Potential for Water-Quality Degradation of 

Interconnected Aquifers in 

West-Central Florida

By P. A. METZ and D. L. BRENDLE

U.S. Geological Survey

Water-Resources Investigations Report 96-4030

Prepared in cooperation with the

SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT

Tallahassee, Florida

1996
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

Any use of trade, product, or firm names in this publication is for descriptive purposes only

and does not imply endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be 

purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Earth Science Information Center

Suite 3015 Open-File Reports Section

227 North Bronough Street P.O. Box 25286, MS 517

Tallahassee, Florida 32301 Denver, CO 80225-0425
Contents III

CONTENTS

Abstract ................................................................................................................................................................................. 1

Introduction .......................................................................................................................................................................... 1

Purpose and Scope ...................................................................................................................................................... 2

Previous Investigations................................................................................................................................................ 2 

Acknowledgments ...................................................................................................................................................... 2

Description of Study Area ........................................................................................................................................... 2

Hydrogeologic Framework ................................................................................................................................................... 4

Surficial Aquifer .......................................................................................................................................................... 4

Intermediate Aquifer System ...................................................................................................................................... 4

Floridan Aquifer System ............................................................................................................................................ 6

Factors Influencing Vertical Borehole Flow.......................................................................................................................... 7

Methodology and Instrumentation.........................................................................................................................................10

Results and Interpretation of Geophysical Well Data............................................................................................................12

Impeller Flowmeter Well Log Analysis ......................................................................................................................19

Heat-Pulse Flowmeter Well Log Analysis ..................................................................................................................26

Water Quality ........................................................................................................................................................................31

Chloride .......................................................................................................................................................................31

Sulfate .........................................................................................................................................................................45

Dissolved Solids .........................................................................................................................................................45

Potential for Water-Quality Degradation ..............................................................................................................................46

Estimated Magnitude of Interaquifer Flow ..........................................................................................................................46

Quality of Water Improvement Program ...............................................................................................................................48

Summary and Conclusions ....................................................................................................................................................51

Selected References...............................................................................................................................................................53
IV Contents

FIGURES 

1. Map showing location of study area ........................................................................................................................ 3

2. Correlation chart showing hydrogeologic framework.............................................................................................. 5

3. Schematic of a properly constructed well open to a single aquifer, and a corroded well and an improperly 

 constructed well that can allow water quality contamination between multiple aquifers ....................................... 8

4. Map showing generalized head difference between the intermediate aquifer system and the 

 Upper Floridan aquifer, September 1993 ....................................................................................... .......................... 9

5. Map showing generalized head difference between the intermediate aquifer system and the

 Upper Floridan aquifer, May 1994 ............................................................................................. .............................. 11

6. Sketch showing the components of the impeller flowmeter..................................................................................... 12

7. Photograph of a borehole video camera with the impeller flowmeter attachment in a 12-inch open borehole

 at a depth of 479 feet below land surface ................................................................................................................. 13

8. Sketch showing the components of the heat-pulse flowmeter ................................................................................. 14

9. Map showing locations of wells measured using various geophysical logging techniques..................................... 18

10. Map showing locations of wells in which internal flow was detected using the impeller flowmeter and the

maximum recorded borehole flow in gallons per minute......................................................................................... 20

11-16. Graphs showing:

11. Composite geophysical log for ROMP 20 well in Sarasota County ............................................................... 21

12. Composite geophysical log for Oscar Sherer State Park well in Sarasota County........................................... 22

13. Composite geophysical log for Utopia No. 1 well in Sarasota County ........................................................... 23

14. Seasonal flow measurements for Utopia No. 1 well in Sarasota County and hydrographs of the

intermediate aquifer system and the Upper Floridan aquifer, October 1992 through October 1993 ............... 24

15. Seasonal flow measurements for Utopia No. 1 well in Sarasota County and hydrographs of the

intermediate aquifer system and the Upper Floridan aquifer, November 1993 through October 1994 ........... 25

16. Composite geophysical log for Hickory Street well in Sarasota County with Production No. 3 well under

nonpumping and pumping conditions .............................................................................................................. 27

17. Map showing locations of wells measured with the heat-pulse flowmeter and the maximum recorded flow

measurement in the borehole in gallons per minute................................................................................................. 29 

 18. Graph showing composite geophysical log for Schroeder Manatee Ranch No. 8 well in Manatee County 

using the heat-pulse flowmeter................................................................................................................................. 30

19-24. Maps showing generalized distribution of:

19. Chloride in water from the intermediate aquifer system .................................................................................. 39

20. Chloride in water from the Upper Floridan aquifer.......................................................................................... 40

21. Sulfate in water from the intermediate aquifer system..................................................................................... 41

22. Sulfate in water from the Upper Floridan aquifer ............................................................................................ 42

23. Dissolved solids in water from the intermediate aquifer system...................................................................... 43

24. Dissolved solids in water from the Upper Floridan aquifer ............................................................................. 44

 25. Map showing the area where there is a potential for water-quality degradation as a result of interconnected 

 aquifers and locations of wells that have been plugged ........................................................................................... 47

 26. Map showing locations of wells in the study area that are reported and estimated to be open to both the

 intermediate aquifer system and the Upper Floridan aquifer ................................................................................... 49

27. Map showing grid network with cumulative downward and upward flow rates for wells open to both the 

intermediate aquifer system and the Upper Floridan aquifer .................................................................................. 50

TABLES

1. Selected data for measured wells............................................................................................................................ 15

2. Records for wells using the heat-pulse flowmeter.................................................................................................. 28

3. Chloride, sulfate, and dissolved solids concentrations in water from selected wells............................................. 32
Contents V

CONTENTS

CONVERSION FACTORS, VERTICAL DATUM, ABBREVIATIONS, AND ACRONYMS

Multiply By To obtain

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

foot per minute (ft/min) 0.3048 meter per second

mile (mi) 1.609 kilometer

foot squared per day (ft2

/ d) 0.0290 meter squared per day

square mile (mi2

) 2.590 square kilometer

million gallons per day (Mgal/d) 0.04381 cubic meters per second

gallons per minute (gal/min) 0.06308 liter per second

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a 

geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, 

formerly called Sea Level Datum of 1929.

Abbreviated water-quality units:

mg/L milligrams per liter

μS/cm microsiemens per centimeter at 25 degrees Celsius

 Acronyms

GIS = Geographical Information System

QWIP = Quality of Water Improvement Program

ROMP = Regional Observation and Monitor Well Program

SWFWMD = Southwest Florida Water Management District

USGS = U.S. Geological Survey

WUP = Water Use Permits
Introduction 1

The Potential for Water-Quality Degradation of 

Interconnected Aquifers in West-Central Florida

By P. A. Metz and D. L. Brendle

Abstract

Thousands of deep artesian wells were drilled 

into the Upper Floridan aquifer in west-central Florida 

prior to well-drilling regulations adopted in the 1970’s. 

The wells were usually completed with a short length 

of casing through the unconsolidated sediments and 

were left open to multiple aquifers containing water of 

varying quality. These open boreholes serve as a 

potential source of water-quality degradation within 

the aquifers when vertical internal borehole flow is 

induced by hydraulic-head differences. This potential 

for water-quality degradation exists in west-central 

Florida where both the intermediate aquifer system 

and Upper Floridan aquifer exist. 

Measurements of caliper, temperature, gamma, 

fluid conductivity, and flow were obtained in 87 wells 

throughout west-central Florida to determine the 

occurrence of interaquifer borehole flow between the 

intermediate aquifer system and the Upper Floridan 

aquifer. Flow measurements were made using an 

impeller flowmeter, a heat-pulse flowmeter, and a 

video camera with an impeller flowmeter attachment. 

Of the 87 wells measured with the impeller flowmeter, 

17 had internal flow which ranged from 10 to 300 gallons per minute. A heat-pulse flowmeter was used in 

19 wells in which flow was not detected using the 

impeller flowmeter. Of these 19 wells, 18 had internal 

flow which ranged from 0.3 to 10 gallons per minute. 

Additionally, water-quality samples were collected 

from specific contributing zones in wells that had 

internal flow. 

Analysis of geophysical and water-quality data 

indicates degradation of water quality has occurred 

from mineralized ground water flowing upward from 

the Upper Floridan aquifer into the intermediate aquifer system through both uncased boreholes and corroded black-iron well casings. In areas where there is a 

downward component of flow, data indicate that potable water from the intermediate aquifer system is artificially recharging the Upper Floridan aquifer through 

open boreholes.

A geographical area was defined where there is 

a potential for water-quality degradation due to 

improperly cased wells. This area was delineated 

based on where there is an upward component of 

ground-water flow and where there is an occurrence of 

poor-quality water. The delineated area includes parts 

of Hillsborough, Manatee, Sarasota, Charlotte, 

De Soto, and Hardee Counties.

To prevent further contamination of the aquifers, the Southwest Florida Water Management 

District began the Quality of Water Improvement Program in 1974 to restore hydrologic conditions altered 

by improperly constructed wells or deteriorating casings. As of May 1994, more than 3,000 wells have 

been inspected and approximately 1,350 have been 

plugged. To minimize interaquifer contamination, 

existing wells, especially ones with black-iron casing, 

should be inspected and, if necessary, repaired with 

new casing or plugged. 

INTRODUCTION

Thousands of wells were drilled into the Upper 

Floridan aquifer in west-central Florida from 1900 to 

the early 1970's to obtain water for irrigation. Because 

potable water is also available in the intermediate 

aquifer system, most early irrigation wells that penetrated the more productive Upper Floridan aquifer 

were constructed so that they also were open to the 

intermediate aquifer system. The wells usually were 

completed with a short length of casing through 
2 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

unconsolidated sediments and were open to multiple 

aquifers with varying water quality. A confining unit 

exists between the two aquifers, but these open boreholes provide a conduit for ground water to move from 

zones of higher head to zones of lower head, thus 

shortcutting the slower route of leakage through the 

confining units.

Sutcliffe (1975) reported that, in Charlotte 

County, highly mineralized ground water had moved 

up the boreholes of many abandoned irrigation wells 

and had resulted in a deterioration of water quality in 

the shallow zones. Florida administrative code 

requires new wells to be constructed to prevent aquifer 

interconnection. However, a large number of existing 

multiple aquifer wells remains and the extent of aquifer degradation and exact area affected are unknown. 

In 1992, the U.S. Geological Survey (USGS), in cooperation with the Southwest Florida Water Management 

District (SWFWMD), began a study to determine if 

there was a potential for water-quality degradation due 

to improperly cased wells. The area of concern 

includes the southern half of the Southwest Florida 

Water Management District where both the intermediate aquifer system and Upper Floridan aquifer exist. 

This area includes all of De Soto, Hardee, Manatee, 

and Sarasota Counties and parts of Charlotte, Highlands, Hillsborough, and Polk Counties (fig. 1).

Purpose and Scope

This report describes the occurrence of interaquifer flow and defines a geographical area in westcentral Florida where there is a potential for groundwater quality degradation as a result of internal borehole flow in wells that are open to multiple aquifers 

containing water of varying quality. The occurrence of 

interaquifer borehole flow and the extent of waterquality degradation between the intermediate aquifer 

system and the Upper Floridan aquifer were determined by collecting and analyzing geophysical logs, 

head difference maps, and water-quality data. The 

report presents a description of the hydrogeologic 

framework, aquifer head difference maps, well inventory data, composite geophysical logs of wells open to 

multiple water-bearing zones, maps of wells with 

interaquifer flow, a table of water-quality data, and 

maps of water quality. A data base of geophysical log 

information was established during this study to 

describe interaquifer flow characteristics. 

Previous Investigations

The first study assessing the potential for waterquality degradation of interconnected aquifers in this 

area was done by Sutcliffe and Joyner (1966) who suggested that selective casing of wells or plugging could 

improve the quality of water produced from a well. 

Sutcliffe (1975) reported that nonpotable ground water 

had moved up the boreholes of many abandoned irrigation wells in Charlotte County. Boggess and others 

(1977) reported that saline water intrusion was related 

to well construction in Lee County. Wilson (1977) 

determined that the practice of drilling irrigation wells 

with many hundreds of feet of borehole open to multiple aquifers facilitated interaquifer flow in De Soto 

County. Healy (1978) documented many uncontrolled 

flowing artesian wells and concluded that the wells 

were the principal means for the deterioration of freshwater in the area because of upward leakage of saltwater into the shallow artesian aquifers. La Rose (1990) 

investigated the effects of a well-plugging program on 

the ground-water quality in Lee County and reported a 

slight decrease in chloride concentrations on a local 

scale. Hutchinson (1992) documented numerous 

improperly cased wells in Charlotte and Sarasota 

Counties that had upward internal borehole flow.

Acknowledgments

The authors are grateful to individual well owners and to public and private organizations for providing 

information on wells used for this study and for permitting the collection of water samples, geophysical logs, 

and hydrologic measurements. The authors would especially like to thank Albert Morris, Vincent Pelham, and 

Robert Parker of the Quality of Water Improvement 

Program at the Southwest Florida Water Management 

District in Venice, FL, for providing information and 

the location of many of the wells used in this study. 

Description of Study Area

 The study area includes the southern half of the 

Southwest Florida Water Management District where 

both the intermediate and Floridan aquifer systems 

exist. This area covers about 4,700 mi2, and includes 

De Soto, Hardee, Manatee, and Sarasota Counties and 

parts of Charlotte, Highlands, Hillsborough, and Polk 

Counties (fig. 1).
Introduction 3

Figure 1. Location of study area.

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

OF AREA

LOCATION

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′ 28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

STUDY AREA

FLORIDA

Harbor

Charlotte 

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River
4 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

The study area lies entirely in the mid-peninsular 

physiographic zone described by White (1970) and 

includes four subdivisions: the Polk Upland, the Lake 

Wales Ridge, the De Soto Plain, and the Gulf Coastal 

Lowlands. The subdivisions correspond approximately 

to several marine terraces or plains that were formed by 

marine regressions during the Pleistocene Epoch. The 

inland boundary of each subdivision is delineated by a 

low scarp or break in slope that represents the position 

of a former marine shoreline (Wilson, 1977). The Polk 

Upland is a broad sandy area that ranges in altitude 

from 100 to 245 ft above sea level. On the eastern side 

of the Polk Upland lies a part of the Lake Wales Ridge 

that ranges in altitude from 100 to 245 ft above sea 

level. This long, narrow ridge is a series of subparallel, 

eroded, sandy ridges with intervening valleys that contain numerous lakes. The De Soto Plain is a broad, gently sloping plain that ranges in altitude from 30 to 100 ft 

above sea level. The Gulf Coastal Lowlands, which 

encompasses a large part of the Peace River valley to 

the Gulf of Mexico, consists of poorly drained, lowlying land at altitudes of 30 to 40 ft above sea level in 

central and southwestern De Soto County to less than 

5 ft above sea level along the coast (White, 1970). 

The climate of the study area is subtropical 

humid and is characterized by warm, relatively wet 

summers and mild, relatively dry springs. Annual rainfall averages about 53 in. and varies seasonally with 

more that half the total rainfall occurring from June 

through September (Palmer and Bone, 1977). 

In addition to seasonal variations, rainfall also tends to 

be distributed unevenly throughout the area at any 

given time, especially during the summer. This uneven 

distribution occurs because most summer rainfall in 

Florida is derived from localized, convective thunderstorms. Winter rainfall generally results from cold, 

frontal-type air masses that move from north to south 

and occurs over wide areas.

HYDROGEOLOGIC FRAMEWORK

The hydrogeologic units underlying the study 

area consist of deposits of sand, clay, marl, and carbonate rocks that were primarily deposited in a marine 

environment. Principal hydrogeologic units consist of 

the surficial aquifer, the intermediate aquifer system, 

and the Floridan aquifer system (Southeastern Geological Society, 1986). These hydrogeologic units, their 

equivalent stratigraphic units, and brief lithologic 

descriptions are presented in figure 2.

Surficial Aquifer 

The surficial aquifer is contiguous with land 

surface and overlies the intermediate aquifer system. 

This aquifer is composed principally of unconsolidated to poorly indurated clastic deposits (Southeastern Geological Society, 1986). The surficial aquifer 

consists of predominately fine sand, interbedded clay, 

marl, shell, and phosphorite (fig. 2). The water-bearing 

properties of the surficial aquifer are largely dependent 

upon aquifer thickness and grain-size distribution of 

sediments within the aquifer (Wilson, 1977). Thickness of the surficial deposits ranges from about 350 ft 

in Highlands County to about 25 ft near the coast and 

in low-lying areas (Wolansky and others, 1979; SWFWMD, 1994). Transmissivity values for the surficial 

aquifer in the study area range from 600 to 8,000 ft2

/d 

(Wolansky and Corral, 1985). Because of low yield to 

wells and the potential for degradation, the surficial 

aquifer has limited use in most of the study area and 

generally is used for lawn and garden irrigation and 

for livestock watering.

Intermediate Aquifer System

The intermediate aquifer system includes all 

water-bearing units (aquifers) and confining units 

between the overlying surficial aquifer and the underlying Upper Floridan aquifer (Duerr and others, 1988). 

The intermediate aquifer system consists of the undifferentiated deposits of Pleistocene and Pliocene age 

and the Hawthorn Group of Miocene age (fig. 2).

The intermediate aquifer system consists of 

three or more hydrogeologic units (fig. 2): (1) a clayey 

and pebbly sand, clay, and marl upper confining unit 

that separates the water-bearing unit in the intermediate aquifer system from the surficial aquifer; (2) one to 

three water-bearing units composed primarily of carbonate rocks, sand, and discontinuous beds of sand 

and clay; and (3) a sandy clay and clayey sand lower 

confining unit that lies directly over the Upper Floridan aquifer (Ryder, 1985). The diversity in lithology 

of the intermediate aquifer system reflects the variety 

of depositional environments that occurred during the 

Miocene Epoch. These environments of deposition 

included open-marine, shallow-water, coastal-marine, 

fluvial, and estuarine (Gilboy, 1985).

The intermediate aquifer system underlies all of 

the study area and is hydraulically separated from the 

overlying surficial aquifer by the upper confining unit. 
Hydrogeologic Framework 5

Quarternary

Tertiary

Holocene

and

Pleistocene

Series

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Stratigraphic

Surficial sand,

terrace sand,

phosphorite

Undifferentiated

deposits1

Tamiami Formation Hawthorn Group

Peace River

Formation

Arcadia

Tampa 

Suwannee

Ocala Limestone

Avon Park

Oldsmar

Keys

General

Predominantly fine

clay, marl, shell,

Clayey and pebbly

shell, phosphatic.

Dolomite, sand,

silty, phosphatic.

Limestone, sandy,

part in some areas.

Limestone, sandy

Limestone, chalky,

Limestone and hard

intergranular evaporite

Dolomite and limestone

lithology

sand; interbedded

and phosphorite.

sand; clay, marl,

clay, and limestone,

phosphatic, fossiliferous;

sand and clay in lower

limestone, fossiliferous.

foraminiferal, dolomitic,

near bottom.

brown dolomite;

in lower part in some

areas.

with intergranular

gypsum and anhydrite.

Major

Sand

Clastic

Carbonate

Clastic

unit lithologic

unit

and 

Carbonate

Carbonate

with 

evaporites

Evaporites

Hydrogeologic

unit

Surficial aquifer

upper confining

aquifer

 lower confining 

Intermediate Aquifer System Floridan Aquifer System

Upper Floridan

aquifer

Middle Confining

Unit

Lower Floridan

aquifer

Sub-Floridan

Confining Unit

1Includes all or parts of Caloosahatchee Marl and Bone Valley Member.

 Formation

Limestone

Formation

 and

 Cedar

 Formations

System

member

Nocatee

member

 unit

 unit

Figure 2. Hydrogeologic framework.
6 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

The upper confining unit has a low vertical hydraulic 

conductivity and, consequently, retards interaquifer 

flow. However, for most of the study area, the upper 

confining unit transmits, or leaks, water downward 

from the surficial aquifer into the intermediate aquifer 

system, and the system is referred to as a leaky-aquifer 

system (Wilson, 1977). Water is also transmitted 

upward through the upper confining unit into the surficial aquifer and the Peace River in areas where upward 

head gradients exist. 

The water-bearing units of the intermediate 

aquifer system consist of limestone and dolomite. Clay 

beds of wide lateral extent and variable thickness may 

occur interbedded within these water-bearing units 

(Duerr and Enos, 1991). Transmissivities of the waterbearing units of the intermediate aquifer system, 

reported from aquifer tests, range from less than 100 to 

13,000 ft2

 /d (Ryder, 1982). The wide range of transmissivity values for the intermediate aquifer system 

indicates formational heterogeneity that is substantiated by geophysical logs (Hutchinson, 1978). The area 

of highest transmissivity coincides with areas adjacent 

to the Peace River. This high transmissivity indicates a 

more active flow system exists where ground water 

moves upward into the river and enhances development of secondary porosity in the carbonate rock 

(Ryder, 1985). Thickness of the intermediate aquifer 

system ranges from less than 100 ft in central Hillsborough and northern Polk Counties to more than 800 ft 

in southern Charlotte County (Duerr and others, 

1988). 

A lower confining unit lies at the base of the 

intermediate aquifer system and to some extent 

hydraulically separates the intermediate aquifer system from the Upper Floridan aquifer. The lower confining unit has a low vertical hydraulic conductivity 

and consequently retards interaquifer flow. However, 

for most of the study area, the lower confining unit 

transmits, or leaks, water downward from the intermediate aquifer system into the Upper Floridan aquifer, 

and the system is referred to as a leaky-aquifer system 

(Wilson, 1977). Water is also transmitted upward from 

the Upper Floridan aquifer through the lower confining unit to the intermediate aquifer system where 

upward head gradients exist. 

The intermediate aquifer system is used extensively as a source of water for irrigation and public 

and domestic supply. Wells open to the intermediate 

aquifer system generally yield less than 300 gal/min 

(Wilson, 1977). The yield to wells and total withdrawals of water from the intermediate aquifer system are 

greater than those of the surficial aquifer, but are much 

less than those of the deeper Upper Floridan aquifer. 

Floridan Aquifer System

The Floridan aquifer system, as defined by 

Miller (1986, p. 44), is a vertically continuous 

sequence of carbonate rocks of generally high permeability that are mostly of Tertiary age. The rocks are 

hydraulically connected in varying degrees, and their 

permeability generally is an order to several orders of 

magnitude greater than that of the rocks bounding the 

system above and below. In the study area, the Floridan aquifer system consists of two aquifers: the Upper 

Floridan aquifer which contains freshwater and the 

Lower Floridan aquifer which contains highly mineralized water. The Upper and Lower Floridan aquifers 

are separated by the middle confining unit (Miller, 

1986). The Upper Floridan aquifer commonly consists 

of a few highly permeable zones separated by less permeable zones (Johnston and Bush, 1988).

The top of the Upper Floridan aquifer is the 

horizon below which carbonate rocks persistently 

occur. The middle confining unit, which is the base of 

the Upper Floridan aquifer, is characterized by limestone and dolomite that have reduced permeability as a 

result of vertically persistent, intergranular evaporites 

(Southeastern Geological Society, 1986). The rocks 

below the middle confining unit have known or estimated low transmissivity; therefore, freshwater flow is 

limited to rocks above the section with intergranular 

evaporites (Ryder, 1985). This report is limited to 

ground-water flow in the freshwater part of the Floridan aquifer system, or the Upper Floridan aquifer. 

The Upper Floridan aquifer consists of the 

Suwannee Limestone, the Ocala Limestone, and the 

Avon Park Formation of the Oligocene and Eocene 

series (fig. 2). Thickness of the Upper Floridan aquifer 

ranges from approximately 1,000 ft in northern Polk 

County to 1,200 ft in Charlotte and De Soto Counties. 

The Upper Floridan aquifer consists of limestone and 

dolomite that have solution-enlarged fractures. These 

fractures commonly yield abundant supplies of water 

to wells. The most productive part of the aquifer generally corresponds to dolomite sequences within the 

Avon Park Formation. Transmissivity of the Upper 

Floridan aquifer ranges from about 30,000 ft2

/d at the 

Gulf Coast to about 850,000 ft2/d in northeastern De 

Soto County (Ryder, 1985).
Factors Influencing Vertical Borehole Flow 7

The Upper Floridan aquifer is the most productive and widely used aquifer in the study area and supplies more than 10 times the amount of water pumped 

from either the surficial aquifer or the intermediate 

aquifer system. Thousands of wells have been drilled 

into this highly productive aquifer, and it is estimated 

that about 10 percent of these wells are open solely to 

the Upper Floridan aquifer. In the study area, most 

wells completed in the Upper Floridan aquifer are also 

open to the intermediate aquifer system (Metz, 1995).

The Upper Floridan aquifer is used extensively 

as a source of water for industrial, irrigation, public, 

and domestic supply and wells can yield as much as 

5,000 gal/min (SWFWMD, 1994). However, the significance of the Upper Floridan aquifer as a source of 

potable water diminishes as the water quality degrades 

in the southern and western parts of the study area. In 

these areas, the importance of the intermediate aquifer 

system as a source of water increases (Duerr and others, 1988). The term poor-quality water is used in this 

report to indicate water having concentrations of chloride, sulfate, and dissolved solids that exceed 250, 

250, and 1,000 mg/L, respectively. 

FACTORS INFLUENCING VERTICAL 

BOREHOLE FLOW

Vertical flow in an open borehole of a well is 

influenced by well construction, the relative permeabilities of the aquifers, and the head differences between 

aquifers open to the borehole (Keys and MacCary, 

1971). When a well is drilled into an aquifer, the open 

borehole serves as a local conduit in the aquifer matrix. 

Open boreholes may not affect regional flow, but the 

borehole represents a substantial local heterogeneity in 

the immediate flow field (Paillet and others, 1994).

Improperly constructed and corroded wells may 

serve as a source of water-quality contamination 

within the aquifers. A schematic diagram of a properly 

constructed well that is open to a single aquifer and a 

corroded well and an improperly constructed well that 

are open to multiple aquifers is presented in figure 3. 

Where heads in the Upper Floridian aquifer are higher 

than heads in the intermediate aquifer system, highly 

mineralized water may flow upward from the Upper 

Floridan aquifer into the intermediate aquifer system. 

Where heads in the intermediate aquifer system are 

higher than heads in the Upper Floridan aquifer, downward flow may occur through the open borehole 

resulting in a loss of potable water to the aquifer 

below.

The length of the casing in relation to the total 

depth of the well is important in controlling the quantity of water flowing internally. The well casing prevents the borehole from collapsing in unstable 

lithologies and limits aquifer connectivity, thus preventing interaquifer flow. Because potable water usually is available in the intermediate aquifer system, 

most wells that penetrate the more productive Upper 

Floridan aquifer are constructed so that they also are 

open to the intermediate aquifer system. Sproul and 

others (1972, p.10) reported that the internal flow 

within uncased parts of wells open to multiple aquifers 

ranges from about 30 to nearly 100 gal/min in the 

McGregor Isles area in Lee County. 

The head gradient between the aquifers significantly controls the potential for vertical borehole flow 

in wells open to multiple aquifers. Head difference 

information used in this study was obtained from 

potentiometric-surface maps of the intermediate aquifer system and Upper Floridan aquifer. The potentiometric surfaces of the intermediate aquifer system and 

Upper Floridan aquifer in west-central Florida are 

mapped semiannually by the USGS, in cooperation 

with the SWFWMD, during periods when water levels 

are at their highest (September) and lowest (May). 

These maps show potentiometric contours based on 

synoptic measurements of water levels in hundreds of 

wells open to either the intermediate aquifer system or 

the Upper Floridan aquifer. The ARC/INFO GIS system was used as an aid in the construction of the head 

difference maps. GIS coverages were generated from 

digitized potentiometric-surface contour lines. These 

coverages were intersected with a 1-mi by 1-mi grid 

and head values were assigned to each cell by interpolation methods. Head difference maps were generated 

by subtracting the interpolated head values in the 

Upper Floridan aquifer from those in the intermediate 

aquifer system. Contours lines were drawn based on 

equal head difference values.

The head differences between the intermediate 

aquifer system and the Upper Floridan aquifer in September 1993 (Mularoni, 1994 a,b; fig 4) represent conditions at the end of the summer rainy season at a time 

when the aquifers generally are unstressed by irrigation pumpage. In September 1993, heads in the intermediate aquifer system were as much as 70 ft higher 

than heads in the Upper Floridan aquifer near the 

corner of Hillsborough, Manatee, Polk, and Hardee 

Counties. Water is transmitted downward through the 

confining unit and recharges the Upper Floridan 
8 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

PROPERLY

CONTRUCTED

CASING

CASING

SURFICIAL

AQUIFER

OPEN

BOREHOLE

LOWER

CONFINING

UNIT

CORRODED

CASING

CEMENT

GROUT

IMPROPERLY

CASED WELL

INTERMEDIATE

AQUIFER

SYSTEM

CORRODED

WELL WITH

WELL

QUALITY

POORWATER

UPPER

FLORIDIAN

AQUIFER

UPPER

CONFINING

UNIT

OPEN

BOREHOLE

Figure 3. A properly constructed well open to a single aquifer, and a corroded well and an improperly 

constructed well that can allow water quality contamination between multiple aquifers.
Factors Influencing Vertical Borehole Flow 9

Figure 4. Generalized head difference between the intermediate aquifer system and the Upper Floridan aquifer, 

September 1993 (from Mularoni, 1994a,b).

DOWNWARD HEAD GRADIENT

UPWARD HEAD GRADIENT

aquifer system and the Upper Floridan aquifer. Contour

interval 10 feet

LINE OF EQUAL HEAD DIFFERENCE VALUE--Shows 

generalized head difference between the intermediate 

20

0

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Charlotte Harbor

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

40

30

20

10

20

10

30

40

50

60

-10

-10

-20

-20

70

0

0
10 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

aquifer. The head gradient reverses in the southern part 

of the study area where the Upper Floridan aquifer has 

higher heads than those of the intermediate aquifer 

system by as much as 20 ft in western Sarasota County 

and central Charlotte County. In these areas, water is 

transmitted upward through the lower confining unit 

and discharges to the intermediate aquifer system. 

The head differences between the intermediate 

aquifer system and the Upper Floridan aquifer in May 

1994 (Metz and Brendle, 1994 a,b; fig. 5) represent 

conditions near the end of a dry season during which 

extensive irrigation pumpage has occurred. In May 

1994, heads in the intermediate aquifer system were as 

much as 90 ft higher than heads in the Upper Floridan 

aquifer near the corner of Hillsborough, Manatee, 

Polk, and Hardee Counties. These greater head differences are due to large seasonal ground-water withdrawals for irrigation from the Upper Floridan aquifer. 

In the southern part of the study area, heads were 

higher in the Upper Floridan aquifer than the intermediate aquifer system by as much as 20 ft. 

METHODOLOGY AND 

INSTRUMENTATION

A well inventory was conducted to locate wells 

that had a short length of casing; were open to both the 

intermediate aquifer system and the Upper Floridan 

aquifer; and were accessible for the collection of borehole geophysical data. Several hundred wells were 

inventoried to locate wells that met the necessary casing, depth, and accessibility criteria.

The determination of interaquifer flow was 

accomplished by obtaining geophysical logs of caliper, 

gamma, temperature, flow, and fluid conductivity, and 

by the collection of water-quality samples and video 

borehole data. This information provided an understanding of the well construction, contacts between 

hydrogeologic units, zones of inflow and outflow, 

rates of interaquifer flow, chemical properties of water 

in the borehole, and locations of fractures and cavities. 

Three different flowmeters were used to determine interaquifer flow because of the sensitivity and 

limitations of each meter. The three meters were: an 

impeller flowmeter, a borehole video camera with an 

impeller flowmeter attachment, and a heat-pulse 

flowmeter. 

In the initial survey of each well, flow measurements were made using an impeller flowmeter. The 

impeller flowmeter consists of a helical turbine, or 

rotor, that is mounted on a vertical axis in a metal 

cylinder (fig. 6). Measurements were made in a fixed 

position at selected depth intervals in the open borehole and were repeated at these intervals to verify 

readings when internal flow was detected. To obtain 

flowmeter measurements under static conditions in 

artesian flowing wells, the flow was shut off using a 

standpipe or a well capping device.

To calibrate the impeller flowmeter, the instrument was raised and then lowered at a controlled 

speed in the cased part of a well with no internal flow. 

Flowmeter responses were plotted against logging 

speeds to obtain a velocity calibration curve. This calibration method was performed in 4-, 5-, 6-, 8-, 10-, 

and 12-in. diameter wells. Internal flow volume was 

calculated using the relation of cross-sectional area 

and measured borehole velocity. To account for irregular borehole diameters as indicated by caliper logs, all 

reported internal flow values were obtained from calibrated diameters. 

The advantage of utilizing the impeller flowmeter is that high velocities can be recorded with this 

instrument. The limitations of the impeller flowmeter 

are that the direction of flow (either upward or downward) can not be distinguished accurately, and that the 

lower detection limit of the meter is about 5 ft/min. 

Additional geophysical-logging information on instrumentation, calibration, and standardization, is documented by Keys (1990).

In areas where upward and downward flow 

could not be distinguished, the impeller flowmeter was 

connected to a video camera. This design enabled the 

viewer to observe the direction of rotation of the 

impeller assembly hanging approximately 20 in. 

below the borehole video camera. The impeller blade 

turning clockwise indicated downward flow and counterclockwise indicated upward flow. A view of a borehole with the impeller flowmeter attachment is shown 

in figure 7. The advantages of this design are

that the viewer can: (1) observe a continuous profile of 

the well borehole and the direction of flow; (2) locate 

fractures or cavities that may be associated with 

ground water flow to wells; and (3) inspect the casing 

for holes or breaks. The lower detection limit of this 

instrument is also 5 ft/min.
Factors Influencing Vertical Borehole Flow 11

Figure 5. Generalized head difference between the intermediate aquifer system and the Upper Floridan aquifer, May 

1994 (from Metz and Brendle 1994 a,b).

EXPLANATION

DOWNWARD HEAD GRADIENT

UPWARD HEAD GRADIENT

aquifer system and the Upper Floridan aquifer. Contour

interval 10 feet

LINE OF EQUAL HEAD DIFFERENCE VALUE--Shows 

generalized head difference between the intermediate 

20

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′ 28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

10 20 30

40

50

60

70

80

90

20

30 40

50

0

0

10

-10

-20

-20

-10

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

0 5 10 15 MILES

0 5 10 15 KILOMETERS
12 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

To determine flow below the detection limit of 

the impeller flowmeter, the USGS heat-pulse flowmeter developed by Hess (1990) was used. Measurable 

fluid velocities for the heat-pulse flowmeter range 

from about 0.1 to 20 ft/min. Rate and direction of vertical flow, was determined with this flowmeter. Resolution of flow direction was accomplished by using 

two temperature sensors, one above and one below a 

heater grid (fig. 8). When the heater grid received an 

electronic pulse, a parcel of water was heated. If there 

was internal flow in the borehole, either the lower or 

upper temperature sensor detected the heated water. 

Flow concentrating divertors were utilized to direct 

fluid flowing in the borehole through the flow sensor 

tube. The limitation of this meter is that it can not measure fluid velocity above 20 ft/min. 

Water samples were collected from the borehole 

to delineate differences in ground-water quality from 

specific contributing zones in wells that had internal 

flow. A thief sampler connected to the geophysical 

logger was used to collect the discrete samples from 

the specific contributing zones. Water quality constituents analyzed from these samples included chloride, 

sulfate, and dissolved solids.

RESULTS AND INTREPRETATION OF 

GEOPHYSICAL WELL DATA

Borehole geophysical surveys were conducted 

in 87 wells to assess the rate and direction of interaquifer borehole flow in wells open to multiple permeable 

zones. Well records with geophysical logs that were 

obtained in each well are listed in table 1. Location of 

wells with corresponding index number from table 1 

are shown in figure 9. The measured wells consisted of 

irrigation, municipal, recreational, industrial, and temporary observation wells with depths and casing 

lengths ranging from 335 to 1,679 ft and 16 to 454 ft, 

respectively. The following sections of this report 

describe composite geophysical logs of temperature, 

gamma ray, caliper, fluid conductivity, and flow of 

selected wells that characterize the nature of interaquifer borehole flow.

Figure 6. The components of the impeller 

flowmeter.

END CAP

END CAP

4-INCH ALLUMINUM

 PIPE HOUSING

HELICAL IMPELLER 

IMPELLER PIVOT

CONTACT CHAMBER

CONTACT WIRE

SINGLE CONDUCTOR CABLE

 ATTACHMENT POINT
Results and Intrepretation of Geophysical Well Data 13

Figure 7. A borehole video camera with the impeller flowmeter attachment in a 12-inch open borehole 

at a depth of 479 feet below land surface.

ENLARGED OPEN BOREHOLE

IMPELLER FLOWMETER

12-INCH OPEN BOREHOLE
14 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Figure 8. The components of the heat-pulse flowmeter (modified from Hess, 1990).

6-CONDUCTOR CABLE TO

SURFACE EQUIPMENT

ELECTRONICS

SECTION

DOWNWARD FLOW

RUBBER FLOW

DIVERTER

FLOW SENSOR

TUBE

HEATER

GRID

PLAN VIEW

PLAN VIEW

SIDE VIEW

FLOW SENSOR

TUBE

HEATER GRID

THERMISTOR, HEATPULSE SENSOR

UPPER THERMISTOR,

HEAT-PULSE SENSOR

LOWER THERMISTOR,

HEAT-PULSE SENSOR
Results and Intrepretation of Geophysical Well Data 15

Table 1. Selected data for measured wells

[Data type: C, caliper; G, gamma; K, fluid-conductivity; T, temperature; E, electric; FS, impeller flowmeter survey; V, video; VFS, video 

flowmeter survey] Di, diameter of well in inches

Index

no. Site name Latitudelongitude

Depth 

(feet) 

below 

land 

surface 

Casing 

(feet)

Di

Date of 

measurementDate type

Impeller flow 

rate, gallons 

per minute

 1 ROMP TR3-3 Ocala 265531 821948 1,066 120 8 02-25-86 FS 45

 2 Venetia (Berry 9) 270153 822126 620 224 6 06-27-87 FS 11

 3 Venetia (Berry 4) 270203 822137 608 207 6 06-27-87 FS 10

 4 Sorrenta Shores 270932 822835 669 308 6 06-27-87 FS 30

 5 4-Star Tomato Packing 273121 823217 543 200 4 04-07-92 C, G, T, FS 0

 6 Dave Lewis 273214 822896 570 16 8 04-07-92 C, G, T, E, FS 0

 7 Bobby Jones No. 3 272039 822918 574 38 10 04-09-92 C, G, K, FS, V 0

 8 Oscar Scherer State Park 271032 822745 728 294 8 04-10-92 C, G, K, T, FS, 0

 9 ROMP 20 271138 822846 843 73 12 04-14-92 C, G, K, T, E, FS 110

10 Norris Brothers 270535 815745 534 74 6 04-17-92 C, G, T, FS 31

11 Verna P2 272248 821903 604 140 10 04-30-92 C, K, K, T, FS, 58

12 Griffin Deep near Parrish 273536 822603 576 43 8 05-01-92 C, G, K, T, E, FS 0

13 City of Sarasota: Boat Ramp 272052 823254 603 196 6 05-06-92 C, G, K, T, E, FS 0

14 Tropical River Groves: 14 271416 813746 1,492 193 12 05-07-92 C, G, K, FS 0

15 Marshall Deep 272010 814825 437 134 5 06-05-92 C, G, K, T, E, FS 0

16 Pioneer Park 273006 814800 611 315 8 06-08-92 C, G, T, E, FS 0

17 Florida Power and Light 273718 823155 930 104 12 06-10-92 C, G, K, T, E, FS 0

18 ROMP 57 275411 813720 581 160 6 06-11-92 C, G, T, E, FS 0

19 Smith 273103 813637 849 66 5 06-18-92 C, G, K, T, E, FS 0

20 ROMP 123 274031 821504 620 117 8 07-29-92 C, G, K, T, FS 0

21 Walker Farms 271931 822608 668 238 6 08-03-92 C, T, E, FS 0

22 City of Sarasota, Hickory St. 272129 823302 599 46 6 08-04-92 C, K, T, FS, V 300

23 City of Sarasota, 21st St. 272120 823227 548 327 4 08-06-92 C, G, K, T, E, FS 0

24 Busby Deep 273605 820711 996 153 12 08-13-92 C, G, K, T, E, FS, VFS 0

25 Stephens Deep 272442 820152 730 146 10 08-21-92 C, G, T, FS 0

26 Rusty Pot No. 2 271646 821122 1,017 148 10 08-26-92 C, G, T, FS 0

27 Rushing 270633 822204 371 33 6 08-31-92 C, T, FS 0

28 Rusty Pot No. 1 271713 821230 409 83 8 09-03-92 C, FS 0
16 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

29 Schroeder Manatee Ranch No. 44 272338 822127 562 118 12 09-03-92 C, G, K, T, FS 0

30 Kitchen Fish Farm No. 2 270559 815046 570 87 8 09-08-92 C, G, T, FS 0

31 Kitchen Fish Farm No. 1 270559 815101 591 88 8 09-08-92 C, FS 0

32 Schroeder Manatee Ranch No. 26 272525 822328 1,225 82 12 09-09-92 C, G, T, FS 0

33 Schroeder Manatee Ranch No. 38 272255 822349 1,276 454 8 09-10-92 C, G, T, FS 0

34 2X4 Ranch No. 1 270808 814647 545 158 10 09-21-92 C, FS 0

35 2X4 Ranch No. 3 270943 814546 1,679 126 12 09-21-92 C, G, T, FS 0

36 Schroeder Manatee Ranch No. 8 272651 822625 703 64 8 09-22-92 C, G, K, T, FS 0

37 Big Hog 272040 823258 555 90 12 09-30-92 C, G, K, T, FS 0

38 City of Sarasota: Alameda No. 2 272113 823302 537 306 8 10-05-92 C, G, K, T, FS 0

39 Phillipi Estates Park 271613 823201 611 243 5 10-16-92 C, G, K, FS 0

40 Florida State Fish pond No. 2 265615 815435 622 136 10 10-15-92 C, G, K, T, E, FS 0

41 Utopia No. 1 271952 822056 1,260 45 12 10-23-92 C, G, K, T, FS, 180

42 ROMP 43X 273615 812849 1,005 398 8 10-29-92 C, G, K, T, VFS 0

43 Powell Deep 274813 822236 335 26 6 11-18-87 C, G, K, T, E, FS 0

44 Hi Hat No. 12 271731 821849 494 117 12 11-16-92 C, G, T, FS 0

45 Jaceranda Blvd. 270002 822205 494 64 6 11-18-92 C, T, FS 0

46 Sunrise Golf Course 271530 822728 453 127 8 04-25-84 C, G, K, T, E, FS, VFS 0

47 Manatee County Duette 273303 820641 1,184 184 12 12-02-92 C, G, K, T, FS 140

48 Verna Production No. 8 272256 821837 611 140 10 12-04-92 C, K, T, FS 0

49 Trey’s 270429 815644 498 78 6 12-08-92 C, G, K, T, FS 0

50 Kibler Deep 272838 821422 1,129 208 8 12-09-92 C, G, K, T, FS 0

51 Babcock 265316 814334 917 114 4 12-17-92 C, G, K, T, FS 58

52 City of Winter Haven 280356 814454 1,000 87 12 12-17-92 VFS 0

53 E&D Cattleranch 272014 815071 1,110 104 12 12-21-92 C, G, K, T, VFS 0

54 Machata 275510 812768 832 199 12 12-22-92 C, G, T, K, FS 0

55 ELAP 274114 823037 475 29 8 12-23-92 C, G, T, K, FS 0

56 Parrish Grove 273459 822532 583 102 6 12-28-92 C, G, T, K, FS, VFS 0

57 Cargill Phosphate 275859 815129 954 204 20 12-29-92 C, G, T, VFS 0

58 Verna T 0-4 272020 821948 500 140 6 02-09-93 C, G, T, K, FS 0

Table 1. Selected data for measured wells --Continued

[Data type: C, caliper; G, gamma; K, fluid-conductivity; T, temperature; E, electric; FS, impeller flowmeter survey; V, video; VFS, video 

flowmeter survey] Di, diameter of well in inches

Index

no. Site name Latitudelongitude

Depth 

(feet) 

below 

land 

surface 

Casing 

(feet)

Di

Date of 

measurementDate type

Impeller flow 

rate, gallons 

per minute
Results and Intrepretation of Geophysical Well Data 17

59 Amax Deep No. 3 271538 820023 1,547 340 8 02-18-93 C, G, T, FS 0

60 Mc Cormmick Grove 271721 815220 1,004 420 12 03-03-93 C, G, T, FS 0

61 Hudson Farms 270046 815541 1,256 368 12 03-26-93 C, G, T, K, FS 0

62 Verna P-11 272248 821808 550 141 8 04-12-93 C, G, T, K, FS 0

63 City of Sarasota 11th and Oregon 272049 823244 479 43 6 04-14-88 C, G, T, K, FS 0

64 Verna Production No. 23 272247 821702 492 192 10 04-19-93 C, T, K, E, FS 0

65 ROMP 9 270432 820857 760 117 6 04-27-93 C, G, T, K, FS 50

66 City of Sarasota Corehole No.1 272042 823223 1,102 355 4 05-21-93 C, G, T, K, E, FS, V 43

67 Verna Production No. 1 272305 821903 592 136 10 05-26-93 C, G, T, K, FS 0

68 Verna Production No. 5 272248 821846 589 142 10 05-26-93 C, G, T, K, FS 0

69 Brewer 270936 815237 532 74 8 06-17-93 C, G, T, K, FS 0

70 V.C. Hollingsworth 271339 815920 603 63 8 06-29-93 C, G, T, K, FS 0

71 ROMP 5 (temporary well) 265643 814835 1,000 124 6 12-02-93 C, G, T, K, FS 60

72 Ansin 265643 815500 766 108 4 02-14-94 C, G, T, K, FS 16

73 Verna P-20 272248 821719 520 142 10 02-15-94 C, G, T, K, FS 0

74 Verna KME-02 272301 821914 833 350 16 02-15-94 C, G, T, K, FS 0

75 DEP No. 8 274812 814846 610 121 6 02-25-94 C, G, T, FS 0

76 ROMP 7-2 272612 823301 706 336 12 03-18-94 C, G, T, K, FS 0

77 Fisheating Creek Dairy 270237 812721 1,602 230 16 05-02-94 C, T, FS 0

78 Reeder 273850 823135 600 206 8 05-05-94 C, G, T, FS 0

79 General Development No. 8 270554 820038 1,137 269 15 06-01-94 C, G, T, K, FS 0

80 General Development No. 10 270609 820104 1,070 62 8 06-01-94 C, G, T, K, FS 0

81 Boggess No. 19 270454 820157 716 84 10 06-02-94 C, G, T, K, FS 0

82 CF Industries UF-4 273453 820103 389 101 8 07-11-94 C, G, T, K, FS 0

83 Da Costa 265830 815655 928 178 5 09-21-94 C, G, T, FS 0

84 Port Manatee Authority 273753 823241 590 209 6 11-09-94 C, G, T, FS 0

85 Sarasota Co.Stormwater Util. 272016 822606 726 82 8 10-24-94 C, G, T, K, FS 0

86 Verna Production No. 35 272218 821527 600 142 10 01-26-95 C, G, T, K, FS 50

87 ROMP TR-SA-1 272049 823245 1,208 98 10 04-21-95 C, G, T, K, FS 139

Table 1. Selected data for measured wells --Continued

[Data type: C, caliper; G, gamma; K, fluid-conductivity; T, temperature; E, electric; FS, impeller flowmeter survey; V, video; VFS, video 

flowmeter survey] Di, diameter of well in inches

Index

no. Site name Latitudelongitude

Depth 

(feet) 

below 

land 

surface 

Casing 

(feet)

Di

Date of 

measurementDate type

Impeller flow 

rate, gallons 

per minute
18 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

11

48

62

64 67

68 73

74

MANATEE

SARASOTA

1

2 3

4

5

6

7

8

9

10

12

14

15

16

17

18

19

20

21

24

25

26

27

28

29

30

31

32

33

34

35

36

39

40

41

42

43

44

45

46

47

49

50

51

52

53

54

55

56

57

58

59 60

61

65

69

71

72

75

76

77

78

79 80

81

82

83

84

85

86

13

22 23

37

38

63 66

87

Sarasota

53 WELL LOCATION AND NUMBER--Number referenced in table 1

70

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′ 28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Harbor

Charlotte 

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee River River

Figure 9. Locations of wells measured using various geophysical logging techniques.
Results and Intrepretation of Geophysical Well Data 19

Impeller Flowmeter Well Log Analysis

All 87 wells were measured with the impeller 

flowmeter; 17 (20 percent) of these wells had internal 

flow that was detectable with this meter. Internal flow 

rates ranged from 10 to 300 gal/min (fig. 10). Distinct 

patterns in areal distribution of internal flow were not 

observed. It was not unusual to find a well that was 

flowing internally and another well in close proximity 

in which no internal flow was detected. Variations in 

internal flow rates could be attributed to differences in 

well construction, relative permeabilities of hydrogeologic units open to the wells, and head differences in 

the aquifer open to the wells. 

Examples of wells in Sarasota County in which 

internal flow was controlled by well construction were 

the Regional Observation and Monitor Well Program 

(ROMP) 20 well and Oscar Scherer State Park well 

(fig 9. and table 1). ROMP 20 was a temporary flowing monitor well, that had 73 ft of casing and a total 

depth of 843 ft. A composite geophysical log for 

ROMP 20 (fig. 11) shows the effects of a short cased 

well open to multiple producing zones. Analysis of the 

gamma log suggests that the hydrologic contact 

between the intermediate aquifer system and the 

Upper Floridan aquifer occurs where gamma-ray 

activity subsides at approximately 500 ft. The temperature log indicates mixing of slightly warmer water 

with cooler water at the formation contact that suggests an inflow point. The temperature remains nearly 

constant as the water moves up the borehole. Fluid 

conductivities are highest at the bottom of the well, 

and as the mineralized water moves up the borehole, it 

mixes with the fresher water in the zones above. The 

flow log indicates upward borehole flow, and the 

inflow appears to be from a producing zone located 

near the formation contact. The flow continues up the 

borehole until the water exits a large cavity at approximately 80 ft. The internal flow rate was measured at 

approximately 80 gal/min in a 10-in. diameter section 

of the well. This composite log analysis is typical of 

wells that have a short length of casing, are open to 

multiple producing zones, and have an upward component of borehole flow. 

A composite geophysical log for a well that has 

a relatively long length of casing is shown in figure 12. 

The Oscar Scherer State Park well is 2 mi south of 

ROMP 20. Well information is listed in table 1 and the 

well location is shown in figure 9. The well is 728 ft 

deep and has 294 ft of casing. The head differences, 

water chemistry, and aquifer characteristics are similar 

to ROMP 20 but the Oscar Scherer State Park well is 

cased to a deeper depth. The composite geophysical 

log indicates that the casing length of 294 feet limited 

the aquifer connectivity; consequently, no internal 

flow was detected using the impeller flowmeter. Casing beyond the upper permeable zones prevented 

highly mineralized water from entering these zones. 

The heat-pulse flowmeter data is discussed in a later 

section of this report.

For several wells that had internal flow, the flow 

rates were determined to be affected by the head differences between the aquifers. Internal borehole flow 

controlled by head differences is illustrated by composite geophysical logs shown in figures 13, 14 and 

15. Utopia No. 1 well is in northern Sarasota County 

and is 1,260 ft deep with 45 ft of casing (fig. 13). Well 

information is listed in table 1 and the well location is 

shown in figure 9. The gamma log indicates that the 

contact between the intermediate aquifer system and 

the Upper Floridan aquifer is at approximately 450 ft. 

The temperature and fluid conductivity logs indicate 

mixing at approximately 100, 200, 450, and 890 ft; 

these inflections in the log may represent hydrologic 

contacts or water exiting or entering the borehole. 

Downward flow was detected below a depth of 200 ft 

in the intermediate aquifer system at a rate of approximately 75 gal/min in a 12-in. diameter section of the 

borehole. The flow was observed to continue downward to the bottom of the hole. This flow direction was 

verified using a video camera with the impeller flowmeter attachment (fig. 7).

Seasonal flowmeter measurements were made 

in Utopia No. 1 well, from October 1992 through 

October 1994, using the impeller flowmeter to determine the effects that head differences had on internal 

flow rates (figs. 14 and 15). It was observed that the 

flow rates increased and decreased in response to head 

differences between the intermediate aquifer system 

and the Upper Floridan aquifer. For example, as 

shown in figure 14, the flow rates and an accompanying hydrograph indicate that when an approximate 

10 ft head gradient exists between the aquifers, as in 

May, the flow rates increased to 150 gal/min in a 

12-in. diameter section of the borehole. Lowering the 

head in the Upper Floridan aquifer, as a result of 

ground-water development, increased head differences 

between the two aquifers and increased the downward 

flow rate. Conversely, when the aquifers are 

unstressed by irrigation, water levels rebound, such as 

occurs during the summer months, and the head
20 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

MAXIMUM RECORDED 

MAXIMUM RECORDED 

DOWNWARD FLOW 

UPWARD FLOW 

EXPLANATION

0 5 10 15

0 5 10 15 KILOMETERS

MILES

58

50

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

50

180

58

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′

28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

110

31

58

140

45

11

10

30

50

60

43

139

300

16 Englewood

Charlotte Harbor

RATE--in gallons per minute

RATE--in gallons per minute

Figure 10. Locations of wells in which internal flow was detected using the impeller flowmeter and the maximum 

recorded borehole flow in gallons per minute.
Results and Intrepretation of Geophysical Well Data 21

Figure 11. Composite geophysical log for ROMP 20 well in Sarasota County. 1,000 2,000 3,000 4,000 5,000 6,000 7,000

FLUID-CONDUCTIVITY,

DEPTH, IN FEET BELOW LAND SURFACE 

0 10 20

CALIPER DIAMETER,

27 32

TEMPERATURE,

0 200 400 600

GAMMA RAYS,

0 100 200

BOREHOLE FLOW,

0

5 15 28 29 30 31

IN MICROSIEMENS IN INCHES IN DEGREES CELSIUS IN COUNTS PER

SECOND

UPWARD

FLOW AND

MEASUREMENT

DEPTH OF

IN GALLONS PER MINUTE

PER CENTIMETER

AT 25 DEGREES

CELSIUS

100

200

300

400

500

600

700

800

900

 0
22 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

100

200

300

400

500

600

700

800

FLUID-CONDUCTIVITY,

DEPTH, IN FEET BELOW LAND SURFACE 

CALIPER DIAMETER,

22 26 30

TEMPERATURE, GAMMA RAYS,

02 5

BOREHOLE FLOW,

IN MICROSIEMENS IN INCHES IN DEGREES CELSIUS IN COUNTS PER

SECOND

UPWARD

FLOW AND

MEASUREMENT

DEPTH OF

WITH

HEAT-PULSE

FLOWMETER

DEPTH OF

MEASUREMENT

WITH IMPELLER

FLOWMETER

1 3 4

IN GALLONS PER MINUTE

 0

PER CENTIMETER

 AT 25 DEGREES

 CELSIUS

0 10 20 5 15

1,0002,0003,0004,0005,0006,0007,000

0

0 200 400 600

Figure 12. Composite geophysical log for Oscar Sherer State Park well in Sarasota County.
Results and Intrepretation of Geophysical Well Data 23

700

800900

1,000

1,100

1,2001,3001,400

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

DEPTH, IN FEET BELOW LAND SURFACE 

0 4 8 12 16 20 24

CALIPER DIAMETER,

IN INCHES

25 26 27

TEMPERATURE, 

IN DEGREES CELSIUS

0 200 400 600

GAMMA RAYS,

IN COUNTS PER

0 100 200

BOREHOLE FLOW,

SECOND IN GALLONS PER MINUTE

DOWNWARD

FLOW AND

MEASUREMENT

DEPTH OF

 0

FLUID-CONDUCTIVITY,

IN MICROSIEMENS

PER CENTIMETER

 AT 25 DEGREES

 CELSIUS

Figure 13. Composite geophysical log for Utopia No. 1 well in Sarasota County.
24 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

DEPTH, IN FEET BELOW LAND SURFACE 

0 100 200

DOWNWARD BOREHOLE FLOW, IN GALLONS PER MINUTE

OCT. 23, 1992 FEB. 12, 1993 MAR. 25, 1993 MAY 12, 1993 JUNE 10, 1993

0 100 200 0 100 200 0 100 200 0 100 200 0 100 200

JULY 27, 1993

0 100 200 0 100 200

AUG. 30, 1993 OCT. 19, 1993

10

30

0

10

20

WATER LEVEL IN FEET ABOVE

1992 1993

AND BELOW SEA LEVEL

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY. JUNE JULY AUG. SEPT. OCT.

INTERMEDIATE AQUIFER SYSTEM

UPPER FLORIDAN AQUIFER

 0

SEA

LEVEL

DEPTH OF

MEASUREMENT

Figure 14. Seasonal flow measurements for Utopia No. 1 well in Sarasota County and hydrographs of the 

intermediate aquifer system and the Upper Floridan aquifer, October 1992 through October 1993.
Results and Intrepretation of Geophysical Well Data 25

JAN. FEB. MAR. MAY JUNE AUG. SEPT.

0 100 200 0 100 200 0 100 200

DEPTH, IN FEET BELOW LAND SURFACE 

DEC. 16, 1993 MAR. 3, 1994 APRIL 15, 1994 MAY 13, 1994

0 100 200 0 100 200

JUNE 20, 1994 JULY 29, 1994

0 100 200 0 100 200

AUG. 30, 1994

0 100 200

OCT. 21, 1994

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

NOV. DEC. OCT.

10

30

0

10

20

1993 1994

WATER LEVEL IN FEET ABOVE

AND BELOW SEA LEVEL

APR. JULY

INTERMEDIATE AQUIFER SYSTEM

UPPER FLORIDAN AQUIFER

 0

SEA

LEVEL

DOWNWARD BOREHOLE FLOW, IN GALLONS PER MINUTE

DEPTH OF

MEASUREMENT

Figure 15. Seasonal flow measurements for Utopia No. 1 well in Sarasota County and hydrographs of the 

intermediate aquifer system and the Upper Floridan aquifer, November 1993 through October 1994.
26 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

difference is minimal between the Upper Floridan 

aquifer and the intermediate aquifer system. For example, as shown in figure 15, the flow rates and an 

accompanying hydrograph indicate that, when an 

approximate 2 ft head gradient exists between the 

aquifers as in late June, internal flow was not detected 

with the impeller flowmeter. 

In addition to seasonal changes in flow rates, 

shallow and deep producing zones were also affected 

by the head gradient fluctuations. For example, in 

October 1992, between 46 and 190 ft, no flow was 

detected in the upper producing zones (fig. 14). In subsequent flow measurements, evidence of detectable 

flow occurs at varying depths. These variations in flow 

rates can be attributed to changes in head gradients 

between producing zones. When the shallower producing zones were in equilibrium with lower producing zones, as in July 1993, no internal flow occurred. 

When shallower producing zones were not in equilibrium with lower producing zones, as in May 1993, 

internal flow occurred to compensate for the head differences. Internal flow in May 1993 also occurred at a 

shallower depth (between 80 and 100 ft) than it did in 

October 1992 because of larger head differences. 

Lower producing zones were also affected by head 

gradient fluctuations-- for example, as shown in figure 

14 for August and October 1993 between the interval 

450 and 900 ft. 

 During the course of this study, several wells 

had internal flow that was caused by nearby municipal 

or irrigation pumping. Hickory Street well is a monitor 

well for the city of Sarasota and is 599 ft deep with 46 

ft of casing. Production No. 3 well for the city of Sarasota is 549 ft deep with 260 ft of casing and is 30 ft 

from the monitoring well. The composite geophysical 

log for Hickory Street well when the nearby Production No. 3 well was under pumping and nonpumping 

conditions in shown in figure 16. The gamma log does 

not indicate an apparent hydrologic contact between 

the intermediate aquifer system and the Upper Floridan aquifer because there is no subsidence in gamma 

activity. The temperature log indicates that there is 

slightly warmer water mixing with cooler water at 

approximately 80, 260, and 550 ft. Fluid conductivity 

is approximately 3,000 μS/cm from 80 to 550 ft and 

increases to 12,500 μS/cm at the bottom of the borehole. The contact between the intermediate aquifer 

system and the Upper Floridan aquifer may be inferred 

to be at 550 ft because of changes in the temperature 

and fluid conductivity at this depth. There was no 

measurable internal borehole flow in the monitoring 

well using the impeller flowmeter during nonpumping 

conditions of the nearby production well. 

A composite geophysical log for Hickory Street 

well with the nearby production well pumping approximately 350 gal/min is shown in figure 16. A sharp 

interface where the 260-ft casing depth for the production well ends is shown by the temperature, fluid conductivity, and flow logs (fig. 16). The borehole flow in 

the monitoring well was measured using the impeller 

flowmeter at a maximum rate of 300 gal/min. Fluid 

conductivity increased from approximately 12,000 to 

15,000 μS/cm at the bottom of the hole. The composite well log analysis indicates that the nearby pumping 

well induced upward borehole flow to occur within the 

monitor well and caused upward movement of highly 

mineralized water. This highly mineralized water may 

migrate into shallower formations when the pump is 

turned off. 

Heat-Pulse Flowmeter Well Log Analysis

A heat-pulse flowmeter was used in 19 wells 

throughout the study area to measure low flow velocities in wells open to multiple permeable zones. Well 

information is listed in table 2 and the well locations 

are shown in figure 9. The heat-pulse flowmeter was 

used in wells that did not have detectable flow with the 

impeller flowmeter. The measured wells had depths 

and casing lengths ranging from 335 to 1,547 ft and 

26 to 398 ft, respectively. Of the 19 wells measured, 

18 (95 percent) had detectable internal borehole flow 

with maximum values ranging from 0.3 to 10.0 

gal/min. Well locations and maximum recorded flow 

values are shown in figure 17.

Distinct regional patterns of internal flow were 

not observed using the heat-pulse flowmeter and for 

several wells flow direction did not follow regional 

trends from the head difference maps (figs. 4 and 5). 

In addition, several wells had multiple flow zones with 

opposing flow directions. Flow rate and direction were 

very localized for each well. In some instances, localized flow was influenced by a discharge area, such as a 

nearby river, municipal pumping, or agricultural 

pumping. 

 A number of factors must be considered when 

analyzing heat-pulse flowmeter data which include: (1) 

turbulent thermal convection and other secondary flow 

circulations occur within the borehole; (2) actual flow 

regimes are often changing with time as measurements 
Results and Intrepretation of Geophysical Well Data 27

100

200

300

400

500

600

DEPTH, IN FEET BELOW LAND SURFACE 

1,0005,0009,000

13,000

0 8 16 24

CALIPER

25

TEMPERATURE, 

IN DEGREES CELSIUS

0

GAMMA RAYS,

IN COUNTS PER

0 200 400

BOREHOLE FLOW,

IN GALLONS PER MINUTE

27 29 100 200

 DIAMETER,

IN INCHES SECONDS

26 28 30

3,000

7,000

11,000

15,000

UPWARD

FLOW AND

MEASUREMENT

DEPTH OF

0

DURING PUMPING

CONDITIONS

 DEPTH OF

MEASUREMENT

DURING

NONPUMPING

CONDITIONS 

PUMPING

CONDITIONS

NONPUMPING

CONDITIONS

NONPUMPING

CONDITIONS

PUMPING

CONDITIONS

FLUID-CONDUCTIVITY,

IN MICROSIEMENS

PER CENTIMETER

 AT 25 DEGREES

 CELSIUS

Figure 16. Composite geophysical log for Hickory Street well in Sarasota County with Production No. 3 well under 

nonpumping and pumping conditions.
28 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

flows upward from the bottom of the well and exits a 

cavity near 500 ft. Upward flow is also present 

between 330 and 400 feet and exits above 225 feet, 

indicating a leaky casing.

Figure 18 is a composite geophysical log of 

Schroeder Manatee Ranch No. 8 well in Manatee 

County. The well is 703 ft deep and has 64 ft of casing 

(table 2 and fig. 9). The gamma log indicates that the 

hydrologic contact between the intermediate aquifer 

system and the Upper Floridan aquifer is at an approximate depth of 360 ft. Analysis of the heat-pulse flowmeter data and accompanying geophysical logs 

indicates that a small amount of flow occurs at the 

bottom of the well and increases slightly at approximately 560 ft. The low volume flow continued up the 

borehole and the rate increased between 250 to 100 ft. 

Flow between these depths is also indicated on the 

temperature and fluid-conductivity logs.

The heat-pulse flowmeter proved to be a useful 

tool in detecting low-flow volumes and locations of 

the low-flow contributing zones. Of the 19 wells

are made; and, 3) not all permeable intervals may be 

producing vertical flow under ambient conditions. 

These factors are described in detail by Crowder and 

others (1994) and Paillet and others (1994). 

A composite geophysical log of the Oscar 

Scherer State Park well in Sarasota County in which 

the impeller and heat-pulse flowmeters were used to 

determine the occurrence of interaquifer flow is shown 

in figure 12. This analysis indicates that even though 

flow was not detected using the impeller flowmeter, a 

small amount of internal flow was detected in this well 

with the more sensitive heat-pulse flowmeter. The 

heat-pulse flowmeter data indicate two zones of 

inflow and two zones of outflow. From below 500 ft, 

inflow of approximately 1.2 gal/min occurs and continues up the borehole until the flow exits the borehole 

near 500 ft. Above 400 ft, a second flow zone produces upward flow of 1.0 gal/min. Analysis of the 

heat-pulse flowmeter data and accompanying geophysical logs indicate that highly mineralized water 

Table 2. Records for wells using the heat-pulse flowmeter

Index no. Site name Latitudelongitude

Depth 

(feet) 

below 

land 

surface

Casing 

(feet)

Diameter 

(inches)

Date of 

measurement

Heatpulse 

flow rate, 

gallons 

per 

minute

 8 Oscar Scherer State Park 271032 822745 728 294 8 02-16-94 1.2

 19 Smith 273103 813637 849 66 5 02-22-94 0.3

 20 ROMP 123 274031 821504 620 117 8 11-06-92 1.0

 21 Walker Farms 271931 822608 668 238 6 03-05-93 1.0

 24 Busby Deep 273605 820711 996 153 12 02-19-94 8.5

 26 Rusty Pot No. 2 271646 821122 1,017 148 10 02-21-94 10.0

 36 Schroeder Manatee Ranch No. 8 272651 822625 703 64 8 03-05-93 0.7

 37 Big Hog 272040 823258 555 90 12 11-06-92 0.3

 42 Romp 43X 273615 812849 1,005 398 8 02-22-94 0.0

 43 Powell Deep 274813 822236 335 26 6 11-05-92 10.0

 50 Kibler Deep 272838 821422 1,129 208 8 03-04-93 0.5

 56 Parrish Grove 273459 822532 583 102 6 03-03-93 1.0

 58 Verna T 0-4 272020 821948 500 140 6 02-16-94 0.8

 59 Amax Deep No. 3 271538 820023 1,547 340 8 02-18-94 2.0

 61 Hudson Farms 270046 815541 1,256 368 12 02-26-94 3.0

 72 Ansin 265643 815500 766 108 4 02-17-94 2.4

 73 Verna P-20 272248 821719 520 142 10 02-15-94 2.7

 74 Verna KME-02 272301 821914 833 350 16 02-15-94 2.8

 75 DEP No. 8 274812 814846 610 121 6 02-25-94 0.8
Results and Intrepretation of Geophysical Well Data 29

Figure 17. Locations of wells measured with the heat-pulse flowmeter and the maximum recorded flow 

measurement in the borehole in gallons per minute.

MAXIMUM RECORDED 

MAXIMUM RECORDED 

WELL LOCATION AND

DOWNWARD FLOW 

UPWARD FLOW 

RECORDED VALUE

10.0

2.0

RATE--in gallons per minute

RATE--in gallons per minute

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′ 28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

1.0

1.0

0.7

0.3

10.0

0.5

1.0

3.0

1.2

2.0 10.0

0.8

2.7

2.8

0.3

8.5

2.4

0.8

0

0

Charlotte Harbor

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River
30 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

100

200

300

400

500

600

700

800

DEPTH, IN FEET BELOW LAND SURFACE

600700800900

0 8 16 24 26 24 28 0 100 200 0 .50 1.0

FLUID-CONDUCTIVITY, CALIPER DIAMETER, TEMPERATURE, BOREHOLE FLOW,

 IN MICROSIEMENS IN INCHES IN DEGREES CELSIUS IN COUNTS PER

SECOND

IN GALLONS PER MINUTE

GAMMA RAYS,

UPWARD

FLOW AND

MEASUREMENT

DEPTH OF

WITH

HEAT-PULSE

FLOMETER

DEPTH OF

MEASUREMENT

WITH IMPELLER

FLOWMETER

 0

PER CENTIMETER

AT 25 DEGREES

CELSIUS

Figure 18. Composite geophysical log for Schroeder Manatee Ranch No. 8 well in Manatee County using the heatpulse flowmeter.
Water Quality 31

measured with the heat-pulse flowmeter, 18 (95 percent) had measurable internal borehole flow, in comparison, with the 87 wells measured using the impeller 

flowmeter in which 17 (20 percent) had measurable 

internal borehole flow. Further data collection are 

needed, using the heat-pulse flowmeter, to determine 

if internal flow could be detected in all wells penetrating multiple permeable zones.

WATER QUALITY

The water chemistry in the intermediate aquifer 

system and the Upper Floridan aquifer is controlled by 

the lithology and mineralogy of units within each 

aquifer, the residence time of water in contact with the 

aquifer matrix, and the different sources of water that 

recharge each aquifer. The lithology that controls the 

hydrochemistry of the water in the intermediate aquifer system consists of limestone, dolomite, sand, clay, 

and phosphorite. Major sources of recharge water to 

the aquifer include downward leakage from the surficial aquifer in the northern half of the study area and 

upward leakage from the Upper Floridan aquifer in the 

southern half.

The chemical composition of water in the intermediate aquifer system is distinctly different in areas 

where it is recharged by the surficial aquifer, as compared to areas where the Upper Floridan aquifer discharges into the intermediate aquifer system. Ground 

water in the surficial aquifer within the study area is a 

mixed calcium bicarbonate and sodium chloride type; 

in the Upper Floridan aquifer it is a mixed calcium 

magnesium sulfate and sodium chloride type. The 

chemistry of the water in the intermediate aquifer system is a transitional type of ground water between the 

two sources of water moving into the aquifer (Berndt 

and Katz 1992).

The hydrochemistry of water in the Upper Floridan aquifer is controlled by the lithologic composition 

of limestone, dolomite, and gypsum, and by the 

sources of water that recharge the aquifer. In the study 

area, sources of recharge to the aquifer include downward leakage from the intermediate aquifer system 

and the lateral, westward flow of the regional groundwater system. The major ion concentrations of water 

in the Upper Floridan aquifer is affected predominately by processes such as dissolution of gypsum and 

dolomite, calcite precipitation, and seawater mixing 

(Katz, 1992). In the study area, there is a general 

increase with depth in dissolved solids and sulfate 

concentration (Wilson, 1977) . This increase in major 

ion concentrations with depth in the Upper Floridan 

aquifer is supported by the concept that, as temperatures increase with depth, both the solubility and the 

rate of dissolution of most rock minerals increase 

(Hem, 1989).

 The chemical characteristics of the water in the 

intermediate aquifer system and in the Upper Floridan 

aquifer are presented in table 3. The water-quality data 

used in this report are from analyses of water samples 

collected during the course of this study, from historical data of the USGS, and from the Ambient GroundWater Quality Monitoring Program of SWFWMD. 

Analyses are grouped according to the principal aquifer yielding water to each well. In a number of waterquality analyses for the Upper Floridan aquifer, wells 

also were open to the intermediate aquifer system. 

However, because the intermediate aquifer system 

contributes only a fraction of the water to a well that 

also penetrates the more productive Upper Floridan 

aquifer, the chemical analyses are probably more representative of the water in the Upper Floridan aquifer.

The principal chemical constituents in ground 

water within the study area that affect potability are 

chloride, sulfate, and dissolved solids. Generalized 

maps of chloride, sulfate, and dissolved solids concentrations in water from the intermediate aquifer system 

and the Upper Floridan aquifer were developed to 

delineate areas of potential water-quality degradation 

as a result of interconnected aquifers (figs. 19-24).

Chloride

Chloride is one of the predominant anions in 

water from the intermediate aquifer system and the 

Upper Floridan aquifer in the study area. Chloride in 

ground water may be derived from several sources 

including dissolution of aquifer minerals that contain 

chloride; saltwater intrusion; degraded water sources 

such as septic tank seepage, agricultural activities, and 

industrial wastes; and rainfall that contains a small 

amount of chloride ions. In addition, aquifers may 

contain saline or brackish water, which, in part, is 

relict seawater that has not been completely flushed by 

freshwater circulation (Wilson, 1977).

 The maximum chloride concentration permitted 

for public drinking water supplies in Florida is 250 

mg/L (Florida Department of Environmental Regulation, 1985). Throughout most of the study area, the 

chloride concentrations in water from the intermediate 
32 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data

Babcock well 265316081433401 03-12-93 917 300 IA 580 200 1,320 USGS

Englewood well 14 265834082202401 09-22-87 55 44 IA 320 44 980 USGS

Englewood test well C-8 265927082195201 04-09-81 110 56 IA 670 13 1,630 USGS

Englewood test well C-7 270018082201301 04-09-81 120 47 IA 250 16 590 USGS

Venetia (Berry 8) 270032082205801 04-10-81 253 52 IA 830 430 2,170 USGS

Venetia (Berry 7) 270057082210501 04-09-81 185 48 IA 190 210 791 USGS

Englewood deep zone well 3 270106082214101 09-15-87 135 109 IA 70 14 360 USGS

Englewood test well C-9 270112082201201 04-09-81 120 65 IA 270 16 756 USGS

Englewood production well 8 270112082213301 01-14-80 70 58 IA 110 --- 531 USGS

Englewood production well 5 270113082223302 08-05-86 70 40 IA 180 26 650 USGS

Venetia (Berry 3) 270203082210101 01-31-84 315 212 IA 380 600 1,200 USGS

Venetia (Berry 5) 270205082284001 01-30-84 472 290 IA 680 850 1,700 USGS

Manatee Jr. College south well 270219082185801 03-21-84 274 102 IA 1,100 840 2,900 USGS

Manatee Jr. College middle well 270223082185701 03-21-84 158 41 IA 170 30 500 USGS

ROMP TR4-2 270240082235701 05-19-82 475 460 IA 260 720 1,600 USGS

Plantation monitor well 1 280403082220001 03-11-87 180 66 IA 69 53 326 USGS

Plantation monitor well 2 270404082215801 03-11-87 65 52 IA 29 198 228 USGS

Plantation RO test well 2 270407082215801 05-16-82 366 228 IA 358 972 2,058 USGS

Venice Gardens injection monitor 400 270420082230503 06-10-85 400 200 IA 642 1,320 2,930 USGS

Venice RO 6 270534082260901 06-13-82 441 206 IA 300 1,200 2,750 USGS

Venice well 2 270536082253901 06-05-82 140 77 IA 130 415 1,240 USGS

Venice well 35 270542082261801 11-20-87 163 86 IA 110 270 660 USGS

ROMP TR5-1 Hawthorn well 270808082270502 11-23-87 289 275 IA 33 1,200 1,400 USGS

Henry Ranch 1 270822082231101 04-01-81 286 40 IA 30 1,300 1,900 USGS

ROMP TR5-2 upper Hawthorn well 270919082234202 05-06-86 120 100 IA 54 730 1,300 USGS

ROMP TR5-2 lower Hawthorn well 270919082234203 05-06-86 265 245 IA 36 1,100 1,700 USGS

ROMP TR5-2 Tampa well 270919082234204 05-06-86 400 360 IA 38 1,500 2,300 USGS

Ewing Ranch (Holland) 270931082252901 07-09-86 256 44 IA 40 1,500 2,200 USGS

ROMP 19 WS 270959082203003 02-18-82 67 32 IA 56 --- 390 USGS

Sarasota County Historical Society 271222082295201 02-08-82 224 41 IA 36 1,100 1,700 USGS

D.T. Brown 15 (46-43) 270246081424301 09-15-88 408 62 IA 130 62 488 USGS

Nichols Ranch (35) 270359081464401 09-15-87 377 44 IA 55 25 --- USGS

Bill Athey (Foster) 270412081474901 09-03-87 460 112 IA 60 58 361 USGS

Rob Lane (Russell) 270417081575601 09-03-87 411 70 IA 220 190 813 USGS

NAFCO Groves 270540081335101 03-08-89 300 100 IA 360 19 1,090 USGS

Gen. Development T-2 270540082001102 09-12-88 496 393 IA 140 230 737 USGS

Dees--while drilling UF 270725081500701 02-26-88 430 254 IA 69 130 472 USGS
Water Quality 33

Hancock Groves (Brantly) 270803081502401 08-16-88 418 77 IA 120 290 805 USGS

G.P. Wood Hospital 270810081481201 09-19-85 565 70 IA 71 281 644 USGS

Red Hawk Ranch (Nunez) 270858081582201 09-12-88 428 63 IA 90 260 717 USGS

Blocker 271010081505301 09-15-88 450 420 IA 57 60 408 USGS

Bright Hour Ranch 15-21 271015081432101 08-19-88 396 96 IA 89 15 431 USGS

Vance Stansel 271058081471601 08-18-88 335 110 IA 49 31 365 USGS

Minute Maid (44) D-69 271113081543301 06-17-87 384 99 IA 88 87 548 USGS

ROMP 16 Hawthorn 271115081462702 07-24-85 340 300 IA 41 20 214 USGS

Bright Hour Ranch 51-08 271151081410801 08-19-88 335 105 IA 70 3 396 USGS

Bright Hour Ranch 28-11 271228081371101 08-19-88 291 126 IA 14 2 347 USGS

City of Arcadia No. 4 271244081504201 08-16-88 353 112 IA 46 15 380 USGS

City of Arcadia No. 2 271308081522601 07-25-85 372 263 IA 47 16 344 USGS

City of Arcadia No. 1 271310081522701 02-24-89 250 84 IA 45 25 375 USGS

AMAX (Hollingsworth 716) 271407082000401 08-16-88 430 60 IA 57 79 465 USGS

Joshua Tier Barn 3 271512081344701 08-18-88 300 90 IA 35 170 488 USGS

Carl Regan 271517081502201 09-10-87 327 84 IA 42 27 322 USGS

Allen Burtscher (704) 271517081542201 08-16-88 320 130 IA 53 74 496 USGS

Joshua Tier Barn 1 (TRG) 271520081394201 08-18-88 294 105 IA 76 17 360 USGS

Joshua Tier Barn 2 (TRG) 271521081374301 08-18-88 300 150 IA 83 42 424 USGS

Camp Chanyatah No. 3 271624081520001 09-03-87 208 80 IA 24 260 631 USGS

J.H. Brock (50) (D-122) 271713081504901 06-17-87 257 47 IA 35 110 454 USGS

ROMP 26 Hawthorn 271757081493003 07-31-85 180 140 IA 3 109 325 USGS

D.E. Marshall 272012081482501 07-31-85 478 137 IA 21 197 525 USGS

Hollingsworth 751 272014081595701 02-24-89 430 144 IA 13 17 326 USGS

Hazel Williams 272103081480701 02-24-89 199 129 IA 14 4 307 USGS

Hollingsworth 620 272108081582601 02-24-89 335 146 IA 20 250 593 USGS

ROMP 31 Hawthorn 272714081545902 03-29-88 350 130 IA 87 76 550 USGS

Wilbur Robertson (20) 272715081401601 11-23-87 343 103 IA 9 40 217 USGS

Thomas Spuckler 272718081342401 03-08-89 372 231 IA 9 53 229 USGS

ROMP 30 Tampa 272728081474702 08-14-85 316 280 IA 25 142 388 USGS

William Anderson 272917081453901 09-09-87 140 42 IA 14 15 198 USGS

Jeff Surrency (Martens) 272932081492001 09-09-87 177 34 IA 14 110 369 USGS

Scott (T.C. Hart) 604 272924081495701 09-10-87 321 82 IA 11 60 302 USGS

Rowell 273156081451401 08-15-85 267 39 IA 8 9 194 USGS

Charlie Stevens 273345081371701 02-24-89 225 100 IA 3 1 111 USGS

Ed McClelland 273356081371701 02-24-89 226 110 IA 7 22 138 USGS

Ed Jernigan (26) 273403081494701 11-23-87 298 83 IA 7 1 191 USGS

Harold McClelland 273423081371701 02-24-89 210 110 IA 9 3 169 USGS

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
34 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Henderson (Geiger) (624) 273435081444001 11-12-87 293 105 IA 21 110 393 USGS

Dewey Waters 273543081590301 12-09-87 400 90 IA 27 14 251 USGS

Paynes Creek Historical 273714081483101 09-09-87 130 119 IA 39 32 304 USGS

Sweat well Hillsborough HRS34 274533082155202 03-01-89 220 156 IA 4 1 --- USGS

Polk ROMP 55 Suwannee 274730081333801 07-14-87 250 212 IA 8 7 --- USGS

Babcock Florida Corp. 2126 265321081442601 12-22-93 404 42 IA 73 1 486 SWFWMD

Port Charlotte Deep 270133082034601 03-29-94 350 312 IA 745 292 1,698 SWFWMD

Port Charlotte Utility Deep 265920082045601 03-29-94 156 128 IA 77 20 309 SWFWMD

Punta Gorda Heights 265141082002201 01-12-94 125 84 IA 372 71 953 SWFWMD

ROMP 10 Hawthorn (Flowing) 270152082002801 03-21-94 210 110 IA 378 158 878 SWFWMD

ROMP 10 Tampa 270152082002801 03-21-94 488 303 IA 451 242 1,157 SWFWMD

ROMP 11 Deep 265837081561101 03-29-94 335 220 IA 695 259 1,535 SWFWMD

ROMP TR 1-2 L Hawthorn 265026081585401 01-12-94 600 520 IA 931 278 2,014 SWFWMD

ROMP TR 1-2 U. Intermediate 265026081585401 01-12-94 255 218 IA 476 136 1,134 SWFWMD

ROMP TR 3-1 L Hawthorn 265638082130701 03-25-94 400 380 IA 640 460 1,827 SWFWMD

ROMP TR 3-1 U. Intermediate 265638082130701 03-25-94 160 140 IA 950 9 1,773 SWFWMD

ROMP TR 3-3 L Hawthorn 265531082194801 03-20-94 410 370 IA 2,858 493 5,443 SWFWMD

ROMP TR 3-3 U. Intermediate 265531082194801 03-20-94 175 155 IA 1,107 149 2,101 SWFWMD

Rotunda Water Plant 18 265158082171701 03-21-94 146 121 IA 4,503 456 8,600 SWFWMD

State Hwy 74 Dp Well 265646081554501 01-24-94 280 194 IA 122 101 549 SWFWMD

USGS C-1 265127081532501 02-25-94 264 214 IA 1,170 287 2,440 SWFWMD

USGS C-3 265504082000601 03-30-94 205 153 IA 89 4 356 SWFWMD

USGS Tuckers Corner 265124081453701 12-22-93 235 212 IA 35 1 354 SWFWMD

GDU Well T-2 270540082001101 03-14-94 496 393 IA 142 230 679 SWFWMD

NAFCO Groves Intermediate 270540081335101 01-06-94 300 100 IA 275 15 812 SWFWMD

Prairie Creek U. Intermediate 270245081465101 01-06-94 80 60 IA 144 59 639 SWFWMD

Rob Lane (G.V. Russell) 270417081575601 03-31-94 411 70 IA 300 175 879 SWFWMD

ROMP 14 270858081211101 06-23-92 1,249 389 IA 3 6 278 SWFWMD

ROMP 28 272207081260401 02-03-93 2,060 200 IA 5 2 93 SWFWMD

Bradburn Well 275223082195001 12-28-93 80 83 IA 52 15 345 SWFWMD

ROMP TR 9-1 274421082275401 12-21-93 288 124 IA 31 358 778 SWFWMD

Riverside Village 274212082264901 12-21-93 197 40 IA 42 442 909 SWFWMD

El Conquistador North Well 272558082360601 12-20-93 399 49 IA 370 536 1,524 SWFWMD

Horse Shoe Loop Terra Ceia 273347082354101 01-10-94 423 22 IA 232 543 1,303 SWFWMD

Manatee Fairgrounds 273134082344601 12-20-93 273 216 IA 251 719 1,729 SWFWMD

Palma Sola-Wayne Davis 273055082394701 12-20-93 246 196 IA 689 492 2,078 SWFWMD

ROMP 23 Intermediate 271852082104101 01-11-94 363 303 IA 17 5 206 SWFWMD

ROMP TR 7-1 272510082345701 03-09-94 340 320 IA 109 364 844 SWFWMD

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
Water Quality 35

ROMP TR 7-2 U Hawthorn 272612082330101 02-09-94 105 60 IA 75 47 356 SWFWMD

ROMP TR 8-1 Upper Hawthorn 273458082324701 01-07-94 160 100 IA 99 36 514 SWFWMD

City of Sarasota 27th Street 272133082324701 11-18-92 343 45 IA 178 320 767 SWFWMD

Englewood Prod. No. 5 Hawthorn 270113082223301 03-11-94 70 40 IA 815 132 1,823 SWFWMD

Knights Trail Upper Intermediate 270945082234401 02-03-94 140 63 IA 67 212 696 SWFWMD

Mabry Carlton No. 6 271227082084801 03-30-94 369 311 IA 48 232 642 SWFWMD

Macarthur Tract 14DS 270807082123001 05-31-91 210 40 IA 74 32 --- SWFWMD

Manasota Deep Well 14 270137082235301 03-22-94 305 263 IA 54 31 363 SWFWMD

Plantation Hawthorn No. 126 270406082220101 02-24-94 180 66 IA 64 28 364 SWFWMD

ROMP 19 WUAM 270959082203001 03-03-94 205 87 IA 92 56 503 SWFWMD

ROMP 20 Lower Hawthorn 271138082284601 03-10-94 370 250 IA 73 1,530 2,436 SWFWMD

ROMP 20 Upper Hawthorn 271138082284601 03-10-94 125 75 IA 89 698 1,333 SWFWMD

ROMP 22 L. Intermediate 271813082201201 02-18-94 290 230 IA 168 71 632 SWFWMD

ROMP TR 5-1 Tampa 270808082270501 03-11-94 289 275 IA 34 1,004 1,664 SWFWMD

ROMP TR 5-2 L. Hawthorn 270919082234201 02-16-94 265 245 IA 36 1,062 1,789 SWFWMD

ROMP TR 6-1 Tampa 271601082330501 02-09-94 315 300 IA 478 1,093 2,514 SWFWMD

Sarasota Historical Society 271222082295201 03-10-94 224 44 IA 39 1,158 1,996 SWFWMD

Southbay Utilities Deep 271035082285901 02-03-94 450 220 IA 213 1,653 3,035 SWFWMD

Test 18 Blackburn Well 270714082155201 03-15-94 351 282 IA 172 540 1,218 SWFWMD

USGS Well 35 at Venice 270542082261801 03-04-94 163 86 IA 130 371 968 SWFWMD

VO No. 3 270853082090101 03-22-94 350 32 IA 262 448 1,267 SWFWMD

Venice Shallow Wellfield 68 270558082241501 03-04-94 110 76 IA 153 301 911 SWFWMD

Whitaker Bayou Well 272119082325101 02-07-94 337 54 IA 153 170 757 SWFWMD

Babcock well 265316081433401 03-12-93 917 700 UF 920 310 2,020 USGS

ROMP TR3-3 Suwannee well 265531082194803 05-28-87 900 680 UF 8,000 1,100 14,000 USGS

ROMP TR3-1 Suwannee well 265638082130706 02-02-86 620 600 UF 410 470 1,500 USGS

Englewood injection monitor MW-1 265716082205102 02-04-86 550 500 UF 2,400 264 4,490 USGS

North Port onsite monitor well 270058082152502 11-13-87 750 730 UF 7,910 1,450 15,000 USGS

North Port onsite monitor well 270058082152503 11-13-87 600 560 UF 5,400 975 10,900 USGS

Venetia 2 (Berry 4) 270203082213701 02-01-84 608 207 UF 460 730 1,500 USGS

Plantation zone 4 monitor well 270406082215901 03-11-87 650 630 UF 892 1,250 3,520 USGS

Venice Gardens injection monitor 800 270420082230502 06-10-85 800 770 UF 1,116 1,320 3,780 USGS

ROMP TR5-1 Suwannee well 270808082270502 11-23-87 510 492 UF 54 1,400 1,600 USGS

ROMP TR5-2 Suwannee well 270919082234205 05-07-86 700 510 UF 41 1,700 2,500 USGS

ROMP TR5-2 Ocala well 270919082234206 05-06-86 890 850 UF 20 1,600 2,400 USGS

Atlantic Utilities test/injection well 271853082280902 05-19-88 1,240 1,130 UF 117 1,040 1,800 USGS

Hancock and Lawrence 270256081472801 07-09-87 900 700 UF 340 180 954 USGS

Emerald Island Farms C 270313081391001 09-13-88 1,500 610 UF 290 190 954 USGS

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
36 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Smith (Aborgia) W-6073 270333081473101 06-17-87 1,211 685 UF 460 190 1,240 USGS

NAFCO Groves FLRD 270347081342901 03-08-89 1,520 150 UF 290 130 889 USGS

Lettuce Lake 270414081584701 08-05-85 1,190 105 UF 161 207 729 USGS

Cromwell No. 1 270440081434401 09-13-88 1,500 666 UF 92 72 447 USGS

Roper Groves 270442081494301 06-16-87 1,189 640 UF 260 160 864 USGS

Gen. Development M-2 270540082001101 09-12-88 897 605 UF 68 450 915 USGS

General Development 270554082003601 08-19-80 1,411 1,326 UF 200 310 1,090 USGS

Dees (C. Harrison) 270725081500701 02-23-89 1,280 654 UF 120 260 793 USGS

Carlton 2 by 4 No. 5 271023081462301 08-17-88 1,500 540 UF 54 360 784 USGS

D.L. Cullifer 271113081574801 02-23-89 1,315 511 UF 40 340 792 USGS

ROMP 16 Floridan 271115081462701 06-17-87 942 757 UF 39 320 686 USGS

Bright Hour Ranch 35-25 271135081372501 08-19-88 1,478 180 UF 35 110 429 USGS

ROMP 15 Floridan 271232081392201 10-09-85 1,360 575 UF 39 329 658 USGS

Avant Groves 271314081445901 06-16-87 1,412 630 UF 35 320 754 USGS

Joshua J-14 (TRG) 271416081374601 08-18-88 1,492 193 UF 33 330 728 USGS

Cunningham AMAX NPFO 4 271610081565401 08-01-85 1,040 350 UF 30 693 1,240 USGS

W.F. Underhill (Conger) 271653081464701 06-17-87 1,300 460 UF 29 86 384 USGS

Sorrell Groves 17-26 271717081522601 06-17-87 893 511 UF 16 820 1,460 USGS

Joshua J-18.1 (TRG) 271743081374601 08-21-85 698 137 UF 12 216 672 USGS

Joshua J-36 (TRG) 271748081345101 08-18-88 1,361 180 UF 16 360 717 USGS

ROMP 26 Floridan 271757081493002 08-07-85 1,320 580 UF 16 357 701 USGS

Davis 10 Mi Grade 2 272036081384701 12-14-88 1,250 450 UF 12 330 637 USGS

Davis 10 Mi Grade 1 272043081384701 12-14-88 1,200 200 UF 13 290 598 USGS

Circle 5 Ranch (Bowen) 272118081473401 06-30-88 1,345 580 UF 14 3 271 USGS

Schoonover 272403081410501 12-14-88 1,261 425 UF 7 240 485 USGS

Edwin Sasser 272709081591701 06-30-88 1,280 479 UF 15 65 297 USGS

ROMP 31 Floridan 272714081545901 08-14-85 1,152 460 UF 12 101 359 USGS

ROMP 30 Floridan 272728081474701 08-14-85 1,266 380 UF 18 2 485 USGS

Zolfo Springs No. 1 272944081474001 12-09-87 1,002 350 UF 18 170 464 USGS

Zolfo Springs No. 2 272945081474101 12-09-87 933 350 UF 18 180 466 USGS

Albert Carlton 273033081513801 12-13-88 1,280 680 UF 22 22 314 USGS

M.A. Smith 273103081363701 09-25-85 849 66 UF 6 19 136 USGS

Doyle Carlton Jr. 273112081595601 12-13-88 1,360 900 UF 39 22 271 USGS

City of Wauchula No. 4 273254081480601 12-09-87 1,152 420 UF 10 250 535 USGS

Floyd Smith 273337081393301 02-23-89 1,119 178 UF 10 20 206 USGS

Peace Valley Groves 273608082023001 12-14-88 1,160 450 UF 14 64 283 USGS

C.F. Industries A 273744081565301 12-09-87 1,205 600 UF 7 70 258 USGS

C.F. Industries C 273821081564701 12-09-87 950 600 UF 9 79 271 USGS

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
Water Quality 37

City of Bowling Green 4 273821081493901 12-09-87 1,218 418 UF 10 330 646 USGS

Charlotte ROMP TR3-1 Suwannee 265638082130706 02-02-86 620 600 UF 410 470 --- USGS

Charlotte ROMP 10 Deep Creek 917 270152082002801 02-02-86 917 596 UF 180 410 --- USGS

De soto Hancock and Lawrence 270256081472801 07-09-87 900 700 UF 340 180 --- USGS

Sarasota ROMP TR5-2 270919082234205 10-06-87 700 510 UF 44 1,400 --- USGS

De Soto ROMP 16 Ocala 271115081462701 06-17-87 942 757 UF 39 320 --- USGS

De Soto ROMP 26 271757081493002 02-05-86 580 132 UF 14 340 --- USGS

Coca Cola well Highlands 272408081232501 05-31-89 595 546 UF 16 3 --- USGS

Manatee ROMP 32-2 272814082034802 11-02-87 600 560 UF 20 77 --- USGS

Hardee Zolfo Springs 1 272944081474001 02-05-86 1,000 350 UF 17 180 --- USGS

Hillsborough Sun City 1 274318082202801 02-04-86 800 271 UF 11 190 --- USGS

Hillsborough ROMP 48 274427082083701 02-03-86 541 215 UF 15 42 --- USGS

Polk Lake Garfield Nurseries 274910081452201 02-03-86 817 316 UF 8 16 --- USGS

Pebbledale Road 275009081540901 02-23-89 303 288 UF 10 28 --- USGS

ROMP TR 1-2 SWNN 265026081585401 01-12-94 1,184 980 UF 994 264 2,110 SWFWMD

ROMP TR 3-1 SWNN 265638082130701 03-25-94 620 600 UF 454 458 1,532 SWFWMD

ROMP TR 3-3 SWNN 265531082194801 03-20-94 900 680 UF 8,130 1,103 14,990 SWFWMD

Cromwell Well No. 4 270440081434401 03-31-94 1,500 666 UF 380 135 969 SWFWMD

DT Brown G-36 270223081421101 08-12-93 925 632 UF 317 56 652 SWFWMD

Emerald Island Farms 270313081391001 03-31-94 1,300 610 UF 163 140 611 SWFWMD

GDU Well M-2 270540082001101 03-14-94 897 605 UF 103 344 807 SWFWMD

Gen Development Corp Avon Park 270554082003601 03-24-94 1,411 1,326 UF 276 285 1,008 SWFWMD

Hancock & Lawrence 270256081472801 03-25-94 900 700 UF 306 162 809 SWFWMD

Morgan Deep 270410081565201 03-30-94 1,010 208 UF 90 230 679 SWFWMD

ROMP 15 Deep 271232081392201 03-25-94 1,360 586 UF 31 345 734 SWFWMD

ROMP 17 SWNN 271026081583601 01-06-94 670 620 UF 65 382 827 SWFWMD

ROMP 28 272207081260401 12-12-91 2,060 684 UF 11 5 211 SWFWMD

ROMP 123 Deep 274031082150401 01-06-94 620 117 UF 13 16 265 SWFWMD

ROMP 48 274427082083701 02-08-94 541 215 UF 12 46 235 SWFWMD

ROMP 49 SWNN 274546082151601 01-13-94 526 410 UF 13 56 270 SWFWMD

ROMP 50 274240082212701 01-06-94 562 200 UF 13 165 428 SWFWMD

ROMP TR 12-3 280034082323701 04-16-92 345 310 UF 290 59 842 SWFWMD

ROMP TR 9-2 Ocala 274554082233801 01-24-94 677 622 UF 367 452 1,310 SWFWMD

ROMP TR 9-2 Suwannee (Pump) 274554082233801 01-24-94 460 250 UF 172 377 946 SWFWMD

ROMP TR 9-3 Suwannee 274428082251501 01-28-94 525 289 UF 433 908 2,274 SWFWMD

Florida Power & Light at Piney Point 273718082315501 03-14-94 946 104 UF 507 566 1,654 SWFWMD

Manatee Fruit No. 3 272807082401501 01-10-94 492 262 UF 663 590 2,010 SWFWMD

Manatee Fruit-Midway 272738082384701 12-20-93 511 415 UF 198 196 857 SWFWMD

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
38 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Manatee Injection Well 272705082373501 03-09-94 1,150 980 UF 3,760 1,259 7,890 SWFWMD

Midway Groves 272438082325201 03-09-94 796 331 UF 96 500 987 SWFWMD

Myakka Head No. 5 272735082083401 03-04-94 560 514 UF 12 97 326 SWFWMD

Perico Island Well 272949082404001 12-20-93 600 170 UF 546 507 1,880 SWFWMD

ROMP 23-1 Deep 271852082104101 01-10-94 1,000 904 UF 16 438 813 SWFWMD

ROMP 32 Avon Park 272814082034801 01-11-94 1,215 909 UF 11 81 --- SWFWMD

ROMP 33 Suwannee 272728082152901 03-11-94 750 404 UF 17 69 361 SWFWMD

ROMP 39 Avon Park 272728082150501 03-25-94 1,120 950 UF 12 118 370 SWFWMD

ROMP 39 SWNN 272728082150501 04-08-94 700 523 UF 15 127 369 SWFWMD

ROMP TR 7-2 Sh U Floridan 272612082330101 02-09-94 708 358 UF 270 523 1,346 SWFWMD

ROMP TR 7-4 SWNN 272539082292001 01-26-94 800 500 UF 38 344 722 SWFWMD

ROMP TR 7-4 Tampa 272539082292001 01-26-94 500 380 UF 29 230 546 SWFWMD

ROMP TR 8-1 Ocala 273458082324701 01-07-94 680 640 UF 97 479 1,025 SWFWMD

ROMP TR 8-1 Suwannee - pumped 273458082324701 01-07-94 530 390 UF 147 490 1,090 SWFWMD

ROMP TR 8-1 Upper Avon Park 273458082324701 01-07-94 940 900 UF 1,307 717 3,163 SWFWMD

Snead’s Island 273159082373101 01-10-94 525 200 UF 232 663 1,490 SWFWMD

ROMP 40 Avon Park 273851082031501 01-27-94 1,140 408 UF 11 44 224 SWFWMD

City of Sarasota 21st and RR Well 272120082322701 02-09-94 557 120 UF 212 835 1,699 SWFWMD

U Florida Cities Test Well 271619082240201 01-07-94 446 104 UF 40 579 1,069 SWFWMD

Macarthur Tract 10H 271242082171701 03-03-94 312 272 UF 29 354 790 SWFWMD

Macarthur Tract 14FS 270807082123001 02-24-94 550 500 UF 112 489 1,107 SWFWMD

OM-41 270928082172401 03-28-94 750 700 UF 24 753 1,283 SWFWMD

Plantation Monitor Well Suwannee 270406082220101 02-24-94 650 630 UF 966 1,302 3,468 SWFWMD

ROMP 18 SWNN 271137082074801 03-30-94 845 505 UF 33 218 598 SWFWMD

ROMP 19 ELAM 271021082151601 03-03-94 425 410 UF 33 526 1,017 SWFWMD

ROMP 19 WLAM 270959082203001 03-03-94 420 410 UF 31 802 1,347 SWFWMD

ROMP 20 Ocala-Avon Park 271138082284601 03-10-94 1,165 1,105 UF 1,365 1,820 4,753 SWFWMD

ROMP 20 SWNN 271138082284601 03-10-94 840 500 UF 537 1,754 3,415 SWFWMD

ROMP 22 SWNN 271813082201201 02-18-94 635 400 UF 22 378 767 SWFWMD

ROMP TR 4-2 270240082235701 07-19-93 475 460 UF 286 772 1,761 SWFWMD

ROMP TR 5-1 Suwannee 270808082270501 03-11-94 510 492 UF 78 1,552 2,438 SWFWMD

ROMP TR 5-2 Ocala 270919082234201 02-16-94 890 850 UF 20 1,645 2,534 SWFWMD

ROMP TR 5-2 SWNN 270919082234201 02-16-94 630 510 UF 43 1,740 2,704 SWFWMD

Sarasota Co. Test Well No. 1 272316082302601 02-09-94 583 350 UF 68 495 1,009 SWFWMD

Venice 2E 270705082250101 03-04-94 580 514 UF 301 1,701 2,947 SWFWMD

ROMP 14 270858081211101 07-08-92 1,249 689 UF 6 8 150 SWFWMD

ROMP 28 272207081260401 12-10-91 2,060 604 UF 8 8 228 SWFWMD

Table 3. Chloride, sulfate, and dissolved-solids concentrations in water from selected wells --Continued

[ Aq, aquifer; IA, intermediate aquifer system; UF, Upper Floridan aquifer; --- no data]

Site name Identification 

number

Sample

date

Depth 

(feet) 

below 

land 

surface

Casing 

(feet) 

below 

land

surface

Aq

Chloride 

(mg/L)

Sulfate 

(mg/L)

Dissolved 

solids 

(mg/L)

Source of 

data
Water Quality 39

Figure 19. Generalized distribution of chloride in water from the intermediate aquifer system.

< 50

51-100

101-250

>250

WELL LOCATION

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

GENERALIZED DISTRIBUTION OF CHLORIDE CONCENTRATION,

in milligrams per liter

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

PortCharlotte

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor

Gulf of Mexico

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River
40 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Figure 20. Generalized distribution of chloride in water from the Upper Floridan aquifer.

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

PortCharlotte

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

Gulf of Mexico

< 50

51-100

101-250

>250

EXPLANATION

GENERALIZED DISTRIBUTION OF CHLORIDE CONCENTRATION,

in milligrams per liter

WELLLOCATION
Water Quality 41

Figure 21. Generalized distribution of sulfate in water from the intermediate aquifer system.

River

River

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Alafia River

Little Manatee River

Myakka

Peace

Manatee

River

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

Gulf

of

Mexico

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

PortCharlotte

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor

EXPLANATION

GENERALIZED DISTRIBUTION OF SULFATE CONCENTRATION,

in milligrams per liter

< 50

51-100

101-250

>250

WELL LOCATION
42 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Figure 22. Generalized distribution of sulfate in water from the Upper Floridan aquifer.

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

0 5 10 15

0 5 10 15 KILOMETERS

MILES

< 50

51-100

101-250

>250

EXPLANATION

GENERALIZED DISTRIBUTION OF SULFATE CONCENTRATION,

in milligrams per liter

WELL LOCATION

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

Englewood

PortCharlotte

Charlotte Harbor

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM
Water Quality 43

Figure 23. Generalized distribution of dissolved solids in water from the intermediate aquifer system.

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

< 250

251-500

500-1,000

>1,000

EXPLANATION

GENERALIZED DISTRIBUTION OF DISSOLVED SOLIDS

CONCENTRATION, in milligrams per liter

WELL LOCATION

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

PortCharlotte

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor
44 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Figure 24. Generalized distribution of dissolved solids in water from the Upper Floridan aquifer.

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

SOUTHWEST FLORIDAWATER MANAGEMENT

DISTRICT BOUNDARY

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

WELLLOCATION

< 250

251-500

500-1,000

>1,000

EXPLANATION

GENERALIZED DISTRIBUTION OF DISSOLVED SOLIDS

CONCENTRATION, in milligrams per liter

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

FortMyers

Bradenton

St. Petersburg

Arcadia

Lakeland

FortOgden

LakeWales

AvonPark

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

PortCharlotte

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Charlotte Harbor
Water Quality 45

aquifer system and the Upper Floridan aquifer are less 

than 50 mg/L (figs. 19 and 20, respectively). Chloride 

concentrations increase towards the coast, and in water 

from many wells in Charlotte, Sarasota, Manatee, and 

De Soto Counties, concentrations exceed 250 mg/L in 

water from both aquifers. Chloride concentrations 

range from 3 mg/L in the central and eastern regions 

of the study area to about 4,500 mg/L in southern 

Charlotte County in water from the intermediate aquifer system, and from 6 mg/L in the central and eastern 

regions of the study area to approximately 8,000 mg/L 

in southern Charlotte County in water from the Upper 

Floridan aquifer. 

Sulfate

 In the intermediate aquifer system, sulfate is 

derived mostly from upward flow of high-sulfate 

water from the Upper Floridan aquifer and limited 

amounts from pyrite oxidation. In the Upper Floridan 

aquifer, sulfate is derived from mixing of seawater 

with freshwater and from the dissolution of gypsum 

and anhydrite (calcium-sulfate minerals) contained 

principally in the Avon Park Formation (Wilson, 

1977). Two other identified sources of sulfate in 

recharge areas of the intermediate aquifer system and 

the Upper Floridan aquifer are oceanic aerosols and 

the atmospheric oxidation of sulfides (Rye and others, 

1981). 

 The maximum sulfate concentration recommended for public water supplies in Florida is 

250 mg/L (Florida Department of Environmental Regulation, 1985). Throughout most of the study area, the 

sulfate concentrations in water from the intermediate 

aquifer system are less than 100 mg/L. Sulfate concentrations in water from the intermediate aquifer system 

range from approximately 1 mg/L in many parts of the 

study area to slightly more than 1,600 mg/L south of 

the city of Sarasota. The areal distribution of sulfate in 

water from the intermediate aquifer system is highly 

variable (fig. 21). This highly variable distribution of 

sulfate in water from the intermediate aquifer system 

may be from upwelling of high-sulfate ground-water 

from the Upper Floridan aquifer; improperly cased 

wells open to multiple aquifers containing water of 

varying quality; or through leaky and corroded well 

casings in areas of poor-quality water. 

Throughout most of the study area, the sulfate 

concentrations in water from the Upper Floridan aquifer are greater than 100 mg/L (fig. 22). Sulfate concentrations in water from the Upper Floridan aquifer 

range from approximately 2 mg/L in the central region 

of the study area to about 1,800 mg/L near the City of 

Sarasota.

Along the coast and in the Peace River Valley, 

water with high concentrations of sulfate has discharged into the intermediate aquifer system from the 

deeper Upper Floridan aquifer, as indicated on figures 

21 and 22. In Hardee and De Soto Counties, many 

deep irrigation wells tap the Avon Park Formation 

where high concentrations of sulfate occur (Wilson 

1977). Pumping wells that tap these deep formations 

containing high sulfate concentrations may facilitate 

mixing and cause contamination of the upper zones 

when wells are open to multiple units.

Dissolved Solids

Dissolved solids in ground water is a measure of 

the sum of concentrations of dissolved mineral constituents contained in the water. The predominant sources 

of dissolved solids in ground water in the study area 

are mineral dissolution reactions and mixing of seawater with freshwater. Dissolved solids concentrations 

generally increase with depth because as rock temperature increases with depth, the solubility and the rate 

of dissolution of the rock minerals increase.

 The maximum dissolved solids concentrations 

recommended for public water supply in Florida is 

500 mg/L (Florida Department of Environmental Regulation, 1985). However, use of water with concentrations of up to 1,000 mg/L has been permitted when no 

other source is available. The areal distribution of dissolved solids concentrations in water from the intermediate aquifer system is highly variable (fig. 23). For 

approximately half of the study area, the dissolved solids concentrations in water from the intermediate aquifer system are less than 500 mg/L. Dissolved solids 

concentrations range from approximately 100 mg/L in 

northeastern Hardee County to more than 8,600 mg/L 

along the coast in southern Charlotte County. Dissolved solids concentrations in water from the intermediate aquifer system tend to increase along the 

coast and the Peace River Valley, which are natural 

discharge areas for the underlying Upper Floridan 

aquifer (fig. 23).
46 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Throughout most of the study area, the dissolved solids concentrations in water from the Upper 

Floridan aquifer are greater than 500 mg/L and range 

from approximately 130 mg/L in northeastern Hardee 

County to 15,000 mg/L in southern Sarasota County 

(fig. 24). The areal distribution of dissolved solids 

concentrations closely matches the areal distribution 

of chloride and sulfate in water from the Upper Floridan aquifer. In areas where mixing with seawater has 

occurred, chloride is the major component of dissolved solids. In areas where there is a high rate of dissolution of gypsum, sulfate is the major component of 

dissolved solids. 

POTENTIAL FOR WATER-QUALITY 

DEGRADATION

Degradation of water quality may occur in both 

the intermediate aquifer system and Upper Floridan 

aquifer from improperly cased wells open to multiple 

aquifers containing water of varying quality, through 

leaky and corroded well casings in zones of poor-quality water, and from saltwater intrusion. Degradation of 

water quality in the intermediate aquifer system may 

also occur from the natural discharge of highly mineralized water and from ground-water development in 

the underlying Upper Floridan aquifer. 

The Avon Park Formation is a highly productive 

water-bearing unit in the Upper Floridan aquifer. 

Numerous irrigation wells 10 to 16 in. in diameter are 

open to this formation and yield as much as 5,000 

gal/min. In the southern part of the study area, water in 

the Avon Park Formation is highly mineralized and 

may degrade the fresher zones within the Upper Floridan aquifer and intermediate aquifer system when 

wells are open to multiple zones. Induced head gradients could result from irrigation pumpage which 

would increase the amount of upwelling of highly 

mineralized ground water.

In many parts of the study area, particularly in 

Manatee, Sarasota, and Charlotte Counties, the use of 

black-iron casing for well construction has been widespread. This type of casing deteriorates relatively rapidly because of the corrosive effects of high chloride 

and sulfate concentrations in the ground water. These 

corroded wells may leak highly mineralized water into 

overlying fresher zones in areas where there is an 

upward component of flow. In addition, contamination 

of underlying aquifers has occurred from downward 

flow of saltwater through the corroded casings of 

wells drilled in areas adjacent to tidal water bodies in 

Lee County (Boggess and others, 1977).

Ground-water development may affect the magnitude of flow, the natural flow direction, and the 

water quality between the aquifers. In the southern 

part of the study area where the Upper Floridan aquifer discharges into the intermediate aquifer system, 

upward flow would be reduced during irrigation periods because head differences are less between the two 

aquifers. During nonirrigation periods, the Upper 

Floridan aquifer heads recover and the upward head 

gradient and flow rate increase between the two aquifers (Metz, 1995). In this discharge area, flow rates of 

highly mineralized water would increase during nonirrigation periods. In the northern part of the study area, 

which is a recharge area, the opposite condition exists. 

During irrigation periods, the downward head gradient 

and flow rate increase between the intermediate aquifer system and Upper Floridan aquifer. In the study 

area, the downward flow gradient could be reversed 

and could extend the area in which upward flow of 

poor-quality water occurs. 

 A geographical area was delineated to determine where a potential for water-quality degradation 

exists because of improperly cased wells. This area 

was delineated based on the location of poor-quality 

water and where there is an upward component of 

flow from the Upper Floridan aquifer. The area of 

poor-quality water was defined by maps of the Upper 

Floridan aquifer where chloride concentrations were 

greater than 250 mg/L (fig. 20), sulfate concentrations 

were greater than 250 mg/L (fig. 22), and dissolved 

solids concentrations were greater than 1,000 mg/L 

(fig. 24). The upward component of flow was based on 

head difference maps between the intermediate aquifer 

system and Upper Floridan aquifer (fig. 4 and 5). 

The area where a potential for water-quality degradation exists includes parts of Hillsborough, Manatee, 

Sarasota, Charlotte, De Soto, and Hardee Counties 

(fig. 25). 

ESTIMATED MAGNITUDE OF 

INTERAQUIFER FLOW

An evaluation was performed to estimate the 

potential magnitude of interaquifer flow in wells open 

to multiple aquifers within the study area. Information 

that was needed for this evaluation was the distribution of wells open to multiple aquifers and the open 

borehole flow rates. A well inventory was performed,
Potential for Water-Quality Degradation 47

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

PLUGGED WELL

AREA OF POTENTIAL 

FOR CONTAMINATION

DUE TO INTERCONNECTED 

AQUIFER WELLS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

82°00′ 81°15′ 83°00′

28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

0 5 10 15

0 5 10 15 KILOMETERS

MILES

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

Base map modified from U.S. Geological Survey

Florida state base, 1:500,000

Charlotte Harbor

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

Figure 25. Area where there is a potential for water-quality degradation as a result of interconnected aquifers and 

locations of wells that have been plugged.
48 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

using the Water Use Permitting (WUP) data base of 

SWFWMD, to determine the occurrence and distribution of interconnected aquifer wells in the study area. 

Water use permits do not delineate wells by aquifer; 

therefore, selection of wells was based on well-construction data, including total depth and cased interval, 

and aquifer depth. Many wells in this data base did not 

have reported casing depths. Metz (1995), conducted a 

detailed inventory of Upper Floridan aquifer wells in 

Hardee and De Soto Counties and concluded that 10 

percent of wells are open only to this unit; the remaining wells are open to both the intermediate aquifer system and Upper Floridan aquifer. Therefore, for the 

purpose of this evaluation, wells that had no reported 

casing depth were considered open to both the intermediate aquifer system and Upper Floridan aquifer. 

From this above approach, approximately 8,000 wells 

were reported and estimated to be open to both the 

intermediate aquifer system and the Upper Floridan 

aquifer (fig. 26). This inventory is considered incomplete because some wells were installed prior to well 

permitting regulations and well information is 

unknown or was not reported correctly. Even though 

this information is incomplete, it gives an indication of 

the number and distribution of wells that may provide 

a conduit for ground water to move from zones of 

higher head to zones of lower head, thus circumventing the slower route of leakage through the confining 

units. 

In this evaluation, interaquifer flow rates 

obtained from the measurements made by the impeller 

and heat-pulse flowmeters were used to estimate the 

potential magnitude of interaquifer flow. A degree of 

error must be considered to be inherent in this evaluation because interaquifer flow rates in wells were not 

measured concurrently. For the flow rates to be accurate in this method of evaluation, all measurements 

must be made concurrently because flow rates may 

increase or decrease seasonally. 

A Geographical Information System (GIS) was 

used to aid in the estimation of interaquifer flow rates 

in wells open to both the intermediate aquifer system 

and the Upper Floridan aquifer. The ARC/INFO GIS 

system was used for the input data-base design and the 

calculation of interaquifer flow rates for the approximate 8,000 wells. A 1-mi by 1-mi grid was used to 

assign a location to each well and to total the number 

of wells in each grid cell (fig. 27). An interpolated 3-

dimensional flow surface was created with measured 

flow rates from both the impeller and heat-pulse flowmeters (fig. 10 and 17). Flow rates were assigned 

either an upward or downward flow direction based on 

field observations and head difference maps. This 

interpolated flow surface was then intersected with the 

grid network containing the apportioned wells. The 

total number of wells in each grid cell was multiplied 

by the assigned flow rate to obtain a cumulative flow 

rate for each cell. Cumulative flow rates were then 

summed for upward and downward flow direction. 

Using this approach, an estimated cumulative 

downward flow rate of 127 Mgal/d is being lost to the 

Upper Floridan aquifer from the intermediate aquifer 

system through interaquifer wells. This loss of water 

to the Upper Floridan aquifer may result in a loss of 

artesian pressure in the intermediate aquifer system 

and may change the natural flow gradient in some 

regions of the study area. Since the water of the intermediate aquifer system is of better quality than that of 

the Upper Floridan aquifer, this downward flow 

should not adversely affect the water quality of the 

Upper Floridan aquifer.

 An estimated cumulative upward flow rate of 

85 Mgal/d is discharging into the intermediate aquifer 

system from the Upper Floridan aquifer through interaquifer wells. The location of upward and downward 

flow through open boreholes in gallons per day is 

shown in figure 27. The estimated upward flow is 

considered low in Sarasota County because there are 

no records for many of the wells in the central part of 

the county. In Charlotte County, many wells were 

plugged, well records were nonexistent, or many wells 

were not drilled into the deeper Upper Floridan aquifer 

because the water was highly mineralized. In the 

majority of this designated area of upward flow, concentrations of chloride, sulfate, and dissolved solids 

exceed 250, 250, and 1,000 mg/L, respectively, and 

this upward borehole flow is contaminating the intermediate aquifer system. 

QUALITY OF WATER IMPROVEMENT 

PROGRAM

 Southwest Florida Water Management District 

began the Quality of Water Improvement Program 

(QWIP) in 1974 to restore hydrologic conditions 

altered by poorly installed wells or deteriorating 

casings. More than 3,000 wells have been inspected 

and approximately 1,350 have been plugged (fig. 25) 

as of May 1994. Hutchinson (1992) concluded that 
Quality of Water Improvement Program 49

0 5 10 15

0 5 10 15 KILOMETERS

Base map modified from U.S. Geological Survey MILES

Florida state base, 1:500,000

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS POLK

CHARLOTTE

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

HARDEE

DE SOTO

MANATEE

HIGHLANDS

EXPLANATION

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15

28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

WELLS OPEN TO THE

INTERMEDIATE AQUIFER SYSTEM

AND UPPER FLORIDAN AQUIFER

Harbor Charlotte 

Figure 26. Locations of wells in the study area that are reported and estimated to be open to both the intermediate 

aquifer system and the Upper Floridan aquifer.
50 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Figure 27. Grid network with cumulative downward and upward flow rates for wells open to both the 

intermediate aquifer system and the Upper Floridan aquifer.

EXPLANATION

ESTIMATED UPWARD AND DOWNWARD

APPROXIMATE BOUNDARY 

BETWEEN AREAS OF 

UPWARD AND DOWNWARD 

FLOW THROUGH OPEN BOREHOLES--

in gallons per day

0 - 50,000

50,001 - 100,000

100,001 - 150,000

150,001 - 200,000

GREATER THAN 200,000

CHARLOTTE

DE SOTO

HARDEE

Tampa Bay

PASCO

HILLSBOROUGH

PINELLAS

POLK

LEE

GLADES

HENDRY

OSCEOLA

SARASOTA

MANATEE

HIGHLANDS

45′ 45′

45′

45′

15′

15′

30′ 30′

30′

83°00′ 82°00′ 81°15′

28°15′

28°00′

27°00′

26°30′

Fort Myers

Bradenton

St. Petersburg

Arcadia

Lakeland

Fort Ogden

Lake Wales

Avon Park

Wauchula

Tampa

Sarasota

Englewood

Port Charlotte

SOUTHWEST FLORIDA WATER MANAGEMENT

DISTRICT BOUNDARY

APPROXIMATE BOUNDARY OF THE INTERMEDIATE AQUIFER SYSTEM

AREA OF UPWARD FLOW

AREA OF DOWNWARD FLOW

Charlotte Harbor

FLOW

0 5 10 15

0 5 10 15 KILOMETERS

Base map modified from U.S. Geological Survey MILES

Florida state base, 1:500,000

Gulf

of

Mexico

Alafia River

Little Manatee River

Myakka

Peace

River

Manatee

River

River
Summary and Conclusions 51

dissolved solids concentrations in water from a supply 

well decreased 50 percent after a nearby uncontrolled 

flowing artesian well was plugged. 

Sutcliffe and Joyner (1966) conducted a detailed 

study in Sarasota County using packers in wells for 

isolating various strata within an existing well for the 

collection of water samples and measurements of 

water levels. They concluded that: (1) better quality of 

water may be obtained in some areas by selectively 

casing wells; (2) contamination of the water within the 

various producing zones of a well may occur even 

though the well has flowed continuously; and 3) 

improperly cased flowing wells, which are capped and 

contain water of poor quality, rapidly contaminate all 

the strata in the area to the extent that the strata that 

formerly contained good water no longer contain 

potable water. 

Through an understanding of the hydrogeologic 

system in the study area, various techniques can be 

evaluated and undertaken to promote the most efficient and beneficial use of the ground-water resource. 

Alternative techniques that could help prevent further 

contamination of the aquifers include: (1) accurate 

reporting of well construction and use by land owners 

and well drillers; (2) selective casing of wells to obtain 

better water quality; (3) continued plugging of wells; 

and (4) inspection and monitoring of wells with blackiron casing in areas of poor-quality water. 

SUMMARY AND CONCLUSIONS

Thousands of deep artesian wells were drilled 

into the Upper Floridan aquifer in west-central Florida 

prior to the adoption of well-drilling regulations in the 

1970’s. The wells usually were completed with a short 

length of casing through the unconsolidated sediments 

and were left open to multiple aquifers containing 

water of varying quality. These open boreholes serve 

as a source of water-quality degradation within the 

aquifers when vertical flow is induced by hydraulichead differences. The area where there is a potential 

for water-quality degradation because of interconnected aquifers includes the southern half of the 

Southwest Florida Water Management District where 

both the intermediate aquifer system and Upper Floridan aquifer exist. 

 The hydrogeologic units underlying the study 

area consist of deposits of sand, clay, marl, and carbonate that were deposited primarily in a marine environment. Principal hydrogeologic units are the 

surficial aquifer, the intermediate aquifer system, and 

the Upper Floridan aquifer. The Upper Floridan aquifer is the most productive aquifer in the study area and 

supplies more than 10 times the amount of water 

pumped from either the surficial aquifer or the intermediate aquifer system. Most wells that penetrate the 

Upper Floridan aquifer are constructed so that they are 

also open to the intermediate aquifer system. 

In wells open to multiple aquifers, well construction, the relative permeabilities of the aquifers, 

and the head differences between aquifers control the 

magnitude of vertical borehole flow. In September 

1993, heads in the intermediate aquifer system were as 

much as 70 ft higher than heads in the Upper Floridan 

aquifer near the corner of Hillsborough, Manatee, 

Polk, and Hardee Counties. Water is transmitted 

downward through the confining unit and recharges 

the Upper Floridan aquifer. The head gradient reverses 

in the southern part of the study area where the Upper 

Floridan aquifer has higher heads than those of the 

intermediate aquifer system by as much as 20 ft in 

western Sarasota County and central Charlotte County. 

In these areas, water is transmitted upward through the 

lower confining unit and discharges to the intermediate aquifer system. 

The head differences between the intermediate 

aquifer system and the Upper Floridan aquifer in May 

1994 represent conditions near the end of a dry season 

during which extensive irrigation pumpage has 

occurred. In May 1994, heads in the intermediate aquifer system were as much as 90 ft higher than heads in 

the Upper Floridan aquifer near the corner of Hillsborough, Manatee, Polk, and Hardee Counties. In the 

southern part of the study area, heads were higher in 

the Upper Floridan aquifer than the intermediate aquifer by as much as 20 ft.

The determination of interaquifer flow was 

accomplished by obtaining geophysical logs of caliper, 

gamma, temperature, flow, and fluid conductivity, and 

by the collection of water-quality samples and video 

borehole data. Three different flowmeters were used to 

determine interaquifer flow-- an impeller flowmeter, a 

heat-pulse flowmeter, and a borehole video camera 

with an impeller flowmeter attachment because of the 

sensitivities and limitations of each meter. The advantage of the impeller flowmeter is that it can be used to 

measure high velocities. The limitations of the impeller flowmeter are that the direction of flow (either 

upward or downward) can not be distinguished accurately, and the meter has a lower detection limit of 
52 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

about 5 ft/min. The advantage of the heat-pulse flowmeter is that low-flow volumes and locations of the 

low-flow contributing zones can be detected. The limitation of the heat-pulse flowmeter is that velocities 

greater than 20 ft/min can not be measured accurately. 

In areas where direction of internal borehole flow 

could not be distinguished, the impeller flowmeter was 

connected to a video camera. The design proved to be 

useful in this study and enabled the viewer to observe 

a continuous profile of the well borehole and the direction of flow, to locate fractures or cavities associated 

with ground-water flow, and to inspect the casing for 

holes or breaks. 

 Borehole geophysical surveys were conducted 

in 87 wells throughout the study area to assess the 

nature of interaquifer borehole flow in wells open to 

multiple permeable zones. During the initial survey of 

each well, flow measurements were made using an 

impeller flowmeter. Of the 87 wells, 17 (20 percent) 

had detectable internal flow using the impeller flowmeter. The internal flow rates ranged from 10 to 300 

gal/min. A heat-pulse flowmeter was used in 19 wells 

in which flow was not detected using the impeller 

flowmeter. Of 19 wells measured, 18 (95 percent) had 

detectable internal borehole flow, with values ranging 

from 0.3 to 10 gal/min. 

Composite geophysical logs of fluid conductivity, caliper, temperature, gamma, and flow and waterquality data indicate that mineralized ground water 

from the Upper Floridan aquifer has moved upward 

through many open boreholes into the overlying 

fresher water zones in areas where there is an upward 

component of flow. Composite geophysical logs and 

water-quality data also indicate potable water from the 

intermediate aquifer system is artificially recharging 

the underlying Upper Floridan aquifer in areas where 

there is a downward component of flow. Monthly 

measurements of internal flow were made using the 

impeller flowmeter and indicate that flow rates change 

in response to seasonal head differences between the 

intermediate aquifer system and the Upper Floridan 

aquifer. Head changes between the aquifers, as a result 

of ground-water development, may increase recharge, 

reduce discharge, or may reverse the natural flow 

direction between the intermediate aquifer system and 

Upper Floridan aquifer. 

The chemical composition of water in the intermediate aquifer system is distinctly different in areas 

where the surficial aquifer recharges the intermediate 

aquifer system as compared to areas where the Upper 

Floridan aquifer discharges into the intermediate aquifer system. The intermediate aquifer system contains a 

transitional type of ground water with chemistry 

reflecting the two sources of water moving into the 

aquifer and the water can be characterized as a mixed 

calcium bicarbonate, calcium magnesium sulfate, and 

sodium chloride type. Water in the Upper Floridan 

aquifer can be characterized as a calcium magnesium 

sulfate and sodium chloride type. The chemistry of the 

water in the Upper Floridan aquifer is predominately 

affected by processes such as dissolution of gypsum 

and dolomite, calcite precipitation, and seawater mixing. 

 Ground water in the intermediate aquifer system and the Upper Floridan aquifer with the lowest 

chloride, sulfate, and dissolved solids concentrations 

occurs in recharge areas in northeastern Polk County 

and Highlands County. Ground water in the intermediate aquifer system and the Upper Floridan aquifer with 

the highest chloride, sulfate, and dissolved solids concentrations occurs in discharge areas along the coast 

and in the Peace River Valley. For most of the study 

area, water in the Upper Floridan aquifer is more mineralized than that in the overlying intermediate aquifer 

system. 

 Degradation of water quality can occur in the 

intermediate aquifer system from the natural discharge 

of highly mineralized water from the underlying 

Upper Floridan aquifer. Degradation of water quality 

may also occur in both the intermediate aquifer system 

and Upper Floridan aquifer through saltwater intrusion, improperly cased wells open to multiple aquifers 

containing water of varying quality, and leaky and corroded black-iron well casings in areas of poor-quality 

water. A geographical area where there is a potential 

for water-quality degradation because of improperly 

cased wells was defined. This area was delineated 

based on an upward component of flow and the occurrence of poor-quality water. The delineated area 

includes parts of Hillsborough, Manatee, Sarasota, 

Charlotte, De Soto, and Hardee Counties. 

An evaluation was performed to estimate the 

potential magnitude of interaquifer flow in wells open 

to multiple aquifers within the study area. This evaluation used a Geographical Information System to estimate interaquifer flow rates in wells open to both the 

intermediate aquifer system and the Upper Floridan 

aquifer. An estimated cumulative downward flow rate 

of 127 Mgal/d is artificially recharging the Upper 

Floridan aquifer from the intermediate aquifer system 
Selected References 53

through interaquifer wells. An estimated cumulative 

upward flow rate of 85 Mgal/d is artificially discharging into the intermediate aquifer system from the 

Upper Floridan aquifer through interaquifer wells. In 

most of this area of upward flow, concentrations of 

chloride, sulfate, and dissolved solids, exceed 250, 

250, and 1,000 mg/L, respectively, and this upward 

borehole flow may be contaminating the upper zones.

 In 1974, Southwest Florida Water Management 

District began the Quality of Water Improvement Program to restore hydrologic conditions altered by 

poorly installed wells or deteriorating casings. As of 

May 1994, more than 3,000 wells have been inspected 

and approximately 1,350 have been plugged. Studies 

indicate that better quality of water may be obtained in 

some areas by plugging wells and by selectively casing wells in zones of poor-quality water. 

SELECTED REFERENCES

Berndt, M.P., and Katz, B.G., 1992, Hydrochemistry of the 

surficial and intermediate aquifer systems in Florida: 

U.S. Geological Survey Water-Resources Investigations Report 91-4186, 24 p.

Boggess, D.H., Missimer, T.M., and O’Donnell, T.H., 1977, 

Saline-water intrusion related to well construction in 

Lee County, Florida: U.S. Geological Survey WaterResources Investigations Report 77-33, 29 p.

Crowder, R.E., and Paillet, F., and Hess, A., 1994, High resolution flowmeter logging- A unique combination of 

borehole geophysics and hydraulics; Part I; Flowmeter 

techniques and equipment development: Proceedings 

of the Symposium on the Application of Geophysics to 

Environmental and Engineering Problems, March 26-

30, 1994, Boston, Massachusetts.

Duerr, A.D., and Enos, G.M., 1991, Hydrogeology of the 

intermediate aquifer system and Upper Floridan aquifer, Hardee and De Soto Counties, Florida: U.S. Geological Survey Water- Resources Investigations Report 

90-4104, 46 p.

Duerr, A.D., Hunn, J.D., Lewelling, B.R., and Trommer, 

J.T., 1988, Geohydrology and 1985 water withdrawals 

of the aquifer systems in southwest Florida, with 

emphasis on the intermediate aquifer system: U.S. 

Geological Survey Water-Resources Investigations 

Report 87-4259, 115 p.

Florida Department of Environmental Regulations, 1985, 

Public drinking water systems, in Florida Administrative Code: chap. 17-22.

Gilboy, A.E., 1985, Hydrogeology of the Southwest Florida 

Water Management District: Brooksville, Southwest 

Florida Water Management District Report, 18 p.

Healy, H.G., 1978, Appraisal of uncontrolled flowing artesian wells in Florida: U.S. Geological Survey WaterResources Investigations 78-95, 26 p. 

Hem, J.D., 1989, Study and interpretation of the chemical 

characteristics of natural water (3rd ed.): U.S. Geological Survey Water-Supply Paper 2254, 263 p.

Hess, A.E., 1990, Thermal-pulse flowmeter for measuring 

slow water velocities in boreholes: U.S. Geological 

Survey Open-File Report 87-121, 70 p.

Hutchinson, C.B., 1992, Assessment of hydrogeologic conditions with emphasis on water quality and wastewater 

injection, southwest Sarasota and west Charlotte Counties, Florida: U.S. Geological Survey Water-Supply 

Paper 2371, 74 p.

Hutchinson, C.B., 1978, Appraisal of shallow ground-water 

resources and management alternatives in the upper 

Peace and eastern Alafia River basins, Florida: U.S. 

Geological Survey Water-Resources Investigations 

Report 77-124, 57 p. 

Katz, B.G., 1992, Hydrochemistry of the Upper Floridan 

aquifer, Florida: U.S. Geological Survey Open-File 

Report 91-496, 37 p.

Keys, W.S., and MacCary, L.M., 1971, Application of borehole geophysics to water-resources investigations: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book. 2, chap. E1, 126 p.

Keys, W.S., 1990, Borehole geophysics applied to groundwater investigations: U.S. Geological Survey Techniques of Water-Resources Investigations, book 2, 

chap. E2, 150 p. 

Johnston, R.H., and Bush, P.W., 1988, Summary of the 

hydrology of the Floridan aquifer system in Florida 

and in parts of Georgia, South Carolina, and Alabama: 

U.S. Geological Survey Professional Paper 1403-A, 

24 p. 

La Rose, H.A., 1990, Geohydrologic framework and an 

analysis of a well-plugging program, Lee County, Florida: U.S. Geological Survey Water-Resources Investigations Report 90-4063, 26 p. 

Metz, P.A., 1995, Hydrogeology and simulated effects of 

ground-water withdrawals for citrus irrigation, Hardee 

and De Soto Counties, Florida: U.S. Geological Survey 

Water-Resources Investigations Report 93-4158, 83 p.

Metz, P.A., and Brendle, D.L., 1994a, Potentiometric surface of the intermediate aquifer, west-central Florida, 

May 1994: U.S. Geological Survey Open-File Report 

94-529, 1 sheet.

———1994b, Potentiometric surface of the Upper Floridan 

aquifer, west-central Florida, May 1994: U.S. Geological Survey Open-File Report 94-528, 1 sheet.

Miller, J.A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, 

Alabama, and South Carolina: U.S. Geological Survey 

Professional Paper 1403-B, 91 p.
54 Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida

Mularoni, R.A., 1994a, Potentiometric surface of the intermediate aquifer, west-central Florida, September 1993: 

U.S. Geological Survey Open-File Report 94-80, 

1 sheet.

———1994b, Potentiometric surface of the Upper Floridan 

aquifer, west-central Florida, September 1993: U.S. 

Geological Survey Open-File Report 94-81, 1 sheet.

Paillet, F.L., Crowder, R.E., and Hess, A., 1994, High resolution flowmeter logging-A unique combination of 

borehole geophysics and hydraulics; Part II- Borehole 

applications with the heat-pulse flowmeter: Proceedings of the Symposium on the Application of Geophysics to Environmental and Engineering Problems, 

March 26-30, 1994, Boston, Massachusetts. 

Palmer, C.E., and Bone, L.P., 1977, Some aspects of rainfall 

deficits in west-central Florida, 1961-1976: Southwest 

Florida Water Management District Hydrometeorological Report no. 1, 19 p.

Ryder, P.D., 1982, Digital model of predevelopment flow in 

the Tertiary limestone (Floridan) aquifer system in 

west-central Florida: U.S. Geological Survey WaterResources Investigations Report 81-54, 61 p. 

———1985, Hydrology of the Floridan aquifer system in 

west-central Florida: U.S. Geological Survey Professional Paper 1403-F, 63 p.

Rye, R.O., Back, W., Hanshaw, B.B., Rightmire, C.T., and 

Pearson, F.J., Jr., 1981, The origin and isotopic composition of dissolved sulfide in ground water from 

carbonate aquifers in Florida and Texas: Geochimica et 

Cosmochimica Acta, v. 45 no. 10, p. 1941-1950.

Southeastern Geological Society, 1986, Hydrogeological 

units of Florida: Florida Geological Survey Special 

Publication no. 28, 8 p.

Southwest Florida Water Management District, 1994, Artesian well plugging work plan, Quality of Water 

Improvement Program: January 1994.

Southwest Florida Water Management District, 1994, 

Aquifer characteristics within the Southwest Florida 

Water Management District, June 1994: 111 p.

Sproul, C.R., Boggess, D.H., and Woodard, H.J., 1972, 

Saline-water intrusion from deep artesian sources in 

the McGregor Isles area of Lee County, Florida: 

Florida Bureau of Geology Information Circular 75, 

30 p.

Sutcliffe, Horace, Jr., 1975, Appraisal of the water resources 

of Charlotte County, Florida: Florida Bureau of 

Geology Report of Investigations 78, 53 p. 

Sutcliffe, Horace, Jr. and Joyner, B.F, 1966,Packer testing in 

water wells near Sarasota, Florida: Ground Water, v.4, 

no. 2, p. 23-27.

White, W.A., 1970, The geomorphology of the Florida 

Peninsula: Florida Bureau of Geology Bulletin no. 51, 

164 p.

Wilson, W. E., 1977, Ground-water resources of De Soto 

and Hardee Counties, Florida: Florida Bureau of 

Geology Report of Investigations no. 83, 102 p.

Wolansky, R.M., and Corral, M.A., Jr. 1985, Aquifer tests in 

west-central Florida, 1952-76: U.S. Geological Survey 

Water-Resources Investigations Report 84-4044, 127 

p.

Wolansky, R.M., Spechler, R.M., and Buono, Anthony, 

1979, Generalized thickness of the surficial deposits 

above the confining bed overlying the Floridan aquifer, 

Southwest Florida Water Management District: U.S. 

Geological Survey Water-Resources Investigations 

Open-File Report 79-1071, 1 sheet.