Title: Northeastern Manasota Basin Hydrologic Investigation
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 Material Information
Title: Northeastern Manasota Basin Hydrologic Investigation
Physical Description: Book
Language: English
Publisher: Seaburn and Robertson, Inc. , Water Resources Consultants, Tampa, Florida
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Spatial Coverage: North America -- United States of America -- Florida
 Notes
Abstract: Jake Varn Collection - Northeastern Manasota Basin Hydrologic Investigation
General Note: Box 28, Folder 18 ( Northeastern Manasota Basin Hydrologic Investigation - June, 1980 ), Item 1
Funding: Digitized by the Legal Technology Institute in the Levin College of Law at the University of Florida.
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Bibliographic ID: WL00004740
Volume ID: VID00001
Source Institution: Levin College of Law, University of Florida
Holding Location: Levin College of Law, University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Full Text















NORTHEASTERN MANASOTA BASIN

HYDROLOGIC INVESTIGATION








Prepared for

Southwest Florida Water Management District

And

Manasota Basin Board






Prepared by

Seaburn and Robertson, Inc.
Water Resources Consultants
Tampa, Florida


June, 1980







SEABURN AND ROBERTSON, INC.
Water Resources Consultants

offics:cutive Square ALTON F. ROBERTSON, P. E.
5510 Gray Street GERALD E. SEABURN, Ph.D., P.E.
Suite 118
Tampa. Florida 33609
meln.o Bod3184 September 2, 1980
Tampa, Florida 33623
phone:
(813) 870-2792
(813) 870-2823


Manasota Basin Board Of The
Southwest Florida Water Management District
5060 U.S. Highway 41, South
Brooksville, Florida 33512

Re: Northeastern Manasota Basin Hydrologic Investigation
SRI Project No. 78152

Gentlemen:

Seaburn and Robertson, Inc. takes pleasure in transmitting to you our report
entitled "Northeastern Manasota Basin Hydrologic Investigation." This report
summarizes the findings of our investigation to locate favorable areas in the
Northeastern Manatee County for withdrawal of potable groundwater. -This
study was authorized by the Manasota Basin Board and the Southwest Florida
Water Management District on September 29, 1978. The objectives of the study
were to assess the hydrogeology, water quality and ecology of the project
area, to locate suitable groundwater supplies for regional-scale water supplies,
and to predict the impacts expected from withdrawals at these selected sites.

The project area, consisting of about 400 square miles in northeastern Manatee
County is presently devoted largely to agriculture which uses considerable
amounts of irrigation water. Water quality in the Floridan aquifer is the
principal limiting factor for groundwater development for potable water supply.
Sulfate, fluoride, and total dissolved solids exceed drinking water limits in
many parts of the area and these constituents also increase in concentration
with depth in the aquifer.

Four sites were delineated in the project area as suitable areas for large
scale groundwater withdrawals. The amounts of water available from each site
ranged from 12 to 30 mgd. The total amount of water available from all four
sites is about 45 mgd. These four areas were further subdivided into nine
subareas for more detailed study.

Withdrawals at the rates indicated above from these areas are not expected to
have any impact on the surface waters (streams and lakes) nor on the environ-
mentally sensitive parts of the project area because of the extensive and
highly effective confining unit overlying the Floridan aquifer. This confining
unit effectively retards vertical groundwater movement between the surface
water aquifer and the underlying Floridan aquifer.










Manasota Basin Board Of The
Southwest Florida Water Management District
September 2, 1980

Page Two

It was a distinct pleasure for Seaburn and Robertson, Inc. to conduct this
important water resource planning study and we hope that the results can be
used to guide the rational development of water resources in the Manasota
Basin. We appreciate the support of the Southwest Florida Water Management
District staff as well as the District and Basin Board Members during the
preparation of this report.

Sincerely yours,
SEABURN AND ROBERTSON, INC.
Water Resources Consultants


Alton F. Robertson, P.E.
Principal-In-Charge



John E. Darling, Jr.
Project Manager
AFR/lrb



















SEABURN AND ROBERTSON, INC. si













TABLE OF CONTENTS


Page

LETTER OF TRANSMITTAL ii

LIST OF ILLUSTRATIONS vi

LIST OF TABLES x

FACTORS FOR CONVERTING ENGLISH UNITS TO METRIC UNITS xi

EXECUTIVE SUMMARY 1

Geologic Conditions Favorable for Groundwater Development 4
Hydrologic Conditions Favorable to Groundwater Development 5
Water Quality Conditions Favorable for Groundwater Development 7
Conclusions 14
Recommendations 19

INTRODUCTION 21

Purpose and Scope 21
Description of the Project Area 25
Previous Investigations 27
Investigation Approach 31

Well Inventory and Water Quality Sampling 33
Aquifer Performance Testing 33
Soil Borings 33
Geophysical Logging 33
Aerial Photogrammetry 34
Environmental Assessments 34
Other Hydrologic Information 34

Acknowledgements 36
Investigators 37

GEOLOGY 38

Soils 38
Geomorphology 40

General Description 40
Stream Patterns 44
Karst Activity 46


-iii-











TABLE OF CONTENTS (Continued)


Lithology and Stratigraphy 53

Lithology 53
Stratigraphy 60

Geologic Conditions Favorable for Groundwater Development 68

HYDROLOGY 69

Rainfall 69
Evapotranspiration 71
Surface Water 73
Groundwater 78

Aquifer Descriptions 78
Aquifer Withdrawal Tests 79
Potentiometric Heads and Groundwater Flow 84
Water Use 95 .

Hydrologic Conditions Favorable to Groundwater Development 99

WATER QUALITY 104

Water Quality Sampling Program 108

Well Inventory 108
Surface Water Quality Sampling 108
Groundwater Quality Sampling 112

Results of the Water Quality Sampling Program 114

Surface Water Quality Analyses 114
Groundwater Quality Analyses 120
Variations in Groundwater Quality With Depth and Formation 134
Stability of Potable/Non-Potable Groundwater Interface 144

Water Quality Conditions Favorable for Groundwater Development 150

ECOLOGY 154

Introduction 154
Endangered Biota 165
Environmentally Sensitive Areas 166


-iv-











TABLE OF CONTENTS (Continued)


Page

LOCATION AND EVALUATION OF POTABLE GROUNDWATER SUPPLY AREAS 173

General Hydrogeologic Constraints 173
Water Quality Constraints 175
Areas Selected 177
Ecology 178
Conjunctive Use 183

OPTIMUM GROUNDWATER AVAILABILITY 189

Digital Model 189
Applications of the Model 192
Description of the Modeled Area 192
Results of Simulated Pumping 195

Description of Simulations 196

Simulation Check 204
Groundwater Availability 204

CONCLUSIONS AND RECOMMENDATIONS 211

Conclusions 211
Recommendations 214

REFERENCES CITED 217

SELECTED BIBLIOGRAPHY 222

APPENDICES

I AQUIFER TEST DATA 232

II SELECTED VEGETATION COMMUNITY MAPS 248

III DIGITAL MODEL MATRICES 256













LIST OF ILLUSTRATIONS


Figure Page

1 Location of Project Area. 23

2 Map of Project Area Showing Location of Major Streams 26
and Highways.

3 Soil Distribution and Associations in the Northeast 39
Manasota Basin.

4 Physiographic Map of the Northeastern Manasota Basin 42
Study Area and Vicinity.

5 Karst Features and Stream Patterns in the Northeastern 45
Manasota Basin Study Area.

6 Major Lineaments Mapped in the Northeastern Manasota Basin 51
Study Area.

7 Geologist Logs Borehole Locations. 56

8 Cross Section Location of Gamma Ray Geophysical Logs. 57

9 Natural Gamma Ray Geophysical Logs in Cross-Section, 58
Northeast Manasota Basin.

10 Structure Contour Lines on Top of the First Dolostone 62
Unit, Hawthorn Formation.

11 Structure Contour Lines on Top of the Sandy Micritic 63
Limestone, Tampa Limestone.

12 Structure Contour Lines on Top of the Calcarenitic Lime- 64
stone, Suwannee Formation.

13 Structure Contour Lines on Top of the Foram Zone, Ocala 65
Group.

14 Structure Contour Lines on Top of the "Hard Brown Lime", 66
Avon Park Formation.

15 Location of Precipitation Stations in the Northeast 70
Manasota Basin Vicinity.


-vi-











LIST OF ILLUSTRATIONS (Continued)


Figure Page

16 Average Monthly Precipitation and Evaporation Northeast 72
Manasota Basin.

17 Location and Extent of Drainage Basins. 74

18 Location of Soils Borings and Aquifer Test Sites, 81
Northeast Manasota Basin.

19 Well Location Maps for Aquifer Test Sites 4 and 5. 82

20 Estimated Water Table Surface, November-December, 1979. 85

21 Estimated Potentiometric Surface of the Hawthorn Formation, 87
1963-1979.
22 Potentiometric Map of the Floridan Aquifer, 1934, Central 89
and Southern Florida.

23 Potentiometric Surface of the Floridan Aquifer, Sept., 90
1954 and June, 1955, Manatee County, Florida.

24 Potentiometric Surface, Eastern Manatee County, Florida, 91
September, 1978.

25 Potentiometric Surface, Eastern Manatee County, Florida, 92
May, 1978.

26 Estimated Potentiometric Head Difference Between the 94
Hawthorn and Suwannee-Ocala-Avon Park Units, 1978.

27 Areas of Most Favorable Aquifer Hydraulic Characteristics. 103

28 Location of Data Collection Sites in Northeast Manasota 109
Basin Study Area.

29 Sulfate Concentrations for Selected Surface Water Sites, 117
1978 and 1979.

30 Fluoride Concentrations for Selected Surface Water Sites, 118
1978 and 1979.
31 Total Dissolved Solids Concentrations for Selected Surface 119
Water Sites, 1978 and 1979.
32 Composite Map of Sulfate Ion Concentrations in the Floridan 125
Aquifer, 1978-1979.
-vii-











LIST OF ILLUSTRATIONS (Continued)


Figure Page

33 Sulfate Concentrations in Selected Wells. 127

34 Composite Map of Total Dissolved Solids Concentrations 128
in the Floridan Aquifer, 1978-1979.

35 Total Dissolved Solids Concentrations in Selected Wells. 129

36 Composite Map of Fluoride Ion Concentrations in the 131
Floridan Aquifer, 1978-1979.

37 Fluoride Concentrations in Selected Wells. 132

38 Location of Wells for Water Quality Versus Depth Data. 137
(From Sutcliffe and Joyner 1968)

39 Selected Water Quality Parameter Concentrations Versus 138
Depth.

40 Selected Water Quality Parameter Concentrations Versus 139
Depth.

41 Selected Water Quality Parameter Concentrations Versus 140
Depth.

42 Fence Diagram Showing Stratigraphy and Water Quality, 145
Northeast Manasota Basin.

43 Locations of Cross-Sections for Stratigraphy and Water 146
Quality Fence Diagram.

44 Areas Showing Well Penetration for Potable Groundwater 149
Development.

45 Composite Map of Groundwater Quality Conditions. 151

46 Environmentally Sensitive Areas. 170

47 Areas of Favorable Hydrologic Characteristics. 176

48 Areas Suitable for Future Potable Groundwater Supply 180
Development.

49 Area of Simulated Drawdown in the Potentiometric Surface 199
of the Floridan Aquifer that Results from Pumping at the
Rate Indicated.


-viii-











LIST OF ILLUSTRATIONS (Continued)


Figure Page

50 Area of Simulated Drawdown in the Potentiometric Surface 201
of the Floridan Aquifer that Results from Pumping at the
Rate Indicated.

51 Area of Simulated Drawdown in the Potentiometric Surface 202
of the Floridan Aquifer that Results from Pumping at the
Rate Indicated.

52 Area of Simulated Drawdown in the Potentiometric Surface 203
of the Floridan Aquifer that Results from Pumping at the
Rate Indicated.

53 Detailed Sites Suitable for Future Potable Groundwater 205
Supply Development.

54 Ratio of Drawdown Versus Pumping Rate at Various Distances. 206

55 Drawdown Produced at Various Distances by a Pumping Well. 207

EXECUTIVE SUMMARY

Figure Page

A Areas of Most Favorable Aquifer Hydraulic Characteristics. 6

B Composite Map of Groundwater Quality Conditions. 8

C Environmentally Sensitive Areas. 10

D Areas Suitable for Future Potable Groundwater Supply 12
Development.

E Detailed Sites Suitable for Future Potable Groundwater 13
Supply Development.


-ix-













LIST OF TABLES


Table Page

1 Soil Association in the Northeast Manasota Basin 41
Study Area.

2 Lithology of Geologic Formations in the Northeast 55
Manasota Basin.

3 Summary of Average Rainfall Amounts for Selected Stations 71
in the Vicinity of the Project Area.

4 Summary of Streamflow Data in the Vicinity of Northeast 75
Manatee County.

5 Estimated Average Annual Streamflow from the Project Area. 76

6 Summary of Hydraulic Coefficients, Determined from Aquifer 80
Tests, in the Northeast Manasota Basin.

7 Summary of Estimated Groundwater Use for Agricultural 96
Crops in Manatee County, Florida, 1978.

8 Summary of U.S.G.S. Water Quality Data, Northeast 105
Manasota Basin.

9 Well Inventory Data for Wells Sampled in the Northeast 110
Manasota Basin.

10 Results of Analyses of Groundwater Samples Collected in 115
October, 1978, and March, June and October, 1979, at
Selected Sites in the Northeast Manasota Basin.

11 Results of Chemical Analyses of Groundwater Samples 121
Collected in October, 1978, and March, June and October,
1979 at Selected Sites in the Northeast Manasota Basin.

12 Results of Analyses of Downhole Samples, Northeast 135
Manasota Basin.

13 Endangered, Threatened, Rare and Species of Special 167
Concern of Manatee County, Florida, 1980.

14 Results of Simulated Withdrawals in Northeast Manasota 197
Basin.












FACTORS FOR CONVERTING


ENGLISH UNITS TO METRIC UNITS


ENGLISH

Inches (in)

Feet (ft)

Miles (mi)

Square Miles (smi)

Acres (ac)

Gallon (gal)
Acre-Feet (ac-ft)

Gallons Per Minute (gpm)

Million Gallons Per Day (mgd)

Cubic Feet Per Second (cfs)
Gallons Per Day Per Foot
(gpd/ft)
Gallons Per Day Per Square
Foot (gpd/ft2)

Gallons Per Day Per Cubic
Foot (gpd/ft3)


Miles Per Hour (mph)

Feet Per Day (ft/day)

Feet Per Mile (ft/mi)


MULTIPLY BY

2.540

3.048 x 10-1

1.609
2.590

4.047 x 10-3

3.785
1.233 x 103

6.309 x 10-2

4.381 x 10-1

2.832 x 10-1

8.053 x 10-1


4.057 x 10-2

7.482 x 10-3


1.609

3.048
1.894


10-1

10-1


METRIC

Centimeters (cm)

Meters (m)
Kilometers (km)

Square Kilometers

Square Kilometers

Liter (1)
Cubic Meters (m3)

Liters Per Second

Liters Per Second

Liters Per Second


(km2)

(km3)




(l/s)

(l/s)

(1/s)


Square Meters Per Day (m2/d)


Meters Per Day (m/d)


Liters Per Day Per Cubic
Meter (1/d) /m3

Kilometers Per Hour (kph)

Meters Per Day (m/d)
Meters Per Kilometer (m/k)


-xi-













NORTHEASTERN MANASOTA BASIN HYDROLOGIC INVESTIGATION


EXECUTIVE SUMMARY


With the addition of the Manasota Basin to the Southwest Florida Water

Management District in 1977, the District staff and the Manasota Basin

Board have begun the development of a Comprehensive Basin Water Management

Program. One element of this program involves the location and evaluation

of potential potable groundwater supply sites.


On September 29, 1978, the Manasota Basin Board and the Southwest Florida

Water Management District authorized Seaburn and Robertson, Inc. to conduct

the Northeastern Manasota Basin Hydrologic Investigation. The purpose of

this investigation was to locate the most favorable areas in northeastern

Manatee County for withdrawal of potable groundwater. Existing private

uses of water for citrus irrigation, phosphate mining, domestic supplies

and others were not to be considered limiting factors to the location of

potable groundwater supplies during this study because the objective was

to locate hydrologically favorable areas.

The project area consists of about 400 square miles in northeastern Manatee

County. Land use in this area is principally agricultural. Vegetable

farming, citrus and cattle production are the major products.

The objective of the investigation was to assess the hydrogeology, water

quality, and ecology of the project area, to locate suitable groundwater

supply areas for regional-scale water supplies, and to predict the impacts












expected from withdrawals at these selected sites. Specific elements

of the investigation were to:

1. Evaluate the optimum quantities and quality of potable ground-

water that could be developed within the project limits.

2. Evaluate the effects of withdrawals on the potentiometric surface

of the Floridan aquifer system, surficial aquifer levels, and

surface water bodies.

3. Evaluate the possibility of saltwater intrusion or water quality

degradation by groundwater withdrawals.

4. Evaluate the possibilities of augmenting groundwater supplies

by artificial recharge from surface water sources where feasible

within the project limits.

5. Evaluate impacts to the hydrologic and environmental systems

resulting from groundwater withdrawals or conjunctive use.

6. Evaluate the areas within the project limits most suited to

future potable groundwater development.


The study was divided into two phases. The preliminary phase consisted

of a review and evaluation of available hydrologic data pertinent to the

project area. The preliminary phase was completed in February, 1979, and

a report entitled "Status Report Northeastern Manasota Basin Hydrologic

Investigation", was submitted to summarize the available data and to indi-

cate the scope of work for the second phase. That second phase, which

consisted of detailed field data collection and evaluation for selected

areas is the subject of this report.


-2-











Field data collection included three aquifer pumping tests, geophysical

well logging of ten wells, 81 soils borings, inventory of approximately

400 wells, quarterly water quality sampling of about 60 wells, and environ-

mental mapping of sensitive vegetation communities. Extensive hydrologic

and water quality evaluations were conducted. Computer simulations of

groundwater withdrawals from selected sites within the project area were

also performed.

Geologic information was collected from the literature, well construction

information, drillers' logs and from geophysical logging of selected wells.

Additional geologic information included the study of surface depressions

and photolineaments (fracture traces). These were assembled to assist in

locating suitable groundwater supply areas.

Available data about aquifer hydraulics were assembled and supplemented

by site-specific aquifer pumping tests conducted during this investigation.

These data were used in simulations by the digital model to evaluate

aquifer response to groundwater pumping. The areal extent and distribu-

tion of the aquifers within the project area were mapped.

Water quality was determined by sampling wells within the project area

and mapping of selected water quality parameters. The water quality was

a significant aspect to locating potable groundwater supply areas. The

vertical and horizontal extent of selected water quality constituents were

investigated.












An overall environmental assessment of the project area was conducted, and

a more detailed assessment of environmentally "sensitive" vegetation com-

munities was performed for selected areas.

The Pinder-Trescott digital computer program was calibrated for the area

and used to simulate water level response to selected pumping rates at

selected sites.

The most favorable areas for the development of potable groundwater

supplies were determined by studying a series of composite maps. The

maps contain hydrogeologic, water quality and ecologic data and indicate

areas with the most favorable conditions for potable water development

in each of these categories. These maps became a decision matrix and

were used to locate and rank the suitability of the areas according to

the particular category.

The geologic aspects of the project area were found to be of little

consequence in site selection. These aspects are similar throughout the

area and the presence of extensive confining units (dense clays and lime-

stones) will generally enhance groundwater development by isolating the

surficial aquifer and eliminating or reducing the impacts on terrestrial

and aquatic vegetation.

Geologic Conditions Favorable for Groundwater Development

Results of the geologic investigation indicate four general conditions

favorable to development of groundwater. They are:











1. Limited recent sinkhole development,

2. Hydraulically inactive fracture systems that do not allow inter-

change of surface and ground water,

3. Extensive and permeable carbonate rock systems consisting of a

combination of the Suwannee/Ocala/Avon Park units, and

4. Extensive confining strata composed of the Hawthorn/Tampa

units separating the artesian and surficial aquifers.

Tests to determine aquifer hydraulics which were conducted during this

investigation indicate that the most productive section of the Floridan

aquifer is the Suwannee/Ocala/Avon Park units. Overlying units con-

taining surficial sands and clays and the Hawthorn/Tampa formations

are much less productive although limited production can be obtained from

these upper aquifers. Figure A indicates the areas containing the most

favorable aquifer hydraulic characteristics such as high transmissivity

and low leakance. Additionally, an area of apparent rejected recharge

is indicated in the southern part of the project area.

Hydrologic Conditions Favorable to Groundwater Development

There are seven hydrologic conditions favorable to major groundwater develop-

ment in selected parts of the project area.

They are:

1. Moderate to high transmissivity associated with the Suwannee/

Ocala/Avon Park aquifer unit,

2. Considerable differences of water levels between the Hawthorn

and Suwannee/Ocala/Avon Park especially near the headwaters of

the Manatee River,



























































EXPLANATION


AREA OF FAVORABLE ....
CHARACTERISTICS








0 | \ PROJECT BOUNDARY
2- N t
SCALE, MILES i BS FROM DOT MAP ULY, 1974)ABURN AND ROBERTSON,IN
SEABURN AND ROBERTSON, INC.



FIGURE A. -AREAS OF MOST FAVORABLE AQUIFER HYDRAULIC CHARACTERISTICS.
-6-










3. Discharge (rejected recharge) from the Hawthorn in the vicinity

of Tatum Sawgrass,

4. Availability of surface water for possible dilution of mineralized

groundwater,

5. Availability of Manatee River stream bed for transportation of

groundwater to treatment and distribution facilities,

6. Low leakance from surficial aquifers to underlying producing

zones, and

7. Extensive quantities of groundwater beneath the project area.

Water Quality Conditions Favorable for Groundwater Development

Water quality conditions were found to be the limiting factor to the

development of potable groundwater supplies. In parts of the project area,

the most productive units of the Floridan aquifer (Suwanee/Ocala/Avon

Park units) contain waters with sulfate, total dissolved solids and
fluoride concentrations exceeding potable water standards. The Hawthorn/

Tampa formations generally contain potable water with the exception that

fluoride concentrations, greater than 1.4 mg/l, are evident in the north-

eastern.part of the project area. Figure B shows the areas of favorable

water quality conditions within the Suwanee/Ocala/Avon Park units of the

Floridan aquifer.

Specific water quality conditions favorable to potable water development

are easily determined by comparison to published and accepted standards.

Three general conditions were found to be important:

1. Stability of the potable/non-potable "interface" during

pumping conditions,





















































EXPLANATION

MOST FAVORABLE AREA

F MARGINALLY FAVORABLE
I AREA

LEAST FAVORABLE AREA





00.51 2 3 ___
SCALE, MILES I BSE FROM DOT MAP (JULY. 1974)
SEABURN AND ROBERTS

FIGURE B. -COMPOSITE MAP OF GROUNDWATER QUALITY CONDITIONS.
-8-










2. The degree to which potable standards may be exceeded, and

3. Water quality characteristics were independent of pumping

or seasonal fluctuations in water levels.


An assessment of the ecologic character of the project area was conducted

to locate areas containing sensitive environmental communities and to

identify endangered biota within the project area. Figure C shows the

general extent of environmentally sensitive areas. Detailed vegetation

community mapping was also conducted in selected areas. However, because

of the extensive confining clay and dense limestones underlying the

project area, these sensitive areas will not be impacted by groundwater

withdrawals from the Suwannee/Ocala/Avon Park units.

Possible conjunctive use of surface water and groundwater was evaluated

as a factor for locating potable groundwater supply areas. For the

purpose of this report conjunctive use was defined as the recharge of

groundwater sources from surface water or surficial aquifer sources.

Because of the relatively impermeable confining units existing in the

project area, the use of surface waters for recharge through natural methods,

such as increasing head gradients, is not effective. Artificial methods

of recharge by connector wells, recharge wells or injection facilities is

hydrologically feasible as a water management procedure in the north-

eastern Manasota Basin. These methods, however, will require detailed

site-specific evaluations to determine the most appropriate and cost-

effective method of conjunctive use.




























































EXPLANATION


ENIRCNMENTALLY SENSITIVE
Q AMA



SEE APPENDIX I FOR
SELECTED COMMUNITY MAPS


00.51 C 2 3 4
SCALE, MILES I


FIGURE C. -ENVIRONMENTALLY SENSITIVE AREAS.
-10-











Four major areas were designated as areas most favorable for development

of large (regional-scale) quantities of potable groundwater. These areas,

shown on Figure D, were ranked according to the various factors evaluated.

Surrounding the favorable areas are marginally favorable areas which are

limited by various constraints, but principally by water quality condi-

tions where constituents approach or exceed potable water standards.

Outside of the marginally favorable areas the remainder of the project

area is generally unfavorable for reliable, long-term potable groundwater

supplies because of poor water quality conditions within the major pro-

ducing units of the Suwannee/Ocala/Avon Park.

The digital computer model used to evaluate the impacts expected for each

site at selected pumping rates indicated optimum rates that ranged from 12 mgd

to 30 mgd. Optimum potable groundwater availability for the four most

favorable areas is about 45 mgd. Little, if any, impact would result in

the surficial aquifer or surface waters as the result of withdrawing these

quantities from the Floridan aquifer.


The four most favorable areas were further subdivided to exclude environmen-

tally sensitive portions of the larger areas. The locations of the detailed

sites,as shown on Figure E, consider the presence of environmentally
sensitive vegetation communities and the proximity to areas of less favorable

water quality. This initial refinement of the favorable areas was done to

avoid even the remote possibility of impacts to the sensitive areas and the
encroachment of poor water quality, should the confining units not be continuous

within an area or if withdrawals interfere with other adjacent uses. The


-11-

















































EXPLANATION
AREA DESIGNATION .I
AREA SUITABLE FOR ........ MYAKKA CTY
GROUNDWATER SUPPLY -
SITES .






I __ PROJECT BO90UNDARY

SCALE, MILES ASE FROM DOT MAP (JULY, 1974)
SEABURN AND ROBERTSON. INC.

FIGURE D.-AREAS SUITABLE FOR FUTURE POTABLE GROUNDWATER
SUPPLY DEVELOPMENT.
-12-



























































FIGURE E.- DETAILED SITES SUITABLE FOR FUTURE POTABLE GROUNDWATER
SUPPLY DEVELOPMENT. -13-












detailed sites provide the greatest degree of flexibility for the

development and management of potable groundwater supplies in the north-

eastern Manasota Basin.


Detailed wellfield evaluations, design and subsequent well construction,

as recommended in this report, will be necessary to develop the optimum

quantities of groundwater from the favorable areas. Additionally, optimum

potable groundwater development within these areas may require evaluation

of existing and competing groundwater uses in the vicinity of the most

favorable areas at the time of development.


Reliable regional-scale groundwater supplies are reasonably assured from

the favorable areas. Limited, local supplies may be developed from the

less favorable areas within the northeastern Manasota Basin.

Conclusions


Within the northeastern Manasota Basin there are several favorable potable

groundwater supply areas. Four general areas have been delineated in the

north-central and eastern portions of the project area. Nine detailed

sites result from subdivisions of the general areas. Reliable, long-term,

regional potable groundwater supplies can be developed from these areas.

Withdrawal rates from these separate areas range from 12 to 30 million

gallons per day. The optimum quantity for withdrawal for the total area

is estimated to be about 45 million gallons per day. These estimates are

based on pumping from the most productive sections of the Floridan aquifer,

the Suwannee/Ocala/Avon Park units. Optimum quantities of potable ground-

water development from these areas will have to consider existing and


-14-











proposed competing uses at the time of development. In addition, detailed

well field design, well construction, and changes in groundwater use in

the project area can affect these estimates. At these rates of withdrawal,

little impact upon environmentally sensitive areas, water quality or the

regional water resources will result.


Aquifer characteristics in the project area indicate that locating well

fields to capture rejected recharge is not a feasible alternative. Arti-

ficial injection of surface waters would be required to achieve substantial

conjunctive use of water in the area.

Groundwater quality conditions are the limiting factor to locating potable

groundwater supply sites in the project area. Concentrations of sulfate,

total dissolved solids and fluoride exceed recommended potable limits in

many parts of the project area. Sulfates and total dissolved solids

concentrations show a close correlation and generally increase with

depth in the aquifer. High fluoride concentrations generally occur in

the Hawthorn/Tampa unit.


The areal variations of water quality in the project area do not appear

to change with seasons or pumping rates. Upconing of poor quality water

in the most favorable areas identified in the report is limited by

impermeable limestone units below the Suwannee/Ocala/Avon Park unit.

The stability of the potable/non-potable interface can be maintained

with the recommended well design and aquifer penetration discussed in

this report. Environmentally sensitive areas within the project area will

not be adversely affected by pumping from the Floridan aquifer.


-15-












1. The geologic character of the project area is typical

of west-central Florida; Karst features exist, however,

surface activity (sinkholes) is relatively old and gen-

erally represents conditions in the limestone units

nearest land surface. There is little hydraulic connec-

tion between these surficial deposits and the lower

Floridan aquifer. A relatively continuous confining

strata supports the surficial aquifer across the project

area.

2. The most productive portion of the Floridan aquifer is

the Suwannee/Ocala/Avon Park unit. This unit is approxi-

mately 600 feet thick and about 50 billion gallons of

water are contained in storage. Aquifer characteristics

for this entire producing unit indicate transmissivities

ranging between 300,000 to 870,000 gpd/ft. Wells tapping

this unit typically produce 1,000 to 1,500 gpm. Leakance

through the Hawthorn Formation for recharge to the Suwannee/

Ocala/Avon Park is estimated to be 1 x 10-5 gpd/ft3.

3. Water levels in the aquifer have declined slightly over

recent years and seasonal fluctuations are about 30 feet.

Generally these water levels return to previous wet season

levels. During each year, water level changes in the aquifer

can be considerable, but the net water lost is negligible.

4. No water level changes will occur in the surficial aquifer

as a result of pumping the Suwannee/Ocala/Avon Park unit.


-16-











5. The overlying Hawthorn/Tampa unit is less productive than

the Suwannee/Ocala/Avon Park unit and separates the uncon-

fined aquifer from the Floridan. Some limited local sources

of supply are derived from the Hawthorn/Tampa unit. However,

these supplies are not reliable for large scale production.

6. Aquifer characteristics in the project area indicate that

the location of wells to enhance the conjunctive use of

surface waters to naturally recharge groundwater supplies

is not a feasible alternative. Significant head differ-

ence exists between the Suwannee/Ocala/Avon Park unit and

the Hawthorn/Tampa formations in the north and central

parts of the project area to allow for artificial recharge.

7. Groundwater quality is the limiting factor to locating

potable groundwater supply sites in the project area.

Concentrations of sulfate, total dissolved solids and

fluoride exceed recommended potable limits in many parts

of the project area. Sulfates and total dissolved solids

concentrations show a close correlation and generally

increase with depth in the aquifer. High fluoride concen-

trations generally occur in the shallow Hawthorn/Tampa unit.

8. The areal distribution of water quality conditions in the

project area does not appear to change with changes in

water levels. Upconing of poor quality water in the most

favorable areas identified in the report is very unlikely


-17-











because of impermeable limestone units below the Suwannee/

Ocala/Avon Park unit. The stability of the potable/non-

potable interface can be maintained by using the recommended

depths of aquifer penetration.

9. Environmentally sensitive (water table dependent) areas

exist within the project area. Pumping from the Floridan

aquifer will not impact these areas because of the confining

unit beneath the surficial aquifer that permits little leakage

from the water table.

10. The most favorable areas for development of reliable

regional potable groundwaters are in the north-central

and eastern parts of the project area. Areas outside the

most favorable areas are limited chiefly by water quality

conditions. The Hawthorn/Tampa formations are limited by

production quantities. Some local supplies may, however,

be developed in these areas, but with less reliability

and at reduced rates of withdrawal.

11. The results of the investigations presented in this report

are regional and based on data collected primarily from

existing wells. Sufficient detail is available to reliably

locate areas favorable for potable groundwater development.


-18-














Recommendations


The results of investigations presented in this report are regional and

are based on data collected primarily from existing wells. The studies

are sufficiently detailed to locate areas favorable for potable groundwater

development. Development of potable groundwater should be accomplished

only after site-specific drilling, testing and water quality monitoring

to verify these regional data and evaluations. The following are specific

recommendations resulting from this investigation:

1. Regional-scale potable groundwater supplies should be developed

only in the most favorable areas indicated in this investigation.

The development of potable groundwater supplies outside the most

favorable areas has a greater probability of water quality problems

and cannot be considered to be reliable long-term supplies. Lesser

quantities for local supplies may be developed from the Hawthorn/

Tampa units in other than the most favorable areas, but with

lesser reliability for good water quality.

2. Well field design should be conducted by qualified engineers

or hydrologists familiar with proper procedures using the results

and well construction criteria developed during this investigation.

3. Potable groundwater supply wells located in the favorable areas

should be cased through the Hawthorn/Tampa formation to reduce

fluoride concentrations in the water supply. The Hawthorn/Tampa


-19-












formations should be used only to produce small local supplies

of potable water in the project area.

4. Well penetration into the Suwannee/Ocala/Avon Park unit should

generally be limited to the depths that will prevent any possible

upcoming.

5. An annual water quality sampling program should be conducted in

the northeastern Manasota Basin to determine water quality

variations that may develop. Completion reports of all new wells

constructed in the area should contain complete drinking water

quality analysis.

6. A detailed water use inventory should be conducted in the

northeastern Manasota Basin in order to thoroughly evaluate

existing use in the most favorable areas.

7. The economic feasibility and site-specific feasibility of

augmentation of surface water by groundwater should be evaluated

for the vicinity of Lake Manatee and in the headwaters of the

Manatee and Little Manatee Rivers.


-20-














NORTHEASTERN MANASOTA BASIN HYDROLOGIC INVESTIGATION


INTRODUCTION


Purpose and Scope


The Manasota Basin Board is one of ten Boards that comprise the Southwest

Florida Water Management District. The Manasota Basin consists of Manatee

and Sarasota Counties with the major population centers predominantly

along the coast on the Gulf of Mexico.


Municipal potable water supplies in the Manasota Basin are obtained

primarily from the Manatee River in Manatee County and well fields in

Sarasota County. Coastal groundwater supply sites are limited in both

counties because of high mineral concentrations. Some of these mineralized

waters are used by blending with fresher water or for desalination. To

meet the expanding demands for water, major groundwater supplies will

have to be developed. Groundwater uses inland are primarily for agricultural

irrigation and for phosphate mining anticipated in the northeastern

portion of Manatee County. Concern for the proper development and manage-

ment and the efficient use of the water sources within the Manasota

Basin has prompted the development of Basin-wide water management planning.

This planning effort was undertaken in 1977 to prepare a Comprehensive

Water Management Program. The Comprehensive Program is being developed

by the Southwest Florida Water Management District staff, and selected

elements are being prepared by private consultants under the direction

of the District.


-21-


Nommmom-












The District and the Manasota Basin Board anticipate that there will

be an increasing competition for available groundwater resources among

agriculture, municipalities and the phosphate mining industry.

Consequently, one goal of the Manasota Basin Comprehensive Water

Management Program is to identify potential potable groundwater supply

sites. To further this goal, the Northeastern Manasota Basin Hydrologic

Investigation was proposed by the Southwest Florida Water Management

District to identify and evaluate potable groundwater sources within

that portion of the Basin.


On September 29, 1978, the Manasota Basin Board of the Southwest Florida

Water Management District authorized Seaburn and Robertson, Inc. to

conduct the Northeastern Manasota Basin Hydrologic Investigation. The

purpose of the investigation was to identify and evaluate available potable

groundwater supply sites within the northeastern portion of the Manasota

Basin, Figure 1. Hydrologic, geologic, water quality, and environmental

studies were conducted to accomplish the purpose of the investigation and

areas were to be chosen where groundwater would meet potable water quality

standards and have the ability to provide a reliable, long-term, major

supply. Existing or proposed groundwater uses were not considered as

limiting factors for the suitability of a particular site.


-22-




































A N


"ta




0
EXPLANATION RAS T

PROJECT AREA

SCALE, MIS

I 0





FIGURE I LOCATION OF PROJECT AREA.

-23-












The specific objectives of the investigation were to:

a. Evaluate the optimum quantity and quality of potable groundwater

that could be developed within the project limits.

b. Evaluate the effects of withdrawals on the potentiometric surface

of the Floridan aquifer system, surficial aquifer levels, and

surface water bodies.

c. Evaluate the possibility of saltwater intrusion or water quality

degradation due to groundwater withdrawals.

d. Evaluate the possibilities of augmenting groundwater supplies

by recharge from surface water sources, where feasible within

the project limits.

e. Evaluate impacts to environmental systems, such as terrestrial

and aquatic vegetation, resulting from groundwater withdrawals

or conjunctive use.

f. Indicate areas within the project limits most suited to future

potable groundwater development.


The scope of this study is limited to the project area previously described

even though information from investigations of adjacent areas provided

much useful data. Because of the extent of the project area the evaluations

are directed toward generalized sites rather than toward specific

locations. Within this general scope of work sufficient detail is provided

to guide site specific studies to locate potable supply well fields.


-24-










This report summarizes the results of the study and describes the method-

ologies, evaluations and presents a description of the areas found to be

most favorable for development of potable groundwater supplies.


Basic data collected during the course of the project and voluminous

compilations of drillers reports, logs, and water quality lab results are

contained in a separate volume entitled "Basic Data Report Northeastern

Manasota Basin Hydrologic Investigation."

Description of the Project Area


The project area, approximately 400 square miles, consists of the eastern

one-half of Manatee County (Figure 2). The area is bounded on the north

by Hillsborough County and on the east by Hardee and DeSoto Counties. The

southern boundary of the area is Highway 780 and the western boundary is

the line between Range 19 and 20 East.

The project area is about 25 miles east of the Gulf of Mexico in an area

referred to as the Central Highlands (White, 1970) and for the most part

reflects a series of eroded marine terraces formed during Pleistocene

geologic time. Land surface elevations within the project area range from

about 40 feet to 140 feet above msl. The highest elevations are in the

northeastern part of the project area.


The predominant soil type in the project area is the Leon-Immokalee, which

is a slowly drained soil and consists of large tracts of Pine-Palmetto

Flatwoods. These soils are extensively used for agriculture, particularly


-25-













































EXPLANATION

~- STATE ROADS Is S
STREAMS MYKA C ----







0 05 \ 3 PROJECT BOUNDARY

SCALE, MILES i 3ASE FROM DOT MAP (JULY. 1974)
SEABURN ANO ROBERTSON, INi

FIGURE 2.-MAP OF PROJECT AREA SHOWING LOCATION OF MAJOR
STREAMS AND HIGHWAYS.
-26-











for pasture grasses and livestock production, because the land is nearly

flat and water table conditions are favorable. The natural vegetation

most prominent in the project area consists of slash pine, some long-leaf

pine, scrub oaks, saw palmetto, runner oak, wiregrass and some bitter

gallberry.

The major rivers in the project area are the Little Manatee, Manatee and

Myakka Rivers and their tributaries, which eventually discharge into Tampa

Bay or the Gulf of Mexico. Large parts of the area are poorly drained

and contain many ponds, marshes and swamps.

Population in the project area is largely rural with widely scattered

houses and farms. A few small towns are located at Duette, Myakka Head,

and Myakka City. Agriculture, including vegetable farming, livestock

and citrus production, are the major agricultural activities in the area.

Phosphate mining operations are anticipated in the northeastern part of

Manatee County which will considerably alter the current patterns of

agricultural land use.

Previous Investigations


Since 1958, numerous hydrogeological investigations relevant to the

groundwater resources of the northeastern Manasota Basin have been conducted

in Manatee County and surrounding counties. The reports pertinent to this

study are described below.


-27-










H. M. Peek (1958 ab), investigated the geology and groundwater resources of

Manatee County. This investigation concentrated primarily on that portion

of the county west of the project area. A map of the potentiometric surface

for June, 1955 was prepared, along with a map showing areas of artesian

flow. The chemical quality of groundwater in Manatee County was described.

An aquifer test at a site west of the project area was conducted to

determine the transmissivity and storage coefficient of the Floridan

aquifer.

H. M. Peek (1959) reported on the hydrogeology of southwestern Hillsborough

County adjacent to the project area. The report included information on the

transmissivity and storage coefficient of the Floridan aquifer. Additionally,

a map of the potentiometric surface of the Floridan aquifer for May,

1953, was prepared showing areas of artesian flow.

W. J. Carr and D. C. Alverson (1959) described the stratigraphy of the

middle Tertiary-age rocks for part of west-central Florida. These descrip-

tions were correlated with the rocks of Manatee County and were used in

the evaluation of the thickness of geologic units in the project area. The

water resources of Hillsborough County adjacent to the project area were

investigated by C. G. Menke, E. W. Meredith, and W. S. Wetterhall (1961).

Aquifer coefficients for the Floridan aquifer were determined. Potentio-

metric surface maps for the Floridan aquifer were included for the period

September and October, 1958.

C. S. Chen (1965) studied the Paleocene and Eocene stratigraphy of Florida,

including areas within and adjacent to Manatee County. His interpretations


-28-











were made from cuttings, cores and electric logs. Isopach-lithofacies

maps, structure maps, and lithologic cross sections were presented.

The groundwater resources of nearby Polk County were investigated by

H. G. Stewart, Jr. (1966). Groundwater movement within Polk County was

described and estimates were made of the amount of groundwater moving

into other adjacent counties. Detailed descriptions of the hydrogeology

of the various rock units were presented. Structural geologic maps and

potentiometric surface maps were included in the report. Pumping tests

were made to determine aquifer hydraulic coefficients.

H. Sutcliffe, Jr., and B. F. Joyner (1968) conducted an exploratory test

well program in the Myakka River Basin. The results of the test drilling

program yielded geologic and water quality information for formations as

deep as the Tampa Limestone. Four of the test holes were in the northeastern

Manasota Basin project area.

An engineering report on artificial recharge through deep wells at the

Florida Power and Light Company Reservior in the northwesternmost portion

of the project area was conducted by Black, Crow and Eidsness, Inc. (1973).

The report described the hydrology and water quality of the deeper geologic

units. Aquifer tests were conducted to determine pertinent hydraulic

coefficients.

An assessment of the groundwater resources of the Verna Wellfield in adjacent

Sarasota County was made by Geraghty and Miller, Inc. (1974a). The report


-29-











concluded that the wells producing highest concentrations of sulfate

penetrated the Suwannee Formation and that deeper wells would yield

increasingly high amounts of sulfate.

The groundwater hydrology of the Beker Phosphate Property in eastern

Manatee County was studied by Richard C. Fountain and Associates (Beker

Phosphate Corporation, 1974). The investigations on the site included

subsurface geological studies, water quality sampling, an inventory of

water use, monitor well installation, geophysical logging and an aquifer

test of the lower Ocala and upper Avon Park formations. Aquifer

coefficients were calculated from the test data.


At the W. R. Grace & Company's Four Corners Mine in northeastern Manatee

County and southeastern Hillsborough County, P. E. LaMoreaux & Associates,

Inc. (W. R. Grace and Company, 1975), conducted an analysis of the site

hydrogeology. That work included a well inventory, water quality sampling,

and aquifer testing.

An investigation of the hydrogeology of the Swift Agricultural Chemicals

Corporation's Manatee Mine site was conducted by William F. Guyton &

Associates (1976a-d). Detailed geologic descriptions of the materials

encountered in the boreholes and a comprehensive geophysical logging and

borehole flow study are presented. The report also includes a well

inventory for this area in easternmost Manatee County. Groundwater quality

samples and a test drilling and aquifer testing program provided a substantial

contribution to the data base of the present study. Aquifer coefficients

were calculated from the data generated during the testing. A multi-layer

model to simulate site hydrology was developed and used to predict the

impact of groundwater withdrawals at the site.
-30-











The groundwater resources of DeSoto and Hardee Counties were described

in detail by W. E. Wilson (1977a). The report provides an extensive

discussion of long-term and seasonal changes of the potentiometric

surface in the two-county area. Particular emphasis is placed on

groundwater quality maps for selected chemical constituents.

An investigation by W. E. Wilson (1977b) resulted in simulated changes

in groundwater levels that may result from pumping for proposed phosphate

mining in West-Central Florida, including Manatee County, for the periods

1985 and 2000. Included within the report were regional maps of

transmissivity, confining bed thickness, leakance coefficients, storage

coefficient, Florida aquifer thickness maps and simulated potentiometric

surface.


The hydrologic effects of withdrawing groundwater from the Floridan

aquifer at the Phillips Petroleum Company phosphate mine in DeSoto

County and southeasternmost Manatee County were investigated by Geraghty

and Miller, Inc. (1978). The studies yielded geologic data, groundwater

quality information, and geophysical logs. Aquifer coefficients were

determined from pumping tests.


Investigation Approach

The identification and evaluation of areas of possible groundwater supply

requires study of considerable hydrologic, geologic and water quality

information pertinent to the area of interest. Because of the large size

of the project area, approximately 400 square miles, the Northeastern

Manasota Basin Hydrologic Investigation was subdivided into two phases:


-31-











a first phase consisting of data collection and review and identification

of additional data needs, and a second phase for further field data

collection, testing, analysis, and preparation of recommendations.

The first phase involved the collection and review of existing hydrologic

data, studies and reports pertinent to the project area. Data collected

and reviewed in the preliminary phase came from previous hydrologic and

engineering studies in the general area as previously discussed. Sources

of recent hydrologic information were the U.S. Geological Survey, the

Manatee County Agricultural Extension Service and the Soil Conservation

Service. The Southwest Florida Water Management District provided numerous

hydrologic reports, Development of Regional Impact reports and data

collected from the District's Regional Observation and Monitor Well Pro-

gram in Manatee County. Other data were available from the Florida Bureau

of Geology. The phase was completed and summarized in February, 1979, in a

report entitled, "Status Report of Northeastern Manasota Basin Hydrologic

Investigation". That report also provided a detailed description of the

required field data collection and testing to be accomplished during the

final phase. This approach resulted in a field data collection, testing

and analysis program consisting of several tasks, each designed to maximize

the use of existing groundwater wells and ongoing District programs.

The second phase of the project progressed through the several tasks of data

collection and analysis, culminating in the development of a ranking system

that consisted of a series of maps and figures of the hydrologic data

available. Areas most favorable for development of potable water supplies

were then indicated by considering these maps together.


-32-















Well Inventory and Water Quality Sampling


Over 400 groundwater wells were inventoried in the project area. Well

construction permit data and consumptive use permit information were

used in the inventory. Water quality sampling program was done quarterly

and provided additional data regarding water quality variations over the

area during periods of low and high potentiometric surface level.


Aquifer Performance Testing


Three aquifer tests were conducted at selected irrigation wells within

the project area to obtain additional data about aquifer hydraulic

characteristics. These data supplemented other available information

and were useful in the aquifer simulation model.


Soil Borings


Soil borings were performed at six selected locations within the project

area to obtain information about soils, water table elevations and surficial

clay or hardpans. The locations were selected in areas considered for

further hydrologic evaluations. A total of 83 borings were made to depths

of about 40 feet below land surface.


Geophysical Logging


Ten existing irrigation wells were logged using borehole geophysical tech-

niques by Southwest Florida Water Management District during the course of

this study. The logs consisted of caliper, resistivity, gamma activities,


-33-













temperature, and fluid velocity. Down-hole water quality samples

were also collected. This task was performed to refine geologic

descriptions and to determine water quality variation with depth

throughout the project area.


Aerial Photogrammetry


Black and white, and false-color infrared photographs were obtained

for the project area. These photographs were used for several purposes

including the well inventory and soils and vegetation mapping. They

were also useful for delineation of drainage basins and mapping of

geomorphologic features.


Environmental Assessments


Available ecologic and biologic data in existing Development of Regional

Impact reports were collected and evaluated. Site-specific mapping of

environmentally "sensitive" communities was completed by field visits to

selected potential groundwater supply areas.


Other Hydrologic Information


Considerable practical hydrologic information was obtained from local

residents, farmers, well drillers, and agricultural specialists during

the investigation. These discussions regarding drilling problems and

practice and groundwater uses provided much empirical data about water

quality, well construction and water level fluctuations.


-34-











Following the completion of the field data collection and testing, a

description of the hydrogeologic system was completed and areas for

additional evaluations were determined.


The geologic, hydrologic, water quality and ecologic factors determined to

be favorable and unfavorable for development of groundwater were mapped

to facilitate decisions about overall area selections. The possibility of

conjunctive use of surface water to recharge groundwater sources and

the effect of current water management practices were also considered to
determine the most favorable areas. Overlays of this series of maps were

used then to evaluate specific areas and detailed sites.


Further evaluations of the selected areas were made using these geologic,

hydrologic, water quality, ecologic, conjunctive use and water management

factors and data discussed above. These factors formed the elements of the

ranking matrix with the addition of various quantities of groundwater

withdrawals used to evaluate hydrologic impacts estimated for the selected

areas. Hydrologic impacts were estimated for the selected areas using

various hydrologic models including digital computer programs.

The following sections of this report describe the project area in terms

of the above factors and present the results of the field data collection,

testing, evaluations and hydrologic analysis of areas for development of

potable groundwater supplies. The latter sections of this report present

the graphical matrix of maps and overlays used to locate and evaluate the

areas and specific sites considered favorable for potable groundwater

development.


-35-












Acknowledgements


This investigation was authorized by the Southwest Florida Water Management

District Governing Board, Bruce A. Samson, Chairman, D.R. Feaster, Executive

Director, and the Manasota Basin Board:

Mr. B.T. Longino, Chairman,

Mr. Gordon D. Hartman, Vice-Chairman,

Mr. Randolph Snell, Secretary,

Mr. J. Lynn Harrison, Member,

Mr. Michael Stuart, Member, and

Mr. John J. Whelan, Member.


Richard V. McLean, Southwest Florida Water Management District Project

Manager, directed the project for the District assisted with data

acquisitions and provided many useful suggestions during the course of

the investigation and report preparation. The late Mr. Fred Roberts

provided considerable assistance during the geophysical logging. The

assistance of the U.S. Geological Survey, the Manatee County Health

Department and the SWFWMD laboratory are also gratefully acknowledged.

Special acknowledgement and appreciation is accorded to the entire agri-

cultural community in Manatee County, without whose cooperation and assistance,

this investigation would have been more difficult. We are especially

grateful to the following ranchers, farmers, and agricultural specialists:
Mr. Joe Cincotta B & C Farms,

Mr. Jim Blackwelder Rutland Ranch,


-36-










Mr. Elbert Walker Rutland Ranch

Mr. Jim Luttrel Tropicana Products, Inc.

Mr. Tom Kibler Kibler Ranch,

Mr. Clarence Harrison Scheorder Manatee

Mr. Terry Montgomery Manatee County, Agricultural Extension Services,

Mr. I. H. Stewart U. S. Conservation Service

Mr. Paul Elsberry Elsberry Farms,

Mr. Bill Sexton Kibler Ranch,

Mr. Lee Sirmans Pacific Packing Co.,

Mr. Willie Tedder Pacific Packing Co.,

Mr. John McDonald Cannon Well Drilling,

Mr. Terry Mullins Rainbow Ranch, and

Mr. Harry Cannon Cannon Drilling

Investigators

The Northeast Manasota Basin Hydrologic Investigation was performed by

hydrologists and geologists of Seaburn and Robertson, Inc. Mr. John E.

Darling, Jr., managed the investigation under the general supervision of

Mr. Alton F. Robertson, P. E. Geohydrologic and geochemical aspects

of the investigation were conducted by Mr. Robert L. Westly and Mr. John

C. Miller, respectively.

Environmental phases of the investigation were performed by Biological

Research Associates under subcontract to Seaburn and Robertson, Inc.

Mr. Richard J. Callahan, Jr., and Mr. William B. Carey conducted the

investigation for Biological Research Associates.


-37-











GEOLOGY


The geology of the study area has been studied and described in previous

investigations. Field reconnaissance conducted to collect geologic

information supplemented the existing data and literature. The geologic

aspects of the area are discussed in detail as they relate to the

potential for production of potable water from the aquifer that are a

part of this geologic framework.


Soils


Unconsolidated marine sands and clay are the parent materials from which

the soil of the Northeastern Manasota Basin Project Area were derived

(Caldwell and others, 1958). The soils generally have a sandy surface

layer and are low in organic materials. They have a low supply of

plant nutrients and are generally strongly acid, except in scattered

localities where lime layers are within a few feet of the surface. Soils

located in topographic low areas tend to have a greater organic accumula-

tion, chiefly muck, that is the parent material.

Figure 3 is a map of soil associations in the Northeastern Manasota Basin

Project Area. Soil associations are well-defined groups of soils that

occur in close geographic association. Each delineation on the soil

association map represents a group of soils that occur together in nature


-38-
















RZIK ~22


SOIL ASSOCIATIONS

I TA-mIA ~IU*KA
2 POULLO ST. LUCI 10
4 IMOuAL9u amCELi
S mlAA POMMaIw.- *ASi


7 WSAU0Q* IAOINRTOM- WAK KA
* PLACC0 SASINg4N
9 01L AY MAMATlE- 1MP&NO
10 P M n1T11 W MS MSp W
SCMJ!t. MLS \
0 I 3
.m ..


AFMM aue 1 or COmN*CCMCNVC PAtMIn (r1. (s.

SEASURN ANO ROBERTSON. INC.


FIGURE 3.-SOIL DISTRIBUTION AND

MANASOTA BASIN. -39-


ASSOCIATIONS IN THE NORTHEAST


Rz1g


4221










to form a distinctive landscape. A soil association consists of one or more

major soils and at least one minor soil, and is named for the major soils.

Table 1 summarizes the general characteristics of the soil associations

and their flooding potential.

The Soils Association map is useful to predict the impact of large-scale

groundwater withdrawals on wildlife habitats. Soils associations 8, 9

and 10, as shown in Figure 3 and in Table 1 are indicated as "good" for

wetland wildlife. All of the other soils associations are classed as

poor to very poor for wetland wildlife, and only poor to fair for woodland

and openland wildlife (Florida Department of Administration, 1976). Soils

associations 1 and 2 have well drained soils and the greatest depth to

water table. These soils occur chiefly on topographic highs.

Geomorphology

Geomorphology is the science concerned with the general configuration of

the Earth's surface; specifically, the study of the classification,

description, nature, origin and development of present land forms and

their relationship to underlying structures. The land forms of the North-

eastern Manasota Basin Project Area are described below and an evaluation

is made regarding the implications of these land forms to groundwater

supplies and to the environmental impacts of groundwater withdrawal.

General Description

The Northeastern Manasota Basin Project Area is in the west central

portion of the Mid-Peninsula Zone of the Florida peninsula (White, 1970).

Parts of three major physiographic features are included within the project

area: the Polk Upland; the DeSoto Plain, and the Gulf Coastal Lowlands (Figure 4).


-40-















Table 1. Soil Association in the Northeast Manasota Basin Study Area 1/


Refe
Numo


10 Fresh Water Swamp and
Marsh


renea
er / Soil Association

1 Tavares-Myakka



2 Pomello-St. Lucei



4 Immookalee-Pomello


5 Myakka-Pomello-Basinger



6 Myakka- Immokalee-8asinger



7 Wabasso-8radenton-Myakka






8 Placid-Basinger

9 Delray-Manatee-Popano


Flooding
Potential


Moderately well to
poorly drained
soils not subject
to flooding


-41-


/Florida Division of State Planning, Bureau of Comprehensive Planning (1975).

/Reference number refers to areas on Figure 3.


General Description

Moderately well drained soils sandy
throughout and poorly drained sandy
soils with weakly cemented sandy
subsoil

Moderately well drained sandy soils
with weakly cemented sandy subsoil
and excessively drained soils sandy
throughout

Poorly and moderately well drained
sandy soils with weakly cemented
sandy subsoil

Poorly and moderately well drained
sandy soils with weakly cemented
sandy subsoil and poorly drained
soils sandy throughout

Poorly drained sandy soils with
weakly cemented sandy subsoil and
poorly drained soils sandy through-
out

Poorly drained tandy soils with a
weakly cemented sandy subsoil layer
over loamy subsoil; poorly drained
soils with thin sandy layers over
loamy subsoil; and poorly drained
sandy soils with weekly cemented sandy
subsoil

Very poorly and poorly drained soils
sandy throughout

Very poorly drained soils with thick
sandy layers over loamy subsoil; very
poorly drained sandy soils with loamy
suosoil and poorly drained soils
sandy throughout

Very poorly drained soils subject to
prolonged flooding


Poorly and very
poorly drained
soils subject to
flooding














I








H ILLSSOROUH CO. POLK CO.
SHAROEE C







MANATEE CO.
SARASOTA COC.P

AT 0ODESOT I

\ol




4-42-

0 5 10 1
SCALE, MILES
SCHARLOTETE CO
AFTER WHITE, 1970 \ \SEABURN AND ROBERTSON, INC.
FIGURE 4.-PHYSIOGRAPHIC MAP OF THE NORTHEASTERN
MANASOTA BASIN STUDY AREA AND VICINITY.
-42-











The Polk Upland, located in the northeastern portion of the project area

is a relatively flat area with elevations between 100 and 135 feet above

msl. The southern edge is an inconspicuous but persistent scarp, the

toe of which is at 75 to 85 feet elevation, that separates the Polk

Upland from the DeSoto Plain. The origin of this scarp is not well

understood, but most probably it is an erosional marine scarp made by

a Gulf of Mexico shoreline at Wicomico sea level.


The DeSoto Plan extends across the western and southern portions of the

project area with a very flat surface. It is possibly a submarine plain

made during Wicomico time, because there are no beach ridges or other

lineal features to suggest relict shorelines (White, 1970). The

southern edge of the DeSoto Plain is about 10 miles south of the Polk

Upland scarp. The DeSoto Plain is separated from the Gulf Coastal low-

lands by a scarp between 40 to 60 feet elevation.

The southwestermost portion of the project area lies in the Gulf Coastal

lowlands. Tatum Sawgrass and the Myakka River are located in this area.


-43-











Stream Patterns


Superimposed upon the major physiographic features are three principal

streams and their tributaries. The South Fork Little Manatee River

(see Figure 5) is characterized by a relatively deep river valley. Where

the river leaves the Polk Upland, its valley depth is in excess of 60

feet. The Little Manatee River valley tends to make numerous right-

angle turns (Figure 5) which may be indicative of fracture patterns

developed in rock units beneath the river valley.

The Manatee River extends into the project area as a straight channel

for more than 10 miles. As the North Fork of the Manatee River leaves

the Polk Upland, the valley is greater than 50 feet deep. Right-angle

turns are also common in the upper reaches of the Manatee River.


The Myakka River is very different from the previous two rivers. In the

lower 7 miles, before it leaves the project area, it lies in a broader

river plain where it meanders considerably. The valley depth of this

river is only about 35-40 feet. At a point 7 miles upstream from the

southwest edge of the project area the Myakka River turns abruptly

northward for 8 miles, passing through the Long-Ogleby Swamp. Again,

right-angle deviations in the valley are common in the upper reaches.


-44-



















































C
4 .4,


*:h'.' A -



J.0 4~.. .
00 3,F4
t :
f6.r e tO


43 1 43 '


3/ -, 3.V.


S.







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--p *


'II
.4 4' 3 ~


.3


EXPLANATION
0 O OUC
*- MAJOR AREA OF SUSSIDNC
O OR 80UNOARY OF OC:NE IS
NOEFINITE
.,-s'RESEOR BO9UNOARY













00.5 2 3 4
SCA I MILS N
SCALE, MLES I


.4^ a.7 .,- -
.a ,f #; 4. ; y- 3 \
'.*4 1/- g )- 3 .' ." -' -- '
~c ':' "* "* *
'1t ~ 4. ~ P:


*; ** -** 7^r 0.* .
*.. a
:*
'.1 t S. -'
\ 4'.*4.*.'. `a- *. 4 ,q\ -


SI SEA8URN ANO ROBERTSON, INC.
I I I I


FIGURE 5.-KARST FEATURES AND STREAM PATTERNS IN THE NORTH-

EASTERN MANASOTA BASIN STUDY AREA.
-45-


.ZEiJ


RZZ


I__ ___


qTZO











Karst Activity


Karst is a type of topography that is formed over limestone, dolomite,

or gypsum deposits. The surface is characterized by closed depressions
(dolines), caves, and underground drainage caused by solution of these

underlying deposits. This topography is very common in Florida.

There appear to be three distinct types of closed karst depressions or

dolines in Florida. The first is the collapse sink, which is generally

steep-sided, rocky and large diameter. These form when a cavity in a

soluble rock such as limestone enlarges to a size that can no longer

support the weight of overlying soil and rock.



A second type of closed karst depression is the ravelling sink,

common in Florida, caused by erosion or ravelling of the overburden into

limestone cavities. For such an event to occur, however, the cavernous lime-

stone must be overlain by relatively pervious unconsolidated sediments, the

water table in the overburden must be higher than that of the potentio-

metric water level in the limestone, and the limestone must be breached

into the cavernous zone creating a point of high recharge to the limestone

aquifer from the overlying unconsolidated sediments. The movement of

water from the upper zone carries sediment downward into the cavity which

eventually results in either a small diameter collapse or slow lowering

of the land surface.


-46-











A third type of closed karst depression is the solution sink. More common

than the collapse sink, they are not a result of physical disturbance of

the underlying carbonate rock, but are the result of chemical solution of

the rock, generally over a large area, accompanied by removal of the

dissolved material to other areas by moving groundwater. This solutional

activity takes place very slowly and is evident at land surface as large

circular areas that are seasonally wet.

Within the project area the limestones are covered by a considerable thickness

of low permeability materials (as low as 1.1 x 10-6 cm/sec, Ardaman &

Associates, Inc., 1975) that decrease the rate at which near-surface

acidic groundwaters move downward and react with the limestone. The result

is a considerably subdued karst terrain characterized by many small,

shallow, closed depressions filled with muck and wetlands-type vegetation.

These depressions, probably small solution sinks, are a result of the

gradual dissolution of limestone at depth. Estimates by the Florida

Bureau of Geology (1972), indicate that the lowering of the ground surface

due to this type of solution activity in other parts of the state occurs

at the rate of one foot every five to six thousand years. This is probably

the case at present in the project area where all of the dolines are less

than 5 feet deep, although they may be filled with sediment.

To understand the impact that karst activity has had on the ground-

water resources of the project area, all readily visible karst

features were mapped using stereo-paired aerial photographs. All circular

or oval, closed depressions (dolines) were mapped and are shown on Figure 5.


-47-











The aerial photography used for the karst features mapping was of three

different types:


1. 1:24,000 stereo-unpaired prints, black and white, Mark Hurd

Aerial Surveys, Inc., December 10, 1972,

2. 1:80,000 stereo-paired, color IR, 9 x 9 contact prints, Mark

Hurd Aerial Surveys, Inc., December 10, 1972, and

3. 1:24,000 stereo-paired, black and white, 9 x 9 contact prints,

Florida Department of Transportation, December 20, 1977 to

January 10, 1979.

Inspection of the stereo-paired aerial photographs revealed that there

has been no collapse sinkhole activity during the past 10 years. Mr. I.H

Stewart, District Conversationist, Soil Conservation Service, in Manatee

County (personal communication) reports that since his residency in Manatee

County began in 1950, he has not been made aware of any sinkhole activity

of the collapse type in the project area. Most likely, karst activity in

the area was greater in the past. Present higher sea levels or a subsiding

land mass have apparently decreased the head difference in the aquifers, such

that this major cause of karst solutional activity is not as dynamic as it

once was.


The small, closed depressions or dolines are not the only karst features

in the project area. Figure 5 shows the location of the Tatum Sawgrass and

Long-Ogleby Swamp. During the geologic past, when head differences between


-48-












the water-table aquifer and the Floridan aquifer were greater, these

two wetlands areas were forming as large karst lakes. Sellards (1910)

developed a hypothesis that many Florida lake basins had been formed

by a sequential development of similar sinks, earlier ones being filled

with sediment in the center of the lake, while newer ones developed along

the shoreline. These "Sellards type" lakes are to be found in the project

area as large swampy areas with plugged sinks around the edge. Particularly

good examples are the Tatum Sawgrass, Long-Ogleby Swamp, and the large

shallow depressions northwest of Long-Ogleby Swamp. Examples of

geologically recent sinks that formed out from the edges of the former lakes are

those to the east of Long-Ogleby Swamp. These sinks, about one mile from

the edge of the present swamp (Figure 5) are aligned in a manner that

mimics the shape of the swamp (former lake).

Straight or slightly curving lines, not due to stratigraphic contacts or

man-made features and generally unaffected by topography, are considered

surface manifestations of vertical to near-vertical zones of fracture

concentration in bedrock. Such lines, called fracture traces and lineaments,

are expressed at the surface by aligned surface sags or depressions, gaps in

ridges, soil tonal changes indicating soil moisture variations, springs, seeps,

sinkholes, vegetation alignment or vegetation type and height changes,

straight stream and valley segments, and abrupt valley or lake shore

alignment. It has been shown that these fracture traces (less than one

mile long) observed on aerial photographs are generally underlain by zones

of localized weathering, increased permeability and porosity (Parizek,

R.R., 1976). These features are expressions of bedrock rupture and are


-49-










visible even when covered by as much as 300 feet of residual or transported

soils (Wobber, F. J., 1967). A detailed fracture-trace map of the project

area was not prepared because it is likely that the fractured rock causing

surface traces is not the deeper portion of the Floridan aquifer, which is

the major source of groundwater supplies. The rocks containing these

fractures are probably limestones of the Hawthorn and Tampa units.

However, the 1:80,000 scale 9 x 9 stereo-paired color infrared contact

prints were used to map large-scale surface feature lineaments (lineations

greater than one mile long observable on aerial photographs). As mentioned

previously, the three principal streams in the Northeastern Manasota

Basin Project Area tend to change their flow direction rather abruptly. This

is because of geologic controls determined by faulting and extensive fracturing

of the rock. Vernon (1951) first recognized this in Citrus and Levy Coun-

ties, and he prepared a map of northern and central peninsular Florida

that indicates some of these major fracture trends. Paralleling these

major trends are innumerable smaller-scale fractures that also influence

stream orientation. These stream valley trends tend to be in two dominant

directions, northeast-southwest and northwest-southeast. The trends

correspond with those observed in other parts of Florida (Vernon, 1951;

Yon, 1966; and Miller, 1977).

Figure 6 shows the major lineaments that have been detected in the study

area. Some of the lineaments extend as far as 12 miles. And, while a

good number appear as long, straight stream segments, there are others

that cut directly across the land surface. Long trends of sinkholes

often have the same orientation as the streams, and may be controlled

by similar deep fracture zones.
-50-









R201 ~ZI! q 22


*. LAKE

.. .. ., o.., -



SEXPL- ANAT
































DO 00UJNE
S *.. *. \, ', .., -. 0 ...* .' / <"
,. ". _





















0 0.3 -
i. ,-' .' : *. '' --


*. ,. *. : .. *,: y ..












SCALE, MILES I.
"W *" o0 .. .









SI SEASURN AND ROERTSON, !NC.
-/.1''






























FIGURE 6.- MAJOR LINEAMENTS MAPPED IN THE NORTHEASTERN -









MANASOTA BASIN STUDY AREA.
-51-
e ., "-.. j. ,, :- ',


SA .. ;



"" EINT ", "* _J *, I % ,S ,
S.. ,1 ,' .',



.. ..,~ 'i /- '


S. ,, .- r" .0
EXPLANATION "R A !.
-51-


















MANASOTA 8ASIN STUDY AREA.

-51-


RZ06


RZIE


R22E











It is expected that groundwater withdrawals in the Northeastern Manasota

Basin Project Area will have minimal impact on sinkhole activity at land

surface. Heavy agricultural pumping in the area for more than 20 years

has caused no new sinkhole activity. Hydrologic conditions have changed

greatly since June, 1955, when as Peek (1958a) reports, artesian flow

conditions existed from the Long-Ogleby Swamp down the Myakka River to and

including the Tatum Sawgrass (Figure 5). Heavy pumping in Manatee County

and adjacent counties appears to have lowered the potentiometric surface

such that in May, 1979, a decline of 20 feet since 1955 had been established

(Wolansky and Others, 1979). Older sinkholes, if containing material of

sufficient permeability, may be locally reactivated. However, the downward

movement of the land surface in these sinkholes at present must be very

slow, despite the pumping, for sinkhole activity in the region has not

been detected.

Sinkhole formation tends to be favored by the following conditions:

1. The occurrence of permeable limestones in which a cavity system

has been developed through dissolution by groundwaters,

2. A water table higher than the potentiometric surface of the

artesian aquifer,

3. The limestones are overlain by a relatively thin layer of uncon-

solidated sediments, and

4. Overlying sediments are usually well drained and permeable.


-52-











In the project area only conditions 1 and 2 are common and for this

reason it is unlikely that sinkhole formation will increase in the study

area as a result of further groundwater withdrawals.

Lithology and Stratigraphy

Lithology

The lithology and stratigraphy of the Northeast Manasota Basin is described

in this section to indicate the characteristics and location of geologic

units that may affect the development of groundwater supplies. Lithology

was described first; correlated to published regional descriptions and

geologic formation names assigned to particular groups of lithologic

characteristics based on the correlation. The stratigraphy was then devel-

oped by locating the depths to the geologic formations at selected sites

and constructing structure contour maps indicating the top of the formations.

Lithology is the description of physical characteristics of rocks and is

used to assign geologic formation names to groups of rocks with similar

characteristics. Numerous investigators have described the lithology

of rocks in the vicinity of the project area largely by the inspection of

borehole cuttings. Peek (1958a) described the lithology of rocks

beneath western Manatee County and southern Hillsborough County

(Peek, 1959). The lithology of Polk County has.been described by Stewart

(1966). Wilson (1977a) described the lithology of rocks in DeSoto and

Hardee Counties and Bishop (1969) reports on the rocks in Sarasota County.


-53-










The lithology beneath the project area is similar to that found in

surrounding areas and is summarized in Table 2. This table was constructed

after evaluating 25 logs of borehole cuttings from wells in eastern Manatee

County analyzed by geologists of the Florida State Bureau of Geology,

the U.S.G.S. (Wilson, 1977a) and William F. Guyton and Associates

(Guyton, 1976b and 1976c). The borehole locations are shown on Figure 7.

Formation names (e.g., Hawthorn) were assigned to the lithologic descriptions

by correlating them to a summary description of all the formations in the

District (MacGill, 1976, unpublished).

Table 2 shows that the project area is underlain by a sequence of sand,

phosphate sands and clay, limestones and dolostones. These units are

typical of Central Florida. The upper sediments are unconsolidated quartz

sands which contain the water table throughout most of the County. Underlying

the upper sediments are the unconsolidated phosphatic sands and clays of

the Bone Valley and Upper Hawthorn Formations. Because uranium associates

with the phosphatic fraction of these formations, they are easily identi-

fied by gamma ray geophysical logs of wells. Figures 8 and 9 show the

locations of geophysical logging and gamma ray logs obtained in the project

area. There are two rock units of relatively high gamma radiation indicated.

The small unit that occurs at about msl is probably related to the phosphatic

sand of the Bone Valley Formation. The zone of relatively lower radioactivity

beneath the Bone Valley is probably the Upper Hawthorn.


-54-










Table 2. Lithology of Geologic Formations in
The Northeast Manasota Basin


Average Average Depth
Thickness To Top (feet
Series Formation Lithology (feet) below I.s.)


Recent Quartz Sand: Medium, subangular, non-indurated, 35
with some iron stain and some clay cementation.
Recent to
Pliocene Bone Valley Phosphate, Sand, Gravel and Clay: Medium quartz
and sand, quartz, sand non-indurated, clay yellow-gray, 90 35
Upper Hawthorn moderately indurated, fissile. Phosphate sand 5
percent of sample.

Lower Dolostone and Phosphate Sand: Some chert, poorly
Hawthorn indurated, phosphate sand 10-20 percent of samples; 225 125
dolostone is microcrystalline.
Miocene
Tampa Limestone: Micrite with quartz sand, well indurated,
Limestone high percent of allochems, trace of phosphate. 115 350
Quartz sand generally 10-30 percent and sometimes
100 percent of sample.

Oligocene Suwannee Limestone: Calcarenite, trace to no quatrz sand,
Limestone moderately to well indurated, fossils are forams and 275 465
echinoids.

Upper Limestone: Calcarenite, 90% allochems Unknown
Part
Ocala
Group
Limestone: Chalky, nodular, granular, fragmental,
some oolite, generally very fossiliferous, cream,
Ocala white, some buff; occasional dolomite in lower part, 220 740
Group sucrosic to dense and cherty, yellowish brown to
dark brown and gray.


Dolomite: Slightly calcitic to calcitic, medium to
finely crystalline, euhedral, replacement, sparsely
Upper fossiliferous (small echinoids and relic molds after 172 960
fossils), hard, dark tan to yellow brown with sparse
black specks? Crystalline carbonate.
Eocene Dolomite: Medium to finely (rarely finely to very
finely) crystalline, euhedral, dense, hard, dark
Avon Park 2/ yellow brown, scattered black layering and mot- 95 1130
tling: Crystalline carbonate. A videotape taken
Lower through this unit shows it to be characterized by
numerous caverns (some very large, greater than 10
feet in vertical dimension) with well developed
vertical connections.


1/ Description from Wilson, 1977.
2/ Description from Guyton, 1976.


-55-
























































VANATU COUNTY
SARAOTA COUNTY


EXPLANATION


aOP WEOLOGstS LoS

SEE APPENDIX I FOR BORING LOGS









PROJECT SOUN

SCALE, MILES ASE FROM OOT MAP (JULY. 1974)
SEAE

FIGURE 7.- GEOLOGIST LOGS BOREHOLE LOCATIONS.

-56-










































EXPLANATION

*SR2 LOCATION AND NUJMK OF WLU. ,.....` ,MYAKK QT
j ,- A^ ..

SR 5 |



00 1 \ E) PROJECT SOUNDARY (
SCALE, MILES 8ASe FROM DOT MAP (JULY, 1974)
SEABURN AND ROBERTSON, INC.

FIGURE 8.- CROSS SECTION LOCATION OF GAMMA RAY GEOPHYSICAL
LOGS. -57-












100-


0-


100-


-i
200'

---
< 300-
U)

(0
-i



UJ
hi


600-




l 700 -


800-
I-
L










900-
I--











1000-


1100-


SR4


WELL NUMBER

SR6


SR7


SR8


SRIO











----Y
IL














EXPLANATION
- I. LOG RATE: 20 COUNTS/
IN2/ SEC.
2. TIME CONSTANT: 2

NOTE: LOGS PERFORMED BY
SWFWMD ROMP DIVISION.


FIGURE 9.- NATURAL GAMMA RAY GEOPHYSICAL LOGS IN CROSS-SECTION, NORTHEAST MANASOTA BASIN.


I
SEABURN AND ROBERTSON,INC.


SAIIURN AM) ROBERTSONs INC.


-; -- ---------------~-i--a91~cl~,.,,,










The Lower Hawthorn Formation is characterized by a dolostone and phosphatic

sand unit. Most of the unit is indicated by the second, broader zone of

radioactivity on Figure 8. Below the Hawthorn Formation lies the micritic

limestone of the Tampa Limestone. Micritic limestone consists mostly of

chemically precipitated carbonate mud. The Tampa Limestone in the project

area is a micritic limestone with a high percent of carbonate and quartz

grains. The sandy unit of the Tampa Limestone discussed by Wilson (1977)

does not consistently occur in eastern Manatee County. However, geologists

descriptions and geophysical logs indicate that the unit contains sufficient

sand in places to require borehole liners to prevent sloughing of sand into

open boreholes. Hydraulic data from tests performed in the area (Guyton,

1976a) indicate the micritic fraction of the unit probably fills the inter-

connected pore spaces in the rock sufficiently to cause the unit to have a

relatively low transmissivity.

Below the Tampa Limestone lies the calcarenitic limestone of the Suwannee

Limestone Formation. This type of limestone is composed primarily of

detrital calcite particles of sand size. The Suwannee Limestone in the

project area is a consolidated rock containing foram and echinoid fossils

and little or no sand. Hydraulic data (Guyton, 1976a) indicate that inter-

connected pore space is generally open or fractures exist to allow the

Suwannee to function as a producing aquifer unit.

Below the Suwannee Limestone Formation is a sequence of three limestone

units called Ocala Group. The Ocala Group has been described by Vernon

(1951) and Puri (1974). They are the Crystal River (Ocala Limestone),


-59-










Williston, and Inglis members, from top to bottom within the Group. The

geologist's logs indicate the upper member (Crystal River) of the Group

to be composed almost entirely of various allochems (limestone fragments,

fossils and fossil fragments). Hydraulic data (Guyton, 1976a) indicate that

the Crystal River and Willison members do not contribute significant

quantities of water to wells but act as semi-confining units between the

upper and lower Floridan aquifer units. The Inglis member apparently

produces sufficient water to identify it hydraulically with the top of

the Avon Park Limestone.

The Avon Park Limestone which underlies the Ocala Group is described in

Table 2 as adopted from a description of cuttings from a phosphate company

test well near Duette, Florida (Guyton, 1976a). Local well drillers suggest

that selected units within this dolomitic formation (locally termed the

"hard brown lime") produce substantial quantities of water to wells through-

out the area. Puri and Winston (1974) report this formation is one of the

most transmissive units in South Florida.

Guyton (1976a) reports that below the Avon Park lie the evaporite units

of the Lake City. No supply wells in the project area penetrate this unit.

Because of its low transmissivity it is considered to be the basal confining

unit of the aquifer system in eastern Manatee County.

Stratigraphy

Stratigraphy is the description of the arrangement and geographical dis-

tribution of geologic formations. The best description available for the

project area previous to this investigation is given in a series of structure


-60-










contour maps (MacGill, 1976, unpublished) which show the tops of the geologic

units, regionally. Because this investigation is directed toward develop-

ment of groundwater supplies, it was important to locate the stratigraphic

units with reasonably distinct and aerially continuous hydrologic character-

istics. MacGill's maps do not necessarily show this in the project area

because little or no weight is given to hydrologic characteristics in the

preparation of the maps.

For this reason, stratigraphy in the project area was described from

evaluations of geologists' logs, drillers' logs, results of a geophysical

logging and aquifer testing program performed during the investigation,

review of various literature and existing stratigraphic maps. Evaluations

were made based on characteristics of the rocks that could be easily

identified with the available data and that represent particular hydraulic

units (i.e., an aquifer or confining unit).

The evaluation resulted in the location of five units within eastern Manatee

County that potentially will effect development of groundwater supplies.

These units are shown by structural contour maps in Figures 10 through 14.

The first unit is a dolostone dolomiticic limestone) which is located near or

at the top of the Hawthorn Formation. The top of this unit forms a

broad shallow trough trending west to east then south across the area (Figure 10).

Data used in constructing the map is limited, therefore, the trough shape

is highly interpretive. This unit is a low yielding artesian aquifer that

actually forms part of the confining system overlying the major producing


-61-
































































FIGURE 10.- STRUCTURE CONTOUR LINES ON TOP OF THE FIRST
DOLOSTONE UNIT, HAWTHORN FORMATION.
-62-

























































EXPLANATION


LINK SHOWN ALTI'rJ
OP STmIUCTUNE SUMAC


00.5SCAE,
SCALE, MILES


FIGURE II.- STRUCTURE CONTOUR LINES ON TOP OF THE SANDY
MICRITIC LIMESTONE, TAMPA FORMATION.
-63-






















































EXPLANATION


--.0 L- Ne SHOWnm ALTMUDE
OF STaUCTUL SUJNC


I oN
SCALE, MILES i &AS FROM OOT MAP (JULY, 1974)
Su SEABURN AND ROBERTSON, INC.

FIGURE 12.- STRUCTURE CONTOUR LINES ON TOP OF THE CALCARENITIC
LIMESTONE, SUWANNEE FORMATION.
-64-




























































EXPLANATION


.-IoO-


LINE SHOWmN ALTITUDE
OPV.STXUCTUMK SUIFCE


00.5 E, M E
SCALE, MILES


FIGURE 13.- STRUCTURE CONTOUR LINES ON TOP OF THE FORAM ZONE,
OCALA GROUP. -65-
























































EXPLANATN


-LINE SHOWl ALTITrLE
OF STRUCTURE SUmat


SCALE, MILES N


FIGURE 14.- STRUCTURE CONTOUR LINES ON TOP OF THE HARD BROWN
LIME", AVON PARK FORMATION.
-66-











aquifer in the project area (i.e., Suwannee/Ocala/Avon Park). Wells

completed in this unit are used chiefly for domestic supply.

The second stratigraphic unit is a sandy micritic limestone, indicative

of the Tampa Limestone. The top of the unit forms a broad shallow basin

extending southwest into Sarasota County (Figure 11). A closed depression

in the basin lies beneath the Myakka River between State Road 70 and State

Road 64. Wells are not generally completed in this unit because the

common occurance of sand causes open boreholes to collapse. This unit is

the lower portion of the confining system to the Suwannee/Ocala/Avon Park

aquifer.


The third stratigraphic unit located beneath eastern Manatee County is a

calcarenitic limestone unit in the Suwannee Limestone. This unit also

appears to be a broad basin (Figure 12). It is the effective top of the

Floridan aquifer in eastern Manatee County.

Figure 13 shows the top of the fourth stratigraphic unit in the project

area. The geologists' logs indicate this unit may be a marker bed for

the top of the Ocala Group and probably represents the Crystal River

member of the Group. The unit is a broad trough closed toward the north-

east. Guyton (1976a) reports that the Ocala Group acts as a poor semi-

confining unit between the Suwannee and Avon Park Limestone with changes

in water levels heads in one unit being effectively communicated through

the Ocala Group to the other unit.


-67-










The "hard brown line" is the fifth stratigraphic unit mapped in the

project area (Figure 14). This unit was mapped using descriptions from

forty driller's logs from wells in the area. It probably represents the

top of the dolomitic unit of the Avon Park Limestone.

Geologic Conditions Favorable for Groundwater Development

The results of the geologic investigation of the project area indicate

that there are four general conditions favorable to development of

groundwater. They are:

1. Limited or no recent sinkhole development,

2. Hydraulically inactive fracture systems that do not readily transmit

surface water vertically to aquifers,

3. Extensive and permeable carbonate rock systems composed of the

combination of the Suwannee-Ocala-Avon Park units, and

4. Extensive overlying confining system composed of the Hawthorn-

Tampa units.

Each of these conditions is prevalent throughout the project area. There

are no geologic conditions unfavorable to the development of groundwater

supplies within the project area.


-68-












HYDROLOGY


Hydrology is the study of the occurrence, magnitude and distribution of

water in the atmosphere and lithosphere. Movement of water between the

atmosphere and the lithosphere is often depicted as the hydrologic

cycle. In this hydrologic cycle, water occurs as precipitation, evaporation

and transpiration of surface water and groundwater.


The natural hydrologic cycle in the project area has not changed signi-

ficantly for many hundreds of years. Pumping of groundwater for irrigation

has been the major influence to the system imposed during the past two

decades. More recently the construction of two large reservoirs potentially

influences the hydrologic cycle in the area.

Rainfall


National Weather Service maintains three rainfall stations in the vicinty

of the project area from which data were used in this study: Arcadia,

Bartow and Bradenton (Figure 15). Table 3 lists pertinent average rainfall

amounts recorded during the period of record at each station.


-69-




























































FIGURE 15.- LOCATION OF PRECIPITATION STATIONS IN THE NORTHEAST
MANASOTA BASIN VICINITY.
-70-










Table 3. Summary of Average Rainfall Amounts for Selected Stations in
the Vicinity of the Project Area.


Period of Rainfall
Record Avg. Annual Maximum Minimum
Station (yrs) (in) (month) (in) (month) (in)


Arcadia 77 55.43 June 9.07 Nov. 1.84

Bartow 93 55.24 July 8.74 Nov. 1.96

Bradenton 15 56.35 Aug. 9.55 Nov. 1.91


The weighted average monthly rainfall is depicted graphically on Figure 16.

The water year is characterized with a dry season occurring in the spring

(March through May) and a summer wet season (June through September).

Summer thunderstorm activity produces about 60 percent of the annual

rainfall. The remaining amounts are generally produced as a result of

winter season frontal activity although rainfall in the fall and winter

is sporadic.

Evapotranspiration

Evapotranspiration (ET) is the combined loss of water from evaporation

from the soil and water surfaces and transpiration from vegetation surfaces.

Direct measurements of ET are very difficult and because of this ET is often

computed from meteorological records using a model developed by Penman (1948).

Daily values of ET from 1948 to 1975 were calculated from which monthly totals

and average monthly values were computed. Monthly total ET ranged from


-71-





















I0


54-


1-4-




O J F M A M J J A S O N D
MONTH
WAERAGE PRECIPITATION (THIESSEN METHOD) 19I5-77

10-

9g- TOTAL= 38.72

8-

7

36-


-
S4-








J F M A M J J A S 0 N D
MONTH
AVERAGE EVAPORATION (PENMAN EQUATION)


SOURCE* N.O.A.A. SEABURN AND ROBERTSON, INC.

FIGURE 16.- AVERAGE MONTHLY PRECIPITATION AND EVAPORATION,

NORTHEAST MANASOTA BASIN.
-72-










high amounts in excess of 6.0 inches in June and July to low amounts less

than 1.0 inch in December and January. Average monthly values of ET in

inches shown below are depicted graphically on Figure 16.



Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.


1.26 1.59 2.86 3.70 5.16 5.17 5.05 4.71 3.60 2.83 1.51 1.15



Surface Water


Surface water in the project area consists of streams, lakes, impoundments

and ponds. There are three major river basins in the project area; Little

Manatee River, Manatee River and Myakka River Basins. Within the project

area each basin drains toward the west and eventually discharges into the

Gulf of Mexico or Charlotte Harbor. Figure 17 shows the drainage boundaries

of each of the river basins and the major tributaries to each river as

well as the location of flow gaging stations in the project area.

Continuous streamflow records have been collected for the Little Manatee

River, Manatee River and Myakka River by the U.S.G.S. at these stations

and pertinent information about these streams is shown in Table 4.

Based on these long term records, the average annual unit discharge for

the project area is about 1.0 cfs/smi. Using this value to estimate the

average annual discharge of all streamflow from the project area results

in an estimated total discharge of 327 cfs (211 mgd). (See Table 5)


-73-




























MANATEE RIVER
DRAINAGE BASIN


EXPLANATION

--_ DRAINAGE
DIVIDE


A
02300100


STREAM
GAGING
STATION
NUMBER


AND


0SCE, MILES
s E., MILES


FIGURE 17.-LOCATION AND EXTENT OF DRAINAGE BASINS.
-74-










Table 4.-Summary of Streamflow Data in the Vicinity of Northeast Manatee
County.


Station
Name


Myakka River
at Myakka City

Myakka River nr
Sarasota, FL

Manatee River
nr Myakka Head

L. Manatee River
nr Ft. Lonesome

L. Manatee River
nr. Wimanma


U.S.G.S.
Station
Number

02298608


02298830


02299950

02300100

02300500


Length of Drainage
Record Area
(yrs) (sqmi)

5 125


42 229


12 65.3

15 31.4

39- 149


-75-


Discharge
Max
(cfs)

3100


8670


3130

1700


14,000


Min


0


0


0

0

0.78


254

64.6

27.9


170


Mean











Table 5.-Estimated Average Annual Streamflow from the Project Area.



Drainage Estimated Average
Drainage Area Annual Discharge
Basin (sq mi) (cfs)


L. Manatee River 37 37

Manatee River 146 146

Myakka River 144 144

Total 327 327


-76-










In addition to the streams, there are numerous lakes, reservoirs, and ponds

within the project area that influence the hydrologic cycle. Small man-

made ponds (less than 1-2 acres) are commonly used for irrigation supplies

and cattle watering throughout the area. Larger ponds and lakes which

occur naturally throughout the area are found in karst depressions and

are usually internal drainage sinks that are hydraulically connected to the

water table aquifer. These lakes and ponds may be dry during part of

the year and may flood to the point of overflowing into other lakes and

stream channels at other times.

Long-Ogleby Swamp and Tatum Sawgrass are low-lying swamps and wetlands in

the southern part of the project area along the Myakka River. These swamps

overflow into the Myakka River and although discharge from these areas is

not known, it is thought to vary directly with water levels in the shallow

groundwater system.

Two large man-made reservoirs are located in the project area. Parrish

Lake, shown in Figure 17, is a 4000 acre cooling pond constructed by

Florida Power and Light for the Little ManateePlant (Willow Power Plant).

The pond is located adjacent to the Little Manatee River near Parrish and

about 25 mgd of water is withdraw from the river as make up cooling water

to the pond.

Lake Manatee is a man-made reservoir on the Manatee River (Figure 17).

The 2,000 acre impoundment has a capacity of about 41,000 ac-ft and is

used to supply raw water to the Manatee County Utilities System. The

reservoir is designed to supply 30 mgd, however, a recent investigation,

(Bromwell, 1980), indicates that 50 mgd may be available from the reservoir.

-77-










These reservoirs, lakes and ponds are hydraulically connected to the

water-table aquifer and recharge to the deeper aquifer is minimal. The

consistent confining units underlying the water-table aquifer signifi-

cantly retards vertical movement of recharge water into the Floridan aquifer.

Conjunctive use of the surface water and groundwater resources will require

artificial means for accomplishment. Injection of surface water into the

limestone aquifers by means of recharge wells may provide a method of water

storage for later extractions, however, natural enhancement of recharge

as a general matter is not feasible in this area.


Groundwater

Aquifer Descriptions

Guyton (1976 b) characterized the groundwater system in the project area

near Duette, Florida, as consisting of the following hydrologic units:

1. Shallow aquifer,

2. Hawthorn/Tampa, and

3. Suwannee/Ocala/Avon Park.

He reported yields from the shallow aquifer during aquifer pumping tests

from 28 to 32.5 gpm and transmissivity values from 2,000 to 14,000 gpd/ft.

The major confining unit to the Floridan aquifer lies beneath the shallow

aquifer and includes the Hawthorn and Tampa Formations. Guyton estimated

that the coefficient of leakance for this unit was between 1 x 10"4 and

1 x 10-5 gpd/ft3 in the Duette area.


-78-










Below the Hawthorn/Tampa confining unit lies the Suwannee/Ocala/Avon

Park aquifer unit. Water levels in the Suwannee and Avon Park forma-

tions are the same under nonpumping conditions, they diverge when the

Avon Park is pumped. This suggests that the Ocala is less transmissive

and may be a leaky semi-confining unit but that the Suwannee, Ocala,

and Avon Park operate as one aquifer unit over a long period of time.

Transmissivity values were reported by Guyton to be 17,500 and 770,000

gpd/ft in the Suwannee and Avon Park, respectively, near Duette, Florida.

Aquifer Withdrawal Tests

A summary of aquifer hydraulic coefficients reported at a number of sites

in the project area are listed in Table 6 and shown on Figure 18.

Three sites were selected to conduct aquifer pumping. tests to supplement

existing hydraulic data in the project area. Irrigation production wells

open to the Suwannee/Ocala/Avon Park unit were selected. All testing was

conducted in existing wells and interference from irrigation pumping was

unavoidable. For this reason, only two of the tests provided satisfactory

information for further evaluations.

Site 4 consisted of two pumped wells and two monitor wells (Figure 19).

The pumped wells were about 1,050 and 1,180 feet deep and cased to about

200 and 250 feet, respectively. The wells were open from the Hawthorn

into the Avon Park unit. The test was performed using a withdrawal rate

of 3,000 gpm for 3,000 minutes (2.08 days). The data were analyzed by

the Hantush Inflection Point method (Hantush 1960, 1964) and by the Chow

method described by Kruseman and De Ridder (1976). The analyses accounted


-79-






Table 6. -Summary of Hydraulic Coefficients, Determined from Aquifer Tests, in the Northeast Manasota Basin.

Test 1/ Transmissivity Storage Leakance Geologic Unit(s)
Site (gpd/ft) Coefficient (gpd/ft ) Open to Well Source

1 17,900 Shallow P. E. LaMoreaux (1975)
170 7.08 x 10-5 0 HAW -do-
170,000 6.4 x 10-4 2.6 x 10-2 TPA/SUW/OC/UAP2 -do-
2 870,000 8.2 x 10-4 SUW/OC/UAP Black, Crow & Eldsness (1973)
3 2,000 14,000 Shallow Guyton & Associates (1976)
-4-5
Very Low 10-4 to 10-5 HAW -do-
17,500 SUW -do-
1,0003/ OC -do-
770,000 AP -do-
4 332,000 .2 x 10-3 2 x 10-2 HAW/TPA/SUW/OC/UAP4/ Seaburn & Robertson, Inc.
5 340,000 1 x 10-3 -do- -do-
6 6,152 2.12 x 10-2 Shallow Geraghty & Miller, Inc. (1974)
7 2,000 4 x 10-2 Shallow -do-
15,000 2 x 10-2 HAW/TPA -do-
8 1,200,000 4 x 10-4 6 x 10-4 SUW/OC/AP Geraghty & Miller, Inc. (1976)


1/ Reference No. refers to locations on Figure 18.


2/


UAP = Upper Avon Park.


3/ Interpreted from an approximation of permeability resulting from model simulations by Guyton (1976).
4/ Tampa unit may not be open to well.




























e ,.




04a- ma-

** ,








*









EXPLANATION =
SOILS BORINGS SERIES T O
APPROXIMATE BORING ...., MYAKKA *T--.
LOCATION j 5 /
/y' LOCATION AND DESIGNATION 3 /" /
OF AQUIFER TEST SITES / / ..
(SEE TABLE 6 FOR TEST / .. --" "" "
RESULTS) .. o




00I I PROJECT BOUNDARY
SCALE, MILES I SA FROM COT MAP (JUL., 1974)1
'SEABURN AND ROBERTSON, INC.

FIGURE 18.-LOCATION OF SOILS BORINGS AND AQUIFER TEST SITES, NORTHEAST
MANASOTA BASIN. -81-






























EXPLANATION


S2 VWTER TABLE
MONITOR WELL

+2 FLORIAN
MONITOR WELL

* PUMPED WELL



N

I

0 1000 2000
SCALE,FEET


I SEABURN AND ROBERTSON. INC.
FIGURE 19.- WELL LOCATION MAPS FOR AQUIFER TEST SITES 4 AND 5.


-82-


I


AQUIFER TEST SITE 4


~sd


OAK KNOLL -*


AQUIFER TEST SITE 5


3.0 MILES
TO SR 64


2 X 9t


,4o'


WaTERBURY

I


"-









for the varying radii to the pumping wells by a method described by

Wilson (1977). In this analysis the distance from each observation well

to an effective center of pumpage, r, was computed as follows: the

products of the logarithm of the distance to each pumping well and the

discharge of each well were summed and divided by total discharge; r equals

the antilog of that quotient. Transmissivity and storage values are

averages determined from analyzing drawdown and recovery at the monitor

well by both methods. The leakance value was obtained from the analysis

of drawdown data only, using the Hantush inflection point method. Because

of regional pumping interference the recovery data were not sufficient to

permit a leakance value to be calculated. The analyses indicate hydraulic

coefficients for the Hawthorn/Tampa/Suwannee/Ocala/Avon Park unit are:

T = 332,000 gpd/ft (44,382 ft2/day)

S = 2 x 10-3

L = 2 x 10-2 gpd/ft3 (2.7 x 10-3 day-1)

Site 5 consisted of the pumped well and three monitor wells (Figures 18

and 19). The pumped well was about 1,250 feet deep and cased to about

250 feet; open from the Hawthorn into the top of the Avon Park unit.

The wells used to monitor level responses during the test included a

water table well and two wells open to the Floridan aquifer similar to the

pumped well. The test well was pumped at about 1,000 gpm, while withdrawal

and recovery water level data were collected. Background water level

changes during the test were estimated from water level measurements

leading into and following the test. Field data are contained in

Appendix I.

The test data were analyzed using the Chow method for leaky aquifers as










described by Kruseman and De Ridder (1976). Because the well is open to

a number of producing units, the transmissivity (T) and storage (S) values

reported below represent values for the entire open hole section. The

analytical results indicate that hydraulic coefficients for the Hawthorn/

Tampa/Suwannee/Ocala/Avon Park unit are:

T = 340,000 gpd/ft (45,451 ft2/day)

S = 1 x 10"3

The data collected was not sufficient to analyze for leakance because of

regional water level trends and some local interference.

Hydraulic data indicate that the Hawthorn Formation is the least trans-

missive while the Avon Park is the most transmissive. Most major wells

in the Northeast Manasota Basin project area, however, are open to the

entire Hawthorn/Tampa/Suwannee/Ocala/Upper Avon Park system. Therefore,

the hydraulic coefficients determined from existing wells describe

the aquifer response to pumping from the deeper high producing portion

of the aquifer.

Potentiometric Heads and Groundwater Flow

The shallow auger boring program indicated that the surficial aquifer water

surface (water table) was generally about four feet below land surface during

November and December throughout the project area. Figure 18 indicates

the locations of the selected soils borings. Figure 20 shows the estimated

altitude of the water table aquifer across the project area determined by

subtracting four feet from the topographic contours. The shallow auger

borings completed during this investigation provided site-specific water


-84-



























































EXPLANATION


-45-UNE SHOWING ALTITUDE OF WATER
TABLE SURFACE


SCALE, MILES I


FIGURE 20.- ESTIMATED WATER TABLE SURFACE, NOVEMBER -DECEMBER, 1979.
-85-











table data used to prepare this map and indicated that the water table

ranged from three to five feet below land surface throughout the project

area. Groundwater flow in the shallow aquifer is toward the southwest,

regionally, and toward stream valleys, locally. The variations of

water levels in the shallow aquifer across the project area from the

northeast part to the southwest part is about 75 feet.

A map of the potentiometric surface in the Hawthorn unit was constructed

from water level data reported in driller's logs of wells completed between

1963 and 1979 (Figure 21). The construction of the map assumes that

water levels did not change greatly during the period. This is thought

to be reasonable because the potentiometric surface of the underlying

aquifer has not changed more than annual fluctuations and because of the

permeability of the unit itself. The map is the best available estimate

of Hawthorn water levels throughout the project area.

Regionally, the Floridan aquifer potentiometric surface has been mapped

by several investigators. Because wells constructed in the project

area are usually open to the Suwannee/Ocala/Avon Park, these maps represent

potentiometric surface across that combined aquifer unit. Water levels

in this unit in the vicinity of Duette, Florida are 60 to 90 feet lower

than water levels in the Hawthorn, but similar to water levels in under-

lying units (Guyton, 1976a). During this investigation, water levels

were as much as 40 feet below the level of the Hawthorn across

the project area.


-86-




















































EXPLANATION


--,0 LINE SHOWING
ALTITUDE OF THE
POTENTIOMETRIC
SURFACE


SCALE, MILES I


FIGURE 21.-ESTIMATED POTENTIOMETRIC SURFACE OF THE HAWTHORN
FORMATION, 1963-1979. -87-




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