Geologic framework of the lower Floridan aquifer system, Brevard County, Florida ( FGS: Bulletin 64 )

MISSING IMAGE

Material Information

Title:
Geologic framework of the lower Floridan aquifer system, Brevard County, Florida ( FGS: Bulletin 64 )
Series Title:
Bulletin - Florida Geological Survey ; 64
Physical Description:
x, 90 p. : ill., maps ; 28 cm. +
Language:
English
Creator:
Duncan, Joel G.
Evans, William L.
Taylor, Koren L.
Florida Geological Survey
Donor:
unknown ( endowment ) ( endowment )
Publisher:
Florida Geological Survey
Place of Publication:
Tallahassee, Fla.
Publication Date:
Copyright Date:
1994

Subjects

Subjects / Keywords:
Aquifers -- Florida -- Brevard County   ( lcsh )
Floridan Aquifer   ( lcsh )
Genre:
bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Bibliography: p. 77-81.
Statement of Responsibility:
by Joel G. Duncan, William L. Evans III and Koren L. Taylor ; in cooperation with Florida Dept. of Environmental Regulation, Bureau of Drinking and Ground Water Resources, UIC, Criteria and Standards, DER Contract #WM351.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:

The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
ltqf - AAA1617
notis - AKS7744
alephbibnum - 002089186
oclc - 32707875
lccn - 95622284
issn - 0271-7832 ;
System ID:
UF00000521:00001

Table of Contents
    Title Page
        Page i
        Page ii
    Letter of transmittal
        Page iii
        Page iv
    Table of Contents
        Page v
    List of Illustrations
        Page vi
        Page vii
        Page viii
    Acknowledgement
        Page ix
    Abstract
        Page x
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
    Structural geology
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
    Lithostratigraphy
        Page 14
        Page 15
        Page 16
        Page 17
    Depositional environments
        Page 18
        Page 19
        Page 20
    Geophysical character of the lower Floridian aquifer system
        Page 21
    Dolomitization in the lower Floridian aquifer system
        Page 22
        Page 23
        Page 24
    Hydrogeology
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
    Ground-water chemistry analysis
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
    Discussion and conclusions
        Page 76
    References
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
    Appendices
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
    Plates
        Page 91
        Page 92
        Page 93
        Page 94
        00025_Page_21
        00047thm
        00049thm
        00050thm
        00052thm
        00056thm
        00057-9_Page_1thm
        00064_Page_1
        i
        ii
        iii
        iv
        ix
        v
        vi
        vii
        viii
        x
Full Text



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


UNIVERSITY OF Fl.-""' LIBRARIES









DEPARTMENT
OF
ENVIRONMENTAL PROTECTION


SCIENCE
LIBRARY,


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


I I







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 LO GY ................................................................................................................ 5
Regional Structural Fram ework....................................................................................................... 5
Structural Fram work of Brevard County ....................................................................................... 5

LITHO STRATIG RAPHY .........................................................................................................................14
General Stratigraphy ..................................................................................................................... 14
Paleocene Cedar Keys Form action ............................................................................................. 14
Lower Eocene O ldsm ar Form action ............................................................................................. 14
M middle Eocene Avon Park Form action ......................................................................................... 16
Upper Eocene O cala Lim stone ................................................................................................ 17
M iocene Hawthorn G group ............................. .... ........... ............................................ ..........18
Pliocene to Holocene Undifferentiated .......................................................................................18

DEPO SITIO 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

HYDRO G EO LO GY................................................................................................................................ 25
General Hydrogeologic Sum m ary of the Floridan Aquifer System ........................................ .........25
Hydrogeology of the Middle 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
G eotherm al G radients..................................... .......... .. ...................................................... 49

G RO UND-W ATER CHEM ISTRY ANALYSIS....................................................................................57
Introduction .............................................................................................................................57
Prim ary W ells ........................................ ... ............................................................................... 60
M erritt Island ........................................ ................................................. .............................. 60
South Beaches............................................... .. .......... ......... .. .... .......... ...................... 64
D. B. Lee .......................................... .................. .... ................... ................................... 68
Secondary W ells ...........................................................................................................................71
Harris Corporation............................................ .................................................................... 71
G rant Street ..............................................................................................................................73
Port M alabar ........................................................................................ ....................................74
W est M elbourne.............................. ..................................................................................... 74
Hercules, Inc. .................................................................................... .....................................75

DISCUSSIO N AND CO NCLUSIO NS ............................................................. ............................. 76




v






R EFER E N C ES .................................................................................................................................77

APPENDICES .......................................................... ..........................................................82
A. Hydrogeologic summaries of injection well sites............................. ........ ...............82
A l. M erritt Island Injection W ell .................................................................. .............................83
A2. South Beaches Injection Well............................ ..............................................................84
A 3. D B Lee Injection W ell .......................................................................... ....................... ....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. Basem ent faults of peninsular Florida ........................................................... .......... .......................

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
Indian R iver counties ............................................................................................................... 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 m monitor w ells ................................................................................. ........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 nito r w e lls ........................................ .................................................. ............................52

32. Background readings for the D. B. Lee injection and monitor wells prior to the
first injection test..................................................................................................................... 53

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 "character-
ized 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-south-
east through the southeastern portion of the
county (White, 1970).

Coastal communities in Brevard County, like
many others in Florida, have experienced a sub-
stantial population increase over the past sever-
al 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 by-
products. A favored solution utilizes injection-
disposal 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 sys-
tem is necessary in formulating protective crite-
ria 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 under-
standing 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, injec-
tion well tests, borehole videos, geophysical
logs, and monitor well water chemistry informa-
tion.
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 injec-
tion well included in the study and was chosen
as a control well outside the primary study area
for comparison purposes.






Florida Geological Survey


0 5 10 15 MILES
0 5 10 15 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


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Figure 2. Geomorphologic features of Brevard and Indian River
counties (modified from White, 1970).


LEGEND


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0 5 10 15 MILES
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Figure 3. Map showing the location of the A-A' cross section
(Plates 1-3) and the injection wells.





Bulletin No. 64


STRUCTURAL GEOLOGY

Regional Structural Framework

In Florida, Mesozoic and Cenozoic sediments
overlie an eroded basement rock complex rang-
ing from Precambrian to Jurassic (Barnett,
1975). The Peninsular Arch (Figure 4), the
dominant structural feature of Florida, is a north-
west-southeast trending positive basement ele-
ment 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) sub-
Zuni subcrop map shows that basement rock in
Brevard County consists of Middle Cambrian
Osceola Granite with possible Jurassic vol-
canics 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 down-
thrown to the east.

The most prominent structural feature influ-
encing 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 miss-
ing 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 fault-
bounded 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 rever-
sals in the vicinity of Vernon's proposed fault.
Scott (personal communication, 1991) interpret-
ed 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 aver-
age 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 possibil-
ity 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 identifica-
tion more confident. However, faulting is proba-
bly not restricted to this area. After detailed cor-
relation of injection well geophysical logs
(gamma-ray and sonic), a sequence of correla-
tive marker horizons can be recognized and the
thickness of specific stratigraphic intervals rela-
tive to the marker horizons can be determined






Florida Geological Survey


SUWANNEE
STRAITS


LEGEND


AXIS OF POSITIVE
FEATURE


AXIS OF NEGATIVE
FEATURE


STUDY AREA


S BOUNDARY OF
NEGATIVE FEATURE


-N-

I


0 50 100 150 200 MILES Q

0 100 200 300 KILOMETERS

SCALE






Figure 4. Pre-Cenozoic structural features of Florida and
south Georgia (from Miller, 1986).


re






Bulletin No. 64


LEGEND


STRIKE-SLIP FAULT


NORMAL FAULT
(box on cown
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 -


3SAU NOSE


IT JOHNS


GULF
BASIN


APALACHICOLA
EMBAYMENT


LEGEND


-BREVARD
PLATFORM


AXIS OF POSITIVE
FEATURE

AXIS OF NEGATIVE
FEATURE


STUDY AREA


BOUNDARY OF
NEGATIVE FEATURE


-N-

i1


0 50 100 150 200 MILES


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 1 (
-- I ROCKLEDGE e-1710 U
VELL 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 C
/ CD
DBL I
S-1884'
A 70' missing secti n -2086'-\






3- 1 835'
1833' G
+ 70' Missing section 8 1368 HC8 HC
I / q/-1918 S \
/ -1918 -1855'
J0')
/ 1851'
i/ /



0 5 MILES
0 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, uncon-
formity, 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 approx-
imately -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 appropri-
ate 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 football 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 struc-
turally 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 some-
where 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 opera-
tions, 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 sec-
tions in the D. B. Lee and West Melbourne wells
could be interpreted in terms of two unconformi-
ties 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 sepa-
rate unconformities representing two unique epi-
sodes 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 col-
lapse structures. Conceptually this explanation
would entail a sinkhole-like collapse and sedi-
ment in-fill with subsequent differential com-
paction and subsidence across the karst feature
(Figure 8). A shortened section could occur be-
tween the hypothesized subsided sediment and
the karst depression floor. However, the sedi-
ment package overlying the karst feature should
be thicker overall relative to non-karst well loca-
tions. Detailed correlation of marker beds indi-






Bulletin No. 64

















LEGEND

'X' MARKER BED KARST FILL

'Y'MARKER BED 'Z'MARKER BED
UNCONFORMITY


/ / / / / / / / / / / / // / / / / / / / // // /


// 7 / / 7 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


S- - 'X' MARKER BED





//RTENED SECTION/ N / / KARST FILL /
BETWEEN AND THICKER SECTION BETWEEN AND 'Y







E DUE TO DIFFERENTIAL / /
COMPACTION/SUBSIDENCE / / .
T VER KARST FILL STRUCTURE
S I I I //// /// //
3%C 3%C 3C 3a 3C / /Z' MARKER BED/
- - - - - -
//// //// //// ////X




Florida Geological Survey


cates that such stratigraphic relationships are
not apparent between boreholes in Brevard
County and a karst collapse origin for the short-
ened sections in the D. B. Lee and West Mel-
bourne 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 con-
sistently highly indurated nature than in lime-
stones. Moderately- to poorly-indurated mud-
stones, wackestones, packstones and grain-
stones may act as mechanical boundary layers
preventing the vertical propagation of fractures
from dolostone beds. However, several core
samples of poorly to moderately-indurated car-
bonates did have slickensided surfaces but
lacked well defined fracture planes. The slick-
ensides may be the unique expression of frac-
ture-related strain consistent with the mechani-
cal 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 moderate-
ly-indurated mudstone sequence and have dip
angles of approximately 50 degrees. The frac-
tures have well developed, polished slickensid-
ed 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 short-
ened 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 displace-
ment faulting (<50 feet of throw). A second pos-
sible fault, downthrown to the west with north-
south 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 Florida-
Bahama 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 plat-
form 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 compres-
sion associated with Caribbean-North American
plate convergence. Convergence-related stress-
es 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 dis-
placement (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 interbed-
ded 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 car-
bonate platform that existed from late
Cretaceous through Late Oligocene.

Dunham's (1962) carbonate classification sys-
tem 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 classifica-
tion system also distinguishes between mud-
supported 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 uncon-
formably 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 gunteri except
in the highly recrystallized dolostones of the
upper Cedar Keys section (Miller, 1986).


The top of the Cedar Keys Formation accord-
ing 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 (dolo-
stone) that lies between the pelletal, predomi-
nantly 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 uncon-
formable (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 con-
trasts 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 gyralis 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
PLEISTOCENE PLEISTOCENE-HOLOCENE SYSTEM
SEDIMENTS

TERTIARY PLIOCENE TAMIAMI FORMATION
INTERMEDIATE
CONFINING UNIT
OR
MIOCENE HAWTHORN GROUP AQUIFER SYSTEM



OLIGOCENE SUWANNEE LIMESTONE FLPRIRAN
AQUIFER
S UPPER OCALA LIMESTONE FLORIDAN SYSTEM

SL AQUIFER MIDDLE CONFINING
MIDDLE AVON PARK FORMATION UNIT
I L SYSTEMLOER
J 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).


r
CD

Z
z

p
0)
0^





Florida Geological Survey


stone, mudstone, and dolostone and a lower
section of predominantly well-indurated, crys-
talline 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 acces-
sory 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 esti-
mates, is moderate to high.

Dolostones of the upper Oldsmar Formation
are microcrystalline to finely crystalline and fos-
sils 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 inter-
val. 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 lime-
stones and dolomites (dolostones) of various
textures that lies between the gray, largely
micritic limestones and gray dolomites (dolo-
stones) 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 grayish-
orange dolostones commonly containing organ-
ics. Cherty dolostones are typical of the lower-
most 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 sL. 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 indurat-
ed wackestones and packstones containing
abundant Dictyoconus s. foraminifers. Below
this interval, the Avon Park Formation is charac-
terized by interbedded dolostones and lime-
stones. The principal allochems are whole
foraminiferal tests and echinoderm skeletal frag-
ments. 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 gamma-
ray 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 thick-
ly-bedded and massive units of the lower Avon
Park Formation.

Grain-supported limestones are only moder-
ately 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-relat-
ed 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 coarser-
grained dolomite crystals than the surrounding
matrix. Sucrosic texture is common in very fine-
to fine-grained dolostones.

Induration is generally high in all the Avon
Park dolostones. Pore type, porosity, and per-
meability 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 cal-
citic 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 dolomiti-
zation was an important diagenetic process
affecting these rocks.


The lowermost Avon Park Formation is char-
acterized by intervals of nodular chert and cher-
ty dolostones. Silicified burrows encased in
dolostone were present in the West Melbourne
core from 1,700 to 1,705 feet BLS. Also, frac-
ture-filling chert was apparent in cores from sev-
eral 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 approx-
imate 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 dur-
ing 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 com-
posed chiefly of foraminifera, bryzoan and echi-
noid fragments and a lower member of cream to
white, fine-grained, poorly to moderately indurat-
ed, micritic, miliolid-rich limestone. The contacts
between the underlying Avon Park Formation
and the overlying Hawthorn Group are uncon-
formable (Chen, 1965). In Brevard County, the
Ocala consists of white to very light orange,
medium grained, poorly to rarely moderately
indurated, interbedded packstone and wacke-
stone 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 over-
lies the Ocala Limestone and consists of
interbedded olive to yellowish-gray, poorlyin-
durated calcareous clay, quartz sand, wacke-
stone 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 dolo-
stones comprising the Floridan aquifer system
was deposited on an extensive carbonate plat-
form that existed from Late Cretaceous through
Oligocene. Carbonate sediments are intrabasi-
nal deposits and are primarily the product of car-
bonate-precipitating organisms that thrive in
warm, shallow tropical seas. Depositional envi-
ronments 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 deposi-
tional 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 stratigraphically-
equivalent cored intervals in the available cores,
poses severe limitations on the degree to which
reasonable lower Floridan depositional environ-
ment interpretations can be made. Observations
regarding depositional environments for the pur-
poses of this study were based entirely on infor-
mation derived from core and thin section exam-
ination. 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, wacke-
stones, packstones and dolostones of the upper
Oldsmar have sedimentary structures and verti-
cal facies variations that are indicative of tidal
flat deposition (Shinn, 1983). The most repre-
sentative 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, wacke-
stones, and packstones (Appendix A). Common
allochems include peloids, foraminifera, high-
spired gastropods (molds and casts) and echin-
oderm 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 uncon-
formable 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 sedi-
mentary 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 suprati-
dal 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 inter-
vals 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 float-
ing 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 mineralog-
ical suite of this interval that includes glauconite,
pyrite, cellophane 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 deposi-
tional 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 carbon-
ates may record a significant, and possibly
rapid, sea level rise since tidal flat deposits con-





Florida Geological Survey


training subaerial exposure features occur imme-
diately 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 cellophane 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 inter-
face under similar conditions to that of glau-
conite and consequently is common in glau-
conitic sediments.

Pyrite occurs as subhedral to euhedral crys-
tals in combination with glauconite. Pyrite crys-
tals are commonly found within or form rims
around glauconite peloids. Pyrite forms in
organic, muddy sediments under reducing con-
ditions (Miall, 1984) similar to those required for
glauconitization which occurs at the oxidation-
reduction 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 vol-
canic ash blown northward from erupting volca-
noes associated with subduction along the
Caribbean and North American plate boundary.

The lower Oldsmar Formation is characterized
by highly recrystallized, unfossiliferous dolo-
stones. Original depositional textures that may
have been present have been totally obliterated
by dolomitization, making environmental inter-
pretations impractical.

Avon Park Formation

A diversity of carbonate depositional environ-
ments 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 indica-
tive of low energy tidal flat to high energy shoal-
ing 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-ener-
gy wackestone at the base to high-energy grain-
stones at the top (Appendix A5). High angle
cross beds are common in grainstones and
packstones. Some zones of coarse to gravel-
sized "lag" were noted at the base of cross-bed-
ded strata. Allochemical grains are dominantly
skeletal.

The top of the beach sequence is capped by a
peloidal grainstone (at 1,174 feet BLS) contain-
ing 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 cross-
bedded 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 char-
acter 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 wash-
out in the moderately indurated limestones rela-
tive to the overlying and underlying well indurat-
ed 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 struc-
tures. No bedding features of any kind were evi-
dent as the section is apparently highly biotur-
bated. Bioturbation typically signifies lower-ener-
gy conditions and slower sedimentation rates
(Friedman and Sanders, 1978). At approximate-
ly 1,400 feet BLS a one-foot-thick interval of bur-
rowed, oolitic grainstone (oolite) is present sug-
gesting 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 inter-
val, an approximately six-inch-thick section of
irregular to wavy algal laminated and moderate-
ly 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 cen-
tral Florida and concluded that except for a 10-
foot section, all of the cored interval was "char-
acterized 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 proce-
dures includes gamma-ray, sonic, caliper, and
induction resistivity. Lower Floridan aquifer sys-
tem carbonates have characteristic responses
to each geophysical tool which depend primarily
on lithofacies type, mineralogy, porosity, water
chemistry, and borehole conditions. The follow-
ing discussion focuses on the general geophysi-
cal 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 poorly-
to 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 vari-
ations 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 lime-
stones due to abundant saltwater-saturated
pore space in the rock.

A unique mineralogical assemblage within the
uppermost Oldsmar Formation imparts a distinc-
tive geophysical property to the interval resulting
in a highly correlative marker horizon (Plates 1,






Florida Geological Survey


2 and 3). Glauconite, clay, and cellophane are
common accessory minerals within an interbed-
ded 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 differ-
ences 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 poros-
ity 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 per-
cent 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 distin-
guishing relatively low porosity zones from rela-
tively 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 possi-
bly 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 cav-
ernous zones are extremely low and approach, if
not equal, that of the formation water alone.


Several sections of the Floridan aquifer sys-
tem have gamma-ray signatures that are correl-
ative 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 gamma-
ray 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 convec-
tion of saltwater within the Florida Platform, as
proposed by Kohout (1965), could provide the
circulation and mixing mechanism for dolomiti-
zation of much of the Floridan aquifer system
carbonates (Hanshaw et al., 1971). The lateral
and vertical movement of the saltwater-freshwa-
ter 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.
/ nn sonic


0 API UNITS 100 INCREASING POROSITY

LEGEND


LIMESTONE


S 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 Geological Survey


the Floridan aquider system (Hanshaw el al.,
1971).

A recent Isotopic study by Cander (1991]
argues against a mixing-zone origin for perva-
sive dolostones of the Avon Park Formation.
Candor (1991) found that Avon Park Formation
dolostones "have heavy oxygen and carbon iso-
topic compositions and coeval Middle Eocene
87Sr/86Sr isotopic compositions, indicating that
the Avon Park Formation underwent massive
dolomitization by normal to hypersaline seawa-
ter during the Middle Eocene, essentially con.
temporaneous with deposition." He concluded
thai the Avon Park Formation in central peninsu-
lar 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 isolope compositions in the Avon Park
Formation, recognized a late-stage of mixing-
zone dolomite that is present locally in areas
near the present coastline. The mixing-zone
dolomite nucleated on and overgrew earlier
marine-slage dolomite and does not replace
Limestone (Cander, 1991), Mixing-zone dolo-
stones of the Avon Park Formation are dark
brown, dense, hard, non-porous, and highly
crystalline In contrast to the generally highly
porous, relatively soIT, chalky, and poorly crys-
talline marine dolostones elsewhere in the Avon
Park Formation (Cander, 1991). Doloslones
having similar texture and color to mixing-zone
dolostones described by Cander (1991) are pre-
seni in the Avon Park Formation of Brevard
County.

Randazzo at al., (1977) in their study of upper
Avon Park dolostones of west-central Florida
recognized three principal textures indicative of
diHerent dolomitization processes: 1) dolomitiza-
tion by total replacement, 2) dolomitization by
aggrading porphyroid and coalescive neomor-
phism, and 3) dolomilization by selective
replacement. Original depositional texture is
preserved in total replacement dolostones


(Randazzo et al., 1977). Porphyroid dolomitiza-
tion is characterized by scattered, euhedral
dolomite rhombs distributed throughout lhe rock
(Randazzo et al., 1977). The amount ol dolomite
present is dependent on how long dolomitization
has been taking place (Randazzo el al., 1977).
Selective dolomite replacement texture occurs
as a result ol partial dolomitization ol allochems
or matrix {Randazzo el al., 1977),

Randazzo and Hickey (1978) acknowledged
the mixing-zone model's role In dolomltizatlon of
Avon Park carbonates in west-central Florida.
They concluded that some Avon Park supratidal
carbonales were partially dolomltlzed penecon-
temporaneously with sedimentation. Alter burial,
the supratidal sediments along with those from
other depositional environments were exposed
to multiple periods ol dolomitization resulting
from a laterally and vertically migrating sallwa-
ter-lreshwaler interface and a ground-water mix-
ing zone (Randazzo and Hickey, 1978).

Current dolomitization models, such as the
mixing-zone and sabkha, remain highly control.
versial. Hardie (1987) questioned Ihe validity ol
mixing-zone and sabkha models based on sev-
eral lines ol evidence. Hardie's objections to the
mixing-zone model included the following: 1)
thermodynamic problems associated with using
calculations based on ordered dolomite lorma-
tion rather (han the more appropnale and realis-
tic disordered dolomite; 2) lack ol replacement
dolomite in known modern coastal mixing
zones; 3) the lack of dissolution in calcilic lime-
stones underlying dolostones ol alleged mixing
zone origin. Hardie (1987) favored a direct pre-
cipitation origin for contemporaneous sabkha
dolomite instead of a replacement origin. Hardie
based his hypothesis on the generalization that
contemporaneous dolomite only lorms al low
temperalutes by direct precipitation since
replacement dolomite apparently requires much
longer reaction times on the order of 10,000
years or greater (Hardie, 1987).





Bulletin No. 64


Both penecontemporaneous and diagenetic
dolomltlzation processes have apparently affect.
ed lower Floridan aquifer system carbonates in
Brevard County. Dolostones associated with
algal laminations and subaerial exposure sur-
faces are likely supratidal and at least partly
peneconlemporaneous in origin. Partial, matrix
selective dolomitization is common in many of
the lower Floridan aquifer system dolostones
and may be an important factor In the develop-
ment of moldic porosity (Murray, 1960). Murray
(1960) suggested that where only partial dolomi-
tization occurs, porosity can be created by the
dissolution of non-replaced calcium carbonate
remaining in the rock, possibly during periods of
subaerial exposure. The origin of massive,
regionally pervasive dolostone sequences within
the lower Floridan is best explained by marine
dolomitization, probably penecontemporaneous
with deposition in a tidal flat environment.

HYDROGEOLOGY

General Hydrogeokogic Summary of the
Floridan Aquifer System

Four major hydrogeologic units occur in penin-
sular Florida (SEGS, 1986). These are the surfi.
cial aquifer system, the intermediate confining
unit or intermediate aquifer system, the Floridan
aquifer system and the sub-Floridan confining
unit (Figure 10). The Floridan aquiler system
consists of the upper Floridan aquifer system,
the middle conlining unit and the lower Floridan
aquifer system. The hydrogeology for only the
middle confining unit and lower Floridan aquiler
system will be discussed in delail.

The upper-most hydrologic unit in the study
area is the surlicial aquifer system which is com-
prised of a thin blanket ol terrace and Iluvial
sands, shell beds and sandy limestone of
Pliocene, Pleistocene and Holocene age. In
Brevard County, the surlicial 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 aquifer under water able conditions
and is an important source of drinking water lor
more than half of Brevard and Indian River
counties (Scott et al., 1991) (Figure 12).

The intermediate confining unit in Ihe study
area is associated with the Hawthorn Group.
The Hawthorn Group sediments separate the
overlyir;g surficial aquifer system and the under-
lying Floridan aquiler system. These sediments
consist of a low-permeability sequence of sili-
clastic sediments and carbonates which elfec-
tively confine the Floridan aquifer system
throughout most of the study area (Plate 3). The
intermediate aquifer system is not well devel-
oped in eastern central Florida and is not an
important 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 condi-
tions.

The Floridan aquifer system, as declined 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 vary-
ing degrees. Permeability is typically several
orders of magnitude greater than those rocks
that bound the system above and below,

In Brevard County, the Floridan aquifer sys-
tem generally consists of two major permeable
zones (Plate 3) separated by a middle confining
unit of tower permeability (Miller, 1986). The
upper and lower Floridan aquifer systems and
the middle confining unil are comprised of a
sequence of Paleocene to Eocene carbonates.
These carbonates may be hydraulically connect-
ed or separated based upon highly variable
local geoJogic conditions.

In the lower Floridan aquifer system of south-
ern Florida, there is a subzone of highly frac-
tured and cavernous dolostone which exhibits
high transmissivities (Miller. 1986}. The cav-





Florida Geological Survey


- -




U -





-







I nrcvard Cratyn I


I [ndian River County


LEGEND


VELL LnCATECN&

.. SLJURFICIAL AQUIFER SYSTEM

AREAS HERE SURFECIAL ADU]FER
SYSTF I[S PRTHARY SUPPLIER [E
DR1NK3NG VATER









-hi


C, I In at PIS
I I p rt S I (.CLBCTIS
SC4LE







Figure 12. Areas of surficial aquifer system use, Brevard
and Indian River counties (after Scolt et al.,
1991).






Bulletin No. 64


ernous and Iractured nature of Ihe dolostone
commonly causes boulder size pieces of dolo-
slone to be dislodged during the drilling process
giving rise to the term olderdr Zone" by drillers
and subsequently adopted by Kohout (1965)
and later authors. In areas where the salinity of
the waters in the Boutder 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 ol the hydrogeology of the
middle confining unit, lower Floridan aquiter sys-
tem and Boulder Zone is presented in subse-
quent sections ol this report

Numerous Tertiary regressive/transgressive
sequences have produced a diverse carbonate
lithology in the Floridan aquifer system (Plate 1),
A typical sequence of deposition would vary
from low energy, open platform, micrilic sedi-
ments grading into progressively higher energy
packstones or grainstones characteristic of a
shoallng environment to low energy, tidal flat,
fine-grained sediments. As a result of these
numerous sea level fluctuations and subsequent
diagenetlc changes, locally variable, complex
hydrogeologic conditions exist throughout the
Floridan aquiler system.

The Floridan aquifer system does not neces-
sarily conform to either lithostraligraphic or
chronostratigraphic boundaries and therefore,
the lop of the Floridan aqulier system (Figure
10) coincides with the uppermost vertically-con-
tinuous, permeable, Eocene lo Lower Miocene
carbonate beds (SEGS, 1986}, In the study
area, the top of the Florldan aquifer system is
contiguous with the lop of the Eocene Ocala
Limestone (Figure 10) and occurs at elevations
ranging trom -100 to deeper than -350 feet
NGVD (Figure 13). The thickness of the Floridan
aquifer system in the study area ranges
between 2,300 to more than 2,900 feet and gen-
erally increases to the south (Figure 14) (Scott
etal.. 1991).


Recharge ID the Floridan aquifer system is
directly associated with the degree of hydraulic
confinement of the system. The highest rates of
recharge occurs in northern Brevard County
where the Floridan aquifer system is unconfined
or poorly confined (Figure 15), Sinkholes that
breach the intermediate confining unit and pro-
vide hydraulic communication between the surfi-
cial aquifer system and the Floridan aquifer sys-
tem can result in either recharge to or discharge
Irom the Floridan aquifer system. In the study
area recharge will occur in northern Brevard
County and western Indian River County (Figure
15). Discharge to the surlicial aquiler system will
occur in areas of artesian flow (Figure 16).

The potentiometric surface and regional hori-
zonlal flow of Ihe Floridan aquifer system are
also related to the degree of confinement. The
potentiometric surface of the upper Floridan
aquifer system In the study area ranges from
approximately 5 to 40 leet (Figure 17) and later-
al flow is generally south. Where the potentio-
metric surface is higher than the surface eleva-
tion, artesian tfow will occur (Figure 16).
Artesian conditions are present over most of the
study area. In areas where there is relatively
poor or non-existenI confinement, and where
land surface is higher than the potentiometric
surface, (i.e., western Indian River County) arte-
sian conditions are absent (Figure 16) and
recharge to the 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 heterogeneity.

Massively bedded anhydrite usually occurs in
the lower two-thirds of Paleocene rocks (Miller,
1986). The top of the sub-Floridan confining unit
(Figure 19) is declined in terms of a permeability
contrast that limits the depth ol active ground-
water circulation and does not represent any
particular stratigraphic or time unil (Figure 10).
The injection and monitor wells in the study area
are not deep enough to encounter the sub.
Floridan confining unit.







Florida Geological Survey


LrrI
WELL LXA IJINM

-dUlr rC.VD ELEVAIl Tr
3' 1IL FLEl:MUM MLaIFFR
SY01EN
rp l[r IHr[RVAL. IN raEr
nDP L run." irH


P CBAILE bl4.L FAL I







1f


SCALE
1 5 r cmll
I .Ir:I l


Figure 13, Top of the Floridan aquifer system (Ocala
Limestone), Brevard Counly.


..1





Bulletin No, 64


F2 /o

f 2400
I ./


LEGEND


* VELL L..CATI]NS


CONTOUR INTERVAL: DO FEET


2900




rd County --"
IF.
SIr M Piffa C ,t. 2800 -
PWT- --


._270DO


I I II Is nEJ"
r u i a at n [
4 ? 6 5 It tLTKiCME
SCALE


Figure 14. Thickness of the Florldan aquifer system, Brevard
and Indian River counties (after Scott et al.,
1991).






Florida Geological Survey


LEGEND


* VEL.L LOCATIONS


AREAS OF NATURAL eECHARGL


w


,EL


WHO

PH


I..


Bfrevarcj Coilnty


1- Incln R;ver C-jnity


.-- ._
"_Chf


II


GFF RAI .l NErDE c( .n/yr)

VER' LOD (2G in/yr>

VERY LUW' 10 KIkRArL
<2 tO ,n/yr ;,
H [-I I 1CIU O ir i/yr.)






4
-i-


I
_I


s s. a a ruthc
I I 31 s F1n iX.DIT'I
SCALE




Figure 15. Floridan aquiler system recharge potential.
Brevard and Indian River counties (after Scott et
al,, 1991}.





Bulletin No. 64


LEGEND


WELL LOCATIONS
AREAS OF ARTESIAN FLOV








-

I


S 1 ri Ew a 1 cL k
SEALE


Figure 16. Areas of artesian flow from the Floridan aquifer
system, Brevard and Indian River counties (after
Scott et al., 1991).





Florida Geological Survey


I -


( c/

t--.. K


LEGEND


I nr -; r













I rv Eird LerIrnty

S40
I t [nrJnrn. O v:-.. r I-r


WELL LOCATIONS

CONTOUR INTERVAL: 5 FEET

DATUM NGVD


0 5 II T5 M KuS
a 5 10 is f l Z5 chLD EERS
SCALE

Figure 17. Floridan aquifer system potentiometric surface,
Brevard and Indian River counties (alfer Scott et
al., 1991).





Bulletin No. 64


- ~
-- -- .-- .--- -1


--------.-----
S-- - - -,- -- -

--
- - - -

- - -




-77--'--777(-


LEGEND


a VEL_ LOCATIONS


TRANSH[SSE[V]T
3 2
i3 ID X 20 ft/day

3
300 250 X ID Ft/day













-N-
IL


5 14i Tr uiJ
II 6 rS II .5 ls Itirw
SCALE


Figure 1B. Estimated transmissivity of the upper Florldan
aquiler system, Brevard and Indian River counties
(after Miller, 1986).




33





Florida Geological Survey


i -4400

/ -_50


I--- ID





J--- 3OD-- .---" ,
I .i

-3C PH


LEGEND


S 'ELL L DCATI NS


CDATOLS. ]NTERVAL. 11E FEET


K- .


Brcvacrd Cci.aty
-. ]ndia River" ClI unty

\ ---3100


ar
~1 w

I K


6 1 IS M E 5
1 LI Is il JLwJ.Ih S:
L~ALL







Figure 19. Top of the sub-Floridan confiining unit, Brevard
and Indian River counties (after Miller, 19B6),




34


- -^noi


i





Bulletin No. 64


Hydrogeology of the Middle Confining Unit
of the Floridan Aquifer System

The upper and lower Floridan aquifer systems
are separated by a middle confining unit (Miller,
1956) (Plate 3). Locally this zone of confinement
may contain thin zones of moderate to high per-
meability; however, as a whole, the unit acts as
a single confining unit within the main body of
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 con-
fining unit because of the lack of strong contrast
in permeability between these three zones
(Miller, 1986).

The middle confining unit in the study area
consists of dense dolostone with interbedded
limestones located immediately below Ihe "B"
marker bed of 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
porosilies of less than 20 percent, and lithologic
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 transit time on
the sonic logs as the limestones of the upper
Floridan aquifer system abruptly grade into low
porosity (less than 20 percent), dense, micro-
crystalline dolostones that make up the middle
confining unit (Plate 3).

The top of the middle confining unit in the
study area is between -600 to -1,100 feel NGVD
and depth generally increases to the southeast
(Figure 20 and Plate 3). The thickness of the
middle confining unit ranges from 110 to 250
feet and decreases toward 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 signif-
icance of local geologic variation (Plate 4),

Quantitative field data and aquifer tests that
describe the water transmitting characteristics of
the middle confining unit were analyzed for the
Merritt Island injection well (Appendix Al).
Horizontal hydraulic conductivity Is estimated at
2.7 X 10-4 cm/s, vertical hydraulic conductivity Is
1.8 X 10-B cm/s 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 sys-
tem; however, the available data is insulficient
to accurately make this determination,

Hydrogeology of the Lower Floridan
Aquifer System

The lower Floridan aquifer system consists of
all beds that lie below the middle confining unit
(Plate 3) and above the sub-Floridan confining
unil (Miller, 1986). If the middle confining unit is
absent (i.e., South Beaches injection well), the
upper boundary of the lower Floridan can be
declined geochemicalty. The geochemical bound-
ary (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 of
limestones and dolostones with highly variable
carbonate matrices. The higher porosily, less
dense limestones of the lower Floridan aquiler
system are geophysically identified where a
slight decrease in gamma-ray activity and an
increase in sonic interval transit time occurs
(Plate 3).

Geophysical and lilhologic evaluations of the
injection wells indicates that the top of the lower






Florida Geological Survey


*1*


I
LE EN[IP
L
w(LL. L.3CA Iw'

Chil41UP INTERVAL* LD. FEET

-* NrGV: ELEVAr N rapQ
rF THE RIDDLE
CODFININrG lHr'

IRI4ML FAULr wl1M
TECTn ON DOWMNrntoWN
BLOCK

PROBABE NrIAML
r#UL..T


V
/
S TRUCru F L CElNIJ ,
/ INFERLEti
/
/





I


'11
If









1


* I


/ 0
/
2


I N1 MlU1
3 1 H I UkIElL
SCALE


Figure 20. Top of the middle confining unit, in central Brevard
County.


I 0
in

II i
I, I





Bulletin No. 64


H /--




30' LEGEND


VELL LDCATIONS

230- THICEKNESS (FEET) OF
THE MIDDLE CONF]NING
I a Dp UNT T




90,





EL r re rv0-L CCotnty -w

o [rdn RIver County


HI







S I I m Ad nrF.rmaLI
ZsrLE





Figure 21. Thickness of the middle confining unit of the Floridan
aquifer system lor the injection wells in Brevard and
Indian River counties.





Florida Geological Survey


Floridan aquifer system is located at approxi-
mately -1,000 feet 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-waler movement in the lower Floridan
aquifer system and middle confining unit has not
been adequately determined due to lack of reli-
able head data and to the transitory effects of
ocean. Earth and atmospheric tides (Meyer,
1989). However, direction of water movement
can be inferred indirectly from temperature,
chemical and isotopic data (Kohout, 1965).
Kohout (1965) proposed that ground water is
moving upward from the lower Floridan aquifer
system through the circulation of cold seawater
inland through the lower part of the Floridan
aquifer system. Higher Ilow values result where
the upper and lower Floridan aquifer systems
are continuous or where zones of secondary
porosity such as fractures and dissolutional
karstic features occur. Geophysical logs and
borehole videos indicate that possibility for
numerous fracture zones in the lower Floridan
aquiler system (Plate 3).

The quantitative methods used to describe
aquifer parameters are usually based on homo-
geneous, isotropic conditions in a granular
medium that assumes laminar flow. On a
regional scale these methods may be satisfaclo-
ry (Bush and Johnson, 1988); however, locally,
the lower Floridan aquifer system is extremely
heterogeneous, and fractured carbonates are
strongly anisotropic with respect to orientation
and number of fractures (Freeze and Cherry,
1979). Turbulent flow is common in karstic envi-
ronments such as the Boulder Zone (Domenico
and Schwartz, 1990). Therefore, local hydrolog-
ic analysis for transmissivity, hydraulic conduc-


tivity and confinement within a fractured medium
should be viewed with skepticism.

The carbonates ol the lower Floridan aquiler
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 con-
sullting firms (Appendix A) indicate that vertical
groundwater movement in the lower Floridan
aquifer system is generally low with values less
than 10-4 cm/s in the vertical direction (Appendix
A), Horizontal hydraulic conductivity (when ana-
lyzed) was higher with values no greater than
10-3 cm/s (Appendix A). Transmissivity values
for the lower Florldan 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/ft (Appendix
A1, A6 and A8).

Boulder Zone

The Boulder Zone (Kohoul, 1965) is a sub-
zone of the lower Floridan aquifer system con-
sisting of dolostones that display vertical and
horizontal fractures and cavities. The Boulder
Zone is a zone of high transmissivity which
records a period when paleowater tables were
at a level that resulted in karstification of the
upper part of the carbonate sequence (Vernon,
1970). Where the overlying dolostone is effec-
tively confining, the Boulder Zone is used exlen-
sively for receiving liquid wastes because of
high transmissivilies (Appendix A). The Boulder
Zone has no stratlgraphlc significance and can
exist at any level or locale where paleocondi-
lions allowed karstic processes to occur,

The Boulder Zone in the study area is gener-
ally located in the Middle Eocene Oldsmar
Formation at a depth of approximately -2,000
feet NGVD between the glauconite marker bed
and the "C" marker bed (Figure 24 and Plate 3).
Thickness of the Boulder Zone is locally variable




Bullelin No. 64


--lO00




---"


I- "13
" -1]B4


-1200


-300


LEGEND]


S VJELL LOCATIONS

CrJNTOUR INTERV AL LOG FEET
----- ortours From HMller's;
(1986.) regional map5
-Courtuurs estinated with
,n ject;on well dooto

-iNi NGVLU Elevat;onr Top (feet)
OF the lower Flor;.dan
aquifer system in the
injection welts





< I


7' -1400 ,
S-1500
L .., ..


I 3 as mLKmIi*E
SC II L
rEC ..E.


Figure 22. Top of the lower Floridan aquifer system, Brevard and
Indian River counties (modified Irom Miller, 1986),





Florida Geological Survey


LEGEND


/ / I ELL LOCATIONS
S1700
/ ED CNIUUR INTERVAL. L00 FEET

// BEL


PGS.
1800 *
1900

.2000





Indian R.veraT'y --
\ ___--- __--L

I 1700 .

S1600 1700
....-._

9 9 E 15 WLET

SCALC




Figure 23. Thickness of the lower Floridan aquiter system,
Brevard and Indian River counties (after Miller, 1 986)





Bulletin No. 64


7/ KJ






I ILL

-, 2 Ee---l0 -

/ \ -19. NGVD
-205 e *GS THE
r -i 100 -20571 S T DEPT




V r evaGed County





LI- 2 -2300 [Mian River County

-2500 -2400

I ^. --
-?5QOO '-


LEGEND


WELL LOCATIONS

R INTERVAL: ]i0 FEET


ER'5 ESTIMATES


MATES FROM INJECTION WELLS

I ELEVAT[DN (ft): TOP OF
BOULDER ZDNE
H TO TOP OF BOULDER
NOT DETERMINED




-N-


1


I I NI n ILES
S iI r5 CAPs ac
SCALE(


Figure 24. Top of the Boulder Zone. Brevard and Indian River
counties (modified from Miller, 1986),






Florida Geological Survey


and ranged between 85 to 190 feet (Plale 3).
The cavernous nature of the Boulder Zone in
peninsular Florida diminishes northward (Miller,
t986) (Figure 24),

The carbonates immediately overlying the
Boulder Zone consist of interbedded wacke-
slones, packstones and dolostones of the upper
Oldsmar Formation (Plates 1 and 3). Porosities,
estimated from the sonic logs, are generally
greater than 20 percent. Geophysical logs, sam-
ples and borehole videos suggest that this zone
is Iractured in some injection well boreholes
(Plate 3).

Where the Boulder Zone is utilized for waste
disposal, there is a traditional view that the
dense dolostone immediately above and below
the Boulder Zone contains no secondary porosi-
ty and operates as a confining layer. However, a
study of four injection sites along the east coast
of Florida by Safko and Hickey (1992) conclud-
ed that Iracture porosity is the principal type ol
secondary porosity both within the Boulder Zone
and the dolomitic rocks that lie above it. The
present study utilizing core samples, borehole
videos and geophysical logs, supports this
hypothesis.

Confining Layers

Possible confining 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 lay-
ers delineated by the various consulting firms
(Plate 3 and Appendix A), Criteria used for
defining layers of confinement are based on
geophysical logs and lithologic samples. In gen-
eral, non-vuggy, fractureless micritic limestone
and or microcrystalline dolostone with sonic log
porosities less than 20 percent, that are trace-
able and correlative in the subsurface between
the injection wells, are defined as confining lay-
ers,


There is a well defined, highly correlative and
widespread glauconilic, micritic wackestone
located in the uppermost Oldsmar Formation
(Plates 1 and 3). The glauconite marker bed is
located approximately 60 to 235 feet above the
Boulder Zone (Plate 3). Porosities estimated
from sonic logs range between 10 to 37 percent
and fracturing and/or vuggy lithology is absent.
This layer Is between 35 to 45 feet thick and
appears to be a well defined zone of confine-
ment (Plates 1 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-s to 106 crrVs
supporting the assumption that this layer is con-
fining.

Locally, above the glauconite marker bed,
there is a 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 the Florida
Geological Survey (Plate 3).

Geophysical logs, borehole videos and litho-
logic samples suggest that the lower Avon Park
confining zone contains fractures and/or vuggy
lithology. The data are insufficient to determine
the degree of Iracture connectivity within these
layers and it is not known whether these layers
can transmit water via the fracture network.
Thus, it is not known if the lower Avon Park con-
lining zone is a good confining layer,

The rocks underlying the Boulder Zone are
dense micro-crystalline dolostones with porosi-
ties less than 15 percent. These dolostones are
fractured in places and extend below the total
depth of the injection wells. These carbonates
appear to be a layer of confinement (Plate 3).

Fractures and Vertical Flow

As stated previously, analysis of geophysical
logs, Ilthologic samples and borehole videos
indicate that numerous fractures exist through-





Bulletin No. 64


oul the lower Floridan aquifer system (Plate 3).
When determining confining properties, the
presence or absence of Iracture systems is
extremely important. Fracture systems, with the
proper orientation and connectivity, can trans-
port water through rocks that appear to be con-
fining.

Given the right geologic setting, brittle rocks of
low porosity are most susceptible to fracturing
(Domenico and Schwartz, 1990). Dolostone is
considered one of the most fracture-prone sedi-
mentary rocks, second only to quartzite
(Stearns, 1967) (Figure 25). Van Golf-Racht
(1982) cites three cases where stress related
fractures may occur.

1. In response to folding and/or faulting;
2. Deep erosion or removal of the overburden,
which will produce dilferential 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 the study area (see Lithostraligraphy and
Structural sections for further discussion) and
further support Safko and Hickey's (1992)
hypothesis of vertical fracturing of doloslones
overlying the Boulder Zone.

Increases in hydraulic conductivity due to sec-
ondary porosity can occur as a result of dissolu-
tion of limestone by circulating ground water
moving along fractures and bedding planes.
Analyses 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 injec-
tion wells (Plate 3). Normal faulting in the area
where the West Melboume 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
properties 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 extend through a confining
layer or are nol interconnected, then Ihe rock
cannot transmit water via the fracture network.
As previously staled, there is strong evidence
for fractures throughout the rocks within the
lower Floridan aquiler system. The degree ol
connectivity between these fractures is not
known and the water transmitting character is
uncertain.

Dissolutional enlargement ol fault planes and
fractures within zones of relatively impermeable
carbonates can dramatically increase vertical
and lateral hydraulic conductivity and result in
localized transport of different waters through
potential confining layers. Fault planes can func-
tion as conduits causing water to breach confin-
ing 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 from
each other by a confining layers) should
demonstrate contrasting hydrologic behavior.
Distinct hydrologic systems which respond simi-
larly suggest a hydraulic connection. Dilferences
in head values and fluctuation between the
monitor and injection walls Indicate hydraulic
separation. When the hydraulic heads Iluctuate
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


L'I







C L





I

L] THOLOGY


V)
-11
LJ
I-

LJ
Li
i.


-r
I-
LA
Li


87


Average Iracture density for several common rock
types naturally deformed in the same physical
environment (alter Steams, 1967).


628










C:-'


700


6on


bcla


400


300


[00


too


Figure 25.




















-P{OTENTIJMETRIC SURFACE OF INJ[CIlN ZONE


LEGEND



-. FLOW



>- FRACTURES


w

(D


Z
0

0)
OF


SI I I I I I I I I I I POTENTIOMETRIC

-- __ _= IINORMAL
1 1 QUIER SYSTE FAULT





- ------ ----------
-- -------- -------

-CONFINING- .... .-- CAVERN

LAYER 4 7
~ WATER TABLE





"ION ZONE N G
--- -- -- -- ---- --- -----
---- ----------~------ -----
----------------------








-- ------------ -- --7-r-_-_- ---- -- -- -- -- -- -- -
----- ------------------------------------





















Figure 26. Hypothetical hydrogeologic conditions which could result in vertical

flow of different waters.
-- -- -- -------------- -- -
- - - - - - - -
- - - -~ - - - - - -
- - - - - - - - - - -BL
- - - - - - - -



--- --- --- ---------------------------- -----
---------------------------------- --------

------------- --------------------------------






Figure 26. Hypohetical hydrogelogic condition which could reult in vertica
flow of different waters. ZON




Florida Geological Survey


of atmospheric pressure, rainfall, river and lake
stages; and man-induced causes (Domenico
and Schwartz, 1990). External loading stresses
can cause similar hydraulic behavior (i.e., water
level fluctuations in wells) in separate hydrogeo-
logic systems,

Because Brevard County is located adjacent
to the Atlantic Ocean, oceanic tidal loading has
a noticeable impact on hydraulic head fluctua-
tions in wells that penetrate confined aquifer
systems. The response of water levels in wells
due to oceanic tidal loading occurs as a result of
three processes:
1. Mechanical loading of the 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,

Aquifer Loading

Mechanical loading of the aquifer at its ocean-
ic extension causes the water level in a well to
increase at high tide and decrease at low tide.
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 lime lag (Enright, 1990) (Figure 27).

Responses to earth tides in wells occur, by
definition, at the same frequencies as ocean
slides, but are orders of magnitude smaller (the
largest are 0.5-1 inches). Because of a differ-
ence in phase and amplitude, any earth tidal
Iluctuations near the coast typically is masked
by the oceanic tidal Iluctuations. The net effect
of earth tides is to decrease by a small amount
the amplitude ol oceanic tidal fluctuations
(Parker and Springfield, 1950: Gregg, 1966;
Bredehoeft, 1967; Enright, 1990).

An inverse relationship exists between baro-
metric pressure and water levels in wells. An
increase in barometric pressure is transmitted to
the confined aquiler system through the overly-


ing confining layer and the aquiler 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 sup-
ported 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 baro-
metric pressure (Domenico and Schwartz, 1990;
Enright, 1990). This relationship is demonstrat-
ed in Figure 28 where the D. B. Lee monitor
wells are inversely responding to the increases
and decreases of barometric pressure.

If a well system 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 corre-
sponding fluctuations of water levels. These
stresses may conceal the true behavior of the
aquiler syslern(s) in response Io injection tests.

For example, the simultaneous increase in
well pressure within the monitor 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
injection well tests, the monitor well hydraulic
head responses to atmospheric and ocean tidal
loading may mask the effect of the injection test
on the monitor wells. Therefore, in order to iso-
late Ihe hydraulic head response of the monitor
wells to the injection test, the ocean tidal and
atmospheric loading influences need to be
removed by determining the lidal efficiency and
barometric efficiency of the aquifer(s) in which
the wells) are located. Methods for determining
tidal and barometric efficiency are described by
Jacobs (1940) and Domenico and Schwartz
(1990).













o = JiSATQSCon
t = T.ire


Figure 27. Response of water in a well penetrating a confined aquifer to oceanic
tidal loading (modified Irom Enright, 1990),





Florida Geological Survey


BARUWTHE[C rnC Uir5


It.JclONm YELL


v&JV








JV d w
lh;f\^


18
19
I34
LI-


1-



12





0'.




1-2
2.B

1.9

1.7
iC'5 Li


I I I I
OS@02 o6/04


Imw rnor mfrcR WELL





Irel r11i il]NI r VULL


2 05/14 05/L6 ./.ia 0,/20 0 /22 0/~a24 O15/2 06/2fB ./3D


WAY J.IE, 1989


4
TIDAL rFTLhUIA tIS Al MILKitO t rFL[OP DA
1.3
-J



SMEAN $CA LEvL.
'

01/lt 5/14 cI/16 05/18 0,5/0 IP/2E 05/24 05/26
1988


Figure 28. The effect of oceanic tidal loading and barometric
loading on water levels in the D. B. Lee injection and
monitor wells (Dala from Geraghty and Miller, 1988).


ou" r--._ ._


14.8 -



]4.7


I I I I I I I I I I I I I I I I I I I I I




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 partially filter the effects of diurnal
tidal loading (Figure 28) on the confined aquifer
systems. Similar patterns of hydraulic 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,B00-foot monitor
wells (Figure 31) demonstrate patterns of
hydraulic head fluctuations that are suspiciously
similar. Both wells are located in a highly frac-
tured 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 wells, or they may be
reacting to external loading stresses such as
barometric pressure (Figure 28). Hydro Designs
(1989) conducted four injection/recovery tests
on the D. B. Lee injection and monitor well sys-
tem. 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 lo 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 injection flow was automatically
reduced in steps by the injection pumps in oper-
ation (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 moni-
tor wells (see Ground-Water Chemistry Analysis
this report) supports this conclusion. The exact
cause of the upward leakage cannot be deter-
mined. 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
confinement between injection and monitor
zones would occur If the fracture network is con-
nected. It is also feasible that both lack of con-
flnement 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 Platform 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 temper-
ature near the cold sea water bodies averages
about 60 degrees F and increases to 106
degrees F along the central axis of the Florida
Plateau (Kohoul et aJ-, 1977). Horizontal and
vertical temperature distributions suggest that
cold, dense sea water flows inland through cav-
ernous 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 sub-
marine springs on the continental shelf (Kohout
et al., 1977) (Figure 35),

Borehole temperature logs, provided by the
various consulting firms were closely inspected





Florida Geological Survey


HARRIS


MONITOR

1990 1991


W"L LS


* Sr-ALLO'w' MON I I kW'E I
430" 5b0'
( DEEF MON[TOR W'ELL
L527' ]535'


S.


- ..
--1


4..0 -
3.8

3.4


2.8

2.6-
J, 4



18
1.G



:.0
0.8




0.6
0.4
F..?


I,
C


\


..






I


iI


6/28 8/3


I I -I 4
L/1 .5 3/i? 4/17


I
5,2 P


NINTH/ DAY








Figure 29. Comparison of hydraulic head values between the
two Harris Corporation monitor wells (data from
DER, 1991),


/'L
// "
..."/


6/28


;+




Bulletin No. 64


PORT


HALABAR


MO NITOR


WELLS


1989


- 1991


* SHALLOW MONITOR WELL
400' 472'
C DEEP MONITOR WELL
1534' 1630


I I I
1H/19 2/5


I I I I I
6/28 9/8 11/19
MONTH/DAY


I I
2/5


1 1 1 I
4/17 6/28


Figure 30. Comparison of hydraulic head values between two
Port Malabar monilor wells (data from DER, 1991 a).


36-
34-
32-
30-
28-
G-
26-
24-
22-
20-
18-
16
14 -
12 -
10 -
8 -
6-
4
2-


I I
4/17


__


19 9 19













20)
19 m
Is-
17_ INJECTION WEL-
IG-
15 IH
14- J TE "--- .__





1- ISi F-DT MOI]TER wEL 0
z
-'.L

S2.L -- C
2. 30 -(



S 6- E 30 FOOT HDONo O WELL

2.4-



2.-
e- 7---:----' ----- --
1.9 --
L.8 0 18CO FOOT HO4ITnR '/ELL

I I I I I I I I I I I I II I I
o05'] 05/14 05/16 DO/18 cs5/~ 05.-'2 05/24 05/21 06.2'8 Ct/33G 060 c '/03
MAY .LINE. 1922





Figure 31. Comparison of hydraulic head values over time
between the D. B. Lee injection and monilor wells
(data modified from Geraghly and Miller, 1988).





Bulletin No. 64


& SHALLOW. MINr'C 'WE.LL


4'


a JNIERMEDIATE MCNETOR well


a DEEP MONITOR WELL


a INJECT]DN VELL


10iooa i -
10 N 30


40 50 60 70 80


TIME (HOURS)
o000 1I MARCH DIDM 22 MARCH, 198


Figure 32. Background readings for the D. B. Lee injection and
monitor weBls prior to the injection tests (data Irom
Hydro Designs, 1989).


2 00
1.95
] 90
1 .RS
L.80
1.75
1 70
1.67)
155
1,50


5.2D

5.00
4.90
4.80
4.7D


450


6.45
6.40
6.35
6.30
6.25 -
620
6.15 -
6.10 -
6,05
6.00 -
5.95

30.00 -

25.00

20.00

].l0 -






Florida Geological Survey


- 190
1.88
L.86
1.84
].82
].BD
1,78
1,76
1.74
[,72

Li '5.LO
S 5.OB
CY
5.08

C3 5.04
5.D4
z 5.02

u 4.9 1
50D

> 4.96
0
m 4,94
4.92
4.90
Li 4.9Q


6.45

6.-A

6.35

6.30

6.25


6.20



0.00
,QQ


25.00 -


'O.OO 1
20.00 1 ---
15.00 I


a SHALLOd MON]TC1R VELL


- [ETERMED]ATE MONITfOR VE'-L


4 DEEP MDNITOR WELL


I----.--- --


* INJECTIONN WELL


0 10 20 3D 40
1IME (MINUTES)
0717 0817 23 MA'CH, 1989


Figure 33. Results of first D. B. Lee injection test (data from
Hydro Designs, 1989),


~-0 O-


_--U


I I


50 61






Bulletin No. 64


1.85



1.77

1.70

1.65


].60

5.15
5.10
5.05
5.00
4 95
4 90

4.95
4.30
4 1I


6.40
6.35
6.30
6.25
6.20
6.15
6.10
6.03
L 6A.0K


SSHALLOW MONITOR 'ELL


u [NIERMED[ATE MONITOR VELL


Q DEEP MOD[TDR WELL


* INJECTION WELL


0 200 40D 600 800 LO00 1200
T[ME MINUTESS)
0845 22 MARCH -, 02OD 23 AREDR 19B9


Figure 34.


Recovery of D, B, Lee injection and monitor wells
after first injection test (data from Hydro Designs,
1989).


35.00
30.00
25.00


L5.00
LO.DD
5.00
0.0a



















Graucind waterr Dvlidle


I 4


rIprTC l rjArO


- - - .--- -


5' l;.'l -0
-


ioC -U'U 11-'
LI




2O -C
.


lr
2C0 --- -


3500 -



4503-

5DDO


55 C-


I- J


55 F
"-. ---.



"1 1.. 148: "

/ \V 7 7 7 7 7 /r -'


- - --- -- - - - -
r ,- - - --- -------- -
- -


TE'P EPATUPE PRFF]L
.. i:F-=3 ,' b frl 4A3ClU t.'


I,, I


1i.t>!er urT l-1r 13r y-t l-t

rfdrlIr ccfininc Ljnit'-
na_ r --- -


klTve Fil-,r"; Pr r, tn


lower Fltriidor aq".4tr yr.tc


I 1 1 I11 7
syo3- FIoridc.." car n.n.;n t _- -

Id.er Keyi 4 r e -- -- -


3 B 16 ILIPETEPp
S.CLE APPODx:i-AE


l11 1110 143 190
I I I I I


TEHFERAPbRr 'F


- i.41T *WAT.R Fi 3j'

Smi F:rESH 'ATEP F.r-j

4 CA EPhRN

FR PCIU 1 5

-- TEHPEATIjPE RECrFLE


Hypothetical hydrogeologic cross section through peninsular Florida
demonstrating the concept of cyclic flow of seawater induced by geo-
thermal heating (modified from Kohout et al., 1977).


5~'ro 1. u"f "1. .- ; :j


Figure 35.


-.-.----- .-.-... I n $ P + e =. i.r @ r. t -.----. ---.. ---....


. . I .. . .. ..


I I '


1 I *--


I 7


i





Florida Geological Survey


for any anomalous temperature decreases.
Temperatures generally ranged between 80 and
112 degrees F at depths greater than 1,000 teeth
and generally increased with depth; therefore.
no cyclic or convective circulation is suspected
in the study area. Temperature decreases have
been documented in south Florida where the
Straits of Florida are adjacent to the Florida
Platform, The occurrence of convective circula-
tion should be investigated when injection wells
are proposed for Ihese areas.

GROUND-WATER CHEMISTRY ANALYSIS

Introduction

Water-quality data, confining zone, and injec-
tion zone information for seven wells in Brevard
County and one well in Indian River County
(Hercules Corporation) were analyzed for this
investigation. Three wells, the Merritt Island,
South Beaches, and D. B. Lee Injection wells,
were chosen for detailed study because of obvi-
ous trends observed in water-quality data. For
these wells, confining, injection, and monitor
zone lithologies were examined to determine
any physical properties that might help explain
observed monitor zone contamination.
Determining the mechanical integrity ol the injec-
lion wells was beyond the scope of this study.

The injection intervals of all eight wells occur
in the Boulder Zone of the lower Floridan aquifer
system (Figure 36), in the Oldsmar Formation
(with the possible exception of the Port Malabar
injection interval where the Boulder Zone is not
well developed; see Plate 3). This zone is gener-
ally highly fractured and cavernous, with trans-
missivity values ranging up to 21 million gpd/ft
(Haberfeld, 1991). The high transmissivities in
the injection zone, and pumping rates which can
be tens-of-millions of gallons per day, result in
only minimal increases in wellhead pressure in
most wells (Haberfeld, 1991), This implies the
possibility that the injected waters are circulating
freely. Fractures, discontinuities, and cavities in


the designated confining zones of the wells
could provide conduits lor the circulating water.

The injected Iluids are generally low-salinity,
treated municipal waste water. Industrial waste
waters are injected at the Harris Corp. and
Hercules, Inc. sites. Injected waters are less
dense than formation water, and since fluids in
the injection and lower monitor zones are highly
saline, "contamination" from injected fluids will
be seen as freshening trends in monitor well
data. For example, such trends show up as a
decrease in total dissolved solids (TDS) and/or
chloride concentration, Occasionally, marked
increases in these parameters are observed,
and this is attributed to deeper saline waters
being displaced upward by injected fluids (J.
Haberfeld, DER, personal communication,
1991).

Nitrogen content is monitored because treated
waste water will generally have higher nitrogen
concentrations than ambient formation water. It
is measured as total kjeldahl nitrogen (TKN}.
which is organic nitrogen plus ammonia. Another
important measurement is the depth at which the
TDS value exceeds 10,000 mg/L. United States
Environmental Protection Agency guidelines
slate that the TDS value of formation waters in
an injection zone must exceed 10,000 mg/., so
consultants note the depth at which the transi-
tion occurs. For the transition depths, only pre-
injection values are available.

The TDS, chloride, and TKN are among the
parameters tracked in the various monitor
zones, and these three were chosen for close
investigation because time series data on them
are available for the monitor zones of the injec-
lion wells.

The three primary wells are the Metritt Island,
Ihe South Beaches, and the D. B. Lee injection
wells. These are discussed first, and are fol-
lowed by summaries of data lor the Harris Corp.,
Grant Street, Part Malabar, West Melbourne.
and Hercules, Inc. injection wells.
















I -
Ld
Mi


W


3-J
L I l
. _
S3r


K-7 r.. -4-v r.- --.2 Mi


I-I
V II V
4 --' c; ,-c
E Cl

-1-4.5 mi.+- 4 ni.- -L


F.: PLA T ION


[] ]JECTION ZONE

I CONFINrING ZL-NE

1-.:-,0 r-;..' TDS
CONTACT

SMON:TOPR znNL

To- OF THE .L]DDL F
CONF]N[r,3 UNIT
AS DEFINEDD IN
THfS BULLETIN


rfiR.1AT[C-J CONTACT

CA -. ErFeNJS


30'0


300o 3005'







Figure 36. Relationships ol monitor, confining, and injection zones ol the study
wells (data from consultant reports).


^r
*I3:

CL
1C1 J


0



500




100C -


1500 -


2500 -




2500 -





Bulletin No. 64


in this section, the definitions of the extent of
confining, injection and monitor zones are those
made by the consultant companies during
drilling. The consultants chose the placement of
monitor zones based on their definitions, so the
water-quality data from the monitor zones are
analyzed and discussed in lerms of those defini-
lions.

However, the consultants' hydrogeological
interpretations often differ Irom those of the
Florida Geological Survey (FGS). Charac-
teristically, their deiinilions 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 the glauconite marker
bed. These units are discussed in the
Hydrogeology of the Middle Confining Unit
of the Floridan Aquifer System and the
Hydrogeology of the Lower Floridan Aquiler
System. Plate 3 shows the confining zones
delineated by the FGS geologists.


In addition to the definitions of confining, injec-
tion and monitoring zones, the consultants'
reports provided background water-quality data.
The Bureau of Drinking and Ground Water
Resources of the DER provided the lime series
water-quality data taken from the monitor wells
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 sup-
plemented by geophysical log data, whenever
possible.

The description of samples involved determin-
Ing lithologies and physical properties. Physical
properties determined for each sample include
color, porosity, permeability, grain size. indura-
tion, cement type, sedimentary structures,
accessory minerals, and presence or absence


of fossils. These descriptions are a part of the
FGS well-lile database. General lithologies are
illustrated on Plates 1. 2, and 3.

The lithologic descriptions were also correlat-
ed with geophysical logs (for example, see Plate
1). When possible, porosily values calculated
from sonic logs were used to supplement the
descriptions.

Monitor zone water-qualily data were exam-
ined to ascertain if there has been any migration
of injection or formation waters due to pumping.
Vertical migration of injection waters would be
indicated by falling TDS and chloride concentra-
tions, and by rising TKN concentrations. If verti-
cal migration or contamination occurred, these
Irends would be most prominent in data trom the
lower monitor zones.






Florida Geological Survey


Primary Wells

Merritt Island

At the Merritt Island site, there are two closely
spaced injection wells completed in the Oldsmar
Formation at a total depth of 2,500 feet BLS.
The monitor well has an upper monitor zone
from 128 to 340 feet BLS in the Ocala
Limestone, and a lower monitor zone extending
from 1.470 to 1,500 feet BLS in the Avon Park
Formation (Appendix Al). The confining zone,
as defined by Geraghty & Miller, Inc. (1986),
extends from 1,600 to 1.850 feet BLS, in the
lower Avon Park and upper Oldsmar
Formations. The uncased injection zone interval
is 1,850 10 2,500 leet BLS in the Oldsmar
Formation.

The lower monitor zone is in dolostone of the
lower Avon Park Formation. The interval from
1,470 to 1,498 feet BLS is dolostone of 10 per-
cent to 20 percent porosily, 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 monitor zone and the confining
zone.

Between the lower monitor zone and the con-
fining zone dolostone is the dominant rock lype.
Below the permeable zone noted above, from
1,518 to 1,530 feet 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 Oldsmar Formations, extending from
1,600 to 1,900 feet BLS. The interval consists of
alternating layers of dolostone, mudstone,
wackestone, and packstone from 1,600 to 1,B30
teet BLS, and dolostone from 1,830 to 1,900
leet BLS. Porosity and permeability are highly


variable throughout this zone. Fractures were
noted in two cored intervals, from 1,720 to 1,723
feet BLS and from 1,620 to 1,B30 feet BLS.

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.,
19B6). 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
mg/L TDS (Freeze and Cherry, 1979). In this
area TOS values exceed 10,000 mg/L at
approximately 1,200 feet BLS.

Data on lower monitor zone water quality
shows changes in all these values since injec-
tion started in January 1987. TDS show a
steady decrease beginning in February 1987,
from over 34,000 mg/L to below 22,000 mg/L in
July of 1991 (Figure 37). Chloride concentra-
tions decreased from over 16,000 mg/. to below
12,000 mg/L (Figure 38). TKN Increased from
19B7 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 the peak is
probably due to the increasing efficiency of the
treatment plant that treats the effluent before it
is injected (J. Haberteld, DER, personal commu-
nication, 1991).

Data from the upper monllor zone show a
slight decrease in TDS values, and chloride and
TKN values vary widely. The change in TDS val-
ues is too small to infer that injected waste
water has traveled that high in the section.

Regression analyses were performed on the
deep monitor well data to determine the signifi-
cance of the observed trends. A high R-squared
value, or coefficient of determination (R is the
correlation coefficient), indicates low scatter of
the data, or a definite relationship between time
and concentration values. The R-squared value












35





E 30
v,'


-J o9
0 25 -



- > 0
SI 20 -
S0 2 MERRITT ISLAND

DEEP MONITOR WELL
1470 1500 FEET
S 15
F-
0
I-


10 I
FEB-87 AUG-87 JAN-88 JUL-88 JAN-89 JUL-89 JAN-90 JUL-90 JAN-91 JUL-91 JAN-92
DATE





Figure 37. TDS values of the Merritt Island well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).


co
1:

z
0
0)














17


16- DEEP MONITOR WELL

E 1470 1500 FEET

z 15
0


Y Z 14 -

wt


0 1

-j
0 13-






I
S 11 -
C)


10 -- I I I II -
FEB-87 AUG-87 JAN-88 JUL-88 JAN-89 JUL-89 JAN-90 JUL-90 JAN-91 JUL-91 JAN-92
DATE




Figure 38. Chloride concentrations of the Merritt Island well deep monitor zone
(data from the DER Bureau of Drinking and Groundwater Resources).


-n
0
(D

0
0
0C
CD
C/)
c
C<












4



SMERRITT ISLAND
E DEEP MONITOR WELL
3- 1470 1500 FEET
L.J

0
F-
Z 2
2 -j






1
_.J


I--
0
I-



FEB-87 AUG-87 JAN-88 JUL-88 JAN-89 JUL-89 JAN-90 JUL-90 JAN-91 JUL-91 JAN-92
DATE




Figure 39. TKN values of the Merritt Island well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).


CD

z
0)
P
CD





Florida Geological Survey


for the chloride plot is 0.92. The TDS value is
0.54, but jumps to 0.74 when the obvious outly-
ing values are removed. For the TKN regres-
sion, values from February 1987 to April 1988
were used, to determine the significance of the
increase in concentration. The R-squared value
for that period is 0.71. These high R-squared
values tend to support the interpretation that
possibly fractures and the general discontinuous
nature of the confining interval have allowed
injected fluids 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 Oldsmar
Formation. There are two separate monitor
wells at the site. The upper Floridan aquifer sys-
tem well monitors the zone from 300 to 350 feet
BLS in the Ocala Limestone, and the lower
Floridan aquifer system well monitors Irom
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 injec-
tion zone extends from 2,081 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,
mudstone, and wackestone, with porosities
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 few
interbedded cherty layers, to 20 percent in the
wackestones and packstones. Bolh induration
and permeability have wide ranges, from low to
high in alternating layers. Siickensides related to


fracturing andlor faulting 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 chlo-
ride value was 14,410 mg/L. In this area TDS
values exceed 10,000 mg/L at approximately
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 fell from over 21,000 mg/L to less than
10,000 mg/L (Figure 40). Chloride values tell
from over 16.000 mg/L to less than 5,000 mg/L,
starting in July 1987 (Figure 41). These changes
are attributed to injection waters rising through
the confining units. Values of TKN show a pat-
tern similar to that of the Merritt Island well lower
monitor zone. There was a rise Irom approxi-
mately 0.5 mg/L to a peak at about 3.0 mg/L,
and then a decline (Figure 42). This is again
attributed to the increasing efficiency of the
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 zone.

Regression results show an R-squared value
of 0.78 lor the observed chloride trend, with the
value increasing to 0.87 when outliers are
removed from the calculations. The R-squared
value for the TDS plot is 0.9. Regression of TKN
values was done for the period Irom Juty 1987
to March 1988, to determine if the increasing
concentration trend was significant. The R-
squared value for that period is 0.88. These val-
ues tend to support the conclusion that the Irac-
tures, cavities, and the discontinuous nature of
the confining zone have allowed migration of
injected fluids into the monitor zone.








22


2 !20
) SOUTH BEACHES
E DEEP MONITOR WELL
S1550 1700 FEET

)J 16 -
0 z
S) 14 -
> V, D


10








AUG-88 JAN-89 JUL-89 JAN-90 JUL-90 JAN-91 JUL-91 JAN-92
DATE





Figure 40. TDS values of the South Beaches well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).
6 ------------------------------------








the DER Bureau of Drinking and Groundwater Resources).














16-
> SOUTH BEACHES
E DEEP MONITOR WELL
4 1550 1700 FEET




oo,
0 I 4
12-
ry

w ) 10-
(0











JUL-87 DEC-87 JUN-88 DEC-88 JUN-89 DEC-89 JUN-90 DEC-90 JUN-91 DEC-91
8 c-


- 6
0
4


2-
JUL-87 DEC-87 JUN-88 DEC-88 JUN-89 DEC-89 JUN-90 DEC-90 JUN-91 DEC-91
DATE




Figure 41. Chloride concentrations of the South Beaches well deep monitor zone
(data from the DER Bureau of Drinking and Groundwater Resources).











s SOUTH BEACHES
DEEP MONITOR WELL

z: 1550 1700 FEET
L.
CD 4
0
r,
I--







:0 < I I I I
3 -













JUL-87 DEC-87 JUN-88 DEC-88 JUN-89 DEC-89 JUN-90 DEC-90 JUN-91 DEC-91
DATE







Figure 42. TKN values of the South Beaches well deep monitor zone (data from
the DER Bureau of Drinking and Groundwater Resources).
-c-
H-



H--













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 con-
fining 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 per-
meability. 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 confin-
ing 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 val-
ues 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 (dolo-
stones) 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 approxi-
mately 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 immedi-
ately 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 infor-
mation, but it can be assumed that background
values were low, in the 1 mg/L range (J.








































10 -
JUL-88


DEC-88 JUN-89 DEC-89 JUN-90
DATE


DEC-90 JUN-91 DEC-91


Figure 43. TDS values of the D. B. Lee well deep monitor zone (data from the
DER Bureau of Drinking and Groundwater Resources).


35


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4 I I I I I I
JUL-88 DEC-88 JUN-89 DEC-89 JUN-90 DEC-90 JUN-91 DEC-91

DATE








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 avail-
able TKN background values for other injection
wells (see, for example, the Merritt Island back-
ground 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 dur-
ing injection, from July 1988 to March 1989,
comprise the first part, and data collected after
injection stopped are in the second part. The R-
squared 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 con-
centrations 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 dur-
ing 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 concen-
trations increased from about 4,000 mg/L to a
high of almost 14,000 mg/L just before injection
stopped. Concentrations then dropped and fluc-
tuated 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 informa-
tion to determine if a confining sequence exists
between 1,900 and 2,000 feet below land sur-
face...," and the report confirms the freshening
trends seen in the deep and intermediate moni-
tor 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.











34-
32
30-
28
E
26-
Z 24-
L J
0 22-
0
aL 20
2-
Z 18-
S16-
I 14
Q 12
i 10

S8

-J 6
4
0
- 2-

0-
JUL-88


DEC-88 JUN-89 DEC-89 JUN-90
DATE


')

CD


DEC-90 JUN-91 DEC-91


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 dolo-
stone, 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 mon-
itor 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 con-
centrations 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-mil-
lions of gallons from month-to-month. TKN val-
ues 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 sepa-
rate 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 val-
ues that start higher than those quoted in the
Hydro Designs report. Further examination of
the water-quality report indicated that the sam-
ples 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-quali-
ty data show trends at this site, but the magni-
tudes of changes are not as great as at other
wells. TDS values decline in a somewhat irregu-
lar manner from just over 27,000 mg/L in mid-
1989 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-1991.

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, prob-
ably 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 per-
meability 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 indurat-
ed. From 1,470 to 1,640 feet BLS the rocks are
interbedded dolostones, mudstones and wacke-
stones. Porosity in the mudstones and dolo-
stones ranges from 5 to 15 percent. The dolo-
stones are well indurated and have low perme-
ability, and the mudstones are poorly to moder-
atley indurated and have low permeability. The
wackestones are moderately indurated, general-
ly 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 interbed-
ded. 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 permeabili-
ty, 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 avail-
able 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 shal-
low monitor zone water-quality data do not show
any significant trends. In this area available data
cannot be used to determine conclusively if ver-
tical 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 poros-
ity 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 mid-
1989, 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 erro-
neous 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 pack-
stone, 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 concen-
tration 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 con-
centration 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 dis-
placed formation water. Again, TDS and TKN
data were not collected until 1990, and no pat-
terns are observed. Data for the middle and
upper Floridan monitor zones also show no pat-
terns.

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 envi-
ronment, diagenesis, and geologic structure.
Variations in these components can result in
considerable differences in local lithofacies,
porosity, permeability, and hydrogeologic char-
acter of the aquifer.

Ground-water chemistry trends for several
injection wells indicate that injected waste liq-
uids are migrating upward through the "confin-
ing" rocks immediately above the injection
zones. Since apparently low permeability dolo-
stones are common in the "confining" sequence,


injected waste waters are probably moving verti-
cally 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 per-
meability locally and serve as conduits for verti-
cal fluid migration. If injected waste fluids
migrate preferentially upward along dissolution-
ally 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 accompa-
nied 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 neu-
tron-density) should be run over the entire bore-
hole of future injection and monitor wells.




Bulletin No. 64


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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 car-
bonate 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. I-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,
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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.

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1986, Hydrogeological units of Florida: Florida Geological Survey Special Publication 28, 8 p.




Bulletin No. 64


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Van Golf-Racht, T. D., 1982, Fundamentals of fractured reservoir engineering: Elsevier, New York.

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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-15890
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-16133
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

SHYDROGEOLOGIC SUMMARY OF MERRITT ISLAND INJECTION WELL


HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY & MILLER, INC. (1984)
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


w


CONFINING LAYER
(DETERMINED BY GERAGHTY & MILLER 1984)


0)
-4,


CLAYS SANDS SILTS ETC


FORMATION LIMITS


a 950 2.710

< 1055' 1




524- 525 2.IX1
SAMPLE 33%
INTERVAL (Ft)


HORIZONTAL HYDRAULIC CONDUCTIVITY (cm/s)
&TRANSMISSIVITY DETERMINED BY PACKER TESTS



VERTICAL HYDRAULIC CONDUCTIVITY (cn/s)
POROSITY (%)
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


*HYDROGEOLOGIC SUMMARY OF SOUTH BEACHES INJECTION WELL


HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM DAMES & MOORE (1985)
LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)


LEGEND


UNDIFFERENTIATED 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 T LOG
INTERVA. FLOW ZONE
1300


TEMPERATURE LOG
INDICATES ZONE
OF FLOW


VERTICAL HYDRAULIC
1547 4 25X10 CONDUCTIVITY (cm/s)
1547 510 SAMPLE INTERVAL
1 FOOT


1000'
SAMPLE 3
INTERVAL 4XI5 3
1100'


TD 2916'


LATERAL HYDRAULIC
CONDUCTIVITY (cm/s)
DETERMINED BY PACKER TESTS


NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE OGLY. FOR
DETAILED INFORMATION REFER
TO PLATES 1-5. TEXT AND
CONSULTANT REPORTS.


"1,
o
-n
03



(D
0
0
(Q




C)


(D


TDO 2916








APPENDIX A3


KHYDROGEOLOGIC SUMMARY OF D. B, LEE INJECTION WELL

HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY & MILLER, INC. (1988)

LOCATION (FT BLS) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)
LITAOLOGY OF FRACTURES OR


TD, 2440


TD- 2440


DEPTH (FT)
BLS



150

255


410







































1904


LEGEND




UNDIFFERENTIATED SEDIMENTS






LIMESTONE AND DOLOSTONE







FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS






CAVERNOUS ZONE




z

CONFINING LAYER c
(DETERMINED BY GERAGHTY 8 MILLER, 1988)







CLAYS SANDS SILTS ETC



FORMATION LIMITS



1772'- 1775' 19X106 VERTICAL HYDRAULIC CONDUCTIVITY DETERMINED FROM LABORATORY
SAMPLE ANALYSIS
INTERVAL
(FEET)


NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE ONLY. FOR
DETAILED INFORMATION REFER
TO PLATES 1-5, TEXT AND
CONSULTANT REPORTS.










APPENDIX A4

HYDROGEOLOGIC SUMMARY OF HARRIS CORPORATION INJECTION WELL

HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM GERAGHTY MILLER, INC. (19860)
LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)
LOCATION (FT BLS)


LEGEND


UNDIFFERENTIATED SEDIMENTS







LIMESTONE AND DOLOSTONE


DEPTH (FT)
BLS


95



330


469





























1930





















TD, 2800


1 0 -
1320' -- .4X- i
SAMPLE
DEPTH



1010
PACKER 3
INTERVAL 12X103
1150


-n

0
-)



CD
0

0
(0

5-
C)



(D
e<


VERTICAL PERMEABILITY ( & POROSITY (%) DETERMINED
FROM LAB ANALYSIS





HYDRAULIC CONDUCTIVITY (cn/s)
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.


FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS






- CONFINING LAYER
(DETERMINED BY GERAGHTY & MILLER, 19860)






CLAYS SANDS SILTS ETC





FORMATION LIMITS





APPENDIX


A5


XHYDROGEOLOGIC SUMMARY OF GRANT STREET INJECTION WELL


HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM HYDRO DESIGNS (1989)


DEPTH (ft) LITHOLOGY
BLS


LEGEND


UNDIFFERENTIATED SEDIMENTS






LIMESTONE AND DOLOSTONE







FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS


70



280


390
































1850


CLAYS SANDS SILTS ETC


CAVERNOUS ZONE
(DETERMINED BY HYDRO DESIGNS, 1989)



FORMATION LIMITS


5 -6 I VERTICAL & HORIZONTAL
203" 3.6XI0 3.XlD HYDRAULIC CONDUCTIVITY
SAMPLE RESPECTIVELY (c,/s)
INTERVAL
1 FOOT

K NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE ONLY. FOR
DETAILED INFORMATION REFER
TO PLATES 1-5. TEXT AND
CONSULTANT REPORTS.


CONFINING LAYER
(DETERMINED BY HYDRO DESIGNS, 1989)


TD, 2700'


z
0
o0)
0)


TD 2700'











APPENDIX A6



HYDROGEOLOGIC SUMMARY OF PORT MALABAR INJECTION WELL

HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM CH2M HILL (1987)
n ,( n LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)


LEGEND


UNDIFFERENTIATED SEDIMENTS






LIMESTONE AND DOLOSTONE


DEPTH (FT)
BLS

100



270


410






























1890



















2820


TDO 3009'


1662'- 1663'
SAMPLE
INTERVAL


-n
-





o
o
CD
0









(D
c


-6 -6 VERTICAL &, HORIZONTAL
-2.9X10 & 6.2X10 HYDRAULIC CONDUCTIVITY (cm/s) &
22% & 13% POROSITY (%) RESPECTIVELY


TRANSMISSIVITY (gpd/fit)
1905- 1912 2.2 USING PACKER TESTS &
SAMPLE THE JACOB MODIFIED METHOD
INTERVAL


NOTE. THIS 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 MILL, 1987)







CLAYS SANDS SILTS ETC




FORMATION LIMITS


TDI 3009'







APPENDIX


HYDROGEOLOGIC SUMMARY OF WEST MELBOURNE INJECTION WELL

HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM CH2M HILL (1986)
LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)
LOCATION (FT BLS)
LITHOLOGY OF FRACTURES OR


LEGEND


DEPTH (FT)
BLS


150



310


430




































1865


A7


UNDIFFERENTIATED SEDIMENTS






LIMESTONE AND DOLOSTONE






FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS





CONFINING LAYER






CLAYS SANDS SILTS ETC



FORMATION LIMITS


1701- 1705.5 3.1X103 33% 3.1X03 29%
SAMPLE VERTICAL &. HORIZONTAL
INTERVAL HYDRAULIC CONDUCTIVITY (cr,/s)
ft) PORISITY (7.)


NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE ONLY. FOR
DETAILED INFORMATION REFER
TO PLATES 1-5, TEXT AND
CONSULTANT REPORTS.


TD 2410









APPENDIX A8



HYDROGEOLOGIC SUMMARY OF HERCULES INC INJECTION WELL


HYDROLOGICAL AND GEOPHYSICAL ANALYSIS FROM CH2M HILL (1979)
LOCATION (FT BLS) LITHOSTRATIGRAPHIC ANALYSIS BY FGS (1992)


LEGEND


DEPTH (FT)
BLS

100







465


580
































2140


LITHOLOGY


UNDIFFERENTIATED SEDIMENTS







LIMESTONE AND DOLOSTONE






FRACTURES OR VUGGY POROSITY
AS INDICATED BY GEOPHYSICAL LOGS






CONFINING LAYER
(DETERMINED BY CH2M HILL 1979)







CLAYS SANDS SILTS ETC




FORMATION LIMITS


SAMPLE 1949 TRANSMISSIVITY (grod/ft)
INTERVAL T=45 FROM PACKER TESTS
(ft) 1959



NOTE, THIS APPENDIX IS A
SUMMATION BRIEF FOR READER
CONVENIENCE ONLY. FOR
DETAILED INFORMATION REFER
TO PLATES 1-5, TEXT AND
CONSULTANT REPORTS.


TD' 3005'


TDi 3005'