S664 S ,ASs ... saos Xo SB. t .. 8630MAP O SLEG AND ADJACENT AREAS TEPLTT TE