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STATE OF FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION
Virginia B. Wetherell, Executive Director
DIVISION OF RESOURCE MANAGEMENT Jeremy A. Craft, Director
FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Chief
BULLETIN No. 64
GEOLOGIC FRAMEWORK of the
LOWER FLORIDAN AQUIFER SYSTEM, BREVARD COUNTY, FLORIDA
By
Joel G. Duncan, William L. Evans III and Koren L. Taylor
In cooperation with Florida Department of Environmental Regulation Bureau of Drinking and Ground Water Resources UIC, Criteria and Standards DER Contract #WM351
Published for the
FLORIDA GEOLOGICAL SURVEY
Tallahassee
1994
UIVERSITY PF RTTIA LIBRARIES
DEPARTMENT
OF
ENVIRONMENTAL PROTECTION
SCIENCE
LIBRA0YA
LAWTON CHILES
Governor
BOB BUTTERWORTH
Attorney General
GERALD LEWIS
State Comptroller
BETTY CASTOR
Commissioner of Education
BOB CRAWFORD
Commissioner of Agriculture
VIRGINIA B. WETHERELL
Executive Director
JIM SMITH
Secretary of State
TOM GALLAGHER
State Treasurer
Bulletin No. 64
Both penecontemporaneous and diagenetic dolornitlization processes have apparently affecl. ed lower Floridan aquifer system carbonates in Brevard County- Dolostones associated with algal laminations and subaerial exposure surfaces are likely supratidal and at least partly peneconlemporaneous in origin, Partial, matrix selective dolomilizat[on is common in many of Ihe lower Floridan aquifer system dolastones and may be an important factor in the developmeni of moldic porosity (Murray, 1960). Murray (1960) suggested that where only partial dolomitization occurs, porosity can be created by 1he dissolution of non-replaced calcium carbonate remaining in the rock, possibly during periods of subaerial exposure. The origin of massive, regionalJy pervasive dolostone sequences within the lower Floridan is best explained by marine dolomitization, probably penecontemporaneous with deposition in a tidal flat environment.
HYDROGEOLOGY
General Hydrogeologic Summary of the
Floridan Aquifer System
Four major hydrogeologic units occur in peninsular Florida (SEGS 1986). These are the surti. cial aquifer system, the intermediate confining unit or intermediate aquifer system, the Floridan aquiter system and the sub-Floridan confining unit (Figure 10]. The Floridan aquifer system consists of the upper Floridan aquifer system, the middle confining unit and the lower Floridan aquifer system, The hydrogeology tor only the middle confining unit and lower Floridan aquifer system will be discussed in detail.
The upper-most hydrologic unit in the study area is the surficial aquiler system which is comprised of a thin blankel of terrace and fluvial sands, shell beds and sandy lirnestones of PJiocene, Pleislocene and Holocene age. In Brevard Countly, the suilicial aquifer system is a permeable unit contiguous with land surface which varies in thickness from 90 to 150 feet (Plate 3). The surficiat aquifer system is an
unconlined aquiter uncier water table conditions and is an important source of drinking water for more than half oi Brevard and Indian River counties (Scott et al., 1991) (Figure 12}.
The intermediate confining unit in the study area is associated with the Hawthorn Group, The Hawthorn Group sediments separate the overly irg surficial aquifer system and the underlying Floridan aquiler system- These sediments consist ot a low-permeability sequence o siliclastic sediments and carbonales which effectively confine he Floridan aquifer system throughout most of Ihe study area (Plate 3). The intermediate aquifer system is not well developed in eastern ceniral Florida and is not an imporlant source of drinking water. Locally, the intermediate confining unit may be breached due to sinkhole activity or erosion; thus, the upper Floridan aquifer system may be under confined, semiconfined or unconfined conditions.
Th~e Floridan aquifer system, as defined by Miller (1986), is a vertically continuous sequence of carbonate rocks of generally high permeability. These middle to upper Tertiary carbonates are hydrauliially connected to varying degrees. Permeability is typically several orders of magnitude greater Ihan those rocks thal bound the system above and below.
In Brevard County, the Floridan aquifer system generally consists of Iwo major permeable zones (Plate 3) separaled by a middle confining unit of lower permeability (Miller, 1986). The upper and lower Floridan aquifer systems and the middle confining unit are comprised of a sequence of Paleocene to Eocene carbonates, These carbonates may be hydraulically connected or separated based upon highly variable local geologic conditions.
In the lower Floridan aquifer system of southern Florida, there is a subzone of highly fractured and cavernous dolostone which exhibils high iransmissivities (Miller, 1986]. The car-
LETTER OF TRANSMITTAL
FLORIDA GEOLOGICAL SURVEY Tallahassee
April 1994
Governor Lawton Chiles, Chairman Florida Department of Environmental Protection Tallahassee, Florida 32301
Dear Governor Chiles:
The Florida Geological Survey, Division of Resource Management, Department of Environmental Protection, is publishing as Bulletin 64, Geologic Framework of the Lower Floridan Aquifer System, Brevard County, Florida, prepared by staff geologist Joel Duncan and research assistants William L. Evans III and Koren L. Taylor. This report presents data on the geology and hydrology of Brevard County. This report is timely because of its detailed examination of the lower Floridan aquifer system, which is used to receive liquid waste products. This information will be of significant value to local, county, and state planners, as well as to the private sector.
Respectfully,
Walter Schmidt, Ph.D.
State Geologist and Chief
Florida Geological Survey
Printed for the
Florida Geological Survey
Tallahassee
1994
ISSN 0271-7832
iv
TABLE OF CONTENTS
PAGE
ACKNOW LEDG EM ENTS ........................................................................................................................ ix
ABSTRACT ............................................................................................................................................... x
INTRO DUCTIO N ...................................................................................................................................... 1
STRUCTURAL G EO LOGY ..................................................................................................................... 5
Regional Structural Fram ework ................................................................................................... 5
Structural Fram ework of Brevard County ........................................................................................ 5
LITHOSTRATIG RAPHY ......................................................................................................................... 14
General Stratigraphy .......................................................................................................................... 14
Paleocene Cedar Keys Formation ............................................................................................... 14
Lower Eocene O ldsm ar Formation ............................................................................................. 14
M iddle Eocene Avon Park Form ation ........................................................................................ 16
Upper Eocene Ocala Lim estone ................................................................................................. 17
M iocene Hawthorn G roup ................................................................................................................ 18
Pliocene to Holocene Undifferentiated ........................................................................................ 18
DEPOSITIO NAL ENVIRO NM ENTS ................................................................................................. 18
O ldsm ar Form ation ............................................................................................................................. 19
Avon Park Form ation .......................................................................................................................... 20
GEOPHYSICAL CHARACTER OF THE LOWER FLORIDAN AQUIFER SYSTEM ......................... 21
DOLOMITIZATION IN THE LOWER FLORIDAN AQUIFER SYSTEM ....................... 23
HYDROG EO LOGY ................................................................................................................................ 25
General Hydrogeologic Sum m ary of the Floridan Aquifer System ............................................... 25
Hydrogeology of the M iddle Confining Unit of the Floridan Aquifer System ................................... 35
Hydrogeology of the Lower Floridan Aquifer System ................................................................... 35
Boulder Zone ................................................................................................................................. 38
Confining Layers ............................................................................................................................ 42
Fractures and Vertical Flow ..................................................................................................... 42
Hydraulic Head in W ells ................................................................................................................ 43
Aquifer Loading .............................................................................................................................. 46
Geothermal G radients .................................................................................................................... 49
GRO UND-W ATER CHEM ISTRY ANALYSIS .................................................................................... 57
In tro d u ctio n ........................................................................................................................................ 5 7
Primary W ells ..................................................................................................................................... 60
M e rritt Is la n d .................................................................................................................................. 6 0
South Beaches .............................................................................................................................. 64
D B L e e ....................................................................................................................................... 6 8
Secondary W ells ................................................................................................................................ 71
Harris Corporation .......................................................................................................................... 71
G ra n t S tre e t ................................................................................................................................... 7 3
Port Malabar .................................................................................................................................. 74
W est M elbourne ............................................................................................................................. 74
Hercules, Inc .................................................................................................................................. 75
DISCUSSIO N AND CO NCLUSIO NS ............................................................................................... 76
v
R E F E R E N C E S ....................................................................................................................................... 77
APPENDICES ............................. -...82
A. Hydrogeologic summaries of injection well sites ..................................................................... 82
Al. Merritt Island Injection Well ................................................................................................ 83
A2. South Beaches Injection Well ............................................................................................ 84
A3. D. B. Lee Injection Well ..................................................................................................... 85
A4. Harris Corporation Injection Well ....................................................................................... 86
A5. Grant Street Injection Well ................................................................................................. 87
A6. Port Malabar Injection Well ................................................................................................. 88
A7. West Melbourne Injection Well .......................................................................................... 89
A8. Hercules, Inc. Injection Well .............................................................................................. 90
ILLUSTRATIONS
Figure Page 1. Map of peninsular Florida showing the location of the study area and the injection well ............. 2
2. Geomorphologic features of Brevard and Indian River counties ................................................. 3
3. Map showing the location of the A-A' cross section and the injection wells ................................. 4
4. Pre-Cenozoic structural features of Florida and southern Georgia .............................................. 6
5. Basement faults of peninsular Florida .......................................................................................... 7
6. Mid-Cenozoic structures affecting the lower Floridan aquifer system .......................................... 8
7. Structure top of the Oldsmar Formation (glauconite marker bed) ............................................... 9
8. Hypothetical model of karst fill structure ..................................................................................... 11
9. Basement (Jurassic) fracture zones of the Florida/Bahama region ............................................ 13
10. Lithostratigraphic/hydrostratigraphic nomenclature for southern Florida .................................. 15
11. Detailed lithostratigraphic column with gamma-ray and sonic log for a portion of the
upper Avon Park Formation in the Merritt Island injection well ................................................. 22
12. Areas of surficial aquifer system use, Brevard and Indian River counties ................................ 26
13. Top of the Floridan aquifer system (Ocala Limestone), Brevard County .................................. 28
14. Thickness of the Floridan aquifer system, Brevard and Indian River counties ........................... 29
15. Floridan aquifer system recharge potential, Brevard and Indian River counties ........................ 30
ILLUSTRATIONS
Figure Page 16. Areas of artesian flow from the Floridan aquifer system, Brevard and Indian River counties ......... 31 17. Floridan aquifer system potentiometric surface, Brevard and Indian River counties ................. 32
18. Estimated transmissivity of the upper Floridan aquifer system, Brevard and
Ind ia n R ive r co unties ....................................................................................................................... 33
19. Top of the sub-Floridan confining unit, Brevard and Indian River counties ................................ 34
20. Top of the middle confining unit in central Brevard County ......................................................... 36
21. Thickness of the middle confining unit of the Floridan aquifer system for the injection wells in
Brevard and Indian River counties ............................................................................................ 37
22. Top of the lower Floridan aquifer system, Brevard and Indian River counties ........................... 39
23. Thickness of the lower Floridan aquifer system, Brevard and Indian River counties ................. 40
24. Top of the Boulder Zone, Brevard and Indian River counties ................................................... 41
25. Average fracture density for several common rock types naturally deformed in the
sam e physical environm ent ........................................................................................................ 44
26. Hypothetical hydrogeologic conditions which could result in vertical flow of different waters ......... 45 27. Response of water in a well penetrating a confined aquifer to oceanic tidal loading ................. 47
28. The effects of oceanic tidal loading and barometric loading of water levels in the
D. B. Lee injection and monitor wells ......................................................................................... 48
29. Comparison of hydraulic head values between the two Harris Corporation monitor wells ...... 50 30. Comparison of hydraulic head values between the two Port Malabar monitor wells ................. 51
31. Comparison of hydraulic head values over time between the D. B. Lee injection
a nd m o n ito r w e lls ............................................................................................................................ 5 2
32. Background readings for the D. B. Lee injection and monitor wells prior to the
first inje ctio n te st .............................................................................................................................. 5 3
33. Results of the first D. B. Lee injection test ................................................................................. 54
34. Recovery of D. B. Lee injection and monitor wells after the first injection test ........................... 55
35. Hypothetical hydrogeologic cross section through peninsular Florida, demonstrating
the concept of cyclic flow of seawater, induced by geothermal heating ..................................... 56
36. Relationships of monitor, confining, and injection zones of the study wells ............................... 58
37. Total Dissolved Solids values of the Merritt Island well deep monitor zone .............................. 61
38. Chloride concentrations of the Merritt Island well deep monitor zone ........................................ 62
39. Total Kjeldahl Nitrogen values of the Merritt Island well deep monitor zone .............................. 63
40. Total Dissolved Solids values of the South Beaches well deep monitor zone .......................... 65
41. Chloride concentrations of the South Beaches well deep monitor zone .................................... 66
42. Total Kjeldahl Nitrogen values of the South Beaches well deep monitor zone .......................... 67
43. Total Dissolved Solids values of the D. B. Lee well deep monitor zone ...................................... 69
44. Chloride concentrations of the D. B. Lee well deep monitor zone ............................................. 70
45. Total Kjeldahl Nitrogen values of the D. B. Lee well deep monitor zone ................................... 72
PLATES IN POCKET
1. Stratigraphic cross section line A-A' with lithostratigraphy
2. Structural cross section line A-A' with lithostratigraphy
3. Hydrogeologic cross section line A-A' with lithostratigraphy
4. Lithostratigraphic column, Gamma Ray log, and Sonic log for the South Beaches injection well
5. Lithostratigraphic column, and Gamma Ray log for the Hercules, Inc. injection well
ACKNOWLEDGEMENTS
The authors would like to express their gratitude to members of the Florida Geological Survey staff and other individuals who contributed to this report. Special thanks to Dr. Thomas Scott for his input and discussions related to the lithostratigraphy and structure of Tertiary rocks in Florida. Also thanks to Dr. Jim Tull for fruitful discussions regarding faulting and fracturing theory.
Graduate Research Assistants Clay Kelly, Tom Seal, and Bob Fisher are thanked for their assistance in describing lithologic samples contained in this report. Thanks to Frank Rupert and Clay Kelly for identifying benthic foraminifera and Mitch Covington for evaluating nannofossils for this study. Thanks to Clay Kelly, Diane Brien and Elizabeth Doll for digitizing geophysical logs used in this report.
Special thanks are extended to Jim Jones and Ted Kiper for preparing figures for this report and to Cindy Collier for typing the manuscript.
The authors are also grateful to Joseph Haberfeld, John Armstrong, Jim McNeal, Rich Deuerling and Marion Fugitt of the Florida Department of Environmental Regulation for their input and interest in this study and for arranging funding for this project under DER Contract Grant #WM 351.
Finally, the authors gratefully acknowledge those staff members of the Florida Geological Survey who reviewed the manuscript: Jon Arthur, Paulette Bond, Ken Campbell, Jacqueline Lloyd, Ed Lane, Dr. Walt Schmidt, and Dr. Thomas Scott.
ABSTRACT
A common problem for coastal communities in Brevard County has been the disposal of liquid waste products. A favored solution utilizes injection-disposal wells whereby liquid waste is pumped underground into highly permeable rocks within the non-potable portion of the lower Floridan aquifer system. Ground-water chemistry data from monitor wells at several Brevard County injection sites suggest that the presence and/or lateral continuity of suitable confining rock above the injection zone is questionable and indicate that a better understanding of the lower Floridan aquifer system is needed. Thus, the purpose of this study is to detail the geologic framework of the lower Floridan aquifer system in Brevard County.
Strata of the lower Floridan aquifer system in Brevard County dip generally to the southeast with an average dip angle of 0.1 degree. Several lines of evidence suggest the possibility of faulting in Brevard County. The inferred faults strike north-south and are downthrown to the west.
Cores of lower Floridan aquifer system strata commonly exhibited some degree of fracturing. In general, fractures appear to be restricted to well indurated or highly cemented carbonates, principally dolostone. Slickensided surfaces, lacking well defined fracture planes, were observed in moderately to poorly indurated limestones.
Strata of the lower Floridan aquifer system in Brevard County are characterized by Paleocene to Middle Eocene, interbedded limestones and dolostones. Limestones are generally fossiliferous, moderately to poorly indurated, and have high primary porosity. Dolostones are typically well indurated and have fossil moldic and vugular porosity.
In Brevard County, the Floridan aquifer system generally consists of two major permeable zones separated by a middle confining unit of lower permeability. The middle confining unit in the study area consists of dense dolostone with interbedded limestones which act as a single leaky confining unit within the main body of the permeable carbonates of the Floridan aquifer system. Carbonates below the middle confining unit in the lower Floridan aquifer system are predominantly low permeability, interbedded dolostones and limestones with zones of moderate to high permeability.
The "Boulder Zone," a subzone of the lower Floridan aquifer system, is the primary injection horizon in Brevard County and consists of highly fractured and cavernous dolostones which exhibit high transmissivities. Above the Boulder Zone, there are layers of carbonates that have confining qualities. Evaluation of geophysical logs, lithologic samples and borehole videos from Brevard County injection wells indicate that numerous fractures exist throughout the lower Floridan aquifer system.
Analysis of monitor zone ground-water chemistry data showed that the majority of the wells in the study exhibit trends in water quality to some degree. These trends, barring wellbore mechanical problems, are attributed to the upward migration of injected waste waters along permeable conduits related to fractures, dissolution cavities, and vertical and lateral lithofacies variations. The middle confining unit of the Floridan aquifer system in Brevard County is probably best described as having a leaky confining character.
Bulletin No. 64
GEOLOGIC FRAMEWORK OF THE LOWER FLORIDAN AQUIFER
SYSTEM, BREVARD COUNTY, FLORIDA
By
Joel G. Duncan, P.G. #396, William L. Evans III and Koren L. Taylor
INTRODUCTION
Brevard County is located on the Atlantic coastline of eastern, central peninsular Florida (Figure 1). White (1970) places Brevard County in the Mid-Peninsular Zone which is "characterized by discontinuous highlands in the form of sub-parallel ridges separated by broad valleys." According to White (1970), the geomorphology of Brevard County consists of, on the east, the Atlantic Coastal Ridge and on the west, the Eastern Valley (Figure 2). Ten Mile Ridge is a discontinuous ridge trending northwest-southeast through the southeastern portion of the county (White, 1970).
Coastal communities in Brevard County, like many others in Florida, have experienced a substantial population increase over the past several decades. Rapid growth and development accompanying the population influx resulted in increased demands on the environment. A common problem has been the disposal of liquid waste products, principally treated municipal sewage and in some cases, industrial waste byproducts. A favored solution utilizes injectiondisposal wells whereby liquid waste is pumped underground into highly permeable rocks of the lower Floridan aquifer system. In Brevard County, ground water within the lower Floridan is highly mineralized and unsuitable as a potable water source. Thus, disposal of injected waste water in this portion of the aquifer system was not considered a problem. Ideally, upward migration of liquid waste into potable portions of the aquifer system is prevented by a confining sequence of impermeable strata overlying the injection zone.
Monitor well data from several injection sites in Brevard County suggest that the presence
and/or lateral continuity of suitable confining rock above the lower Floridan injection zone is questionable. These data indicate that a better understanding of the lower Floridan aquifer system is necessary in formulating protective criteria for future injection projects. The purpose of this study is to detail the geologic framework of the lower Floridan aquifer system in Brevard County. This will contribute to a better understanding of the local aquifer hydrogeology and thus support future injection well practices that maximize resource protection.
This investigation summarizes the geology, hydrogeology, and ground-water chemistry of the lower Floridan aquifer system based on data from seven injection wells in Brevard County and one in Indian River County. Data employed in the study included well cuttings, cores, injection well tests, borehole videos, geophysical logs, and monitor well water chemistry information.
The report focuses on the following aspects of the lower Floridan aquifer system:
1. Structural Geology
2. Lithostratigraphy
3. Depositional environments
4. Dolomitization
5. Geophysical character
6. Hydrogeology
7. Ground-water chemistry analysis
The greatest concentration of injection wells occurs in the Melbourne-Palm Bay area (Figure 3). Merritt Island, approximately 25 miles north of Melbourne, is the northern-most injection site of the study. The Hercules injection site, in Indian River County, is the southern-most injection well included in the study and was chosen as a control well outside the primary study area for comparison purposes.
Florida Geological Survey
5 10 15 MILES
5 10 i15 20 25 KILOMETERS
SCALE
LEGEND
WELL LOCATIONS
MI = MERRITT ISLAND INJECTION WELL
DBL D. B. LEE INJECTION WELL
WM WEST MELBOURNE INJECTION WELL
GS GRANT STREET INJECTION WELL
HC HARRIS CORPORATION INJECTION WELL
PM PORT MALABAR INJECTION WELL
SB SOUTH BEACHES INJECTION WELL
HI = HERCULES INC, INJECTION WELL
Figure 1. Map of peninsular Florida showing the location of the
study area and the injection wells.
2
Bulletin No. 64
z
D LI
zi LD
z
0 0l
DBL
Brevarcd County Indian River County
C'
C'
1-
SB
7
5-
'-5 C'
ffi R I DGES VALLEY
* WELL LOCATION
[I
HI
COUNTY
ST, LUCIE COUNTY
0 5 10 15 MILES
0 5 10 15 20 25 KILOMETERS
SCALE
Figure 2. Geomorphologic features of Brevard and Indian River
counties (modified from White, 1970).
LEGEND
u H
LIJ u
OKEECHOBEE
Florida Geological Survey
Satellite Beach
Be
Melbourne Bead
A/
BREVARD
Fellsmere
LEGEND
WELL LOCATION A A'
CRESS SECTIEN
LO]CATIOUN
~ TOWN OR CITY
LOCATION
.ach
h
1
HI
1 Vero Beach INDIAN RIVER COUNTY
0 5 10 15 MILES
0 5 10 15 20 25 KILOMETERS SCALE
Figure 3. Map showing the location of the A-A' cross section
(Plates 1-3) and the injection wells.
K
Bulletin No. 64
STRUCTURAL GEOLOGY
Regional Structural Framework
In Florida, Mesozoic and Cenozoic sediments overlie an eroded basement rock complex ranging from Precambrian to Jurassic (Barnett, 1975). The Peninsular Arch (Figure 4), the dominant structural feature of Florida, is a northwest-southeast trending positive basement element cored by a large block of Precambrian rock covered by Paleozoic strata (Barnett, 1975). The Peninsular Arch has been a positive feature affecting sedimentation from the Jurassic into the early Cenozoic (Miller, 1986).
Structural Framework of Brevard County
Brevard County lies on the eastern flank of the Peninsular Arch. Depth to basement ranges from approximately -7500 feet in the northwest to -11,000 feet National Geodetic Vertical Datum (NGVD) in the southeast portion of the county (Barnett, 1975). Barnett's (1975) subZuni subcrop map shows that basement rock in Brevard County consists of Middle Cambrian Osceola Granite with possible Jurassic volcanics in the extreme southern portion of the county. An apparently significant subsurface basement fault trends northwest-southeast from near the Florida-Georgia border down through the central portion of Brevard County according to Barnett's (1975) basement structure map (Figure 5). The interpreted normal fault is downthrown to the east.
The most prominent structural feature influencing the lower Floridan aquifer system in Brevard County is the Brevard Platform, described originally by Riggs (1979). Scott (1988) characterized the Brevard Platform as a low relief ridge or platform that plunges gently to the south-southeast and southeast (Figure 6). Both the Ocala Limestone and Hawthorn Group sediments erosionally thin across the Brevard Platform and have erosional upper surfaces (Brown et al., 1962; Scott, 1988). The observed
degree of thinning increases to the north into Seminole and Volusia Counties where both the Ocala Limestone and Hawthorn Group are missing after erosionally wedging out along the flanks of the Sanford High (Vernon, 1951). Riggs (1979) considered the Brevard Platform a southern extension of the Sanford High.
West of the Brevard Platform is the Osceola Low, described by Vernon (1951) as a faultbounded low with a significant thickness of Miocene sediments. Vernon's postulated fault that forms the eastern boundary of the Osceola Low trends north-northwest roughly following the Brevard Osceola County line and is upthrown to the east. Subsurface structure maps constructed on top of the Ocala Limestone for this area indicate anomalous apparent dip directions with possible dip reversals in the vicinity of Vernon's proposed fault. Scott (personal communication, 1991) interpreted the feature as "a possible flexure or perhaps a zone of displacement with 'up' on the east and 'down' on the west."
Strata of the lower Floridan aquifer system in Brevard County dip generally to the southeast away from the Brevard Platform axis at an average angle of 0.1 degree (Figure 7). Apparent dip angles are greater in the Melbourne Port Malabar vicinity ranging from 0.2 to 0.5 degrees locally. Several apparent dip reversals occur along a southeasterly trend from the West Melbourne site to the Port Malabar site.
Several lines of evidence indicate the possibility of normal faulting in Brevard County. The concentration, amount and quality of data in the Melbourne vicinity is much greater than that available in other areas making fault identification more confident. However, faulting is probably not restricted to this area. After detailed correlation of injection well geophysical logs (gamma-ray and sonic), a sequence of correlative marker horizons can be recognized and the thickness of specific stratigraphic intervals relative to the marker horizons can be determjned
Florida Geological Survey
SUWANNEE
STRAITS
LEGEND
AXIS OF POSITIVE FEATURE
AXIS OF NEGATIVE FEATURE
STUDY AREA
BOUNDARY OF NEGATIVE FEATURE
-N-
0 50 100 150 200 MILES )
0 100 200 300
KILOMETERS
SCALE
Figure 4. Pre-Cenozoic structural features of Florida and
south Georgia (from Miller, 1986).
Bulletin No. 64
LEGEND
STRIKE-SLIP FAULT
NORMAL FAULT
(box on down thrown side of
0 5 15 25 35 45 50 MILES
0 5 15 25 35 45 55 65 75 KILOMETERS
SCALE
Figure 5. Basement faults of Peninsular Florida (modified
from Barnett, 1975).
Florida Geological Survey
CHATTAHOOCHEE ANTICLINE ---\
SAU NOSE
JI JOHNS
GULF BASIN
APALACHICOLA EMBAYMENT
LEGEND
- BREVARD PLATFORM
AXIS OF POSITIVE FEATURE
AXIS OF NEGATIVE FEATURE
STUDY AREA
BOUNDARY OF NEGATIVE FEATURE
0 50 100 150 200 MILES 4
0 100 200 300 KILOMETERS SCALE
Figure 6. Mid-Cenozoic structures affecting the lower
Floridan aquifer system (modified from Scott et
al., 1991)
8
Bulletin No. 64
Figure 7. Structure top of the Oldsmar Formation (glauconite
marker bed).
Legend" ( IROCKLEIDGE 0-1710' 1 f DI
W 'ELL LOCATIONS
-1710' NGVD ELEVATION TOP OF THE OLDSMAR FORMATION CONTOUR INTERVAL, 100 FEET
NORMAL FAULT WITH
TEETH ON DOWNTHROWN i
BLOCK/Q)
PROBABLE NORMAL FAULT Iu
/ C
DBL C 1* 1884' C~ z/
+70' mssing sec-ti n O61
N d
/ /
I 7>183: G& 7-19180183 H
Q -1855'
JOPM
& -1851' (%
0 5 MILES O 5 10 KILOMETERS SCALE
Florida Geological Survey
(Plate 1). Marker-bed constrained stratigraphic intervals can then be compared on a well-to-well basis. Any significant variations in thickness within a particular stratigraphic interval can then be evaluated in terms of a possible fault, unconformity, or other geological mechanism.
Anomalously shortened stratigraphic sections are evident in the D. B. Lee and West Melbourne boreholes (Plates 1 and 2). Approximately 70 feet of strata are missing in both wells at two different stratigraphic levels. The omitted section occurs at a depth of approximately -2,086 feet NGVD in the D. B. Lee and
-1,368 feet NGVD in the West Melbourne well. The structure top of the Oldsmar Formation (glauconite marker bed) based on geophysical logs shows that the West Melbourne well is 51 feet higher compared to the D. B. Lee well (Figure 7) which is consistent with the appropriate footwall/hanging wall geometric relationship of a possible normal fault cutting both wellbores where the omitted sections occur (Plate 2). The West Melbourne and Grant Street wells are both located on the footwall or "upthrown" block of the fault and are on strike with respect to the Oldsmar Formation top. Marker beds above the fault cut in the West Melbourne well are structurally lower than the equivalent intervals in the Grant Street well indicating their position on the "downthrown" block of the fault (Plate 2). The fault apparently "dies out" upward above the Ocala Limestone in the Hawthorn Group somewhere between the West Melbourne and Grant Street wells (Plate 2). The similarity in the amount of shortened stratigraphic section or "throw" occurring in the D. B. Lee and the West Melbourne wells and the structural relationships between the West Melbourne and Grant Street wells suggest that the probable fault strikes north-south and is downthrown to the west.
Difficulties encountered during drilling operations, and unusual pump test results in the D. B. Lee injection well, could be a reflection of anomalous structural conditions in this vicinity. Extremely poor recovery on several attempts to
core could be an indication of highly fractured rock that may be associated with faulting in this wellbore. Pump tests (see Figure 33, Hydrogeology Section) conducted on the D. B. Lee injection well showed an almost immediate response in all three surrounding monitor wells (Knapp, 1989) indicating an unexpected high degree of vertical communication within the Floridan aquifer system at this location. This could be the result of a highly fractured injection and confining sequence, direct communication along a fault plane, or injection well mechanical problems. Sonic log cycle skipping and an erratic caliper log observed from approximately 1,150 feet below land surface (BLS) to 2,185 feet BLS could be explained by the presence of fractured rock (Plates 1, 2 and 3). Fracturing is also apparent on borehole videos beginning at a depth of 1,100 feet BLS down to 2,176 feet BLS.
Alternatively, the shortened stratigraphic sections in the D. B. Lee and West Melbourne wells could be interpreted in terms of two unconformities rather than a single fault. However, as the missing sections occur at significantly different stratigraphic levels in the two wells, such an interpretation would have to involve two separate unconformities representing two unique episodes of uplift. This interpretation appears less likely, over such a small stratigraphic interval, than one involving faulting given that the amount of missing section is approximately the same in both wells and the unique circumstances of the D. B. Lee.
Shortened stratigraphic sections in Brevard County wells could be an artifact of karst collapse structures. Conceptually this explanation would entail a sinkhole-like collapse and sediment in-fill with subsequent differential compaction and subsidence across the karst feature (Figure 8). A shortened section could occur between the hypothesized subsided sediment and the karst depression floor. However, the sediment package overlying the karst feature should be thicker overall relative to non-karst well locations. Detailed correlation of marker beds indi-
Bulletin No. 64
LEGEND
'X' MARKER BED E KARST FILL W "'Y'MARKER BED "Z'MARKER BED
UN CONFORMITY
/ / 7 7 / 7 / 7 7 7 7 7 7 7 Z /Z / / / 7 / / / / / /
/ / / -"/ -/ / -, / / 7/ 7/ / "/' "/ "/ "/ "/ "/ "/ "/ "/ '/ '/ '--7--
Figure 8. Hypothetical model of karst fill structure. Note
the apparent thickness between marker beds "X"
and "Z" remains constant even over the karst
structure.
11
TI-R SE RERBEDT X"
MARKER BEDS DUE TOl SUBSIDENCE OVER I I I KARST FILL STRUCTURE- 1- l
(POTRARSTFLFILLTU
. . . ...../.
T-SHDRTENED SECTION KARST FIL/.L A BETWEEN 'Y" AND "'Z. T- DUE TO DIFFERENTIAL -/X
COMPACTION/SUBSIDENCE
T-OVER KARST FILL ST!RUT-RE ,$ E
; ; " ; ; -- ; ;Z-MARKER JBED N_ N_ N - N N N_ N "
"//.1 " "/ "/ e "/"/ 2 4" / ,
Florida Geological Survey
cates that such stratigraphic relationships are not apparent between boreholes in Brevard County and a karst collapse origin for the shortened sections in the D. B. Lee and West Melbourne wells is unlikely.
Core from each of the four wells for which core was available exhibited some degree of fracturing. In general, fractures appear to be restricted to well-indurated or highly cemented carbonates of the Floridan aquifer system in Brevard County. Consequently, fractures are more prevalent in dolostones due to their consistently highly indurated nature than in limestones. Moderately- to poorly-indurated mudstones, wackestones, packstones and grainstones may act as mechanical boundary layers preventing the vertical propagation of fractures from dolostone beds. However, several core samples of poorly to moderately-indurated carbonates did have slickensided surfaces but lacked well defined fracture planes. The slickensides may be the unique expression of fracture-related strain consistent with the mechanical properties of the less indurated carbonate rocks.
The majority of observed fractures are high angle, approaching vertical and are probably tensional in origin. What appear to be shear fractures were observed in core recovered in the Harris #2 within the interval from 1,903 to 1,912 feet BLS. These fractures occur in a moderately-indurated mudstone sequence and have dip angles of approximately 50 degrees. The fractures have well developed, polished slickensided surfaces and could be related to faulting. Other data, such as anomalous differences in marker bed structural elevations between the Harris #2 and the Port Malabar well and shortened stratigraphic sections in the Harris #2 (between 2,000 and 2,130 feet BLS) and the Merritt Island (between 510 and 900 feet BLS) are also suggestive of possible small displacement faulting (<50 feet of throw). A second possible fault, downthrown to the west with northsouth strike, is suggested by the apparent dip
reversal occurring between the Harris #2 and Port Malabar wells (Figure 7 and Plate 2).
Tensional fractures in Brevard County could be related to several different processes in terms of their origin. These processes may include release fracturing as a result of sea level changes, fracturing associated with possible uplift of the Brevard Platform, and tension gash fracturing in proximity to fault planes.
The origin of faulting here is less clear given the apparent passive nature of the North American Atlantic coastal margin and the absence of salt-related tectonics that is typical of Gulf Coastal Plain regions. The most recent major tectonic event involving the FloridaBahama Platform region was the Late Cretaceous through Eocene convergence of the Caribbean plate with the North American plate in the northern Cuba and southern Bahama platform region (Sheridan et al., 1981). Sheridan et al. (1988) explained the present configuration of deep channels and shallow platforms of the Bahamas and Eocene faulting along the Abaco Canyon as the result of north-south compression associated with Caribbean-North American plate convergence. Convergence-related stresses reactivated old (Jurassic) planes of crustal weakness (Sheridan et al., 1988) such as the Abaco and Bahama Fracture Zones of Klitgord, et al. (1984) with possible left lateral shear displacement (Sheridan et al., 1981, 1988). The effect of these stresses along the projected trend of the Bahama Fracture Zone across the Florida peninsula (Figure 9) (and the Florida Atlantic Coastal Margin) has not been addressed, and the possibility of deformation similar to that proposed in the Bahamas cannot be ruled out.
Bulletin No. 64
Figure 9. Basement (Jurassic) Fracture Zones of the Florida/
Bahama Region (after Klitgord et. al., 1984).
13
Florida Geological Survey
LITHOSTRATIGRAPHY
General Stratigraphy
Cretaceous to Holocene strata in Brevard County consist of a thick sequence of interbedded limestone and dolostone overlain by a veneer of siliciclastic sediment. The Floridan aquifer system is characterized by Paleocene to Upper Eocene limestones and dolostones (Figure 10) that form part of an extensive carbonate platform that existed from late Cretaceous through Late Oligocene.
Dunham's (1962) carbonate classification system is utilized in the following discussion of the Floridan aquifer system lithostratigraphy. Carbonate rocks, based on Dunham's method, are classified according to depositional texture with the primary emphasis on the presence or absence of carbonate mud and the abundance of carbonate grains (allochems). The classification system also distinguishes between mudsupported and grain-supported rocks which is the criteria used to separate wackestone from packstone and grainstone.
Paleocene Cedar Keys Formation
The Cedar Keys Formation is a sequence of interbedded dolostones and evaporites unconformably overlying the undifferentiated Cretaceous Lawson Formation and conformably underlying the Lower Eocene Oldsmar Formation (Chen, 1965). The top of the Cedar Keys Formation was described by Chen (1965) as a "distinct lithology consisting of a gray, microcrystalline, slightly gypsiferous and rarely fossiliferous dolomite (dolostone)." Anhydrite with "chicken wire" texture is commonly interbedded with gray to tan dolostone in the lower two-thirds of the Cedar Keys Formation (Miller, 1986). The formation commonly contains the foraminifera species Borelis gunte1ri except in the highly recrystallized dolostones of the upper Cedar Keys section (Miller, 1986).
The top of the Cedar Keys Formation according to Miller (1986) ranges from approximately
-2,200 feet NGVD in northern Brevard County to
-3,000 feet NGVD in southern Brevard County. The Merritt Island, Harris #2, South Beaches, and Port Malabar wells were drilled within this depth range and could have penetrated the upper Cedar Keys Formation. Examination of cuttings over these intervals show a change from grayish and yellowish-brown dolostones characteristic of the lower Oldsmar to a gray dolostone that could be interpreted as Cedar Keys Formation. However, a definitive Cedar Keys Formation top was not identified in these wellbores.
Lower Eocene Oldsmar Formation
Miller (1986) defined the Oldsmar Formation as "the sequence of white to gray limestone and interbedded tan to light-brown dolomite (dolostone) that lies between the pelletal, predominantly brown limestone and brown dolomite (dolostone) of the Middle Eocene and the gray, coarsely crystalline dolomite (dolostone) of the Cedar Keys Formation." The contacts with both the underlying Cedar Keys Formation and the overlying Avon Park Formation are unconformable (Braunstein, et al, 1988). In Brevard County, the Oldsmar Formation top is indicated by a white to light gray, glauconitic, moderately indurated wackestone or packstone which contrasts with the cherty, brown dolostones of the overlying Avon Park Formation. The glauconitic zone has a characteristic gamma-ray and sonic log signature that is correlative between all the injection wells (Plates 1 and 2) and serves as an excellent datum for stratigraphic and structural analyses. Helicostegina gyrali is a common faunal constituent of the glauconitic interval. The top of the Oldsmar Formation ranges from
-1,667 feet NGVD at the Merritt Island site to
-1,918 feet NGVD at the Harris #2 site (Figure 7).
Overall, the Oldsmar Formation consists of an upper section of interbedded packstone, wacke-
LITHOSTRATIGRAPHIC HYDROSTRATIGRAPHIC SYSTEM SERIES UNIT UNIT
QUATERNARY HOLOCENE SURFICIAL UNDIFFERENTIATED AQUIFER PLEISTEOCENE PLEISTOCENE-HOLOCENE SYSTEM SEDIMENTS
TERTIARY PLIOCENE TAMIAMI FORMATION INTERMEDIATE
CONFINING UNIT
OR
MIOCENE HAWTHORN GROUP AQUIFER SYSTEM
OLIGOCENE SUWANNEE LIMESTONE UPPER FLORIDAN
AQUIFER
w UPPER OCALA LIMESTONE FLORIDAN SYSTEM
MIDDLE AQUIFER DE CONFINING LAVONPARK FORMATION UNIT ED SYSTEM LOWER
LLJ LOWER OLDSMAR FORMATION FLORIDAN AQUIFER
SYSTEM
PALEOCENE CEDAR KEYS FORMATION
SUB-FLORIDAN
CONFINING
CRETACEOUS UNDIFFERENTIATED UNIT AND OLDER
Figure 10. Lithostratigraphic/hydrostratigraphic nomenclature for southern
Florida (modified from Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, Southeastern Geological Society
(SEGS), 1986).
co C)
Florida Geological Survey
stone, mudstone, and dolostone and a lower section of predominantly well-indurated, crystalline dolostone. Benthic foraminifera and echinoderm fragments are the principle allochems composing the packstones and wackestones of the upper interbedded sequence. Clay is a common, but minor accessory mineral in the glauconitic wackestones of the upper Oldsmar Formation. Limestones are moderately cemented with a grain-fringing rim of microspar cement; however a pore-occluding, fresh-water, phreatic-spar cement was observed in a well-indurated packstone in the Merritt Island core at 1,720 to 1,723 feet BLS and the West Melbourne core at 1,967 feet BLS. Limestone porosity is generally high (20 to 30 percent) and permeability, based on visual estimates, is moderate to high.
Dolostones of the upper Oldsmar Formation are microcrystalline to finely crystalline and fossils are typically not preserved. Laminations, burrows, mottles, and spar-filled root traces are common in dolostones of the upper interbedded sequence. Porosity is generally five percent or less and permeability is low. Matrix-selective dolomitization is apparent in some Oldsmar Formation dolostones where unaltered calcitic allochems appear to "float" in a finer grained dolostone matrix. Partial replacement imparts a speckled nature to some dolostones in this interval. Cores and geophysical logs indicate the dolostone beds range from approximately five to ten feet thick.
The lower Oldsmar Formation is characterized by grayish-brown, microcrystalline, dense, and generally non-fossiliferous dolostone. The top of this sequence is a distinctive marker horizon ("C" marker bed) on gamma-ray and sonic logs and is correlative throughout the study area (Plates 1 and 2). The gamma-ray log shows increased radioactivity below this horizon relative to the overlying section. The sonic log shows a marked decrease in interval transit time at this point, which is indicative of the low porosities (less than five percent) and permeabilities prevalent throughout much of this interval.
Middle Eocene Avon Park Formation
Miller (1986) defined the Avon Park Formation as "the sequence of predominantly brown limestones and dolomites (dolostones) of various textures that lies between the gray, largely micritic limestones and gray dolomites (dolostones) of the Oldsmar Formation and the white foraminiferal coquina or fossiliferous micrite of the Ocala Limestone." In Brevard County, the Avon Park Formation is characterized by white limestones ranging from grainstone to mudstone interbedded with grayish-brown to grayishorange dolostones commonly containing organics. Cherty dolostones are typical of the lowermost Avon Park Formation.
In Brevard County, the top of the Avon Park Formation is marked by a slight radioactive peak on the gamma-ray log which characteristically coincides with the first occurrence of Dictyoconus .. foraminifers (Plates 1 and 2). The top of the Avon Park Formation varies from
-232 feet NGVD in the Merritt Island well to -443 feet NGVD in the Harris Corporation well. Formation thickness averages approximately 1,500 feet across the study area.
The uppermost Avon Park Formation consists of very light orange to white, moderately indurated wackestones and packstones containing abundant Dictyoconus a. foraminifers. Below this interval, the Avon Park Formation is characterized by interbedded dolostones and limestones. The principal allochems are whole foraminiferal tests and echinoderm skeletal fragments. Organic flecks are common throughout much of the formation. Ooids were present in a middle Avon Park "oolite" in the West Melbourne well. The range of allochemical and textural alteration in dolostones varies from complete preservation to total destruction depending on the particular diagenetic mechanism. A gammaray marker bed, designated the "B" marker bed (Plates 1 and 2), occurs approximately midway through the Avon Park Formation and serves as an excellent reference datum for correlation
Bulletin No. 64
throughout Brevard County. In general, the "B" marker separates more thinly-bedded strata of the upper Avon Park Formation from more thickly-bedded and massive units of the lower Avon Park Formation.
Grain-supported limestones are only moderately indurated with generally high interparticle porosity and high permeability. Minimal amounts of pore-occluding cements are present and most of the porosity is primary in origin. Thin section analysis of middle Avon Park grainstones and packstones shows an isopachous fringing rim of cement surrounding individual grains, indicating possible marine phreatic cementation at the site of deposition (Harris et al., 1985). Possibly early marine cementation provided a rigid framework, thereby limiting the effects of compaction-related porosity reduction in these sediments.
Avon Park Formation dolostones exhibit a wide range of textural diversity due to varying types and degrees of diagenesis. Dolostones have generally subhedral to euhedral crystalline texture and have equigranular to inequigranular crystal fabric (Friedman and Sanders, 1967). Crystal size ranges from microcrystalline to fine. Burrows and vugs commonly contain coarsergrained dolomite crystals than the surrounding matrix. Sucrosic texture is common in very fineto fine-grained dolostones.
Induration is generally high in all the Avon Park dolostones. Pore type, porosity, and permeability are extremely variable throughout the formation. Porosity types include intercrystalline, moldic, intergranular, vugular, and fracture. Moldic porosity is probably the product of matrix selective dolomitization whereby unaltered calcitic allochems remain in the rock and are later dissolved, possibly during periods of subaerial exposure (Murray, 1960). Dolostones speckled with white calcitic allochems (chiefly foraminifera), alternating with moldic dolostones, throughout much of the Avon Park Formation indicate that partial- or matrix-selective dolomitization was an important diagenetic process affecting these rocks.
The lowermost Avon Park Formation is characterized by intervals of nodular chert and cherty dolostones. Silicified burrows encased in dolostone were present in the West Melbourne core from 1,700 to 1,705 feet BLS. Also, fracture-filling chert was apparent in cores from several injection wells (Harris #2, South Beaches). The chert is typically black to gray and highly brittle.
An apparent microfaunal marker horizon occurs within the lower Avon Park Formation in a majority of injection wells. Abundant Operculina cookei occurred at the same approximate stratigraphic level (based on correlation with geophysical log markers) in each well except for the D. B. Lee and West Melbourne sites (Plate 1). The Operculina cookei zone was encountered in the West Melbourne well approximately 80 feet below the equivalent stratigraphic position observed in other wells. The difference in stratigraphic position could be related to inadequate sampling procedures during drilling or poor preservation related to diagenesis. The presence (or absence) of this horizon in the D. B. Lee well was not determined due to limited access to samples.
Upper Eocene Ocala Limestone
The Ocala Limestone, as described by Applin and Applin (1944), consists of an upper member of white, poorly-indurated, porous coquina composed chiefly of foraminifera, bryzoan and echinoid fragments and a lower member of cream to white, fine-grained, poorly to moderately indurated, micritic, miliolid-rich limestone. The contacts between the underlying Avon Park Formation and the overlying Hawthorn Group are unconformable (Chen, 1965). In Brevard County, the Ocala consists of white to very light orange, medium grained, poorly to rarely moderately indurated, interbedded packstone and wackestone with occasional grainstone and mudstone. The principal allochems are foraminifera and echinoderm fragments. The Ocala Limestone micro-fauna commonly includes Lepidocyclina ocalana, Amphistegina pinarensis, and various
Florida Geological Survey
miliolids. The top of the Ocala Limestone is identifiable on gamma-ray logs as a sharp decrease in radioactivity relative to the overlying phosphatic Hawthorn Group sediments (Plates
1 and 2).
The top of the Ocala Limestone marks the top of the Floridan aquifer system in Brevard County (Miller, 1986). Porosity and permeability are generally high throughout the formation since most prImary pore space remains open and well connected. Porosity is both intergranular and moldic, with intergranular as the dominant form. The top of the Ocala Limestone ranges from
-104 feet NGVD at the Merritt Island site to -308 feet NGVD at the Harris Corporation site. Ocala Limestone thickness averages 130 feet.
Miocene Hawthorn Group
The Hawthorn Group in Brevard County overlies the Ocala Limestone and consists of interbedded olive to yellowish-gray, poorlyindurated calcareous clay, quartz sand, wackestone and dolostone. Phosphatic sand- and gravel-sized grains are characteristic accessory minerals of the Hawthorn sediments in the study area. Clay beds of the Hawthorn Group function as the upper confining unit for the Floridan aquifer system in Brevard County (Brown et al., 1962).
Hawthorn Group thickness is highly variable ranging from 20 feet at the Merritt Island site to 235 feet at the Harris Corporation site. The Hawthorn Group thins to the north and west with closer proximity to the Brevard Platform and Sanford High (Scott, 1988). The top of Hawthorn Group ranges from -55 feet NGVD at the Grant Street site to -134 feet NGVD at the D. B. Lee site.
Pliocene Holocene Undifferentiated
Overlying the Hawthorn Group is a sequence of unconsolidated shell beds, clays, and quartz sands that range from Pliocene to Holocene
(Brown et al., 1962). Constraining the age of these sediments is beyond the scope of this study. Total thickness of the Pliocene-Holocene section varies from 90 feet at the Harris Corporation site to 160 feet at the West Melbourne site.
DEPOSITIONAL ENVIRONMENTS
The thick sequence of limestones and dolostones comprising the Floridan aquifer system was deposited on an extensive carbonate platform that existed from Late Cretaceous through Oligocene. Carbonate sediments are intrabasinal deposits and are primarily the product of carbonate-precipitating organisms that thrive in warm, shallow tropical seas. Depositional environments on carbonate platforms are highly variable and as a result vertical and lateral facies can change over very short distances.
Cores offer the optimum means for depositional environment interpretations in terms of subsurface studies. Cuttings are less useful because of their small size and because of the uncertainty associated with cavings. The lack of core in general, and the lack of stratigraphicallyequivalent cored intervals in the available cores, poses severe limitations on the degree to which reasonable lower Floridan depositional environment interpretations can be made. Observations regarding depositional environments for the purposes of this study were based entirely on information derived from core and thin section examination. Core was available for the Merritt Island, West Melbourne, Harris, and South Beaches injection wells and, consequently, environmental interpretive efforts focused on these sites. Depositional environment interpretations focus on the Oldsmar and Avon Park Formations due to the availability of core and emphasis of this study on the geologic framework of the lower Floridan aquifer system.
Bulletin No. 64
Oldsmar Formation
Much of the interbedded mudstones, wackestones, packstones and dolostones of the upper Oldsmar have sedimentary structures and vertical facies variations that are indicative of tidal flat deposition (Shinn, 1983). The most representative sequence of probable tidal flat origin was cored in the Merritt Island well from 1,820 to 1,830 feet BLS. This section consists of interbedded dolostones, mudstones, wackestones, and packstones (Appendix A). Common allochems include peloids, foraminifera, highspired gastropods (molds and casts) and echinoderm fragments. The dolostones are laminated and contain root molds filled with dolospar. Some laminations have been partially disturbed by burrowing. Contacts between the dolostones and limestones vary from extremely sharp and unconformable to gradational. One unconformable contact in this interval has a highly porous and permeable packstone overlying a dense, laminated dolostone containing dolospar-filled root molds. The upper surface of the dolostone is irregular with curved to domal algal laminated structures ("tepee" structures). Deposition of the packstone on top of the tidal flat sequence probably occurred during a brief transgressive phase. The gradational contacts are diagenetic in nature and are the result of either increasing or decreasing degrees of dolomitization. At 1,821 feet BLS, irregular masses or clumps of wackestone with abundant root traces floating in a matrix of dolomite may represent a caliche horizon developed during subaerial exposure.
Andros Island tidal flats serve as an excellent modern analog for the depositional environment of upper Oldsmar carbonates. Many of the sedimentary structures and sequences found in tidal flat sediments on Andros Island (Shinn et al., 1969) are present in upper Oldsmar Formation core. Laminated dolostones of the Oldsmar Formation may be comparable to recent supratidal dolomitic crusts that occur on Andros Island tidal flats (Shinn et al., 1969). Wackestones and
packstones containing root casts, pelloids, and high-spired gastropods are similar to intertidal zone sediments of western Andros Island (Shinn et al., 1969). Stratigraphically equivalent intervals of the upper Oldsmar Formation in other injection wells in Brevard County have lithologic sequences very similar to that of the Merritt Island well. This similarity gives some indication of the tidal flats' potential areal extent, which, at a minimum, would range from the Merritt Island well south to the South Beaches well.
Core at 2,138 feet BLS in the South Beaches well (Appendix A7) has a brecciated texture with angular clasts of grayish-brown dolostone floating in a matrix of yellowish-brown dolostone. This zone may represent a caliche similar to that found at 1,821 feet BLS in the Merritt Island well or perhaps the angular nature of the fragments may be more indicative of a collapse breccia related to karstification.
The uppermost Oldsmar (upper 40 feet of the formation) lacks key sedimentary structures that might be indicative of a specific depositional environment. However, the observed mineralogical suite of this interval that includes glauconite, pyrite, collophane and clay is associated with unique chemical and depositional environmental conditions. Glauconite occurs in the form of well rounded, dark green, sand-sized peloids with concentrations ranging from one to as much as ten percent of the total rock (South Beaches and Port Malabar wells). Glauconitization occurs at the sediment seawater interface at depths of 195 feet down to 3,250 feet in open marine waters with temperatures of 59 degrees F (15 degrees C) or less (Odin and Fullagar, 1988). Low sedimentation rates and bottom turbulence are also necessary for glauconitization and as a result glauconitic sediments represent depositional hiatuses in the sedimentary record (Odin and Fullagar, 1988). Assuming glauconitization proceeds at a minimum water depth of 195 feet, then the uppermost Oldsmar glauconitic carbonates may record a significant, and possibly rapid, sea level rise since tidal flat deposits con-
Florida Geological Survey
taining subaerial exposure features occur immediately below this interval.
Collophane, in the form of rounded peloids, was identified in thin section from the upper Oldsmar glauconitic interval in the South Beaches well (1,881-1,889 feet BLS). Phosphates such as collophane apparently form where phosphate-rich water upwells adjacent to shallow shelves or platforms that border deep marine basins (Friedman and Sanders, 1978). Collophane forms at the sediment-water interface under similar conditions to that of glauconite and consequently is common in glauconitic sediments.
Pyrite occurs as subhedral to euhedral crystals in combination with glauconite. Pyrite crystals are commonly found within or form rims around glauconite peloids. Pyrite forms in organic, muddy sediments under reducing conditions (Miall, 1984) similar to those required for glauconitization which occurs at the oxidationreduction boundary (Odin and Fullagar, 1988).
The origin of the clay is somewhat problematic given the apparent isolation of the carbonate platform from any potential siliciclastic source during this time. Possibly the clay is altered volcanic ash blown northward from erupting volcanoes associated with subduction along the Caribbean and North American plate boundary.
The lower Oldsmar Formation is characterized by highly recrystallized, unfossiliferous dolostones. Original depositional textures that may have been present have been totally obliterated by dolomitization, making environmental interpretations impractical.
Avon Park Formation
A diversity of carbonate depositional environments are represented over the approximately 1,500 feet of vertical sequence that comprises the Avon Park Formation in Brevard County.
Sedimentary structures range from those indicative of low energy tidal flat to high energy shoaling conditions. Most environmental information for the Avon Park Formation is derived from limestones that have undergone low degrees of dolomitization. Much of the dolostone is highly recrystallized with poor preservation of primary textural features.
A sequence of grainstone, packstone, and wackestone in the middle Avon Park Formation (approximately 200 feet below the "B" marker) contains sedimentary structures indicative of beach deposition. A complete vertical beach sequence from offshore at the base to shoreface and foreshore at the top (Benard et al., 1962) can be recognized. The best example of this sequence occurs in the Merritt Island well in the interval from 1,180 feet to 1,250 feet BLS. The lithofacies grades upward from a low-energy wackestone at the base to high-energy grainstones at the top (Appendix A5). High angle cross beds are common in grainstones and packstones. Some zones of coarse to gravelsized "lag" were noted at the base of cross-bedded strata. Allochemical grains are dominantly skeletal.
The top of the beach sequence is capped by a peloidal grainstone (at 1,174 feet BLS) containing abundant tabular to spherical cavities known as "keystone vugs" which are commonly found in uppermost accretion beds of beach foreshore deposits (Dunham, 1970; Scholle et al., 1983). Keystone vugs are indicative of swash-zone deposition and represent cavities formed by trapped air bubbles that develop immediately above sediment which is flushed by onlapping wave action during daily tidal cycles (Scholle et al., 1983). The flushing action forces air out of the underlying sediment's intergranular pore space and upward into the overlying sediment where it can be preserved by early marine cementation (Scholle et al., 1983).
Core below the keystone vug zone consists of peloidal grainstones and packstones much of
Bulletin No. 64
which is cross-bedded. Coarse to gravel-sized "lag" zones are common at the base of crossbedded intervals. The cross-bedded sequence probably represents shoreface sedimentation by currents flowing parallel to the shoreline (Scholle et al., 1983). A transition from offshore to shoreface sedimentation is reflected by decreasing amounts of mud in the sediments as wackestone grades upward into packstone and grainstone.
The beach sequence has a geophysical character that is generally correlative throughout the study area. The carbonates here have an extremely low gamma-ray signal and abnormally high sonic-log porosities due to borehole washout in the moderately indurated limestones relative to the overlying and underlying well indurated dolostones.
The equivalent section cored in the West Melbourne well (1,396-1,404 feet BLS) consists of interbedded grainstone, packstone, and wackestone similar to that in the Merritt Island well with the exception of sedimentary structures. No bedding features of any kind were evident as the section is apparently highly bioturbated. Bioturbation typically signifies lower-energy conditions and slower sedimentation rates (Friedman and Sanders, 1978). At approximately 1,400 feet BLS a one-foot-thick interval of burrowed, oolitic grainstone (oolite) is present suggesting high energy, shoaling conditions were nearby.
Core from 985 to 995 feet BLS in the Merritt Island well consists of laminated, moldic, to vuggy dolostone. At 992 feet BLS in this interval, an approximately six-inch-thick section of irregular to wavy algal laminated and moderately indurated dolostone (dolomudstone) may be indicative of tidal flat deposition. Randazzo and Cook (1987) studied approximately 450 feet of upper Avon Park Formation core from west central Florida and concluded that except for a 10foot section, all of the cored interval was "characterized by tidal mudflat sedimentation."
Sedimentary structures indicative of tidal flat sedimentation included micritic crusts, rip-up clasts, contorted algal laminations, burrows, mottles and thin peat lenses.
GEOPHYSICAL CHARACTER OF THE LOWER FLORIDAN AQUIFER SYSTEM
The typical suite of borehole geophysical logs run as part of injection well-evaluation procedures includes gamma-ray, sonic, caliper, and induction resistivity. Lower Floridan aquifer system carbonates have characteristic responses to each geophysical tool which depend primarily on lithofacies type, mineralogy, porosity, water chemistry, and borehole conditions. The following discussion focuses on the general geophysical characteristics of representative lithofacies and certain key intervals within the lower Floridan aquifer system of Brevard County.
Poorly- to moderately-indurated limestones can be in many cases distinguished from interbedded, highly-indurated dolostones by using borehole geophysical criteria. Boreholes commonly enlarge or "wash-out" across poorlyto moderately-indurated lithologies and remain in gauge across highly-indurated zones during drilling operations. The effect is most apparent on caliper logs where relative borehole size variations can be readily noted. Sonic logs can record erroneously long travel times (i.e., high porosity) across wash-outs due to increased sound wave travel distances making porosity determinations invalid (Gulf Research and Development Company, 1978). A slight effect on the gamma-ray log in terms of reduced radioactivity across these zones can also be recognized. Induction resistivities are typically low in moderately- to poorly-indurated limestones due to abundant saltwater-saturated pore space in the rock.
A unique mineralogical assemblage within the uppermost Oldsmar Formation imparts a distinctive geophysical property to the interval resulting in a highly correlative marker horizon (Plates 1,
Florida Geological Survey
2 and 3). Glauconite, clay, and collophane are common accessory minerals within an interbedded sequence of wackestone and dolostone of the uppermost Oldsmar. The gamma-ray log, in response to this mineralogy, shows a distinct increase of gamma-ray activity across the zone which is correlative throughout the study area. The sonic log response across this interval, although not directly related to this mineralogy, is correlative to a lesser degree among all the injection wells. Sonic log interval transit times are highly variable through the uppermost Oldsmar, apparently reflecting porosity differences between the more porous limestones (approximately 30 percent porosity) and less porous dolostones (approximately 15 percent porosity) of this interbedded interval.
Sonic log response corresponds well to actual lithology in sequences consisting of lower porosity dolostones interbedded with higher porosity limestones. Dolostones in such cases have sonic log curves that peak in the low porosity direction (generally 20 percent or less porosity). Sonic log curves in limestones, on the other hand, peak in the high porosity direction (30 percent or greater). This relationship is especially true of upper Avon Park Formation sections in Brevard County. The Merritt Island sonic log and lithostratigraphic section from 400 to 800 feet (BLS) in the upper Avon Park Formation offers the best example of this property (Figure 11).
Induction resistivity logs can be useful in distinguishing relatively low porosity zones from relatively high porosity zones within the lower Floridan aquifer system. Low porosity, saltwater saturated carbonates are highly resistive and are typically indicative of dense dolostones or possibly calcite spar cemented limestones. Highly porous, saltwater-saturated carbonates have low resistivities and are generally indicative of porous dolostone or moderately to poorly-indurated limestone. Induction log resistivities across cavernous zones are extremely low and approach, if not equal, that of the formation water alone.
Several sections of the Floridan aquifer system have gamma-ray signatures that are correlative throughout Brevard County and serve as excellent datums for stratigraphic and structural analyses. In addition to the uppermost Oldsmar glauconitic zone, the lower Oldsmar Formation contains several correlative gamma-ray marker horizons including the "C" marker bed (Plates 1 and 2). The "B" marker bed (Plates 1 and 2) roughly divides the Avon Park Formation into upper and lower sections. The uppermost Avon Park, from the top down to the "A" marker bed (Plates 1 and 2), has highly correlative gammaray character.
DOLOMITIZATION IN THE LOWER
FLORIDAN AQUIFER SYSTEM
Several investigations into the nature of dolomitization within the Floridan aquifer system have been conducted. Studies done by Hanshaw et al., (1971), Cander (1991), Randazzo and Hickey, (1978), Randazzo and Cook, (1987) and Randazzo et al., (1977), focused on the lower Floridan aquifer system and are summarized in the following discussion.
Hanshaw et al., (1971) hypothesized a mixing zone dolomitization model for Floridan aquifer system dolostones of regional extent. In their model, dolomitization occurs in brackish waters formed where freshwater mixes with seawater along coastal areas or subsurface brines further inland (Hanshaw et al., 1971). Circulating ground water having a Mg/Ca ratio > 1 is the driving force for dolomitization in the mixing zone (Hanshaw et al., 1971). Thermal convection of saltwater within the Florida Platform, as proposed by Kohout (1965), could provide the circulation and mixing mechanism for dolomitization of much of the Floridan aquifer system carbonates (Hanshaw et al., 1971). The lateral and vertical movement of the saltwater-freshwater interface due to sea-level variations, climatic changes, and/or platform uplift or subsidence has also facilitated dolomitization within much of
Bulletin No. 64
MERRITT ISLAND I.W.
/ inn sonic
API UNITS 100 INCREASING POROSITY
'A
LEGEND
LIMESTONE
-Z z A DOLOSTONE
API = AMERICAN PETROLEUM INSTITUTE
300 = FEET BELOW LAND SURFACE
Figure 11. Detailed lithostratigraphic column with gamma-ray
and sonic log for the upper portion of the Avon Park Formation in the Merritt Island injection
well.
23
Florida Geologicaj Survey
the Floridari aquifer system (Hanshaw el al-, 1971).
A recent isolopic study by Cander {1991) argues against a mixing-zone ongin for pervasive doloslones of the Avon Park Formation. Cander (1991) found thai Avon Park Formation dolostones -have heavy oxygen and carbon iso. topic composilions and coeval Middle Eocene 87Sr/86Sr isolopic compositions, indioating thai the Avon Park Formalion underwent massive dolomtization by normal 1o hypersaline seawater during ihe Mididle Eocene, essenlially contemporaneous with deposition." He concluded that the Avon Park Formation in central perirsuiar Florida was deposited in a tidal flal environ. ment under arid climatic conditions analagous to the modern Persian Gulf (Cander. 1991)
Cander (1991), based on stable carbon and oxygen isotope compositions in the Avon Park Formation, recognized a lale-stage of mixingzone dolomite thal is present locally in areas near the present coasiline. The mixing-zone dolomite nucleated on and overgrew earlier marine-stage dolomite and does not replace limestone (Cander, 1991), Mixing-zone dolbstones of the Avon Park Formalion are dark brown, dense, hard, non-porous, and highly crystalline in contrast to the generally highly porous, reialively soil, chalky, and poory crystalline marine doloslones elsewhere in the Avon Park Formation (Cander, 1991). iDoloslonies having similar texlure and color to mixtng-zone dolostones described by Cander (1991) are presenl in the Avon Park Formation oi Brevard County,
Randazzo el aL, (1977) in their study of upper Avon Pak dolostones of west-central Florida recognized three principal lextures indicative of different dolomitization processes: 1) dolomitization by total replacemenl, 2) dolomitization by aggrading porphyroid ano coalescive rneornorphism, and 3) dolomilization by selective replacemeni. Original depositional texture is preserved in total replacemeni dolostones
(Randazzo et al, 1977). Porptlyfoid dolomitizat4on is characterized by scaltered, euhedral dolomite rhombs distributed lhroughoul the rock (Randazzo el al., 1977). The amount ol dolomite present is dependent on 1ow long dolomilization has been taking place (Randazzo et al., 1977). Selective dolomite replacement te.xlure occurs as a result of partial doiomilization ol allochems or matnx (Randazzo et al., 1977),
Randazzo and Hickey (1978) acknowledged the mixing-zone model's role in dolomilization of Avon Park carbonates in west-central Florida. They concluded that some Avon Park supratidal carbonales were partially dolomitize.d penecon. lemporaneously with sedimenlation. Ater burial, the supratidal sediments along with those from other deposilional environmenls were exposed to mulliple periods oi dolomitization resulting irom a laterally and vertically migrating saltwaler-ireshwaler interface and a ground-water mix. ing zone (Randazzo and Hickey, 1978).
Current dolomitizalion models. such as the mixing-zone and sabkha, remain highly conlroversial. Haidie (1987) questioned the validity ol mixing-zone and sabkha models based on severa] lines of evidence- Hardie's objeclions to the mixing.zone model included the following: 1) thermodynamic problems associated with using calculalions base-l on ordered dolomite lormalion rather Than the more appropriate and realistic disordered dolomite; 2) lack ci replacement dolomite in known modern coaslal mixing zones; 3) the lack ol dissolulion in calcitic limeslones underlying doloslones od alleged mixing zone origin. Hardie (1987) favored a direct precipitation origin for contemporaneous sabkha dolomtle instead of a replacement origin- Hardie based his hypothesis on the generalization that contemporaneous dolomite only forms at Low temperalures by cirecl precipitalion since replacement dolomile apparently requires much longer reaction times on the order of 10,000 years or grealer (Hardie, 1967)
Bulletin Na. 64
Both penecontemporaneous and diagenetic dolornitlization processes have apparently affecl. ed lower Floridan aquifer system carbonates in Brevard County- Dolostones associated with algal laminations and subaerial exposure surfaces are likely supratidal and at least partly peneconlemporaneous in origin, Partial, matrix selective dolomilizat[on is common in many of the lower Floridan aquifer system dolastones and may be an important factor in the developmeni of moldic porosity (Murray, 1960). Murray (1960) suggested that where only partial dolomitization occurs, porosity can be created by 1he dissolution of nan-replaced calcium carbonate remaining in the rock, possibly during periods of subaerial exposure. The origin of massive, regionalJy pervasive dolostone sequences within the lower Floridan is best explained by marine dolomitization, probably penecontemporaneous with deposition in a tidal flal environment.
HYDROGEOLOGY
General Hydrogeologic Summary of the
Floridan Aquifer System
Four major hydrogeologic units occur in peninsular Florida (SEGS 1986). These are the surti. cial aquifer system, the intermediate confining unit or intermediate aquifer system, the Floridan aquiter system and the sub-Floridan confining unit (Figure 10]. The Floridan aquifer system consists of the upper Floridan aquifer system, the middle confining unit and the lower Floridan aquifer system, The hydrogeology tor only the middle confining unit and lower Floridan aquifer system will be discussed in delail.
The upper-most hydrologic unit in the study area is the surticial aquifer system which is comprised of a thin blankel of terrace and fluvial sands, shell beds and sandy limestones of PJiocene, Pleislocene and Holocene age. In Brevard Countly, the suificial aquifer system is a permeable unit contiguous with land surface which varies in thickness from 90 to 150 feet (Plate 3). The surficial aquifer system is an
unconlined aquiter under water table conditions and is an important source ot drinking water for more than half oi Brevard and Indian River counties (Scott et al., 1991) (Figure 12}.
The intermediate confining unit in the study area is associated with the Hawttorn Group, The Hawthorn Group sediments separate the overly ir;g surficial aquifer system and the underlying Floridan aquifer system- These sediments consist of a low-permeability sequence ol siliclaslic sediments and carbonales which effeclively confine 1he Floridan aquifer system throughout most of Ihe study area (Plate 3). The intermediate aquifer system is not well developed in eastern ceniral Florida and is not an imporlanl source of drinking water. Locally, the intermediate confining unit may be breached due to sinkhole activity or erosion; thus, the upper Floridan aquifer system may be under confined, semiconfined or unconfined conditions.
The Floridan aquifer system, as defined by Miller (1986), is a vertically continuous sequence of carbonate rocks of generally high permeability. These middle to upper Tertiary carbonates are hydraulically connected to varying degrees. Permeability is typically several orders of magnitude greater Ihan those rocks thal bound Ihe system above and below.
In Brevard County, the Floridan aquifer system generally consists of Iwo major permeable zones (Plate 3) separated by a middle confining unit of lower permeability (Miller, 1986). The upper and lower Floridan aquifer systems and the middle confining unit are comprised of a sequence of Paleocene to Eocene carbonates. These carbonates may be hydraulically connected or separated based upon highly variable local geo logic conditions.
In the lower Floridan aquifer system of southern Florida, there is a subzone of highly fractured and cavernous dolostone which exhibits high iransmissivities (Miller, 1986), The cay-
Florida Geological Survey
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Figure 12. Areas of surficial aquifer system use, Brevard
and Indian River counties (after Scott et al.,
1991).
Bullelin. No 64
ernous and fractured nature of the doioslone commonly causes boulder size pieces of dole. stone to be dislodged during the drillirng process giving rise to Ihe lerm -Boulder Zone" by drillers and subsequenlly adopled by Kohout (1965) and later aulhors- In areas where the salinity of 1he waters in the Boulder Zone is greater than 10,000 mg/L, the Boulder Zone is used as a receiving zone for underground injection of industrial wastes and treated effluent. A more detailed discussion of the hydrogeology ol the middle confining unit, lower Floridan aquifer system and Boulder Zone is presented in subsequent sections of this repod.
Numerous Tertiary regressive/transgressve sequences have pro-duced a diverse carbonate lithology in the Floridan aquifer system (Plate 1). A typical sequence of deposition would vary from low energy, open platform, micnlic sediments grading into progressively higher energy packstones or grainstones cnaracterislic of a shoaling environment to low energy, tidal Ilat, fine-grained sediments. As a result of these numerous sea level Ituclualions and subsequent diagenelic changes, locally variable, complex hydrogeologic conditions exist throughout the Floridan aquiler system.
The Floridan aquiler system does nol necessarily conform 1o eilher lJithostraligraphic or chronostrallgraphic boundaries and lherefore, the top of the Floridan aquifer system (Figure 10) coincides with the uppermost vertically-continuous, permeable, Eocene ro Lower Miocene carbonate beds (SEGS, 1 986). In the study area, the top of the Floridan aquifer system is contiguous with the lop of the Eocene Ocala Limestone (Figure 10) and occurs at elevations ranging from .100 to deeper than -350 feet NGVD (Figure 13). The thickness of 1he Floridan aquifer system in the study area ranges between 2,300 lo more than 2,900 feet and generally increases to the soulh (Figure 14) (Scolt et al., 1991),
Recharge lo ihe Floridan aquifer system is directly associated with the degree of hydraulic confinement of the system. The highest rales of recharge occurs in northern Brevard County where ihe Floridan aquiler syslem is unconfined or poorly confined (Figure 15). Sinholes 1hat breach the niermediate confining unil and provide hydraulic communication between the surficial aquifer system and ihe Floridan aquifer system can result in either recharge to or discharge trom the Floridan aquifer system. In 1he study area recharge will occur in northern Greard County and western Indian River County (Figure 15). Discharge to the surlicial aquifer system will occur in areas of artesian flow (Figure 16)The potenliometric surface and regional hori2gntal flow of the Floridan aquifer syslem are also related to tne degree of conlinement. The potentiometric surface ol the upper Floridan aquifer system in the study area ranges from approximately 5 to 40 feet {Figure 17) and lateral flow is generally soulh. Where tMe potentrometric surface is higher than ihe surface elevation, artesian Ilow will occur (Figure 16), Arlesian conditions are present over most of the study area- In areas where there is relatively poor or non-existeni conlinerment, and where land surface is nigher than 1he potenliometric surface, (i.e., weslern Indian River County) arte. sian conditions are absent (Figure 16) and recharge to 1he Floridan aquifer system may occur (Figure 15). Transmissivity of the upper Floridan aquifer system (Figure 18) is generally higher in the southern portion of the study area but is locally variable because of complex hydrogeologic heterogeneily.
Massively bedded anhydrite usually occurs in the lower two-thirds of Paleocene rocks (Miller, 1986). The lop of the sub-Floridan conlining unit (Figure 19) is defined in terms of a permeability contrast that limils the depth of active groundwater circulation and does not represent any particular stratigraphic or lime uni (Figure 10). The pnjecilion and monitor wells in the study area are not deep enough 1o encounter the subFloridan confIning unit.
Florida Geological Survey
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Bulletin No. 64
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Bulletin No. 64
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Florida Geological Survey
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(alter Miller, 1986).
33
Florida Geological Survey
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Bulletin No- 64
Hydrogeology of the Middle Confining Unit of the Floridan Aquifer System
The upper and lower Floridan aquiler systems are separaled by a middle confining unit (Miller, 1956) (Plate 3). Locally this zone of confinement may contain thin zones of moderate to high permeabitity; however, as a whole, the unit acts as a single confining unit within the main body o! the permeable carbonates of the Floridan aquifer system. The Middle Eocene sediments that make up the middle confining unit are (MilLer, 1986) similar in composition to both the upper and lower Floridan aquifer systems. The middle confining unit is considered a leaky confining unit because of the lack of strong contrast in permeability between these three zones (Miller, 1986).
The middle confinng unit in the study area consists of dense dolostone with interbedded limestones located immediately below the A8marker bed oP the Avon Park Formation (Plate 3). The middle confining unit in the study area is defined as a zone of slightly lower permeability separating two zones of higher permeability. This determination is based upon estimated porosities of less than 20 percent, and lilhologic character determined from geophysical logs and sample descriptions (Plate 3).
The middle confining unit is recognized on geophysical logs by a slight increase in gamma ray activity and (when the carbonates are not fractured) a decrease in interval transil time on the sonic logs as the limestones of the upper Floridan aquifer system abruptly grade into low porosity (less than 20 percent), dense. microcrystalline dolostones that make up the middle confining unit (Plate 3)The top of the middle confining unit in the study area is between .600 la -1,100 feet NGVD and depth generally increases to the southeast (Figure 20 and Plate 3). The thickness of the middle confining unil ranges from 110 to 250 feet and decreases loward the south (Figure
21). Based on lithologic criteria, it appears that the middle confining unit is absent at the South Beaches injection well, demonstrating the signilicance of local geologic variation (Plate 4).
Quantitative tield data and aquifer tests that describe the water transmtting characteristics of the middle confining unit were analyzed for the Merrilt Island injection well (Appendix Al). Horizontal hydraulic conductivity is estimated at 2-7 X 10.4 cm/s, vertical hydraulic conductivity is 1.5 X 10-B cms and transmissivity is 609 gpd/ft (Geraghty and Miller, 1984). Geophysical evi. dence coupled with borehole video observations indicate that the middle confining unit contains fractures at several of the well sites (Plate 3). Locally, vertical fractures may hydraulically con. nect the upper and lower Floridan aquifer system: however, the available data is insufficient to accurately make this determination.
Hydrogeology of the Lower Floridan
Aquifer System
The lower Floridan aquifer system consists of all beds 1hat lie below the middle confining unit (Plate 3) and above the sub-Floridan confining unit (Miller, 1986). If the middle confining unit is absent (Le., Soulh Beaches injection well), the upper boundary of the lower Floridan can be defined geochemically, The geochemicaL boundary (Meyer, 1989) is where the total dissolved solids in the ground water is equal to or greater than 10,000 mg/L (Plate 3),
The rocks of the lower Floridan aquifer system are comprised of a thick, complex sequence 01 limestones and dolostones with highly variable carbonate mairices. The higher porosity, less dense limeslones of the lower Floridan aquifer system are geophysically identified where a slight decrease in gamma-ray activity and an increase in sonic interval transit time occurs (Plale 3}.
Geophysical and lithologic evaluations of the injection wells indicates that the lop of the lower
Florida Geological Survey
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7
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Florida Geological Survey
Floridan aquifer system is located at approximately -1,000 feel NGVD in northwestern Brevard County and increases to -1,500 feet NGVD in southeastern Indian River County (Figure 22). The injection wells are not deep enough to fully penetrate the lower Floridan aquifer system. Miller's regional maps indicate that the thickness of the lower Floridan aquifer system increases in a southeast direction with estimated thicknesses in the study area ranging between 1,500 to 2,000 feet (Figure 23).
Ground-water movement in the lower Floridan aquifer system and middre confining unit has not been adequately determined due to lack of reliable head data and to the transitory effects of ocean, Earth and atmospheric lides (Meyer. 1989). However, direction of waler movement can be inferred indirectly from temperature, chemical and isotopic data (Kohout, 1965). Kohoul (1965) proposed that ground water is moving upward from the lower Floridan aquifer system through the circuJation of cold seawater inland through the lower part of ihe Froridan aquifer system. Higher flow values result where the upper and lower Floridan aquifer systems are continuous or where zones oi secondary porosity such as fractures and dissolutional karstic features occur- Geophysical logs and borehole videos indicate that possibility for numerous Iracture zones in the lower Floridan aquifer system (Plate 3).
The quantitative methods used to describe aquifer parameters are usually based on homogeneous, isotropic conditions in a granular medium thai assumes laminar Ilow- On a regional scale these methods may be satisfactory (Bush and Johnson, 1988): however, locally. the lower Floridan aquifer system is extremely heterogeneous, and fractured carbonates are strongly anisolropic with respect to orientation and number of fraclures (Freeze and Cherry, 1979). Turbulent flow is common in karstic environments such as the Boulder Zone (DomenJco and Schwartz. 1990). Therefore, local hydrologic analysis for transmissivity, hydraulic conduc-
tivity and confinement within a fractured medium should be viewed with skepticism.
The carbonates ol the lower Floridan aquifer system are predominantly low-permeability. interbedded dolostones and limestones with zones of moderate to high permeability (Miller. 1986) (Plates 1, 2 and 3) (Appendix A). Hydraulic conductivity analyses by various consulting firms (Appendix A) indicate that vertical groundwaler movement in the lower Floridan aquifer system is generally low with values less than 10-4 crn/s in the vertical direction (Appendix A). Horizontal hydraulic conductivity (when analyzed) was higher with values no greater than 10-3 cmls (Appendix A). Transmissivity values for the lower Floridan aquifer system above the Boulder Zone were reported only in the Merritt Island, Port Malabar and Hercules injection wells, Transmissivity estimates were variable and ranged between 2.2 to 609 gpd/fl (Appendix Al, A6 and A8).
Boulder Zone
The Boulder Zone (Kohout, 1965) is a subzone of the lower Floridan aquifer system consisting of dolostones that display vertical and horizontal fractures and cavities. The Boulder Zone is a zone of high Ifarsmissivity which records a period when paleowater tables were at a level that resulted in karstilication of the upper part of the carbonate sequence (Vernon, 1970). Where the overlying dolostone is elfectively conlining. ihe Boulder Zone is used extansively lor receiving liquid wastes because of high transmissivillies (Appendix A). The Boulder Zone has no stratigraphic significance and can exist at any level or locale where paleocondilions allowed karstic processes 1o occur.
The Boulder Zone in the study area is generally located in the Middle Eocene Oldsmar Formation al a deplh of approximately -2.,000 feet NGVD between the glauconite marker bed and the "C" market bed (Figure 24 and Plate 3). Thickness ot the Boulder Zone is locally variable
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Figure 22, Top of the lower Floridan aquifer syslem, Brevard and
Indian River counlies (modified from Miller, 1 986).
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Florida Geological Survey
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Figure 23. Thickness of the lower Floridan aquiler system,
Brevard and Indian River counties (after Miller, 1 986).
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Bulletin No. 64
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counties (modified from Miller. 1986).
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Florida Geological Survey
and ranged belween 85 lo 190 feet (Plate 3). The cavernous nature of the Boulder Zone in peninsular Florida diminishes northward (Miller, 1986) (Figure 24).
The carbonates immediately overlying the Boulder Zone consist of inlerbedded wackestones, packslones and doloslones of the upper Oldsmar Formation (Plates 1 and 3). Porosities, estimated from the sonic logs, are generally greater than 20 percent. Geophysical logs, samples and borehole videos suggest thai this zone is fractured in some injection well boreholes (Plale 3).
Where the Boulder Zone is utilized for waste disposal. there is a traditional view that the dense doloslone immedialely above and below the Boulder Zone contains no secondary porosity and operates as a confining layer. However, a sludy ol four injection sites along the east coast of Florida by Safko and Hickey (1992) concluded that fracture porosity is the principal type of secondary porosity both within the Boulder Zone and the dolomlic rocks that lie above it. The present study utilizing core samples, borehole videos and geophysical logs, supports this hypothesis.
Confining Layers
Possible conlining layers above the Boulder Zone, within the lower Floridan aquifer system, were defined conservatively in this study and are not always in agreement with confining layers delineated by Ihe various consulting firms (Plate 3 and Appendix A). Criteria used for defining layers of confinement are based on geophysical logs and lithologic samples, In general, non-vuggy, fractureless micritic limestone and or microcrystalline dolostone with sonic log porosilies less than 20 percent, that are traceable and correlative in the subsurface belween the injection wells, are defined as confining layers.
There is a well defined, highly correlative and widespread glauconitic, micritic wackeslone located in the uppermost Oldsmar Formation (Plates 1 and 3). The glauconite marker bed is located approximately 60 to 235 feet above Ihe Boulder Zone (Plate 3), Porosities estimated from sonic logs range between 10 to 37 percenl and fracturing and/or vuggy lithology is absentThis layer is between 35 to 45 feet thick and appears to be a well defined zone o1 confinement (Plates I and 3). Hydraulic conductivity analyses conducted by the various consulting firms (Appendix A) for the Merritt Island, West Melbourne and Port Malabar injection wells report values ranging between 10-5 to 10'6 cts supporting the assumption that this layer is confining.
Locally, above the glauconite marker bad, there is P zone of rocks with confining qualities (Plate 3). This zone is located in the lower Avon Park Formation and has been delineated as the lower Avon Park confining zone by 1he Florida Geological Survey (Plate 3).
Geophysical logs, borehole videos and tithologic samples suggest that he lower Avon Park confining zone contains fractures ancor vuggy lithology. The data are insufficienl to determine the degree of fracture connectivity within these layers and it is not known whether these layers can transmit water via the fraclure network, Thus, it is not known if I he lower Avon Park confining zone is a good confining layer,
The rocks underlying the Boulder Zone are dense micro-crystalline doloslones wilh porosities less than 15 percent, These dolostones are fraclured in places and extend below the total depth of the injection wells. These carbonates appear to be a layer o1 confinement (Plale 3).
Fractures and Vertical Flow
As slated previously, analysis of geophysical logs, lithologic samples and borehole videos indicate that numerous fractures exist through-
Bulletin No. 64
out the lower Floridan aquifer system (Plate 3). When determining confining properties, the presence or absence of fracture syslems is extremely important- Fracture systems, with the proper orientation and connectivity, can transport water through rocks that appear to be confining.
Given the right geologic setting, brittle rocks od low porosity are most susceptible to fracturing (Dornenico and Schwartz, 1990). Dolostone is considered one of the most fracture-prone sedimentary rocks, second only to quartzile (Stearns, 1967) (Figure 25). Van GolI-Racht (1982) cites three cases where stress relaled Iractures may occur1. In response to folding and/or laulting;
2. Deep erosion or removal of the overburden,
which will produce differenlial stresses that
can cause fractures;
3. Rock volume shrinkage (shrinkage cracks)
where water is lost, for example, in shales
or shaley sands:
Cases 1 and 2 are believed to have occurred in 1he study area (see Lithosiratigraphy and Structural sections for further discussion) and furlher support Safko and Hickey's (1992) hypothesis ol vertical Iracturing of doloslones ovedying the Boulder Zone.
Increases in hydraulic conductivity due to secondary porosity can occur as a result of dissolulion of limestone by circulating ground water moving along fractures and bedding planesAnalyses of the sediment cores, geophysical logs and borehole videos indicate fractured dolostones in and above the injection zone (boulder zone) in the D. B. Lee and other injection wells (Plate 3). Normal faulling in the area where the West Melbourne and D_ B. Lee wells are located could result in increased secondary porosity along the fault plane and enhanced fracturing locally (see Structural Geology section for further discussion).
Hydrogeologically, the most important fracture properlies are orientation, density, aperture opening, smoothness of fracture walls, and most importantly, the degree of connectivity (Domenico and Schwartz, 1990). If a given set of fractures does not exiend through a confining layer or are not interconnected, then the rock cannot transmit water via the fracture network. As previously stated, there is strong evidence for fractures throughout the rocks within the lower Floridan aquifer system. The degree of connectivity belween these fractures is nol known and the water transmiting character is uncertain.
Dissolutional enlargement ol fault planes and fractures within zones of relatively impermeable carbonates can dramalically increase vertical and lateral hydraulic conductivity and result in localized transport of different waters through potential confining layers. Fault planes can lunction as conduits causing water to breach contining layers and bypass monitor wells. Figure 26 is a schematic diagram demonstrating these phenomena.
Hydraulic Head in Wells
By definition, a true impervious layer will not transmit pressure, due to a hydraulic head increase, between confined aquifers. Hydrogeologic units that are separated haom each other by a confining layer(s) should demonstrate conlrasting hydrologic behavior. Dislinci hydrologic systems which respond similarly suggest a hydraulic connection. Differences in head values and fluctuation between the mnilcr and injeclion wells indicate hydraulic separation. When the hydraulic heads fluctuate in a similar pattern a hydraulic connection could be present and vertical flow may be occurring.
However, confined aquifers are compressible and elastic over certain stress ranges and thus respond to changes in forces acting upon them. These stresses include periodic loading by ocean and earth tides, earthquakes; fluctuations
Florida Geological Survey
u "'' s LI:' L0,c'
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Figure 25. Average fracture density for several common rock
types naturally deformed in the same physical
environment (alter Sleams, 1967).
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CONFINING ZONE- --------------------Figure 26. Hypothetical hydrogeologic conditions which could result in vertical
flow of different waters.
Florida Geological Survey I
of atmospheric pressure, rainfall, river and lake stages, and man-induced causes (Domenico and Schwartz, 1990). External loading stresses can cause similar hydraulic behavior (iLe., water level fluctuations in wells) in separate hydrogeologic systems.
Because Brevard County is located adjacent to the Atlantic Ocean, oceanic tidal loading has a noticeable impact on hydraulic head lluctualions in wells that penetrate confined aquifer systems. The response of water levels in wells due to oceanic tidal loading occurs as a result at three processes:
1. Mechanical loading of he aquifer at its oceanic extension;
2. Propagation and attenuation of the pressure wave inland through the aquifer;
3. Flow of ground water between the aquifer and the borehole.
Aquiler Loading
Mechanical loading ot the aquifer at ils oceanic extension causes the water oevel in a well to increase at high tide and decrease at low lide. As wells are located away from the ocean the inland transfer of the pressure wave through the aquifer occurs with a diminishing amplitude and increasing time lag (Enright. 1990) (Figure 27).
Responses to earth tides in wells occur, by definition, at the same frequencies as ocean tides, but are orders of magnitude smaller (the largest are 0.5-1 inches). Because of a diflerence in phase and amplitude, any earth tidal fluctualions near the coast typically is masked by Ihe oceanic tidal fluctuations, The net effect of earth tides is Io decrease by a small amount the arplitude of oceanic tidal flucluations (Parker and Springfield- 1950: Gregg, 1966: Bredehoett, 1967: Enright. 1990).
An inverse relationship exists between baro. metric pressure and water levels in wells. An increase in barometric pressure is transmitled to the confined aquifer system through the overly-
ing conining layer and the aquifer responds with an increase in pressure head. This causes water to flow into the well resuLting in an increase in water level, However, the well has a direct connection with the atmosphere, and because the atmospheric load is partially supported by the aquifer skeleton," the net effect of atmospheric loading is a decrease in water level during increased barometric pressures and an increase in water level during decreased barometric pressure (Domenico and Schwartz, 1990: Enright, 1990)- This relationship is demonstrated in Figure 26 where the D_ B. Lee monitor wells are inversely responding to the increases and decreases of barometnc pressure.
If a well syslern is monitored continuously (such as the D_ B. Lee injection and monitor wells, Figure 28), the response to these external loading stresses can be observed as corresponding fluctuations of water levels. These stresses may conceal ihe true behavior of the aquifer syslem(s) in response in injection testsFor example, the simultaneous increase in well pressure wilhin Iha monilor wells during the injection test could be a result of a hydraulic connection between the injection well and the monitor wells, oceanic tidal loading, a decrease in barometric pressure, or a combination of these phenomena.
When analyzing the aquifer(s) reactions to injeclion well tesis, the monitor well hydraulic head responses to atmospheric and ocean tidal loading may mask 1he efiect of the injeclicn test on the monilor wells. Therefore, in order tio isolate the hydraulic head response ot the monitor wells to the injection test, the ocean tidal and atmospheric loading influences need to be removed by determining the tidal efficiency and barometric efficiency of the aquifer(s) in which the welJ(s) are localed. Methods bor determining tidal and barometric efficiency are described by Jacobs (1 940) and Domenico and Schwarlz (1990).
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tidal loading (rnodified from Enright, 1990).
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Florida Geological Survey
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Figure 28. The effect of oceanic tidal loading and barometric
loading on water levels in the D, B, Lee injection and
monitor wells (Data from Geraghty and Miller, 1988).
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Bulletin No. 64
Hydraulic head results are summarized in Figures 29, 30 and 31 for the Harris, Port Malabar and D. B. Lee wells, The water level readings observed during daily low tides were analyzed for the D. B. Lee wells (Figure 31) In an attempt to parlially filter the effects of diurnal tidal loading (Figure 28) on the confined aquifer systems. Similar patterns of hydrauric head fluctuation within both the Port Malabar and D. B, Lee monitor wells may be indicative of a hydraulic connection between the injection and monitor zones (Figures 30 and 31) at these two sites.
The D. B. Lee 1,500 and 1.800-foot monitor wells (Figure 31) demonstrate patterns of hydraulic head fluctuations that are suspiciously similar. Both wells are located in a highly fractured or vuggy dolostone (Plate 3) and there may be a hydraulic connection between the two. Although not as apparent, the shallow monitor well, located in the middle confining unit, is also exhibiting a pattern of water level fluctuation similar to the two deeper monitor wells. These similar responses could be due to a hydraulic connection between the welis, or they may be reacting to external loading stresses such as barometric pressure (Figure 28). Hydro Designs (1989) conducted four injectiontrecovery tests on the D. B. Lee injection and monitor well system. The results (Figures 32 34) of the first test are presented in this report.
The wells were allowed to stabilize (Figure 32) prior to the first test in order to quantify and remove oceanic tidal loading effects on pressure fluctuations In the monitor wells. The injection/recovery tests were designed so they would not interfere with the normal operation of the plant. Theoretically, the recovery phase should be the mirror image of the injection phase. This, however, was not the case (Figure 34) because the iniection flow was automatically reduced in steps by the injection pumps in operation (Hydro Design, 1989).
A nearly simultaneous increase of hydraulic head in the injection and monitor wells during the injection tests (Figure 33) strongly indicates a hydraulic connection between the injection and monitor zones. A definite trend in the change of water chemistry in each of the monitor wells (see Ground-Water Chemistry Analysis this report) supports this conclusion. The exact cause of the upward leakage cannot be determined. Lack of structural integrity of the well bores is one possibility. The D. B. Lee injection and monitor well system is located in a highly fractured or vuggy dolostone (Plate 3), A lack of conlinement between injection and monitor zones would occur If the fracture network is connecled. It Is also feasible thai both lack ot conlinement and improper well construction could be contributing to upward leakage from the injection zone.
Geothermal Gradients
Deep well temperature surveys In southern Florida have shown that geothermal gradients underlying the Florida Plattorm are affected by the presence of cold sea water. At depths of 1.500 to 3,000 feet the water in the Floridan aquifer system becomes anomalously cooler with depth (Meyer, 1989). The average temperature near the cold sea water bodies averages about 60 degrees F and increases to 10B degrees F along the central axis of the Florida Plateau (Kohoul et al., 1 977). Horizontal and vertical temperature distributions suggest that cold, dense sea water flows inland through cavernous dolostones of the Boulder Zone where it becomes progressively warmed by geothermal heat flow, The reduction of density produces upward circulation. After mixing with less saline water in the upper part of the aquifer, the diluted saltwater flows seaward to discharge by upward leakage through confining beds or through submarine springs on the continental shelf (Kohout et al., 1977) (Figure 35).
Borehole temperature logs, provided by the various consulting firms were closely inspected
F!orda Geolog.cal Survey
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between the D. B. Lee injection and monitor wells
(data mcdified from Geraghty and Miller, 1988).
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monitor wells prior to the injection tests (data from
Hydro Designs, 1989).
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Hydro Designs, 1989).
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Recovery of D. B, Lee injection and monitor wells after first injection tesi (data from Hydro Designs, 1989),
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demorsIrating [he concept of cyclic flow ot seawaler induced by geotIhermal heating (mooidied from Kohout e al,, 1977)
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Florida Geolcgical Survey
icr any anomalous lemperature decreases. Temperatures generally ranged between 80 and 112 degrees F al depths greater than 1.G00 feel and generally increased with deplh; therefore, no cyclic or convective circulation is suspected in the study area. Temperature decreases have been documenled in south Florida where the Strails of Florida are adjacent lo the Florida Platform, The occurrence of convective cilrculalion should be invesligated when injection wells are proposed for Ihese areas.
GROUND-WATER CHEMISTRY ANALYSIS
Introduction
Water-quality data, confining zone, and inieclion zone information for seven wells in Brevard County and one well in Indian River County {Hercutes Corporation) were analyzed for this investigation. Three wells, the Merritt Island, Soulh Beaches, and D. B. Lee injection wells, were chosen for detailed study because o obvious trends observed in water-quality data. For these wells, confining, injection, and monitor zone llhologies were examined lo detewrnme any physical properties that might help explain observed monilor zone contamination. Determining the mechanical iniegity oP the irijeclion wells was beyond the scope of ihis study.
The injection inlervats of all eight wells occur in the Boulder Zone of the lower Floridan aqufer syste1 (Figure 36), in the Oidsma.r Formalion (with ihe possible exception of tMe Port Malabar injection interval where the Boulder Zone is riot well developed; see Plate 3). This zone is generally highly fractured and cavernous, with transmissivity values ranging up lo 21 million gpdift (Haberfeld, 1991)- The high transmissivities in the injection zone, and pumping rales which can be tens-of-millions of gallons per day, result in only minimal increases in wellhead pressure in most werls (Haberfeld, 1991 ), This implies the possibility that ihe injected waters are circulaling freely. Fractures, discontinuities, and -cavities in
tJhe designated confining zones of 'he wells could prov.de conduits !or the ciroua ng water.
The inlected fluids are generally low.sa'inily, treated municipal waste waler. Irdustrial waste waters are inlected at he Harris Corp. and Hercules, Inc. sites. Injecled waters ar less dense than formation water, and sii'ce fluids in the injection and lower monitor zones are high:y saline, "contaminatdon" irOTi ir'jecied fli.ids will be seen as Ireshening trends in mon, or well data. For example, such [rends show Lip as a decrease in tolal dissolved solids (TDS) and,"cr chloride concentration. Occasionally. maKed increases in these parainelers are observed, and this is attribuled to deeper saline waters being displaced upward by injected Iluicis (J. Haberfeld, DEIR, personal cortimuni cation, 1991).
Nitrogen conlenil is monilored oecaise treated waste water will generally have higrier niogen concentrations 1han ambient formation water. It is measured as tolal kjeldahl nitrcge ':TKNI':, which is organic nitrogen plus ammonia. Another important measurement is the depth al which ihe TDS value exceeds 10,000 mgL. Ur-iled Slates Envirorrnental Protection Agency guidelines slate that the TDS value of formalion wale.s in an injection zone mus" exceedJ 10.000 n)'L, -so consultants note 1he depth al wh.ch the transilion occurs. For 1he transition deplhs, only preinection values ate availabe.
The TDS, chloride, and TKN are among the parameters racked in "he ,aiiO.mo nilor zones, arid tnese three were chosen fc.r close anvestigalion because time series data on, them are available for the rmroriilor zones of the injeclion wellsThe three primary wells are the Merrilt Island, the South Beaches, and ilie D. B, Lee ijeclion weils. These are discussed first, and are followed by summaries of dala lor the Harris Corp., Grant Streel, Port Malabar, West Melbourne, and Hercules, Inc. injeclion wells.
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wells (dala from consultan reports).
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Bu!letin No. f.4
In this section, the definitions o the extent of confining, injection and monitor zones are those made by the consultant companies during drilling. The consultants chose the placement ol monitor zones based on their definitions, so the water-quality dala from the monitor zones are analyzed and discussed in terms of those delinitions,
However, the consultants' hydrogeological interpretations often differ from those of the Florida Geological Survey (FGS), Characteristically, their definitions of confinement cover a broad interval. Available data allowed FGS geologists to better delineate confining zones within the lower Floridan aquifer system. These data allowed the definition of three confining zones: the middle confining unit, the lower Avon Park confining zone, and 1he glauconite marker bed. These units are discussed in the Hydrogeology of the Middle Confining Unit of the Floridan Aquifer Syslem and the Hydrogeology of the Lower Floridan Aquifer System. Plate 3 shows the confining zones delineated by the FGS geologists.
In addition to the definitions of confining, injection and monitoring zones, the consultants' reports provided background water-quality dataThe Bureau of Drinking and Ground Water Resources ol the DER provided the lime series water-quality data taken from the monitor welis at each site. Lithologic descriptions were done by FGS geologists. Porosity, induration, and permeability descriptions were based on visuaL inspection of cuttings and cores, and were supplemented by geophysical log data, whenever possib le,
The description of samples involved determining lithologies and physical properties. Physical properties determined for each sample include color, porosity, permeability, grain size, induration, cement type, sedimentary structures, accessory minerals, and presence or absence
of fossils- These descriptions are a part of the FGS well-file database. General lithoiogies are illustrated on Plates 1, 2, and 3.
The lithologic descriptions were also correlated wkth geophysical logs (for example, see Plate 1), When possible, porosity values calculated from sonic logs were used to supplement the descriptions.
Monlor zone water-quality data were examined to ascertain if there has been any migration of injection or formation walers due to pumping. Vertical migration of injection waters would be indicated by falling TDS and chloride concentralions, and by rising TKN concentratons. If verti. cal migration or contamination occurred, these trends would be most prominent in dala Irom the lower monitor zones.
Florida GeologLcal Survey
Primary Wells
Merrilt Island
Al the Merritt Island sile, there are two closely spaced injection wells completed in the Oldsmar Formation at a total depth ol 2,500 feet BLS. The monitor well has an upper monitor zone from 128 to 340 leet BLS ,n the Ocala Limeslone. arid a lower monitor zone extending from 1,470 to 1,500 feel BLS in the Avon Park Formation (Appendix At). The confinLng zone. as defined by Geraghly & Miller. Inc. (1986), extends from 1,600 lo 1,550 feet BLS, in the lower Avon Park and upper Oldsmar Formations. The uncased injeclion zone interval is 1,850 to 2,500 feet BLS in the Oldsmar FormationThe lower monitor zone is in dolostone of the lower Avon Park Formalion. The inlerval from 1,470 Io 1,498 feet BLS is dolostone of 10 percent to 20 percent porosity, good induration, and low to medium permeability. From 1,498 to 1,518 feet BLS the dolostone has 25 percent porosity and possibly high permeability, This more permeable zone extends into the interval between the monilor zone and the confining zone.
8etween ihe lower monitor zone and the confining zone dolostone is the dominanl rock lype. Below the permeable zone noted above, from 1,518 to 1,530 feel BLS the rock averages 10 percent porosity, is well indurated, and has apparently low permeability. The section from 1,530 to 1.599 feet BLS has 30 percent to 35 percent porosity and possibly high permeability.
The confining zone in this area as defined by the consultants occurs in the lower Avon Park and upper Oldmar Formations, extending from 1,600 to 1.900 feet BLS. The interval consists ol alternating layers of doloslone, mucistone, wackeslone, and packslone from 1,600 to 1,830 feet BLS, and dolostone from 1,630 to 1,900 feet BLS. Porosity and permeability are highly
variable lhroughout this zone. Fractures were noted in two cored intervals, irom 1.720 to 1,723 leet BLS and from 1,820 to 1.I30 feel OLS.
The background water-quality report on the lower monitor zone shows that the ambient water quality before injection was as follows: TDS = 34,630 mg/L: chloride = 19,200 mg/L; and TKN = 0-69 mg/l (Geraghty & Miller, Inc., 1OR6}. For comparison, water containing more than 2,000 to 3,000 mg!L TDS is too salty to drink, and seawater has approximately 35,000 rng/L TDS (Freeze and Cherry, 1979)- In this area TDS values exceed 10,000 mg/L at approximately 1,200 feet BLS,
Dala on lower monitor zone waler quatity shows changes in all these values since injection started in January 1967. TDS show a steady decrease beginning in February 1987. from over 34,000 mg!L lo below 22.000 mg/I. in July of 1991 (Figure 37). Chloride concentrations decreased from over 16,000 mg/I. to below 12.000 mg/L (Figure 35), TKN increased from 1 57 when injection began to a high of over 2.6 mg/L in early 1988. Concentrations since then have decreased in an erratic manner (Figure 39). The increase can be attributed to rising injection waters. The decrease after Ihe peak is probably due to the increasing efficiency ot the treatment plant that treats the elfluent belore it is injected (J. Haberleld, DER. personal communication, 1991),
Data from the upper monitor zone show a slight decrease in TDS values, and chloride and TKN values vary widely, The change in TDS values is too smalt to inler that injected waste water has traveled that high in the section.
Regression analyses were performed on the deep monitor well data to determine the significance of the observed trends, A high R-squared value, or coefficient of delermination (R is the correLation coefficient), indicates low scatter o the data, or a definite relalionship between time and concenlralion values. The R-squared value
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Figure 37. TDS values of the Merritt Island well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).
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Figure 38. Chloride concentrations of the Merritt Island well deep monitor zone (data from the DER Bureau of Drinking and Groundwater Resources).
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Figure 39. TKN values of the Merritt Island well deep monitor zone (data from the DER Bureau of Drinking and Groundwater Resources).
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Florida Geological Survey
for the chloride plot is 0-92. The TDS value is 0.54. but jumps to 0.74 when the obvious outlying values are removed. For the TKN regression. values from February 1987 to Aprij 1988 were used, to determine the significance of the increase in concentration. The R-squaied value for that period is 0.71- These high R-squared values tend to support Ihe interpretation that possibly fractures and the general discontinuous nature of the confining interval have allowed injected iluids to migrate vertically through the confining layer.
South Beaches
The South Beaches injection well has a total depth of 2.916 feet BLS in the Oldsrrar Formation. There are two separate monitor wells at the sile. The upper Floridan aquifer system well monitors the zone from 300 to 350 test BLS in the Ocala Limestone, and the lower Floridan aquifer system well monitors from 1,550 to 1,700 feet BLS in the Avon Park Formation (Appendix A2). The confining zone. as defined by Dames and Moore (1985), extends from 1,665 to 2,081 feet BLS in the Avon Park and Oldsmar Formations. The injection zone extends from 2r081 to total depth, but the interval with the most fractures and cavities is from 2,081 to 2,760 feet BLS (Dames and Moore, 1985).
The lower monitor zone, in the lower Avon Park Formation, has interbedded dolostone. mudslone, and wackestone, with porosilies ranging from 10 percent to 15 percent, moder. ate to good induration, and apparently low per. meability.
The confining zone, in the lower Avon Park and upper Oldsmar, has interbedded mudstone, wackestone, packstone, and dolostone layers. Porosities range from five percent in a lew interbedded cherty layers, to 20 percent in the wackestones and packstones. Both induration and permeability have wide ranges, from low to high in altemating layers. Sickensides related to
fracturing ancVor laulting were observed in cores within and above the confining zone.
The background water-quality report (Dames and Moore, 1985) on the lower monitor zone shows that before injection the average TDS value was 23,975 mg/L, and the average chloride value was 14.410 mg/IL. In this area TDS values exceed 10.000 mg/L at approximalely 1,250 leet BLS. No TKN measurements were taken, but nitrogen, measured as nitrate, was
0.03 mg/L.
Dramatic changes in these values have been observed since injection began in May 1987, TDS tell from over 21,000 mg/L to less than 10,000 mg/1 (Figure 40). Chloride values lelL irom over 16.000 mg/L to less than 5,000 mgfL, starting in July 1987 (Figure 41). These changes are attributed to injection waters rising through the confining units. Values of TKN show a pattern similar lo that of ihe Merritt Island well lower momLior zone- There was a rise from approximately 0.5 mg/L to a peak at about 3.0 mg/L, arid then a decline (Figure 42). This is again attributed to the increasing efficiency of (he treatment plant at the South Beaches site. It is not known why the values increased rapidly in mid-1991. No trends were observed in the upper monitor zoneRegression results show an R-squared value of 0,78 tor the observed chloride trend, with the value increasing to 0.87 when outliers are removed from the calculations. The R-squared value lor the TDS plot is 0.9, Regression of TKN values was done for the period from July 1987 to March 1988, to determine if the increasing concentration trend was significant, The Asquared value for that period is 0,88, These values lend to support the conclusion that the Iractures, cavilies, and the discontinuous nature ol the confining zone have allowed migration of injected fluids into the monitor zone.
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Figure 40. TDS values of the South Beaches well deep monitor zone (data from the DER Bureau of Drinking and Groundwater Resources).
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Figure 41. Chloride concentrations of the South Beaches well deep monitor zone
(data from the DER Bureau of Drinking and Groundwater Resources).
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Figure 42. TKN values of the South Beaches well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).
Florida Geological Survey
D. B. Lee
The D. B. Lee injection well has a total depth of 2,440 feet BLS, in the Oldsmar Formation. There are three separate monitor wells at the site (Appendix A3). The upper well monitors the zone from 1,159 to 1,208 feet BLS in the middle Avon Park Formation. The intermediate well, called the deep well in the Geraghty & Miller, Inc. report (1988), monitors the interval from 1,469 to 1,517 feet BLS in the lower Avon Park Formation. The lower well, called the lower Floridan monitor well, monitors from 1,794 to 1,844 feet BLS in the lower Avon Park Formation. The confining zone, as defined by Geraghty & Miller, Inc. (1988), extends from 1,360 to 2,000 feet BLS, with the principal confining part extending from 1,770 to 2,000 feet BLS. The injection zone extends from 2,000 feet BLS to 2,200 BLS.
The confining zone from 1,770 to 1,934 feet BLS is in dolostone of the lower Avon Park Formation. The interval has 10 percent to 15 percent porosity, good induration, and low permeability. There is a cherty zone from 1,800 to 1,810 feet BLS, and a possible clayey layer from 1,914 to 1,922 feet BLS. The rest of the confining zone, which is in the upper Oldsmar Formation, has more variable lithologies. From 1,934 to 1,944 feet BLS the rock is wackestone with 10 percent to 20 percent porosity, poor to moderate induration, and medium permeability. The interval from 1,944 feet BLS to 1,964 feet BLS is dolostone of 5 percent to 15 percent porosity, moderate to good induration, and low to medium permeability. From 1,964 to 2,001 feet BLS the interval consists of wackestones and packstones of 5 percent to 25 percent porosity, poor to good induration, and low to high permeability.
In addition to the widely varying porosity values and permeabilities of the confining zone, many cavities and fractures were observed on borehole video surveys. For example, on one video covering the interval from 1,638 to 1,805
feet BLS six cavities were observed, including one that extended from 1,793 feet BLS to 1,800 feet BLS. Drilling records indicate a cavern from 1,180-1,225 feet BLS. The cavities may have been enlarged by wash-out during drilling. On the same video, fractures were observed at 1,725 feet BLS, 1,740 feet BLS, 1,770 feet BLS, 1,798 feet BLS, and 1,801 feet BLS. Also, in a report on well tests conducted at the D. B. Lee site, Knapp (1989) notes that the "...sequence from 900 feet to 2,000 feet below land surface is dominated by dolomites (dolostones) with lost circulation and caving zones being prevalent throughout the interval..." and "...excessive drilling problems (lost bits, cement overruns, dredging times, hole stabilization techniques, etc.) were caused by the dense dolomites (dolostones) and cavities encountered in this area...." The interpreted normal fault at approximately 2,100 feet BLS occurs within the injection zone and could explain some of the drilling difficulties encountered here.
The background water-quality report of the lowest monitor zone shows a TDS value of 33,700 mg/L, and a chloride concentration of 17,500 mg/L. No TKN values were reported. TDS values exceed 10,000 mg/L at approximately 1,200 feet BLS.
The D. B. Lee well operated from July 1988 to April 1989, and trends in water-quality data show dramatic changes related to the beginning and ending of injection. Beginning in August 1988, TDS values in the deep monitor well declined from over 27,000 mg/L to under 13,000 mg/L in April 1989 (Figure 43). Values immediately began to increase once injection was stopped. The same kind of pattern was seen in chloride values, where there was a decline from over 11,000 mg/L to under 6,000 mg/L. Values again began to increase when injection stopped (Figure 44). Although there are visible trends on the plots, the data are somewhat scattered, probably due to the irregular injection pattern at the site. There was no background TKN information, but it can be assumed that background values were low, in the 1 mg/L range (J.
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Figure 43. TDS values of the D. B. Lee well deep monitor zone (data from the
DER Bureau of Drinking and Groundwater Resources).
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Figure 44. Chloride concentrations of the D. B. Lee well deep monitor zone (data
from the DER Bureau of Drinking and Groundwater Resources).
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Bulletin No. 64
Haberfeld, DER, personal communication, 1991). This assumption is consistent with available TKN background values for other injection wells (see, for example, the Merritt Island background water quality section). When injection began, TKN values began to rise from around 4.0 mg/L to about 12.0 mg/L when injection stopped (Figure 45). The anomalous 34 mg/L value is probably due to sampling or analytical error. Values continued to rise for a short time after injection stopped (approximately 2 months), and then began to decline again. These patterns are best explained by rising injection waters and communication between the injection and monitor zones. One reason that the trends in the lower monitor zone are so prominent is that it is within 220 feet of the top of the injection zone.
For the regression analyses, the chloride and TDS divided into two parts. Data collected during injection, from July 1988 to March 1989, comprise the first part, and data collected after injection stopped are in the second part. The Rsquared value for TDS values during injection is 0.69, and is 0.51 for the period after injection stopped. The values for chloride are 0.74 for both periods. These values seem slightly low because the patterns of declining and increasing concentrations are readily apparent on the graphs. This is probably due to the scatter of the data, most likely caused by fluctuating injection rates. Regression of TKN data was conducted for the time period from July 1988 to July 1989, to assess the significance of the increasing concentrations values. The R-squared value for this period is 0.93.
The intermediate well water-quality data show trends which indicate rising injection water, though the patterns are somewhat erratic and attenuated. In particular, chloride values decreased from a high of approximately 16,000 mg/L to a low of approximately 10,000 mg/L during injection, and increased after injection stopped.
The upper monitor well water-quality data show patterns that indicate increasing salinity. These patterns are most likely related to rising formation water, displaced upwards by injection water. TDS values increased from about 8,000 mg/L to over 17,000 mg/L and chloride concentrations increased from about 4,000 mg/L to a high of almost 14,000 mg/L just before injection stopped. Concentrations then dropped and fluctuated around 9,000 mg/L. TKN values increased from about 1 mg/L to over 12 mg/L.
The changing ground-water chemistry observed in all three monitor zones indicates that the existence of a coherent confining zone in this area is highly questionable. Knapp (1989) concluded that there is "...inadequate information to determine if a confining sequence exists between 1,900 and 2,000 feet below land surface...," and the report confirms the freshening trends seen in the deep and intermediate monitor zones and the increasing salinity of the upper monitor zone during injection (Knapp, 1989). He also concluded, "The rate of change in the water quality indicates that there is a direct conduit from the injection zones into the monitor zones."
Secondary Wells
Harris Corporation
There are two injection wells at the Harris Corp. site, one with a total depth of 2,800 feet BLS and the other completed at 2,333 feet BLS, both in the Oldsmar Formation. The confining zone, as defined by Geraghty & Miller, Inc. (1984), extends from 1,362 to 2,030 feet BLS, in the lower Avon Park and upper Oldsmar Formations. The major injection interval in both wells is from 2,030 to 2,245 feet BLS (Appendix A4). There is a dual zone monitor well at the site, with the upper zone monitoring the interval from 430 to 550 feet BLS in the lower Ocala Limestone and upper Avon Park Formation, and the lower monitor zone extending from 1,527 to 1,535 feet BLS in the lower Avon Park Formation.
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Figure 45. TKN values of the D. B. Lee well deep monitor zone (data from the DER Bureau of Drinking and Groundwater Resources).
Bulletin No. 64
As in the three primary wells, the confining zone in this area contains alternating layers of mudstone, wackestone, packstone and dolostone, with widely varying porosity values and permeabilities, and moderate to good induration (Appendix A4 and Plates 1, 2, & 3). Fractures were observed in core from 1,904 to 1,912 feet BLS.
The background water-quality report (Geraghty & Miller, Inc., 1984) shows that the ambient conditions at the level of the deep monitor zone, before injection began in August 1986, were as follows: TDS = 31,000 mg/L, chloride = 17,000 mg/L, and TKN = <0.04 mg/L. The 10,000 mg/L boundary occurs at approximately 1,200 feet BLS.
Deep monitor zone water-quality data show trends similar to those seen in the three primary wells, though the patterns are more erratic. TDS values declined from over 31,000 mg/L in 1986 to under 25,000 mg/L in 1991, and chloride concentrations declined from over 18,000 mg/L to under 13,000 mg/L in the same period. The more erratic patterns of decline may be due to the variable rates of injection at the site. Injection volumes commonly vary by tens-of-millions of gallons from month-to-month. TKN values did increase to over 2 mg/L by mid-1991, but the trend is not very dramatic. No trends were discernible in the upper monitor zone data.
Grant Street
The Grant Street well has a total depth of 2,700 feet BLS in the Oldsmar Formation. The main confining zone, as defined by Hydro Designs (1989), is from 1,815 to 2,050 feet BLS in the lower Avon Park and upper Oldsmar Formations. The major injection interval extends from 2,035 to 2,700 feet BLS in the Oldsmar Formation (Appendix A5). There are two separate monitor wells at the site. The upper well monitors from 1,100 to 1,150 feet BLS in the upper Avon Park Formation, and the lower well monitors from 1,594 to 1,644 feet BLS in the lower Avon Park Formation.
The confining zone can be divided into two broad categories. The upper section, from 1,815 to 1,880 feet BLS, is predominantly dolostone, with interbedded wackestones and packstones (Appendix A5). Permeabilities are generally low, and porosity ranges from five to ten percent. Induration is generally good. The lower section, from 1,880 to 2,050 feet BLS, is composed mainly of packstone, with a few interbedded wackestone and thin dolostone beds. Permeabilities are generally high, porosity ranges from 15 to 35 percent, and induration is poor to moderate.
The background water-quality report for the lower monitor zone shows a TDS value of 23,600 mg/L, a chloride concentration of 850 mg/L, and a TKN value of 0.5 mg/L (Hydro Designs, 1989). These values appear to be slightly low, because Florida DER monitoring data (unpublished data, 1991) show initial values that start higher than those quoted in the Hydro Designs report. Further examination of the water-quality report indicated that the samples for the background readings were taken soon after the well was developed, and ambient conditions were probably not reestablished at that time. TDS values exceed 10,000 mg/L at approximately 1,250 feet BLS.
Injection began in April 1989. The water-quality data show trends at this site, but the magnitudes of changes are not as great as at other wells. TDS values decline in a somewhat irregular manner from just over 27,000 mg/L in mid1989 to around 17,000 mg/L in 1991. Chloride concentrations show a small but fairly steady decline from over 16,000 mg/L in 1989 to below 13,000 mg/L in 1991. TKN values increased from 2.0 mg/L in 1989 to a high of about 10.0 mg/L in 1990, and then declined to about 5.0 mg/L by mid-1 991.
Data from the upper monitor well show increases consistent with rising formation waters. Background analyses showed a chloride concentration of 215 mg/L, a TDS value of 2.5
Florida Geological Survey
mg/L, and a TKN value of 2.3 mg/L (again, probably low because the analysis was conducted soon after well development). After injection started in April 1989, chloride values rose from about 900 mg/L to over 1,800 mg/L in 1991. TDS values increased from 1,600 mg/L to about 3,200 mg/L. TKN values were very erratic.
Port Malabar
The Port Malabar injection well has a total depth of 3,009 feet BLS in the Oldsmar Formation. The confining zone, defined by CH2M Hill (1987) as an "intra-aquifer low permeability zone," extends from 1,300 to 2,050 feet BLS. The injection zone extends from 2,050 feet to 2,300 BLS (Appendix A6). The dual zone monitor well at the site has an upper monitor zone from 400 to 472 feet BLS in the lower Ocala Limestone and upper Avon Park Formation, and a lower monitor zone from 1,534 to 1,630 feet BLS in the lower Avon Park Formation.
The confining zone from 1,300 to 1,470 feet BLS is predominantly wackestone, with a few interbedded packstone layers (Appendix A6). Porosity ranges from 10 percent to 25 percent and permeability generally appears to be high. In this interval, the rocks are moderately indurated. From 1,470 to 1,640 feet BLS the rocks are interbedded dolostones, mudstones and wackestones. Porosity in the mudstones and dolostones ranges from 5 to 15 percent. The dolostones are well indurated and have low permeability, and the mudstones are poorly to moderatley indurated and have low permeability. The wackestones are moderately indurated, generally have high permeability, and porosity ranges from 15 to 20 percent. From 1,640 to 1,880 feet BLS dolostone is the dominant rock, and there are several zones where chert is thinly interbedded. Porosity in this interval is five percent to 15 percent, permeability is low, and induration is good. From 1,880 to 2,050 feet BLS the rocks are interbedded dolostones, wackestones, and packstones. In the dolostones porosity ranges
from five percent to 15 percent, permeability is low, and induration is good. The wackestones and packstones have porosities ranging from 15 percent to 20 percent, generally high permeability, and are moderately indurated.
The only background water-quality information available for the lower monitor zone is a chloride concentration of approximately 10,890 mg/L (CH2M Hill, 1987). The 10,000 mg/L TDS boundary occurs at approximately 1,450 feet BLS.
Injection at this site started in August 1987. In general, the plots for TDS, chloride, and TKN are irregular, and it is difficult to see any trends. Chloride values drop from a high of over 13,000 mg/L in late 1987, stabilizing around 10,000 mg/L from late 1988 to early 1990. The values increase after early 1990. TDS data are available only from 1989 to the present. The values peak in late 1989 around 25,000 mg/L, and drop off to about 19,000 mg/L in mid-1991. The shallow monitor zone water-quality data do not show any significant trends. In this area available data cannot be used to determine conclusively if vertical migration of injection water has occurred.
West Melbourne
The West Melbourne injection well has a total depth of 2,409 feet BLS in the Oldsmar Formation. The confining interval, as defined by CH2M Hill (1986), extends from 1,600 to 1,980 feet BLS in the lower Avon Park Formation. The injection zone extends from 1,980 to 2,409 feet BLS with the main injection interval extending from 2,000 to 2,200 feet BLS in the Oldsmar Formation (Appendix A7). The monitor zones are a part of the injection well annulus, with an upper zone from 1,234 to 1,306 feet BLS, and a lower zone from 1,410 to 1,450 feet BLS, both in the middle Avon Park Formation.
From 1,600 to 1,840 feet BLS the confining zone as defined by CH2M Hill is dolostone with porosity ranging from five percent to 30 percent,
Bulletin No. 64
depending on the degree of dolomitization. The interval is generally well indurated (Appendix A7). From 1,840 to 1,980 feet BLS the dominant lithologies are interbedded wackestones and packstones with 10 percent to 25 percent porosity and moderate induration. No permeability estimates are available for this interval.
Background water-quality data (CH2M Hill, 1986), taken while the well was being drilled, show a chloride value of approximately 3,500 mg/L at the level of the lower monitor zone. A packer test at the interval from 1,426 to 1,436 feet BLS in the lower monitor zone, shows an average TDS value of 10,150 mg/L. The 10,000 mg/L TDS boundary in this area occurs at approximately 1,450 feet BLS.
Injection at this site started in November 1986. Lower monitor zone water-quality data show a slight increase in TDS from 2,000 mg/L in mid1989, when TDS data were first collected, to 5,000 mg/L in early 1991. There is then a jump to over 11,000 mg/L by mid-1991. Note that the initial TDS values taken in 1989 are markedly lower than the background value of 10,150 mg/L taken in 1986. Water in the monitor zone could have experienced freshening between 1986 and 1989, before the increase in salinity in 1989 to 1991. More likely, the background value is erroneous because it was taken during drilling when ambient conditions would have been disrupted.
Chloride values hold steady around 1,000 mg/L from late-1986 to mid-1989, and then increase to 5,000 mg/L by mid-1991. The initial Florida DER values are again lower than the background readings. However, the increase in chloride concentrations from mid-1989 to 1991 does correspond to the increase in TDS values, indicating that saline formation water is being displaced upwards by injected water.
Hercules, Inc.
The Hercules injection well has a total depth of 3,005 feet BLS in the Oldsmar Formation.
The confining interval, defined by CH2M Hill (1979), is from 1,500 to 2,400 feet BLS in the lower Avon Park and upper Oldsmar Formations. The main injection zone extends from 2,378 to 2,930 feet BLS in the Oldsmar Formation (Appendix A8). There is a separate multizone monitor well with four zones: 1) the upper Floridan, from 466 to 591 feet BLS in the Ocala Limestone, 2) the middle Floridan, from 880 to 931 feet BLS in the upper Avon Park Formation, 3) the lower Floridan, from 1,387 to 1,451 feet BLS in the middle Avon Park Formation, and 4) the primary, extending from 1,905 to 1,963 feet BLS in the lower Avon Park Formation.
The confining zone, as defined by CH2M Hill, from 1,500 to 1,900 feet BLS is primarily packstone, with a few interbedded dolostone layers. The porosity of this section ranges from 20 to 35 percent. The section is generally moderately indurated, and permeability is estimated to be high. From 1,900 to 2,300 feet BLS dolostone dominates, with scattered wackestone and packstone interbeds. Porosity ranges between two percent and 10 percent in the dolostone, and between 15 percent and 25 percent in the interbeds. The section is well indurated and appears to have low permeability. From 2,300 to 2,400 feet BLS wackestones and packstones of 20 percent to 25 percent porosity, moderate induration and medium permeability dominate.
Background water-quality data show that in the primary monitor zone the chloride concentration was 17,350 mg/L, and in the lower Floridan monitor zone it was 4,490 mg/L. A packer test in the interval from 1,949 to 1,959 feet BLS in the primary monitor zone showed values of 17,600 mg/L for chloride, and 28,200 mg/L for TDS.
Injection at the site started in November 1979. However, collection of data on TDS and TKN for the primary monitor zone didn't begin until 1990. and no patterns are discernible. Chloride concentration data fluctuates between 17,000 and
Florida Geological Survey
21,000 mg/L for the period from 1979 to 1991. Interestingly, chloride data for the lower Floridan monitor zone do show a pattern. From 1979 to 1987 values fluctuate between 2,000 and 4,000 mg/L, but then concentrations increase steadily to over 12,000 mg/L by mid-1991, indicating displaced formation water. Again, TDS and TKN data were not collected until 1990, and no patterns are observed. Data for the middle and upper Floridan monitor zones also show no patterns.
DISCUSSION AND CONCLUSIONS
The geologic framework of the lower Floridan aquifer system in Brevard County embodies a shallow water carbonate platform sequence, the character of which has been determined by a diversity of factors including depositional environment, diagenesis, and geologic structure. Variations in these components can result in considerable differences in local lithofacies, porosity, permeability, and hydrogeologic character of the aquifer.
Ground-water chemistry trends for several injection wells indicate that injected waste liquids are migrating upward through the "confining" rocks immediately above the injection zones. Since apparently low permeability dolostones are common in the "confining" sequence,
injected waste waters are probably moving vertically along fractures and possibly along fault planes where present. Fractures commonly observed in borehole cores and videos justify this supposition. Faults, however subtle and small scale, can enhance fracture-related permeability locally and serve as conduits for vertical fluid migration. If injected waste fluids migrate preferentially upward along dissolutionally enlarged fault planes, conceptually, the fault could effectively mask contamination detection in monitor wells depending on the location of the monitor zone relative to the fault.
A more satisfactory understanding of the lower Floridan aquifer system in Brevard County can only be achieved by further study accompanied by the acquisition of additional data. Thorough coring of strata overlying injection zones is highly desirable so that lithofacies and hydrologic characteristics can be adequately detailed. A seismic survey program should be considered in order to identify and map the extent of possible faulting in proximity to current and proposed injection well sites. Because of their value to subsurface geological evaluations, borehole videos and complete geophysical log suites (including gamma-ray, sonic, and neutron-density) should be run over the entire borehole of future injection and monitor wells.
Bulletin No. 64
REFERENCES
Applin, P. L., and Applin, E. R., 1944, Regional subsurface stratigraphy and structure of Florida and
southern Georgia: American Association of Petroleum Geologists Bulletin, v. 28, no. 12,
p. 1673-1742.
Barnett, R. S., 1975, Basement structure of Florida and its tectonic implications: Gulf Coast Association
of Geological Societies Transactions, v. 25, 1975, 21 p.
Benard, H. A., Leblanc, R. J., and Major, C. F., 1962, Recent and Pleistocene geology of southeast
Texas: In Geology of the Gulf Coast and Central Texas guidebook of excursions: Houston
Geological Society-Geological Society of America Annual Meeting, p. 175-205.
Braunstein, J., Huddlestun, P., and Biel, R., (coordinators), 1988, Correlation of Stratigraphic Units of
North America; Gulf Coast Region: American Association of Petroleum Geologists.
Bredehoeft, J. D., 1967, Response of well-aquifer systems to Earth tides: Journal of Geophysical
Resources, v. 72, p. 3075-3087.
Brown, D. W., Kenner, W. E., Crooks, J. W., and Foster, J. B., 1962, Water resources of Brevard
County, Florida: Florida Geological Survey Report of Investigations 28, 104 p.
Bush, P. W., and Johnson, R. H., 1988, Ground-water hydraulics, regional flow, and ground-water
development of the Floridan Aquifer System in Florida and in parts of Georgia, South Carolina, and
Alabama: U.S. Geological Survey Professional Paper 1403-C, 80 p.
Cander, Harris, S., 1991, Dolomitization and water-rock interaction in the middle Eocene Avon Park
Formation, Floridan aquifer: unpublished doctoral dissertation, University of Texas at Austin, 172 p.
Chen, C. S., 1965, The regional lithostratigraphic analysis of Paleocene and Eocene rocks of Florida:
Florida Geological Survey Bulletin 45, 105 p.
CH2M Hill, Inc., 1979, Hydrogeologic Report: Hercules, Inc. injection test well and multizone monitor
well, Indian River Plant (Report No. GN54801.80): Gainesville, Florida.
__, 1986, Engineering Report: Drilling and testing of the deep injection well and annular monitoring tube system, City of West Melbourne Wastewater Treatment Plant, West Melbourne, Florida
(Report No. GN18762.A2): Gainesville, Florida.
__, 1987, Engineering Report: Construction and testing of the deep injection well system, General
Development Utilities, Inc., Port Malabar Wastewater Treatment Plant, Palm Bay, Florida (Report
No. GN16067.PI): Gainesville, Florida.
Dames & Moore, 1985, Report: Deep exploratory/test injection well, South Beaches Waste Water
Treatment Plant for Brevard County, Florida (Job No. 13112-007-26): Boca Raton, Florida.
Florida Geological Survey
Domenico, P. A., and Schwartz, F. W., 1990, Physical and Chemical Hydrogeology: John Wiley and
Sons, New York, 824 p.
Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture: American
Association of Petroleum Geologists Memoir 1, p. 108-121.
1970, Meniscus Cement: In Bricker, 0., ed., Carbonate Cements: John Hopkins University
Studies in Geology No. 19, p. 297-300.
Enright, R. V., 1990, Relating the effects of oceanic tidal loading of a confined aquifer in Sarasota,
Florida, to fluctuations in well-water levels: Master's Thesis, Department of Geology, Florida State
University, 210 p.
Florida Department of Environmental Regulation, 1991a, Port Malabar Monthly Operating Reports:
Bureau of Drinking and Ground Water Resources, UIC, Criteria and Standards,
,1991b, Harris Corporation Monthly Operating Reports: Bureau of Drinking and Ground Water
Resources, UIC, Criteria and Standards,
Freeze, R. A. and Cherry, J. A., 1979, Groundwater: Prentice-Hall Inc., New Jersey, 604 p.
Friedman, G. M. and Sanders, J. E., 1967, Origin and occurrence of dolostones: In Chilingar, G. V.,
Bissell, H. J., and Fairbridge, R. W., Carbonate Rocks: Developments in Sedimentology, 9A:
Amsterdam, Elsevier, p. 267-348.
1978, Principles of Sedimentology: John Wiley and Sons, New York, p. 140.
Geraghty & Miller, Inc., 1984, Construction and testing of the Harris Corporation injection well system
(Report and Appendices): Palm Beach Gardens, Florida.
1986, Construction and testing of the Merritt Island injection wells, Brevard County, Florida
(Report and Appendices): Palm Beach Gardens, Florida.
1988, Construction and testing of an injection well: David B. Lee Wastewater Treatment Plant,
City of Melbourne, Florida (Report and Appendices): Palm Beach Gardens, Florida.
Gregg, D. 0., 1966, An analysis of ground-water fluctuations caused by ocean tides in Glynn County,
Georgia: Ground Water, v. 4, n. 3, p. 24-32.
Gulf Research and Development Company, 1978, Fundamentals of well logging-formation evaluation
1: Gulf Oil Corporation, pp. VIV1 8.
Haberfeld, J. L., 1991, Hydrogeology of effluent disposal zones, Floridan aquifer, south Florida: Ground
Water, v. 29, n. 2, p. 186-190.
Bulletin No. 64
Hanshaw, B. B., Back, A geochemical hypothesis for dolomitization by ground water: Economic
Geology, v. 66, p. 710-724.
Hardie, L. A., 1987, Dolomitization: A critical view of some current views: Journal of Sedimentary
Petrology, v. 57, n. 1, p. 166-183.
Harris, P. M., Kendall, C. G. ST.C., and Lerche, I., 1985, Carbonate cementation a brief review: In
Schneidermann, N. and Harris, P., eds., The Society of Economic Paleontologists and
Mineralogists Special Publication 36, p. 79-95.
Hydro Designs, 1989, Construction and testing of an injection well: Grant Street Wastewater Treatment
Plant, City of Melbourne, Florida: Juno Beach, Florida.
Jacob, C. E., 1940, On the flow of water in an elastic artesian aquifer: Transaction of American
Geophysical Union, v. 22, p. 574-586.
Klitgord, K. D., Popenoe, P., and Schouten, H., 1984, Florida: a Jurassic transform plate boundary:
Journal of Geophysical Research, v. 89, n. B9, p. 7753-7772.
Knapp, M., 1989, Results of testing on the D. B. Lee injection well: Hydro Designs, Juno Beach,
Florida., 35 p.
Kohout, F. A., 1965, Ground-water flow and the geothermal regime of the Floridan plateau: Gulf Coast
Association of Geological Societies Transactions, v. 17, p. 339-354.
Henry, H., and Banks, J., 1977, The geothermal nature of the Floridan Plateau: In Smith, D. L.
and Griffin, G., eds., Florida Geological Survey Special Publication 21, 161 p.
Meyer, F. W., 1989, Subsurface storage of liquids in the Floridan aquifer system in South Florida: U.S.
Geological Survey Open-File Report 88-477, 25 p.
Miall, A. D., 1984, Principles of Sedimentary Basin Analysis: Springer-Verlag, New York, p. 159.
Miller, J. A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of
Georgia, Alabama, and South Carolina: U.S. Geological Survey Professional Paper 1403-B, 91 p.
Murray, R. C., 1960, Origin of porosity in carbonate rocks: In Sedimentary Processes, Diagenesis:
Society of Economic Paleontologists and Mineralogists Reprint Series, no. 1, p. 75-100.
Odin, G. S., and Fullagar, P. D., 1988, Geological significance of the glaucony facies: In Odin, G. S.,
ed., Green Marine Clays, Elsevier, Amsterdam, p. 295-335.
Parker, G. G., and Springfield, V. T., 1950, Effects of earthquakes, rains, tides, winds, and atmospheric
pressure changes on the water in geologic formations of southern Florida: Economic Geology, v.
45, p. 441-460.
Florida Geological Survey
Randazzo, A. F., Stone, G. C., and Saroop, H. C., 1977, Diagenesis of middle and upper Eocene carbonate shoreline sequences, central Florida: The American Association of Petroleum Geologists
Bulletin, v. 61, p. 492-503.
and Hickey, E. W., 1978, Dolomitization in the Floridan aquifer: American Journal of Science,
v. 278, p. 1177-1184.
and Cook, D. J., 1987, Characterization of dolomitic rocks from the coastal mixing zone of the
Floridan aquifer, Florida, U.S.A.: in Sedimentary Geology 54: Elsevier Science Publishers B. V.,
Amsterdam, p. 169-192.
Riggs, S. R., 1979, Phosphorite sedimentation in Florida-a model phosphogenic system: Economic
Geology, v. 74, p. 285-314.
Safko, A., and Hickey, J., 1992, A preliminary approach to the use of borehole data, including television
surveys, for characterizing secondary porosity of carbonate rocks in the Floridan Aquifer System:
U.S. Geological Survey Water Resources Investigations Report 91-4168, 70 p.
Scholle, P. A., Bebout, D. G., and Moore, C. H., eds., 1983, Carbonate depositional environments:
American Association of Petroleum Geologists Memoir 33, 708 p.
Scott, T. M., 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological
Survey Bulletin 59, 148 p.
Lloyd, J. M., and Maddox, G., eds., 1991, Florida's ground-water quality monitoring program:
Hydrogeological framework: Florida Geological Survey Special Publication 32, 97 p.
Sheridan, R. E., Crosby, J. T., Bryan, G. M., and Stoffa, P. L., 1981, Stratigraphy and structure of the
southern Blake Plateau, Northern Florida Straits, and Northern Bahama Platform from multichannel seismic reflection data: American Association of Petroleum Geologists Bulletin, v. 65, n. 12, p.
2571- 2593.
Mullins, H. T., Austin Jr., J. A., Ball, M. M., and Ladd, J. W., 1988, Geology and geophysics of
the Bahamas: in Sheridan, R. E. and Grow, J. A., eds., The Geology of North America, v. 1-2/The
Atlantic Continental Margin: U.S., Geological Society of America, p. 329-364.
Shinn, E. A., 1983, Tidal flat environment: In Scholle, P.A., Bebout, D. G., and Moore, C. H., eds.
Carbonate depositional environments: American Association of Petroleum Geologists Memoir 33,
p. 172-210.
Lloyd, R. M., and Ginsburg, R. N., 1969, Anatomy of a modern carbonate tidal-flat, Andros
Island, Bahamas: Journal of Sedimentary Petrology, v. 39, p. 1202-1228.
Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition,
1986, Hydrogeological units of Florida: Florida Geological Survey Special Publication 28, 8 p.
Bulletin No. 64
Stearns, D. W., 1967, Certain aspects of fracture in naturally deformed rock: In Reicker, R. E., ed.,
National Science Foundation Advanced Science Seminar in Rock Mechanics: Air Force Cambridge
Research Lab Special Publication, Massachusetts, p. 97-118.
Van Golf-Racht, T. D., 1982, Fundamentals of fractured reservoir engineering: Elsevier, New York.
Vernon, R. 0., 1951, Geology of Citrus and Levy counties, Florida: Florida Geological Survey Bulletin
33, 256 p.
- 1970, The beneficial uses of zones of high transmissivities in the Florida subsurface for water
storage and waste disposal: Florida Geological Survey Information Circular 70, 39 p.
White, W. A., 1970, The geomorphology of the Florida peninsula: Florida Geological Survey Bulletin 51,
164 p.
Florida Geological Survey
APPENDICES
APPENDIX A: HYDROGEOLOGIC SUMMARIES OF INJECTION WELL SITES
Al. Merritt Island Injection Well, W-16226" A2. South Beaches Injection Well, W-1 5890 A3. D. B. Lee Injection Well, W-30016 A4. Harris Corporation Injection Well #2, w-15944 A5. Grant Street Injection Well, W-16297 A6. Port Malabar Injection Well, W-1 6133 A7. West Melbourne Injection Well, W-15961 A8. Hercules, Inc. Injection Well, W-14167
*FGS Well file numbers; detailed lithographic descriptions are on file and available from the FGS.
APPENDIX Al
HYDROGEOLOGIC SUMMARY OF MERRITT ISLAND INJECTION WELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY & MILLER, INC, (1994) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992) LOCATION (FT BLS)
OF FRACTURES OR
LEGEND
UNDIFFERENTIATED SEDIMENTS LIMESTONE AND DOLOSTONE FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS CONFINING LAYER (DETERMINED BY GERAP HTY & MILLER 1984)
a3)
CLAYS SANDS SILTS ETC FORMATION LIMITS
>
950 2.7(10
4 1055 1 = 61
SAMPLE 33.
INTERVAL (Ft)
HORIZONTAL HYDRAULIC CONDUCTIVITY orms) &TRANSMISSIVITY GPD/FT) DETERMINED BY PACKER TESTS
'VERTICAL A9DRAULIC CONDUCTIVITY (cm/s) POROSITY IW)
DETERMINED BY LAB ANALYSIS
NOTE- THIS APPENDIX IS A SUMMATION BRIEF FOR READER CONVENIENCE ONLY. FOR DETAILED INFORMATION REFER TO PLATES 1-5, TEXT AND CONSULTANT REPORTS.
APPENDIX A2
*HYDROGEDLOGIC SUMMARY OF SOUTH BEACHES INJECTION A/ELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM DAMES & MOORE (1985) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)
DEPTH (FT) LITHOLOGY BLS
140
240
400
40r>
1899 TO, 2916
LEGEND
UNDIrPERENTIATED SEDIMENTS LIMESTONE AND DOLOSTONE
FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS
CONFINING LAYER
(DETERMINED BY DAMES & MOORE, 1985)
CLAYS SANDS SILTS ETC
- FORMATION LIMITS
1200
FLOW I LOG INTERVA_ FLO) ZONE
1300
TEMPERATURE LOG
INDICATES ZONE OF FLOW
VERTICAL HYDRAULIC
-4 CONDUCTIVITY (cN/sY 1547 25X10 SAMPLE INTERVAL
I FOOT
1000'
SAMPLE 3 INTERVAL 45010
1100 -
TO, 2916'
LATERAL HYDRAULIC CONDUCTIVITY
NOTE, THIS APPENDIX IS A SUMMATION BRIEF FOR READER CONVENIENCE ONLY. FOR DETAILED INFORMATION REFER TO PLATES 1-5, TEXT AND CONSULTANT REPORTS.
-n
C
G)
CD
0
0
C/) (D
APPENDIX A3
HYDRI-GENLGIC SUHMARY OF D, B. LEE INJECTION WELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY & MILLER, INC. (1988) LOCATION (FT OLD) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992) LITROLOGY OF FRACTURES OR
TD, 2440
TD, 24M0
LEGEND
DEPTH (FT)
BLS
150 255
410
1904
1772'- 1775' 1,9X6
SAMPLE
INTERVAL
(FEET)
VERTICAL UHYDRAULIC COIDUCTIVITY (cm/s> DETERMINED FROM LABOPATORY ANALYSIS
NOTE, TAIS APPENDIX IS A SUMMATION BRIEF FOR READER CONVENIENCE ONLY. FOR DETAILED INFORMATION REFER TO PLATES 1-5, TEXT AND CONSULTANT REPO'RTS.
UNDIFFERENTIATEDOSEDIMENTS
LIMESTONE AND DOLOSTONE
FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS
QJ
CAVERNOUS ZONE c (D
z
0
CONFINING LAYER c) (DETERMINED BY GERAGHTY B MILLER, 1962)
CLAYS SANDOS SILTS ETC FORMATION LIMITS
APPENDIX A4
HYDROGEOLOGIC SUMMARY OF HARRIS CORPORATION INJECTION A ELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY & MILLER, INC, (19860) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992) LOCATION (FT BLS)
LEGEND
95 330
469
1930
TD, 2800
1320' .4- X4
SAMPLE
DEPTH
1010,
PACKER INTERVAL I0-3
1150'
UDIFFERENTIATED SEDIMENTS LIMESTONE AND DOLOSTONE FRACTURES OR VUGGY POROSITY AS INDICATED BY GEOPHYSICAL LOGS CONFINING LAYER (DETERMINED BY GERAGATY & MILLER, 1996a) CLAYS SANDS SILTS ETC FORPMATION LIMITS
VERTICAL PERMEABILITY (cMN/s) & POROSITY (.) DETERMINED FROM LAB ANALYSIS
HYDRAULIC CONDUCTIVITY ( /> DETERMINED BY PACKER/PUMP TESTS
NOTE, THIS APPENDIX IS A SUMMATION BRIEF FOR READER CONVENIENCE ONLY. FOR DETAILED INFORMATION REFER TO PLATES 1-5. TEXT AND CONSULTANT REPORTS,
DEPTH (FT)
BLS
-n
0
5
o
G)
CD
0
0
C)
CD
APPENDIX
A15
XHYDRLVELDGIC SUMMARY EF GRANT STREET INJECTION VIELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM HYDRO DESIGNS (1989)
DEPTH (ft) LITHOLOGY
L I
LEGEND
UNDIFFERENTIATED SEDIMENTS LIMESTONE ANO DOLOSTONE FRACTURES OR VUGGY POROSITY AS INDICATED BY GEOPHYSICAL LOGS
70
280
390
1850
CLAYS SANDS SILTS ETC
CAVLERNOUS ZONE (DETERMINED BY HYDRO DESIGNS, 19A9)
= FORMATION LIMITS
5 -A VERTICAL & HORIZONTAL
20:3i 3.6XI05 3D(1 HYDRAULIC COJDUCTI VITY SAMPLE RESPECTIVELY
I FOOT
NOTEi THIS APPENDIX IS A SURMATION BRIEF FOR READER CONVENIENCE ONEY. FOR DETAILED INFORMATION REFER TO PLATES 1-5, TEXT AND CONSULTANT REPORTS
CONFINING LAYER (DETERMINED BY HYDRO DESIGNS, 19G9
TD, 2700'
Q(
CD
z
0 aY)
-P.
TD 2700'
APPENDIX A6
HYDRGEDLDQGIC SUMMARY OF PORT MALABAR INJECTIONL, WELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM CH2M HILL (1987) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)
LEGEND
UNDIPFERENTIATED SEDIMENTS LIMESTONE AND DOLOSTONE
DEPTH (FT)
BLS
100
270
410
1890
2820 TD3009'
1662' 1663' SAMPLE
INTERVAL
-n
5
G-)
CD
0
0
(D
C:) (D
-6 VERTICAL &. AORIZONTAt
-2.9XI0 & 6.2XA0 HYDRAULIC CONDUCTIVITY (cm/s)
22% 13% POROSITY (. RESPECTIVELY
TRANSMISSIVITY (gpd/ft)
1905 1912 2.2 USING PACKER TESTS & SAMPLE THE JACOB MODIFIED METHOD INTERVAL
NOTE TIIS APPENDIX IS A SUMMATION BRIEF FOR READER
CONVENIENCE ONLY. FOR DETAILED INFORMATION REFER TO PLATES 1-5, TEXT AND CONSULTANT REPORTS.
FRACTURES OR VUGGY POROSITY AS INDICATED BY GEOPHYSICAL LOGS CONFINING LAYER (DETERMINED BY CH2M HILL, 1987) CLAYS SANDS SILTS ETC FORMATION LIMITS
TD, 3009'
APPENDIX A7 XHYDRFGEDLFGIC SUMMARY OF WEST MELBOURNE INJECTIN WELL
HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM CH2M HILL (1986) LITHOSTRAT[GRAPHIC ANALYSIS BY FGS (1992) LOCATION (FT BLS)
LITHOLOGY OF FRACTURES OR
LEGEND
DEPTH (FT)
BLS
150 310
430
1865
UNDIFFERENTIATED SEDIMENTS
LIMESTONE AND DOLOSTONE
FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS
CONFINING LAYER
(DETERMINED BY CH2M HILL, 1986
CLAYS SANDS SILTS ETC
FORMATION LIMITS
1701 1705.5 3l' 3 it 9
Tl TS 3 12103 33% &3 AIDO 29. SAMPLE VERTICAL & HORIZONTAL INTEPVAL HYDRAULIC CONDUCTIVITY (cM/s)
(ft) PORISITY (%)
NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE ONLY FOR
DETAILED INFORMATION REFER
TO PLATES 1-5, TEXT AND
CONSULTANT REPORTS.
TO 2410
|
