ALTITUDE, IN FEET BELOW NGVD OF 1929

SURFICIAL

AQUIFER

SYSTEMINTERMEDIATE CONFINING UNIT

UPPER

FLORIDAN

AQUIFER

MIDDLE

CONFINING

UNIT

LOWER

FLORIDAN

AQUIFER

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

INLAND AREA COASTAL AREA

OK-29 STL-223 STL-422 STL-332 STL-352

?

FLORIDA’S TURNPIKE

24

24

24

26

26

28

30

32

28

28

28 26 28

28

26

26

26

26

26

26

28

1

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC

OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY FAULT MAPPED BY BARNETT (1975)

70

60

710

441

FLORIDA’S

1

95

95

95

TURNPIKE

U D

M-1121

M-1326

OK-72 STL-215

STL-217

STL-218

STL-220

STL-225

STL-356

G2-2

G2-3

G3-1

G5-1

G29-14

G29-15

G35-1

G36-1 G36-2

JUPITER

SAILFISH POINT

Hydrogeology, Water Quality, and

Distribution and Sources of Salinity

in the Floridan Aquifer System,

Martin and

St. Lucie Counties,

Florida

Water-Resources

Investigations Report

03-4242

U.S. Department of the Interior

U.S. Geological Survey

South Florida Water Management District

Prepared in cooperation with the
Hydrogeology, Water Quality, and Distribution and 

Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

By Ronald S. Reese

U.S. Geological Survey

Water-Resources Investigations Report 03-4242

Prepared in cooperation with the

South Florida Water Management District

Tallahassee, Florida

2004
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

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: 

U.S. Geological Survey

2010 Levy Avenue

Tallahassee, FL 32310

Copies of this report can be 

purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

888-ASK-USGS

Additional information about water resources in Florida is available on the internet 

at http://fl.water.usgs.gov
Contents III

CONTENTS

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Methods of Evaluation and Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Inventory of Well Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Collection and Analyses of Water-Quality Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Quality Assurance Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Geologic Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Geologic Units and Lithology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Hydrogeology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Surficial Aquifer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Intermediate Confining Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Floridan Aquifer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Upper Floridan Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Middle Confining Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Lower Floridan Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Ground-Water Flow of the Floridan Aquifer System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Potentiometric Surface of the Upper Floridan Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Ground-Water Withdrawals and Recharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Water Quality in the Floridan Aquifer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Classification and Characterization of Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Distribution of Salinity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Upper Floridan Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Lower Floridan Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Salinity Zone Boundaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Distribution of Water Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Isotopic Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Deuterium and Oxygen-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Strontium-87/Strontium-86 and Strontium Concentration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Stable and Radioactive Carbon Isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Temporal Changes in Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Sources of Salinity in the Floridan Aquifer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Relict Seawater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Upward Movement of the Saltwater Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Lateral Encroachment of the Saltwater Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Upward Leakage through Structural Deformities or Dissolution Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Areas of Highest Potential for Increasing Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Appendix I: Inventory of Wells Used in this Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Appendix II: Boundaries of Geologic Units in Selected Wells Penetrating the Floridan Aquifer System as 

Determined for this Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Appendix III: Selected Water-Quality Data Collected from Known Intervals in Wells in the Floridan Aquifer System . . . . 83

Appendix IV: Major Constituent and Field Characteristic Water-Quality Data Collected from Floridan Aquifer 

System Wells in this Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
IV Contents

Plates

1. Map showing location of wells used for geologic mapping in the study and hydrogeologic 

section lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . in back pocket

2. Map showing location of wells with water-quality data used in the study . . . . . . . . . . . . . . . . . . . . . . . in back pocket

Figures

1. Map of study area showing lines of hydrogeologic sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Map showing location of municipal water system wells, wastewater injection wells, aquifer storage and 

recovery test wells, aquifer performance test wells, and Floridan aquifer system monitoring wells used in 

the study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

3. Chart showing generalized geology and hydrogeology in Martin and St. Lucie Counties as defined for 

this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

4-8. East-west hydrogeologic sections:

4. A-A′ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

5. B-B′ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

6. C-C′ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

7. D-D′ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

8. E-E′. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

9. Gamma-ray geophysical log, flow zones, stratigraphy, and hydrogeologic units for well PB-1197 in 

northeastern Palm Beach County . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

10-15. Maps showing: 

10. Anomalous linear structures in the study area mapped in previous studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

11. Altitude of the top of the basal Hawthorn/Suwannee unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

12. Thickness of the basal Hawthorn/Suwannee unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

13. Altitude of the top of the Ocala Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

14. Altitude of the top of the Lower Floridan aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

15. Potentiometric surface of the Upper Floridan aquifer, May 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

16-20. Plots showing: 

16. Relations between water level and time and between chloride concentration and time for wells 

STL-220 and STL-224 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

17. Yearly water withdrawals from Natural Resources Conservation Service monitoring wells in the 

study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

18. Relation between chloride and dissolved-solids concentrations for samples collected in this study. . . . . . . . . .32

19. Sulfate and chloride concentrations for samples collected in this study and relation to a pure 

water-seawater mixing line. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

20. Relation between specific conductance and chloride concentration less than 4,000 milligrams per 

liter for samples collected during this study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

21. Map showing distribution of chloride concentration in the Upper Floridan aquifer . . . . . . . . . . . . . . . . . . . . . . . . . .35

22. Plots showing relation between well depth and chloride concentration less than 4,000 milligrams per 

liter for inland and coastal areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

23-24. Logs showing water-quality data, resistivity geophysical log, salinity zones, and hydrogeologic units:

23. For wells at the Coral Springs Wastewater Treatment Plant in northeastern Broward County . . . . . . . . . . . . . .38

24. For twin wells STL-332 and STL-333 at the Fort Pierce Wastewater Treatment Plant in northeastern 

St. Lucie County. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

25. Map showing altitude of the base of the brackish-water zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

26. Map showing distribution of water temperature in the Upper Floridan aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Contents V

27-32. Plots showing relation between: 

27. Well depth and water temperature for inland and coastal areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

28. Water temperature and chloride concentration less than 4,000 milligrams per liter for inland and 

coastal areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

29. Delta deuterium and delta oxygen-18 in ground water in the study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

30. Strontium and chloride concentrations in ground water in the study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

31. Ratio of strontium-87 to strontium-86 and the inverse of strontium concentration in ground water 

in the study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

32. δ13C and carbon-14, in percent modern carbon in the study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

33. Plot showing water-use and specific conductance data for Natural Resources Conservation Service

monitoring well G35-1, 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

34. Graph showing average monthly total water withdrawals and average chloride concentrations for eight 

production wells at the Jupiter Well Field, January 1996 to July 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

35. Map showing location of monitoring wells and well fields with increasing salinity over time and distribution

of water temperature in the Upper Floridan aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Tables

1. Identification of wells used at municipal water system sites, wastewater injection sites, and aquifer storage

and recovery and aquifer performance test sites in the study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2. Changes in water level and chloride concentration for South Florida Water Management District 

ground-water level monitoring network wells completed in the Floridan aquifer system . . . . . . . . . . . . . . . . . . . . . 27

3. Wells in production at Floridan aquifer system municipal water systems in the study area and their average

withdrawals and aquifer(s) open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4. Depths to salinity zone boundaries in the Floridan aquifer system as determined in this study . . . . . . . . . . . . . . . . . 41

5. Calculated altitudes of a saltwater interface using the Ghyben-Herzberg approximation and comparison 

with altitudes of the base of the brackish-water zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

6. Isotopic data collected in this study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
VI Contents

Conversion Factors, Abbreviations and Acronyms, and Datum

Abbreviations and Acronyms used in this report:

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F - 32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 1929); horizontal 

coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Multiply By To obtain

inch (in.) 25.4 millimeter

inch per year (in/yr) 25.4 millimeter per year

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

square mile (mi2) 2.589 square kilometer

gallon (gal) 3.785 liter

million gallons (Mgal) 3,785 cubic meter

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

square feet per day (ft2/d) 0.09294 square meter per day

mg/L milligrams per liter

ohm-m ohm-meter

μm micrometer

API American Petroleum Institute

FDEP Florida Department of Environmental Protection

GWSI Ground-Water Site Inventory (U.S. Geological Survey database)

NRCS Natural Resources Conservation Service

PMC Percent modern carbon

QWDATA USGS Water Quality Data Base

PDB Vienna Pee dee Belemnite standard

PMC Percent modern carbon

RO Reverse osmosis

SFWMD South Florida Water Management District

SLAP Standard Light Antarctic Precipitation

UEC Upper East Coast 

USGS U.S. Geological Survey

VSMOW Vienna Standard Mean Ocean Water

WWTP Wastewater treatment plant
Abstract 1

Hydrogeology, Water Quality, and Distribution and 

Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

By Ronald S. Reese

ABSTRACT 

The Floridan aquifer system is considered to be a 

valuable source for agricultural and municipal water 

supply in Martin and St. Lucie Counties, despite its 

brackish water. Increased withdrawals, however, could 

increase salinity and threaten the quality of withdrawn 

water. The Floridan aquifer system consists of limestone, dolomitic limestone, and dolomite and is divided 

into three hydrogeologic units: the Upper Floridan 

aquifer, a middle confining unit, and the Lower Floridan aquifer. An informal geologic unit at the top of the 

Upper Floridan aquifer, referred to as the basal 

Hawthorn/Suwannee unit, is bound above by a marker 

unit in the Hawthorn Group and at its base by the Ocala 

Limestone; a map of this unit shows an area where 

substantial eastward thickening begins near the coast. 

This change in thickness is used to divide the study 

area into inland and coastal areas.

In the Upper Floridan aquifer, an area of elevated 

chloride concentration greater than 1,000 milligrams 

per liter and water temperature greater than 28 degrees 

Celsius exists in the inland area and trends northwest 

through north-central Martin County and western St. 

Lucie County. A structural feature coincides with this 

area of greater salinity and water temperature; this 

feature is marked by a previously mapped northwesttrending basement fault and, based on detailed 

mapping in this study of the structure at the top of the 

basal Hawthorn/Suwannee unit, an apparent southeasttrending trough. Higher hydraulic head also has been 

mapped in this northwest-trending area. Another area 

of high chloride concentration in the Upper Floridan 

aquifer occurs in the southern part of the coastal area 

(in eastern Martin County and northeastern Palm Beach 

County); chloride concentration in this area is more 

than 2,000 milligrams per liter and is as great as 8,000 

milligrams per liter.

A dissolved-solids concentration of less than 

10,000 milligrams per liter defines the brackish-water 

zone in the Floridan aquifer system; the top and base of 

this zone are present at the top of the aquifer system 

and within the Lower Floridan aquifer, respectively. 

The base of the brackish-water zone, which can 

approximate a brackish-water/saltwater interface, was 

determined in 13 wells, mostly using resistivity 

geophysical logs. The depth to the saltwater interface 

was calculated using the Ghyben-Herzberg approximation and estimated predevelopment hydraulic heads in 

the Upper Floridan aquifer. In five of six inland area 

wells, the depth to the base of the brackish-water 

zone was substantially shallower than the estimated 
2 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

predevelopment interface (260 feet or greater), whereas 

in five of seven coastal area wells, the difference was 

not large (less than about 140 feet). Confining units in 

the inland area, such as dense dolomite, may prevent an 

interface from forming at its equilibrium position. 

Because of head decline, the calculated interface using 

recent (May 2001) water levels is as much as 640 ft 

above the base of the brackish water zone (in the northern part of the coastal area). 

Isotopic data collected during this study, including deuterium and oxygen-18 (18O/16O), the ratio of 

strontium-87 to strontium-86, and carbon-13 (13C/12C) 

and carbon-14, provide evidence for differences in the 

Floridan aquifer system ground-water geochemistry 

and its evolution between inland and coastal areas. 

Ground water from the inland area tends to be older 

than water from the coastal area, particularly where 

inland area water temperature is elevated. Isotopic data 

together with an anomalous vertical distribution of 

salinity in the coastal area indicate that the coastal area 

was invaded with seawater in relatively recent geologic 

time, and this water has not been completely flushed 

out by the modern-day flow system. 

Upward leakage from the Lower to Upper Floridan aquifer of high salinity water occurs through structural deformities, such as faults or fracture zones or 

associated dissolution features in the inland area. An 

upward trend in salinity is indicated in 16 monitoring 

wells in the inland area, and agricultural withdrawals 

are probably causing these increases. Most of these 

wells are located in areas of elevated Upper Floridan 

aquifer ground-water temperature. Areas of higher 

water temperature could represent areas of greater 

potential for increases in salinity. More detailed 

mapping of the structure of the uppermost geologic 

units in the aquifer system could better define areas of 

deformation. Additionally, high potential exists in 

much of the study area for upward or lateral movement 

of the saltwater interface because of large declines in 

hydraulic head since predevelopment. The northern 

part of the coastal area has the greatest potential for 

movement; however, upward movement of the interface in the coastal area could be retarded by low vertical permeability. The potential for upward or lateral 

movement of the interface in the southern part of the 

coastal area seems to be low, but structural deformation 

could be present in northeastern Palm Beach County, 

allowing for localized upward leakage of saltwater.

INTRODUCTION 

Rapid urban development has raised concern 

about increased water use and the potential for degradation of water quality in the Floridan aquifer system 

in the Upper East Coast (UEC) of southern Florida. 

The UEC is one of four regional planning areas in the 

South Florida Water Management District (SFWMD). 

The UEC Planning Area encompasses about 1,200 mi2 

and includes most of Martin and St. Lucie Counties and 

a small part of Okeechobee County. Water for urban 

and agricultural use in the UEC Planning Area comes 

from surface water, the surficial aquifer system, and the 

Floridan aquifer system.

The Floridan aquifer system constitutes the Upper 

Floridan aquifer, a middle confining unit, and the Lower 

Floridan aquifer. Withdrawal of water from the Floridan 

aquifer system in urban coastal areas for municipal 

supply is projected to increase at a much higher rate than 

withdrawals for irrigation in inland areas (South Florida 

Water Management District, 1998). Currently, withdrawals in the UEC Planning Area are restricted to artesian flow or pumping rates that do not lower hydraulic 

head below land surface, but increased urban demand 

could necessitate increased withdrawals. Most water is 

withdrawn from the Upper Floridan aquifer, but withdrawals from the Lower Floridan aquifer for public 

supply have been increasing in recent years. Because of 

its brackish to saline nature, ground water obtained from 

the Floridan aquifer system for public supply in the UEC 

Planning Area is desalinated by the reverse osmosis 

(RO) method, or blended with freshwater from the surficial aquifer system.

The salinity of the withdrawn Floridan aquifer 

system ground water can vary sharply, and extended 

periods of high withdrawals can contribute to the influx 

of ground water with higher salinity. An understanding 

of relations between water quality, withdrawal rate, and 

aquifer hydraulic head is needed by water managers to 

ensure a sustainable supply of water of adequate quality. Potential sources of higher salinity water in the 

Floridan aquifer system and mechanisms for the movement of this water include relict seawater, upconing or 

upward movement of the saltwater interface, lateral 

encroachment of the saltwater interface along the coast, 

and upward leakage of saline water through structural 

deformities or dissolution features. Mechanisms that 

are occurring or that are most likely to occur need to be 

identified; an understanding of the hydrogeologic 

framework and the flow system history will help in this 

identification. To address these information needs, the 
Introduction 3

U.S. Geological Survey (USGS), in cooperation with 

the SFWMD, conducted a study from April 1999 

through September 2002. The purpose of this study 

was to: (1) identify the most likely sources of higher 

salinity in the Floridan aquifer system, (2) determine 

how these sources could affect ground-water withdrawals, 

and (3) identify areas in the UEC Planning Area that 

are most vulnerable to potential increases in salinity. 

Purpose and Scope

The purposes of this report are to: (1) describe 

the hydrogeologic framework and ground-water flow 

system in the Floridan aquifer system in the study area; 

(2) describe relations between salinity, withdrawal rate, 

and hydraulic head; (3) identify the potential sources of 

higher salinity water in the aquifer system and discuss 

potential flow mechanisms and pathways for movement 

of this water to a production well; and (4) describe areas 

that have high potential for increasing salinity due to 

current or increasing ground-water withdrawals. Data 

are presented for 73 water-quality samples collected 

from the Floridan aquifer system wells with analysis 

for major and minor ions, field characteristics, and 

hydrogen, oxygen, strontium, and carbon isotopes. 

Hydrogeologic sections and contour maps illustrate the 

top of the Floridan aquifer system and a key geologic 

unit contained within it. Additional maps show the spatial distributions of salinity and water temperature and 

the approximate altitude of the top of saline water.

Description of Study Area

The study area encompasses the UEC Planning 

Area, Martin and St. Lucie Counties, and parts of Palm 

Beach and Okeechobee Counties (fig. 1). It is bounded 

by Indian River County to the north, the Atlantic Ocean 

to the east, and part of Lake Okeechobee to the west. 

One deep well (IR-1001) in Indian River County 

located outside the study area, about 2 mi north of the 

St. Lucie County boundary, is used for an additional 

point of control in mapping. Land-surface altitude in 

the study area ranges from sea level to about 60 ft 

above NGVD of 1929. A topographic high, referred to 

as the Osceola Plain (fig. 1), extends southeasterly 

through eastern Okeechobee County, extreme southwestern St. Lucie County, and into western Martin 

County. Excluding this topographic high area, landsurface altitude in the study area is less than 35 ft above 

NGVD of 1929.

Previous Studies

Several studies on the Floridan aquifer system, 

conducted as part of the Regional Aquifer System 

Analysis Program of the USGS (USGS Professional 

Paper 1403 series reports), were used as a basis for this 

report. The hydrogeologic framework of the Floridan 

aquifer system was described over its full extent (all of 

Florida and parts of Georgia, Alabama, and South 

Carolina) by Miller (1986). The ground-water hydraulics, regional flow, and ground-water development of 

the Floridan aquifer system were described for this 

region by Bush and Johnston (1988). Meyer (1989) 

analyzed the hydrogeology and ground-water movement in southern Florida. 

Local hydrogeologic studies conducted in 

Martin, St. Lucie, and adjacent counties include reports 

by Lichtler (1960), Brown and Reece (1979), Mooney 

(1980), Shaw and Trost (1984), Schiner and others 

(1988), Bradner (1994), Duncan and others (1994), 

Lukasiewicz and Switanek (1995), Weedman and 

others (1995), and Reese and Memberg (2000). Areas 

of anomalously high salinity occurring above the 

brackish-water/saltwater interface and in the Upper 

Floridan aquifer were identified in southeastern Florida 

(Reese, 1994; Reese and Memberg, 2000). Local 

hydrogeologic data reports include those by Reece and 

others (1980; 1984) and Lukasiewicz and Smith 

(1996). Modeling studies of the Floridan aquifer 

system in the study area, or a portion thereof, were 

conducted by Bush and Johnston (1988), Tibbals 

(1990), and Lukasiewicz (1992).

Acknowledgments

The author graciously thanks SFWMD personnel 

for their assistance in this investigation. The author 

accompanied Pete Dauenhauer in the field, who 

provided technical assistance, location maps, and 

owner contact information for Upper Floridan aquifer 

monitoring wells that were later sampled. John Cain 

provided potentiometric head data collected since 1986 

from the SFWMD Floridan aquifer system monitoring 

well network. Simon Sunderland provided additional 

data on the Floridan aquifer system monitoring well 

network and data collected from an irrigation well 

monitoring program run by the Natural Resources 

Conservation Service (NRCS). Milton Switanek 

located SFWMD well abandonment geophysical logs 

in the UEC and had them digitized.
4 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

OSCEOLA PLAIN

St. Lucie

River

M-1330

B B ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

0

0

15 MILES

15 KILOMETERS

5 10

5 10 EXPLANATION

WELL LOCATION AND NUMBER

LINE OF HYDROGEOLOGIC SECTION

UPPER EAST COAST PLANNING AREA

FROM SOUTH FLORIDA WATER

MANAGEMENT DISTRICT

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

A

B

C

D

E

D ́

E ́

A ́

B ́

C ́

70

60

710

441

FLORIDA’S TURNPIKE

FLORIDA’S

1

1

95

95

95

TURNPIKE

NORTHERN BOUNDARY

OF STUDY AREA

STL-356

M-1353

STL-379

M-740

M-1125

M-1360 M-1330

PB-1144

PB-1197

M-186

M-744

M-1076

M-1118

M-1121

M-1329

OK-100

OK-9000

STL-225

OK-5

STL-71

STL-220 STL-334

STL-353

STL-354

WA-580

OK-29

STL-216

STL-217

STL-223

STL-224

STL-332

STL-352

STL-422

WA-887

IR-1001

OK-2

OK-202

OK-203

STL-218 WA-1031

Location of

study area

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 1. Study area showing lines of hydrogeologic sections.
Methods of Evaluation and Data Collection 5

The author appreciates the assistance of Marion 

Parsons with the St. Lucie County Soil Conservation 

Service, as well as water or wastewater treatment plant 

personnel. Ms. Parsons provided additional information on the NRCS monitoring wells and assisted in the 

field with sampling several of these wells. Personnel at 

water and wastewater treatment plants assisted in 

sampling and provided data on wells operated by their 

utility. These utilities included Ft. Pierce, Jupiter Water 

Systems, North Martin County, Port St. Lucie, Stuart, 

and Tequesta.

METHODS OF EVALUATION AND DATA 

COLLECTION 

This section describes, inventories, and gives the 

location of wells used in the study. Additionally, the 

collection and analyses of water-quality data, are 

discussed. Finally, results of quality-assurance 

sampling are given. 

Inventory of Well Data

Data for all wells used in this study were inventoried and are presented in appendix I; the data include 

the completed open intervals for each well, if known. 

The depth of the bottom of casing(s) and the total depth 

drilled also are included. A completed interval in a well 

is defined as an interval open to flow. Completed intervals are generally isolated from each other, and from 

other parts of the borehole, through the use of casing 

and cement during construction of the well and usually 

are constructed as open hole in the study area.

Data for most wells used in this investigation are 

stored in the USGS Ground Water Site Inventory 

(GWSI) database. Additional information for the wells 

in GWSI, beyond that provided in appendix I, is available in the database, including land net location 

(section, township, and range) drilling contractor’s 

name, and owner. The prefixes used for USGS well 

numbers in GWSI are “M” for Martin County, “OK” 

for Okeechobee County, “PB” for Palm Beach County, 

and “STL” for St. Lucie County. Wells not included in 

GSWI are those from the SFWMD well abandonment 

program and irrigation wells used in a monitoring 

program by the NRCS. The SFWMD abandonment 

wells have numbers with a “WA” prefix instead of a 

USGS number prefix, and the NRCS wells have a 

number with a “G” prefix. 

Because of the large number of wells used in the 

study, they were grouped by function or purpose, and 

their locations are shown on three maps. All wells used 

for geologic mapping are shown on plate 1. All of the 

source wells for the water-quality data used are shown 

on plate 2. Additionally, municipal water wells, wastewater injection wells, aquifer storage and recovery 

wells, aquifer performance test wells, and Floridan 

aquifer system monitoring wells operated by the 

SFWMD and NRCS used in the study are shown in 

figure 2. Except for the monitoring wells, all the wells 

in figure 2 are described in table 1, grouped by site 

name. Wells CS-I1 and CS-M2, also used in the study, 

are located at the Coral Springs Wastewater Treatment 

Plant (WWTP) about 40 mi south of the study area and 

11 mi west of the coast. 

Depth in a well, as used in this report, refers to 

feet below the measuring point. In most cases, measuring point and land-surface altitudes coincide; however, 

in some instances, the measuring point lies above landsurface altitude. If measurement of a point in a well is 

referenced herein to NGVD of 1929, then the phrase 

“altitude, in feet below NGVD 1929” or simply “feet 

below NGVD of 1929” is used.

Some of the wells used in this study are located 

in close proximity to one another (fig. 2). For example, 

at most wastewater injection system sites, a monitoring 

well was drilled adjacent to an injection well. Monitoring well MW2-2 (M-1353) at the Stuart WWTP in 

Martin County is only 70 ft from injection well IW-2 

(M-1352). Data collected from injection-monitoring 

well pairs and other wells drilled in close proximity at a 

site are treated herein as a single well control point. 

Thus, well M-1353 (shown in fig. 1) also represents 

well M-1352 (fig. 2).

Collection and Analyses of 

Water-Quality Data

A total of 73 water-quality samples were 

obtained from 50 wells and analyzed for major constituents and field characteristics. These constituents 

included calcium, magnesium, sodium, potassium, 

chloride, fluoride, sulfate, bromide, strontium, silica, 

and dissolved-solids concentration. Specific conductance, pH, water temperature, and alkalinity were measured in the field. Isotopic analyses for the strontium87 to strontium-86 ratio (87Sr/86Sr), hydrogen-2 

(deuterium or 2H/1H), and oxygen-18 (18O/16O) were 

made for 56 samples, and isotopic analyses for carbon-13 

(13C/12C) and carbon-14 (14C) were made for 38 

samples. Results from water-quality analyses were 

stored in the USGS water-quality database (QWDATA).
6 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

G3-1

G12-1

G205-5

IR-1001

M-255

M-745

M-1033

M-1034

M-1118

M-1121

M-1125

M-1324

M-1325

M-1326

M-1328

M-1330

M-1349 M-1352

M-1353

M-1357

M-1358

M-1359

M-1360

OK-3

OK-13

OK-23

OK-31

OK-100

OK-9000 OK-9001

OK-9002

PB-747

PB-1144

PB-1166

PB-1167

PB-1133

OIL TEST

PB-1170

PB-1182

PB-1183

PB-1196

PB-1197

PB-1774

STL-215

STL-216

STL-217

STL-218

STL-220

STL-224

STL-225

STL-229

STL-254

STL-255

STL-386

STL-332

STL-333

STL-334

STL-335

STL-342

STL-346

STL-353

STL-355

STL-356

STL-357 STL-379

STL-380

STL-381

STL-382

STL-385

STL-387

STL-388 STL-389

STL-422

G1-1

G2-1

G2-2G2-3

G3-2G3-3

G4-1

G5-1

G6-1

G6-2 G7-1

G7-2

G7-3 G8-1G8-2

G8-3

G8-4

G11-1

G13-1

G14-1

G29-1B

G29-2

G29-3

G29-4

G29-5

G29-6

G29-7 G29-8

G29-9

G29-10

G29-11

G29-13 G29-12

G29-14

G29-15

G35-1

G35-2

G36-1 G36-2

G121-1

M-1356

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

0

0

15 MILES

15 KILOMETERS

5 10

5 10

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

70

60

710

441

FLORIDA’S TURNPIKE

FLORIDA’S

1

1

95

95

95

TURNPIKE

EXPLANATION

M-1330

STL-335

G35-2

WELL LOCATION AND NUMBER

MUNICIPAL WATER SYSTEM SITE

AREA OF INTENSE AGRICULTURAL

WATER USE (LUKASIEWICZ, 1992)

WASTEWATER INJECTION SITE

AQUIFER STORAGE AND RECOVERY OR

AQUIFER PERFORMANCE TEST SITE

FLORIDAN AQUIFER SYSTEM NETWORK

MONITORING WELL OPERATED BY SOUTH

FLORIDA WATER MANAGEMENT DISTRICT

FLORIDAN AQUIFER SYSTEM MONITORING

WELL OPERATED BY NATURAL RESOURCES

CONSERVATION SERVICE--Well number begins

with G (grove number)

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 2. Location of municipal water system wells, wastewater injection wells, aquifer storage and recovery test wells, 

aquifer performance test wells, and Floridan aquifer system monitoring wells used in the study. Site names are given in 

table 1.
Methods of Evaluation and Data Collection 7

Three of the samples were collected from two wells 

(CS-I1 and CS-M2) located outside the study area in an 

effort to evaluate an anomalous vertical distribution of 

salinity considered similar to the distribution in some 

wells along the coast in the study area. 

Field analysis and sampling procedures followed 

are described by Wilde and Radtke (1998). No less than 

three well volumes were purged, and specific conductance was monitored to ensure stabilization prior to 

sampling. Some wells were flowing (left open by the 

owner) upon arrival at the site for sampling. Most 

sampled wells were under flowing artesian conditions, 

making pumping unnecessary. Water temperature was 

measured in a 2-gal bucket, usually filled rapidly to 

minimize sample warming or cooling. Sample bottles 

usually were filled using 1⁄4-in. polyethylene tubing 

connected to a small wellhead valve separate from the 

large flow valve. Water samples collected for major ion 

Table 1. Identification of wells used at municipal water system sites, wastewater injection sites, and aquifer storage 

and recovery and aquifer performance test sites in the study 

[All wells are injection or production wells, unless otherwise noted, and are shown in figure 2. Site name: SFWMD, South Florida 

Water Management District; FDEP, Florida Department of Environmental Protection. Type of site: APT, aquifer performance test site; 

ASR, aquifer storage and recovery test site; B, water-supply well used for blending with freshwater; RO, reverse-osmosis municipal 

water site; WWI, wastewater injection site]

Site name Type of site Wells used in study

C-24 Canal (SFWMD) APT STL-3791, STL-380, STL-3811, STL-3821

Fort Pierce Utilities Authority B STL-385

Fort Pierce Utilities Authority RO STL-422

Fort Pierce Utilities Authority WWI STL-3322, STL-3333

Hercules WWI IR-10012

Joe’s Point RO M-1118

Jupiter (FDEP) ASR PB-747

Jupiter Water Systems RO PB-11963, PB-1197

Kissimmee River at Lake Okeechobee (SFWMD) ASR OK-100 (test well)

Loxahatchee Environmental Control District WWI PB-11702,3

North Martin County Utilities (Jensen Beach) RO M-1356, M-1357

North Martin County Utilities (Jensen Beach) WWI M-13242, M-13253, M-13582

North Port St. Lucie Utilities WWI STL-3342, STL-3353

Port Mayaca on the St. Lucie Canal (SFWMD) ASR M-1360 (test well)

Port St. Lucie Utilities RO STL-3871, STL-388, STL-389

Pratt & Whitney WWI PB-11662, PB-11673

Radnor RO M-1121

Sailfish Point RO M-1349

Seacoast Utilities (Palm Beach Gardens) WWI PB-11822, PB-11833

South Martin Regional Utilities (Hobe Sound) RO M-1359

South Port St. Lucie Utilities WWI STL-2542, STL-2553, STL-3861

St. Lucie County (SFWMD) ASR STL-3551, STL-356, STL-3571

Stuart WWI M-10331, M-10341,2 M-13522, M-13531

Taylor Creek/Nubbin Slough (Lake Okeechobee) ASR OK-9000, OK-9001/OK-90023

Tequesta RO PB-1774

1Single zone monitoring well.

2Injection well at wastewater injection site.

3Dual zone monitoring well.
8 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

analyses and 87Sr/86Sr were filtered using 0.45-μm 

Gelman capsule filters, and bottles collected for cation 

analysis were acidified with nitric acid. Field pH was 

measured using a flow-through chamber to avoid contact 

with the atmosphere during the first year of sampling 

(May to July 2000). During the second year of sampling 

(July and August 2001), water temperature, specific 

conductance, dissolved oxygen, and pH were monitored 

and measured during well purging in a flow cell attached 

to a water-quality multiprobe instrument. Dissolved 

oxygen also was checked for stability at a low level (less 

than 0.5 mg/L) before collecting samples. Alkalinity was 

measured in the field using the inflection point method 

by titration with sulfuric acid. Some wells lacked a wellhead valve appropriate for sampling through tubing. For 

these samples, water was collected using a clean 5-gal 

bucket, and sample bottles were filled from the bucket 

using a peristaltic pump with silicon tubing.

For deuterium and oxygen-18 analyses, unfiltered samples were collected in glass bottles secured 

with polyseal cone caps; for isotopic analyses of 

carbon-13 and carbon-14, a 0.26-gal (1-liter) glass 

bottle with a septum top was filled with 1⁄4-in. tubing 

coming from the well. The carbon isotope bottle was 

flushed (at least two bottle volumes) and filled from the 

bottom up with the end of the tubing inserted to the 

bottom of the bottle to prevent interaction with the 

atmosphere. Immediately after filling the carbon 

isotope bottle, a capsule of 50-percent ammonium 

hydroxide was added to fix (precipitate) inorganic 

carbon, and the bottle was sealed.

Major constituent analyses were performed at the 

USGS laboratory in Ocala, Fla. Analyses followed 

methods prescribed by Fishman and Friedman (1989). 

Charge-balance error for major ions for all samples did 

not exceed 3 percent, and many were less than 1 percent. 

Strontium isotope ratios (87Sr/86Sr) were determined at a USGS research laboratory in Menlo Park, 

Calif., using solid-source mass spectrometry. The ratio 

of unfractionated strontium-88 (88Sr) to 86Sr, assumed 

to be 8.37521, is used as an internal standard to correct 

for stable isotope fractionation, and uncertainties are 

2 x 10-5 (T. Bullen, U.S. Geological Survey, written 

commun., 2000).

The isotopic ratios of deuterium and oxygen-18 

were determined at a USGS research laboratory in 

Reston, Va. Hydrogen isotope analyses were conducted 

at 30 °C using a hydrogen equilibration technique that 

measures deuterium activity (Coplen and others, 1991). 

Oxygen isotope analyses were performed using the 

carbon dioxide (CO2) equilibration technique (at 

25 °C) of Epstein and Mayeda (1953). Stable isotope 

ratios of hydrogen are reported relative to Vienna Standard Mean Ocean Water (VSMOW), as delta deuterium 

(δD) in per mil (parts per thousand), on a scale normalized such that δD = -428 per mil for Standard Light 

Antarctic Precipitation (SLAP). Stable isotope ratios of 

oxygen are reported relative to VSMOW, as delta 

oxygen-18 (δ18O) in per mil, on a scale normalized 

such that δ18O = -55.5 per mil for SLAP. The uncertainties of hydrogen and oxygen isotopic analyses are 

2 and 0.2 per mil, respectively.

Carbon isotope analyses of dissolved inorganic 

carbon in samples were performed by Beta Analytical, 

Inc., in Miami, Fla. Measured carbon-13 ratios (δ13C) 

were calculated relative to the Vienna Pee dee Belemnite (PDB) standard. Determination of carbon-14 (14C) 

was by reduction of sample inorganic carbon to graphite and measurement in an accelerator mass spectrometer. The modern reference standard for this 

measurement was 95 percent of the carbon-14 content 

of the National Bureau of Standards’ Oxalic Acid, and 

calculations were made using the Libby carbon-14 half 

life (5,568 years). Measurements of carbon-14 were 

reported in unnormalized fraction modern carbon and 

apparent carbon-14 age (years before present with 

“present” representing A.D. 1950). Analytical error 

reported by Beta Analytical, Inc., ranged from 0.05 to 

0.1 percent modern carbon (PMC) for carbon-14 

results and 0.1 per mil for δ13C results.

Quality Assurance Samples

Two quality assurance blank samples were 

collected: a blank water sample and an equipment 

blank. The blank water sample was deionized water 

poured directly into sample bottles from the deionized 

water container used to rinse equipment in the field. 

For the equipment blank, deionized water was pumped 

through field equipment in contact with the sample 

(5-gal sample bucket, silicone tubing, a metal threaded 

fitting used to attach to wells on the end of the tubing, 

and filter). Analyses of these blank samples for major 

constituents resulted in virtually all measurements 

being below the detection limit; the exception being 

magnesium for the equipment blank, which had a value 

of 0.002 mg/L. Isotopic analyses of these samples were 

not conducted, and additional samples for quality 

assurance of isotopic analyses were not collected.
Geologic Framework 9

GEOLOGIC FRAMEWORK 

The Floridan aquifer system in southern Florida 

includes, in ascending order from oldest to youngest, 

the following geologic units: upper part of the Cedar 

Keys Formation of Paleocene age, Oldsmar Formation 

of early Eocene age, Avon Park Formation of middle 

Eocene age, Ocala Limestone of late Eocene age, and 

Suwannee Limestone of early Oligocene age (Miller, 

1986). The Hawthorn Group overlies the Suwannee 

Limestone and contains the older Arcadia Formation 

and the younger Peace River Formation (Scott, 1988). 

A basal part of the Hawthorn Group also is included in 

the Floridan aquifer system in this study (fig. 3).

Delineation of the geologic units in the study 

area began with selected wells in which the boundaries 

of units were already known based on geophysical logs 

and lithologic sample descriptions. The gamma-ray log 

was used to extend these boundaries by correlating 

between wells; five east-west hydrogeologic sections 

(figs. 4-8) were constructed to assist in this delineation. 

Lithologic descriptions, if available, also were used to 

help determine boundaries. Boundaries were determined for 112 wells (all of which had a gamma-ray log 

available) in the study area (pl. 1 and app. II). Data 

presented on the sections for each well include a 

gamma-ray log curve and lithologic column, if a lithologic description was available.

Geologic Units and Lithology

The Cedar Keys Formation includes dolomite, 

dolomitic limestone, and anhydrite. The anhydrite is 

present as thick, massive beds in the lower part of the 

formation. The Oldsmar Formation consists of micritic 

limestone and dolomite and is about 1,000 to 1,300 ft 

thick in the study area (Miller, 1986, pl. 5). The lower 

300- to 500-ft section of the Oldsmar Formation, 

locally called the “Boulder zone” (fig. 3), is predominantly dolomite and contains massively bedded, 

cavernous or fractured dolomite of high permeability. 

Zones of similar lithology also can be present in the 

upper part of the Oldsmar Formation.

The Avon Park Formation consists of micritic to 

fossiliferous limestone, dolomitic limestone, and dolostone or dolomite (fig. 3). Fine- to medium-grained 

calcarenite that is moderately to well sorted is present 

in places. Foraminifera characteristic of the Avon Park 

Formation are cone-shaped Dictyoconus sp. (Duncan 

and others, 1994). The top of the Avon Park Formation 

is marked in some places by light-brown, finely crystalline to fossiliferous dolomitic limestone or dolomite 

thinly interbedded with limestone. A thick interval 

containing mostly dolomite, but commonly interbedded with limestone, is commonly present in the middle 

to lower part of the Avon Park Formation.

 The Ocala Limestone consists of micritic or 

chalky limestone, calcarenitic limestone, and coquinoid 

limestone. The limestone is characterized by abundant 

large benthic foraminifera, such as Operculinoides sp., 

Camerina sp., and Lepidocyclina sp. (Peacock, 1983). 

The presence of these foraminifera aids in distinguishing the Ocala Limestone from the overlying Suwannee 

Limestone, where present, and the underlying Avon 

Park Formation.

The Suwannee Limestone of Oligocene age has 

been interpreted by some investigators to be absent in 

the study area (Mooney, 1980; Shaw and Trost, 1984; 

Miller, 1986), whereas others (Lichtler, 1960; Schiner 

and others, 1988; Lukasiewicz, 1992) have mapped this 

geologic unit in Martin, St. Lucie, and adjacent counties. The Suwannee Limestone in southwestern Florida 

predominantly consists of pale-orange to tan, fossiliferous, medium-grained calcarenite with minor amounts 

of quartz sand and rare-to-absent phosphate mineral 

grains. Mooney (1980) describes the limestone interval, known as the Suwannee Limestone by others in the 

study area, as a gray, sandy, calcilutite with minor 

phosphorite and suggests that this interval may be a 

basal unit of the Hawthorn Group; however, Mooney 

(1980) calls it the unnamed limestone unit. Shaw and 

Trost (1984) place this unit within the Hawthorn 

Group, at its base, in the eastern part of the study area, 

and Reese and Memberg (2000) include it in the lower 

part of the “basal Hawthorn unit.” Based on analysis of 

a continuous core in Indian River County, this unit is 

referred to as the “unnamed limestone of early 

Oligocene age” (Weedman and others, 1995). 

Microfossil evidence based on description of 

drill cuttings that supports facies changes and interfingering between Eocene and Oligocene-aged formations 

was found in southern Florida (Winston, 1993; 1995). 

This evidence contradicts the idea that upper boundaries of the Avon Park Formation and Ocala Limestone 

are represented by an unconformity with deposition of 

the unit restricted to a certain period of time, such as 

the Avon Park Formation of middle Eocene age (Miller, 

1986, pl. 2).
10 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Figure 3. Generalized geology and hydrogeology in Martin and St. Lucie Counties as defined for this study.
Geologic Framework 11Figure 4. East-west hydrogeologic section A-A′. See figure 1 for trace of section. NGVD of 1929 is National Geodetic Vertical Datum 
12 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Figure 5. East-west hydrogeologic section B-B′. See figure 1 for trace of section. NGVD of 1929 is National Geodetic Vertical Datum 
Geologic Framework 13 Figure 6. East-west hydrogeologic section C-C′. See figure 1 for trace of section. NGVD of 1929 is National Geodetic Vertical Datum 
14 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Figure 7. East-west hydrogeologic section D-D′. See figure 1 for trace of section. NGVD of 1929 is National Geodetic Vertical Datu
Geologic Framework 15 Figure 8. East-west hydrogeologic section E-E′. See figure 1 for trace of section. NGVD of 1929 is National Geodetic Vertical Datum 
16 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

The Hawthorn Group consists of an interbedded 

sequence of widely varying lithologies and components 

that includes limestone, dolomite, dolosilt, shell, quartz 

sand, clay, abundant phosphate grains, and mixtures of 

these materials. The characteristics that distinguish the 

Hawthorn Group from underlying units are high and 

variable siliciclastic and phosphatic content; color, 

which can be green, olive-gray, or light gray; and 

gamma-ray log response. Intervals high in phosphate 

sand or gravel (as thick as 30 ft) are present and have 

high gamma-ray activity, with peaks of 100 to 200 American Petroleum Institute (API) standard units or more. 

This study follows the geologic terminology similar to that proposed by Reese and Memberg (2000); a 

basal unit is defined as that which underlies a Hawthorn 

Group marker unit and overlies Eocene-aged limestone. 

This basal unit is referred to herein as the basal Hawthorn/Suwannee unit (fig. 3). In Reese and Memberg 

(2000), this unit is referred to as the “basal Hawthorn 

unit.” Gamma-ray log responses indicate that the basal 

Hawthorn/Suwannee unit can commonly be divided into 

two intervals. A lower interval has gamma-ray activity 

similar to, but slightly higher than, the low activity in the 

underlying Ocala Limestone, and an upper interval has 

high gamma-ray activity (figs. 4-8). Generally, the lower 

interval is predominantly limestone, whereas the upper 

interval includes more clay, silt, sand, and phosphate 

grains; however, the contact between these two intervals 

commonly is gradational. The basal Hawthorn/Suwannee unit was defined and mapped in this study because 

of some similar lithologic characteristics throughout the 

unit, and because its boundaries can usually be determined with a gamma-ray log. The lower predominantly 

limestone interval of this unit, near the coast where it 

thickens and may contain only minor to trace amounts of 

phosphate grains, could be equivalent to the Suwannee 

Limestone. An example of this limestone interval is the 

interval from about 1,050 to 1,110 ft below land surface 

in well PB-1197 (fig. 9).

The marker unit that overlies the basal 

Hawthorn/Suwannee unit (fig. 9) is present throughout 

the study area and correlates with a marker unit west of 

the study area in Lee, Hendry, and Collier Counties 

(Reese, 2000) and south in Palm Beach County (Reese 

and Memberg, 2000). The thickness and characteristic 

pattern of the marker unit shown by gamma-ray logs 

remain consistent over large parts of the study area 

(figs. 4-9). The marker unit commonly consists of 

micritic limestone, marl, or clay with minor to trace 

amounts of phosphate grains.

Geologic units that overlie the Hawthorn Group 

include the Tamiami Formation of Pliocene age, the 

Fort Thompson Formation and Anastasia Formation of 

Pleistocene age, and Pamlico Sand of Holocene age 

(fig. 3). These units or facies within them tend to be 

discontinuous and difficult to correlate across the study 

area (Lukasiewicz, 1992).

Structure

Anomalous linear structures (faults, folding, or 

karst-related dissolution and subsidence) have been 

mapped by previous workers in the Floridan aquifer 

system or deeper in the study area (Bermes, 1958; 

Lichtler, 1960; Barnett, 1975; Black, Crow and 

Eidsness, Inc., 1975; Schiner and others, 1988; 

Lukasiewicz, 1992; and Winston, 1995). Most structural features are parallel or subparallel to the coast 

(fig. 10). The feature mapped by Barnett (1975), 

however, trends more northwesterly, from northeastern 

Palm Beach County through western St. Lucie County, 

and has been interpreted to be a normal fault 

downthrown to the southwest and part of a network of 

deep-seated basement faults in peninsular Florida. 

A structural feature, mapped by Lukasiewicz 

(1992), extends along the coast between the mainland 

and the barrier island chain in St. Lucie and northeastern Martin Counties and was identified on the basis of 

structure, permeability contrasts across the feature, and 

study of cores and geophysical logs (fig. 10). The 

extension of this feature to the north coincides with a 

feature in Indian River County mapped as a fault by 

Schiner and others (1988). Mapping of the top of the 

Floridan aquifer system in Indian River County shows 

as much as 350 ft of offset, downthrown to the east, 

along this feature (Schiner and others, 1988). Considerable thickening of the Suwannee Limestone on the 

downthrown side also is indicated. However, marine 

seismic profiling of this feature in Indian River County 

exhibits no obvious displacement of reflectors across it 

in the section from the upper Avon Park Formation and 

Ocala Limestone and above. This feature is attributed 

either to (1) karst-related dissolution and subsidence 

within the limestone units (without regional faulting), 

or (2) the presence of a deep-seated fault below the 

depth of resolution of the seismic profiles (Flocks and 

others, 2001). Likewise, other linear structures previously mapped as faults or inferred faults in the study 

area (fig. 10) may not be faults, at least not at the stratigraphic level of the Upper Floridan aquifer and higher. 
Geologic Framework 17

Figure 9. Gamma-ray geophysical log, flow zones, stratigraphy, and hydrogeologic units for well PB-1197 in northeastern 

Palm Beach County. Flow zones determined from flowmeter and temperature logs and flow measurements while drilling. Well 

is in the Jupiter water systems Florida aquifer system reverse osmosis well field (fig. 2). Also shows completed intervals for 

associated monitoring well PB-1196.
18 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

D

U

INFERRED FAULT--D

is downthrown side and U is

upthrown side

STRUCTURAL FEATURE

BLACK, CROW, AND EIDSNESS, INC.

D U U

U

U

U

U

U

U

D

D

D

D

D

D

D

BERMES

(1958)

WINSTON (1995)

BCE (1975)

BCE

SCHINER AND

OTHERS, (1988)

LUKASIEWICZ (1992)

BARNETT (1975)

LICHTLER (1960)

WINSTON (1995)

WINSTON (1995)

WINSTON (1995)

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 10. Anomalous linear structures in the study area mapped in previous studies.
Hydrogeology 19

The top of the basal Hawthorn/Suwannee unit 

ranges from as shallow as 310 ft below NGVD of 1929 

in the northwestern part of the study area to as deep as 

956 ft below NGVD of 1929 in northeastern Palm 

Beach County (fig. 11). Salient features are a structural 

high area in central St. Lucie County (where altitude is 

as high as 408 ft below NGVD of 1929) and low areas 

along the coast. In places, the top deepens abruptly by 

100 to 200 ft between the mainland and the barrier 

island. Additionally, in south-central St. Lucie County, 

a southeast-trending trough was mapped, although the 

top is below the 600-ft contour that defines the trough 

in only two wells. Abrupt relief along the northern side 

of this trough is indicated by wells STL-355, STL-356, 

STL- 379 and WA-1192. The top is deeper in STL-355 

than WA-1192 by more than 100 ft over a distance of 

less than 0.5 mi. This trough roughly coincides in 

position and trend with the northwest-trending basement fault mapped by Barnett (1975) (fig. 10), and it 

may have resulted, at least in part, from faulting. An 

alternate interpretation, however, is that the two wells 

having altitudes for the top below 600 ft are located in 

small localized depressions formed by karst-related 

dissolution and subsidence. Several circular depressions are present on top of the Ocala Limestone based 

on detailed mapping in northeastern Florida, and these 

depressions probably are ancient sinkholes caused by 

dissolution and collapse at depth (Spechler, 1994).

The thickness of the basal Hawthorn/Suwannee 

unit ranges from 15 ft (well STL-360) in southwestern 

St. Lucie County to as much as 310 ft (well PB-652) 

in extreme northeastern Palm Beach County (fig. 12). 

In the high area on top of the basal Hawthorn/Suwannee unit in central St. Lucie County, the thickness is 

about 50 to 60 ft. The thickness, however, is more than 

100 ft in the eastern part of the study area near the 

coast. The beginning of this eastward thickening is 

shown on hydrogeologic section C-C′ (fig. 6) between 

wells STL-354 and WA-580. The unit does not thicken 

substantially across the area of abrupt relief along the 

northern side of the southeast-trending trough on top 

of the basal Hawthorn/Suwannee unit in south-central 

St. Lucie County described above. 

The 100-ft line of equal thickness that runs 

subparallel to the coast (fig. 12) marks the beginning of 

eastward thickening and is used in this report to divide 

the study area into inland and coastal geographic areas. 

As described later, this demarcation of the study area 

tends to coincide with changes in water quality and 

possible separate flow regimes in the Floridan aquifer 

system. The coastal area is subdivided further into 

northern and southern parts, with the southern part 

representing the area south of the St. Lucie River in 

eastern Martin and northeastern Palm Beach Counties. 

The boundary between inland and coastal areas also is 

shown on four of the hydrogeologic sections (figs. 5-8). 

The entire extent of hydrogeologic section A-A′ (fig. 4) 

is in the inland area. 

The altitude of the upper surface of the Ocala 

Limestone (fig. 13) exhibits features similar to the top 

of the basal Hawthorn/Suwannee unit (fig. 11). The 

southeast-trending trough in south-central St. Lucie 

County inferred in figure 11 also is apparent in figure 

13. Some eastward thickening of the Ocala Limestone 

in the vicinity of the 100-ft-thickness contour for the 

basal Hawthorn/Suwannee unit (fig. 12) also is indicated 

by the hydrogeologic sections (figs. 4-8).

HYDROGEOLOGY 

The principal water-bearing units in the study 

area are the surficial and the Floridan aquifer systems 

(fig. 3). The two aquifer systems are separated by the 

intermediate confining unit, which contains sediments 

of lower permeability. The Floridan aquifer system has 

two major water-bearing zones, the Upper and Lower 

Floridan aquifers, which are separated by a less permeable middle confining unit. The base of the Floridan 

aquifer system is marked by impermeable, massive 

anhydrite beds of the Cedar Keys Formation.

Surficial Aquifer System

The thickness of the surficial aquifer system 

varies from less than 50 ft to greater than 250 ft in the 

study area (Brown and Reece, 1979). The aquifer 

system consists of quartz sand, silts, clay, shell beds, 

coquina, calcareous sandstone, and sandy, shelly limestone. The base of the aquifer system commonly is 

defined where sediments grade from sand into clayey 

sand or clay; however, basal sediments also can consist 

of limestone as shown in figure 6.

The surficial aquifer system provides most of the 

potable water used in the study area (Lukasiewicz, 

1992). It is unconfined and receives recharge from rainfall, canals, lakes, reservoirs, irrigation water, and probably some upward leakage from the Floridan aquifer 

system.
20 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

800

900

700

700

700

700

800

600

500

500

500

400

400

600

TURNPIKE

600

600

425

435

413

470

415

732

598

601

628 510

621

870

697

713

745

780 648

566

661

742

680

657

700

652

817

699

680

730

707

765

340

540

578

370

513

623

343

310

666

883

827

822

956

572

432

441

389

531

536

462 440

540

585

601

452

451

546

564

536

408

580

629

640

598

613

794

534

617

568

515

710

488

616

460

680

565

507 585

555

538 528

490

570

432

400

475

428

450

453

505

475

478

400

480

382

688

450

450

455

454

543

437

430

370

445

430

515

585

678

517

560

510

0

0

15 MILES

15 KILOMETERS

5 10

5 10 EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

70

60

710

441

FLORIDA’S

FLORIDA’S

1

1

95

95

95

TURNPIKE

661 WELL LOCATION AND ALTITUDE--Number is altitude

of the top of the basal Hawthorn/Suwannee unit, in feet

below NGVD of 1929. See plate 1 for local well number

LINE OF EQUAL ALTITUDE OF THE TOP OF THE

BASAL HAWTHORN/SUWANNEE UNIT--In feet below

NGVD of 1929. Hachures indicate depression. Contour

interval is 100 feet. Dashed where approximately located

600

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 11. Altitude of the top of the basal Hawthorn/Suwannee unit. NGVD of 1929 is National Geodetic Vertical 

Datum of 1929.
Hydrogeology 21

100

50

50

50

50

150

100

150

250

200

200

250

150

300

100

200

100

60

65

60

80

80

175

83

43

64 83

40

205

180

55

285

183

50

140

60

157

48

40

173

165

185

105

45

50

170

145

32

50

32

30

82

30

44

30

51

310 210

185

137

165

63

45

28

85

90

53 70

87

141

96

47

65

90

180

150

63

195

190

201

200

192

200

70

80

77

55

15

77

188

70

60

52

72

95

117 84

85

125

87

76

55

70

45

70

55

60

52

70

75

78

212

65

57

55

65

62

63

55

60

55

65

100

95

52

68

160

70

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

60 WELL LOCATION AND THICKNESS--Number is

thickness of basal Hawthorn/Suwannee unit, in feet.

See plate 1 for local well number

LINE OF EQUAL THICKNESS OF BASAL

HAWTHORN/SUWANNEE UNIT--Contour

interval is 50 feet. Dashed where approximately

located

COASTAL AREA--Based on 100-foot-thickness

contour. Remainder is inland area.

150

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 12. Thickness of the basal Hawthorn/Suwannee unit.
22 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

700

800

800

900

900

1,000

1,100

700

700

?

600

900

600

500

500

400

1,000

?

?

485

500

473

550

495

907

681

644

692 593

661

1075

877

768

1030

963

698

706

721

899

728

697

873

817

1002

804

725

780

877

910

372

590

610

400

595

653

387

340

717

1193 1037

1007

1093

737

495

486

417

616

626

515 510

627

726

697

499

516

636

744

686

471

775

819

841

798

805

994

604

697

645

570

725

565

804

530

740

617

579

650

655

612

575 695

519

476

530

498

495

523

560

535

530

470

555

460

900

515

507

510

519

605

500

485

430

500

495

615

680

730

585

720

580

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

WELL LOCATION AND ALTITUDE--Number is altitude of the

top of the Ocala Limestone, in feet below NGVD of 1929. See

plate 1 for local well number

LINE OF EQUAL ALTITUDE ON THE TOP OF THE

OCALA LIMESTONE--In feet below NGVD of 1929. Dashed

where approximately located. Hachures indicate depression.

Contour interval is 100 feet

721

600

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 13. Altitude of the top of the Ocala Limestone. NGVD of 1929 is National Geodetic Vertical Datum of 1929.
Hydrogeology 23

Intermediate Confining Unit

The intermediate confining unit extends from the 

base of the surficial aquifer system to the top of the 

Floridan aquifer system (Southeastern Geological 

Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986). The top of the confining unit is commonly equivalent to the top of the 

Hawthorn Group, but can extend into the overlying 

Tamiami Formation (fig. 3). The lithology of the 

confining unit is variable and includes fine-grained 

sediments, such as clay, marl, micritic limestone, and 

silt, which provide good confinement. The upper 

contact of the intermediate confining unit ranges from 

less than 80 ft below NGVD of 1929 in the extreme 

northwestern part of the study area (northeastern 

Okeechobee and northwestern St. Lucie Counties) to 

greater than 200 ft below NGVD of 1929 in extreme 

southeastern Martin and northeastern Palm Beach 

Counties (Lukasiewicz, 1992). The minimum and 

maximum thicknesses of the unit occur in these same 

areas, being 250 and 750 ft, respectively, and its thickness is 400 to 500 ft in about one-half of Martin and 

St. Lucie Counties. Permeable water-bearing zones 

within this unit are not known to exist.

Floridan Aquifer System

The Floridan aquifer system is defined as a 

vertically continuous sequence of permeable carbonate 

rocks of Tertiary age that are hydraulically connected 

in varying degrees, and whose permeability is generally several orders of magnitude greater than that of the 

rocks bounding the system above and below (Miller, 

1986). The Floridan aquifer system in southern Florida 

predominantly consists of limestone with dolomitic 

limestone and dolomite common in its lower part 

(figs. 4-8). This section presents a description of the 

Floridan aquifer system in the study area, its component aquifers and confining units, and their relation to 

stratigraphic units. 

Upper Floridan Aquifer

In general, the Upper Floridan aquifer is delineated herein on the basis of permeability characteristics, and thus, neither the top nor the base of the Upper 

Floridan aquifer necessarily conforms to formation or 

time-stratigraphic boundaries. Ground water occurs 

under flowing artesian conditions, except in some 

western parts of the study area where it underlies the 

Osceola Plain (fig. 1; Bradner, 1994). The top of the 

Upper Floridan aquifer approximately coincides with 

the top of the basal Hawthorn/Suwannee unit (fig. 11), 

except in the coastal area where it lies within this unit 

at the base of a section with high clay and phosphate 

grain content (figs. 4-9). The top of the aquifer is as 

much as 80 ft below the top of the basal Hawthorn/

Suwannee unit in the coastal area (fig. 8, well 

PB-1144). The base of the aquifer can be approximated 

using the base of the Ocala Limestone (figs. 4-8); 

however, depending on the occurrence of flow zones, 

this boundary can occur within the upper part of the 

Avon Park Formation. The thickness of the Upper 

Floridan aquifer in the study area is about 500 ft 

(Lukasiewicz, 1992). Nevertheless, based on only the 

combined thickness of the basal Hawthorn/Suwannee 

unit and Ocala Limestone (figs. 4-8), the thickness of 

the aquifer could be considerably less. The combined 

thickness of these two units is as low as about 100 ft. 

The Upper Floridan aquifer comprises several 

thin flow zones of high permeability interlayered with 

thicker zones of lower permeability. Flow zones can be 

defined in a borehole through utilization of flowmeter, 

water temperature, and caliper logs. Some of these 

zones in the Upper Floridan aquifer are areally extensive and seem to coincide with formation boundaries. 

Three to four producing zones in the Upper Floridan 

aquifer in the study area were mapped by Brown and 

Reece (1979). Two areally extensive and mappable 

flow zones are present at the base of the Suwannee 

Limestone and Ocala Limestone, respectively (Brown 

and Reece, 1979; Lukasiewicz, 1992).

The shallowest flow zone of the Upper Floridan 

aquifer is 90 ft above the base of the basal Hawthorn/

Suwannee unit in well PB-1197 in northeastern Palm 

Beach County, and the top of the Upper Floridan aquifer coincides with the top of this flow zone (fig. 9, 

1,020 ft below land surface). The base of the Upper 

Floridan aquifer is placed at 1,330 ft deep in well 

PB-1197 near the base of a flow zone.

 Transmissivity of the Upper Floridan aquifer 

was previously mapped in the study area using aquifer 

performance and specific capacity tests (Lukasiewicz, 

1992). Transmissivity varies from 7,000 to greater than 

70,000 ft2/d. A large area with high transmissivity 

(50,000 to 70,000 ft2/d) is in northwestern St. Lucie 

County; the coastal area has transmissivities less than 

13,000 ft2/d. 
24 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Middle Confining Unit

The middle confining unit of the Floridan aquifer 

system lies within the upper part of the Avon Park 

Formation and principally consists of micritic to finegrained, fossiliferous limestone of low permeability 

(fig. 3). Its semiconfining nature in southern Florida is 

based on aquifer tests conducted within the Upper 

Floridan aquifer, which often indicate substantial 

upward leakage (Reese, 2002). The thickness of the 

middle confining unit ranges from 200 to 400 ft in the 

study area (Lukasiewicz, 1992).

Lower Floridan Aquifer

In southern Florida, the top of the Lower Floridan 

aquifer is marked by the shallowest zone of highly 

transmissive dolomite (Meyer, 1989). Thick confining 

units separate this permeable zone and the Boulder 

zone (Miller, 1986). The lithology of these intervening 

confining units is similar to that of the middle confining unit of the Floridan aquifer system, which predominantly is fine-grained to micritic limestone.

The top of an upper permeable unit of the Lower 

Floridan aquifer, marking the top of the aquifer and 

characterized by a flow zone of cavernous dolomite, 

has been previously mapped (fig. 14; Lukasiewicz, 

1992) in the study area. Altitudes of the top of this unit 

range from 900 ft below NGVD of 1929 in the extreme 

northwestern part of the study area in northeastern 

Okeechobee County to greater than 1,400 ft below 

NGVD of 1929 in southeastern Martin and northeastern Palm Beach County. At the SFWMD test well 

STL-379 in central St. Lucie County, the top of this 

unit is at 1,100 ft below NGVD of 1929; here, the 

upper permeable unit is 400 ft thick, mainly consists of 

dolomite, and contains two extensive cavernous dolomite flow zones (fig. 6; Lukasiewicz, 1992). The 

completed interval extending from 1,451 to 1,665 ft 

below land surface (1,434 to 1,648 ft below NGVD of 

1929) at well PB-1197 in northeastern Palm Beach 

County (fig. 9) is included in the upper permeable 

unit of the Lower Floridan aquifer as mapped by 

Lukasiewicz (1992). This productive interval at 

PB-1197, which mainly consists of limestone and 

dolomitic limestone, is locally referred to as the 

middle Floridan aquifer (ViroGroup, 1994).

The upper permeable unit of the Lower Floridan 

aquifer, as defined by Lukasiewicz (1992), may be 

poorly developed in the coastal area. For example, a 

lithologic description for deep injection well M-1352 at 

the city of Stuart WWTP in northeastern Martin County 

(fig. 2) indicates limestone with only minor to trace 

occurrences of dolomite to a depth of 1,920 ft (Montgomery Watson Americas, Inc., 1998). Dolomite is not 

reported to a depth of at least 1,600 ft below NGVD of 

1929 in another well (M-1353) at this site (fig. 7).

Sparse data exist on the transmissivity of the 

upper permeable unit of the Lower Floridan aquifer 

because it is penetrated by few wells. Available data, 

however, indicate that the transmissivity seemed to be 

higher in the Lower Floridan aquifer than in the Upper 

Floridan aquifer. Transmissivity of the upper permeable unit of the Lower Floridan aquifer was determined 

on the basis of multiwell aquifer tests at three sites 

represented by the following production wells: 

PB-1197, STL-380, and OK-9000 (fig. 2 and table 1). 

The transmissivity values (or transmissivity range) 

at these three sites are 32,000 to 132,000 ft2/d at 

well PB-1197 (ViroGroup, 1994), 65,000 ft2/d at 

well STL-380 (Lukasiewicz and Smith, 1996), and 

590,000 ft2/d at well OK-9000 (CH2M Hill, 1989).

The highly transmissive Boulder zone within the 

lower part of the Lower Floridan aquifer ranges in 

depth from 2,500 to 3,000 ft below NGVD of 1929 in 

the study area (Miller, 1986). The thickness of this 

zone ranges from about 300 to 500 ft. 

The lowermost section of the Lower Floridan 

aquifer extends 500 to 600 ft below the base of the 

Boulder zone (Miller, 1986, pl. 17) and consists of 

permeable dolomite or dolomitic limestone of the 

upper Cedar Keys Formation (fig. 3). The lower boundary of the Lower Floridan aquifer is defined by thick 

impermeable anhydrite beds in the lower part of the 

Cedar Keys Formation. 

Ground-Water Flow of the Floridan Aquifer 

System

An understanding of ground-water flow in the 

Floridan aquifer system, both historical (predevelopment) and current, is necessary in order to know what 

effect current or increasing withdrawals could have on 

salinity. In the following discussion, delineation of the 

flow system is made based on the distribution of 

hydraulic head, withdrawals, and recharge. 

The movement of water in any aquifer generally 

is perpendicular to potentiometric surface contours. 

A comparison between predevelopment and current 

potentiometric surface contours suggests that the direction of ground-water flow in the study area has shifted 

over time. 
Hydrogeology 25

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

LINE OF EQUAL ALTITUDE ON THE TOP OF THE

LOWER FLORIDAN AQUIFER--In feet below NGVD

of 1929. Contour interval is 100 feet

1,000

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

1,200

1,200

1,100

1,100

1,000

1,000

900

900

1,400

1,400

1,300

1,300

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 14. Altitude of the top of the Lower Floridan aquifer (from Lukasiewicz, 1992). NGVD of 1929 is National 

Geodetic Vertical Datum of 1929.
26 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Potentiometric Surface of the Upper 

Floridan Aquifer

An estimated predevelopment potentiometric 

surface for the Upper Floridan aquifer in Florida (Bush 

and Johnston, 1988, pl. 4) suggests that flow in the 

study area originally was toward the northeast or eastnortheast (fig. 15). However, the May 2001 potentiometric surface indicates that the direction of flow 

shifted to the north in southern St. Lucie County, southern Okeechobee County, and northern Martin County 

and to a more easterly direction in northeastern 

Okeechobee County and northern St. Lucie County 

(fig. 15). This change in flow direction is attributed to 

withdrawals from the Upper Floridan aquifer in northern St. Lucie and southern Indian River Counties, the 

majority of which was used for agricultural purposes 

(Lukasiewicz, 1992). 

Based on the comparison of the two potentiometric surfaces in figure 15, some decline in water 

level probably has occurred over the entire study area 

since predevelopment (early 1930’s). However, decline 

in eastern Martin and northeastern Palm Beach Counties 

has been minimal. Decline in central and northern 

St. Lucie County and Okeechobee County is greatest 

and ranges from about 15 to 20 ft. Similar decline 

(about 16 to 24 ft) between 1934 and 1984 was reported 

in eastern Indian River County, with most of this 

decline occurring between 1934 and 1971 (Schiner and 

others, 1988). Upper Floridan aquifer water levels 

seemed to stabilize in the study area between 1970 and 

1977, as indicated by hydrographs for three wells in 

Martin County and two wells in St. Lucie County 

(Brown and Reece, 1979, pl. 3).

Recent data suggest the decline in water levels 

could be continuing for much of the study area. 

A SFWMD Floridan aquifer system well network (fig. 2) 

has been used to monitor water levels since 1986 

(Switanek, 1999), and trend analyses of these data were 

made using linear regression (table 2). Two wells in 

western Martin County show a water-level increase of 

2 to 3 ft. Eight wells in central and northwestern 

Figure 15. Potentiometric surface of the Upper Floridan aquifer, May 2001 (from Knowles, 2001). Also shown are 

estimated predevelopment potentiometric contours for the Upper Floridan aquifer (from Bush and Johnston, 1988). 

NGVD of 1929 is National Geodetic Vertical Datum of 1929.
Hydrogeology 27

St. Lucie County indicate a water-level decrease of 

2 to 4 ft. At one of these eight wells, well STL-220 in 

west-central St. Lucie County, a 3-ft decrease in water 

level is indicated during the last 9 years; at another 

well, STL-224 in central St. Lucie County, a 4-ft 

decrease occurred during the last 15 years (fig. 16). 

These decreasing water-level trends could be the result 

of the 2000-01 drought period in central Florida and 

the associated decrease in recharge. A plot of the 

Palmer hydrological drought index for central Florida, 

the recharge area for the Floridan aquifer system, 

shows two major long-term drought periods since 

1986: 1989-90 and 2000-01 (National Climatic Data 

Center, 2003). Each of these two drought periods is of 

similar length and severity. However, data were not 

collected during the 1989-90 drought period from the 

Floridan aquifer system monitoring well network. 

Therefore, the declines indicated for the wells in 

central and northwestern St. Lucie County are not 

conclusive. 

An upward head gradient within the Floridan 

aquifer system is most likely prevalent throughout the 

study area. Water levels of wells completed in the 

Lower Floridan aquifer in Indian River County are 

probably at least several feet higher than wells in the 

Upper Floridan aquifer (Schiner and others, 1988).

Table 2. Changes in water level and chloride concentration for South Florida Water Management District ground-water 

level monitoring network wells completed in the Floridan aquifer system 

[Well locations are shown in figure 2. For most years, head measurements were made twice a year (wet and dry seasons). SFWMD, 

South Florida Water Management District; USGS, U.S. Geological Survey; --, inadequate data. All water-quality data used to 

determine chloride concentration trends are presented in appendix III]

Well number Period of 

record for

 head data

Years of

 record

Change 

in head 

(feet)1

Period of

 record 

for water

sample data

Years of

 record

Number of

 samples

Percent

change in

chloride

USGS SFWMD concentration1

M-255 MF-2 1991-2001 11 -1 1977-2001 24 4 0

M-745 MF-9 1987-2001 15 None 1990-2001 11 3 -7

M-1121 MF-3 1987-2001 15 -2 1990-2001 11 3 10

M-1125 MF-23 1986-2001 16 None 1977-2000 23 3 0

M-1326 MF-31 1986-2001 16 None 1985-2000 15 4 12

M-1328 MF-33 1986-1998 13 2 1989 1 1 --

M-1330 MF-35 1986-2001 16 3 1990-2001 11 3 1

OK-7 OKF-7 1987-2001 15 -1 1987-1997 10 2 0

OK-13 OKF-13 1987-2000 14 1 1988-2000 12 2 -22

OK-23 OKF-23 1987-2001 15 -2 1987-2000 13 4 0

OK-31 OKF-31 1987-2001 15 1 1984-2001 17 5 -5

OK-722 OKF-72 -- -- -- 1990-2001 11 3 207

PB-1144 PBF-1 1986-2001 16 None 1977-2000 23 3 2

STL-215 SLF-3 1986-2001 16 -1 1978-2001 23 4 45

STL-216 SLF-4 1991-2001 11 -2 1978-2000 22 3 -2

STL-217 SLF-9 1992-2001 10 -3 1977-2001 24 8 37

STL-218 SLF-11 1991-2001 11 -2 1978-2000 22 3 34

STL-220 SLF-14 1993-2001 9 -3 1977-2001 24 3 20

STL-224 SLF-21 1987-2001 15 -4 1990-2000 10 4 4

STL-225 SLF-23 1986-1994 9 2 1978-1990 12 2 11

STL-229 SLF-27 1986-2000 15 -3 1977-1990 13 2 1

STL-342 SLF-36 1986-2001 16 -2 1977-2000 23 3 -17

STL-346 SLF-40 1986-2001 16 -2 1990-2000 10 2 2

STL-353 SLF-47 1986-2001 16 1 1988-2000 12 4 -10

STL-356 SLF-50 1986-2001 16 -1 1990-1996 6 2 62

1Based on linear regression fit to data.

2This well is not part of the monitoring well network, and location is shown on plate 2.
28 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Figure 16. Relations between water level and time and between chloride concentration and time for 

wells (A) STL-220 and (B) STL-224. Well locations are shown in figure 2. NGVD of 1929 is National 

Geodetic Vertical Datum of 1929.
Hydrogeology 29

Static head measurements were taken during drilling of 

the open intervals at the Jupiter RO Well Field in northeastern Palm Beach County (Stemle, Andersen, and 

Associates, Inc., 1998). Generally, the head increased 

with depth in each well. The open intervals extended 

from the lower part of the Upper Floridan to the Lower 

Floridan aquifer. At the Jupiter dual-zone monitoring 

well PB-1196 (fig. 9), static head measurements taken 

prior to an aquifer performance test indicated head in 

the lower zone (Lower Floridan aquifer) was about 4 ft 

higher than that in the upper zone (Upper Floridan 

aquifer) (Viro Group, Inc. 1994). Head increase with 

depth is expected within an area of discharge in a 

system where deep circulation of meteoric water is 

occurring. 

Ground-Water Withdrawals and Recharge

Municipalities and agriculture are the largest 

users of Floridan aquifer system ground water in the 

study area. Most water withdrawn was for agriculture, 

with the water used for irrigation, primarily of citrus. 

The area of intense agricultural water use (fig. 2) lies 

within the inland area, which is bordered by the basal 

Hawthorn/Suwannee unit 100-ft thickness contour 

(fig.12). Agricultural well permitting requirements by 

the SFWMD do not include the reporting of water use; 

consequently, withdrawals must be estimated.

Agricultural withdrawals from the Floridan aquifer system in the UEC Planning Area were estimated to 

be 81.8 Mgal/d in March 1990 (Lukasiewicz, 1992). 

This estimate, based on a survey sent to farm owners, 

used the number of hours each month that wells were 

reported to be open and flowing and reported or 

estimated well capacities. Water use was determined 

and plotted for model cells, each representing 1 mi2

for March 1990 (Lukasiewicz, 1992, fig. 22). Water 

use per square mile within the area of intense agricultural water use (fig. 2) is greatest in central and northern St. Lucie County and southern Indian River 

County.

Monthly withdrawal data were collected for 45 

irrigation wells in the study area over the last 6 years 

(1996-2001) in a NRCS monitoring program, and these 

data were summed by water year (fig. 17). A water 

year starts 3 months ahead of the calendar year, beginning on October 1 and ending on September 30. The 

NRCS wells are clustered in 16 groves, and all of these 

groves are located in the area of intense agricultural 

water use (fig. 2). Withdrawals increased during 

drought years 2000 and 2001, and for many of the 

wells surveyed, water used was greatest during this 

period. Well G29-14 in north-central St. Lucie County 

is reported to have had the greatest withdrawal in a 

single year (425 Mgal in the 2001 water year).

Ground-water withdrawals from the Floridan 

aquifer system for municipal water systems in the 

study area (fig. 2) also were determined. Municipal 

well water from the Floridan aquifer system must be 

treated by RO because of the brackish nature of the 

water. For each municipal well field, the average daily 

rate of withdrawal in million gallons per day for a 

particular year, usually 2000, the number of wells in 

production, and the aquifer(s) to which the wells are 

open are given in table 3. Jupiter Water Systems is the 

largest well field; eight wells were reported to withdraw a combined average rate of 5.2 Mgal/d for the 

year 2000. All of the well fields that produce at higher 

rates (greater than 1.0 Mgal/d) have wells open to an 

interval including both the Upper and Lower Floridan 

aquifers. The Fort Pierce Utilities and South Martin 

Regional Utilities Well Fields had not yet been placed 

into production as of 2001, nor had a newly constructed 

well at the North Martin County Utilities Well Field 

as of 2000. The total of the average daily withdrawal 

rates from municipal well systems was 13.7 Mgal/d 

(table 3).

Recharge to the Floridan aquifer system occurs 

to the west and north of the study area in central Florida. Bradner (1994) discusses areas of recharge in 

central and northern Okeechobee County where the 

water table is higher than the potentiometric surface of 

the Upper Floridan aquifer. Model simulations, 

however, indicate recharge rates in these areas are low, 

ranging from 0.2 to 1.0 in/yr. Bradner (1994) states:

Recharge (into the Upper Floridan 

aquifer) due to lateral inflow from adjacent 

areas (around Okeechobee County) probably 

is small because Upper Floridan aquifer 

gradients are relatively flat and transmissivities of the Upper Floridan aquifer are 

relatively low.

A four-layer model of the Floridan aquifer 

system has been constructed for the UEC Planning 

Area (Lukasiewicz, 1992). The surficial aquifer system 

and Upper Floridan aquifer are represented by the 
30 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

0

200

400

600

800

1,000

1,200

1,400

WELL NUMBER

0

100

200

300

400

500

600

WELL NUMBER

2001 WATER YEAR

EXPLANATION

2000 WATER YEAR (missing December

through February for most wells)

1999 WATER YEAR (missing April through

September)

1998 WATER YEAR

1997 WATER YEAR

1996 WATER YEAR (missing October through

February)

WATER USE, IN GALLONS MILLION

WATER USE, IN

GALLONS MILLION

G1-1

G2-1

G2-2

G2-3

G2-4

G2-5

G3-1

G3-2

G3-3

G4-1

G5-1

G6-1

G6-2

G7-1

G7-2

G7-3

G8-1

G8-2

G8-3

G8-4

G11-1

G12-1

G13-1

G14-1

G29-1A

G29-1B

G29-2

G29-3

G29-4

G29-5

G29-6

G29-7

G29-8

G29-9

G29-10

G29-11

G29-12

G29-13

G29-14

G29-15

G35-1

G35-2

G36-1

G36-2

G121-1

upper two model layers, and the two cavernous 

dolomite flow zones of wide areal extent in the upper 

permeable unit of the Lower Floridan aquifer are represented by the bottom two layers. All withdrawals from 

the Floridan aquifer system were assumed to come 

from the Upper Floridan aquifer, and hydraulic heads 

in the lowermost model layer were treated as a constant 

head boundary. About 90 percent of the simulated 

recharge to the Upper Floridan aquifer occurs by leakage from the underlying Lower Floridan aquifer. Under 

stressed conditions, this result indicates that upward 

flow in the aquifer system dominates lateral flow.

Figure 17. Yearly water withdrawals from Natural Resources Conservation Service monitoring wells in the 

study area. For wells G35-1, G35-2, G36-1, G36-2, and G121-1, data were not collected for the 1996 water 

year and for the first 6 months of the 1997 water year. A water year starts 3 months before the calendar year, 

beginning on October 1 and ending on September 30. Well locations are shown in figure 2.
Water Quality in the Floridan Aquifer System 31

WATER QUALITY IN THE FLORIDAN 

AQUIFER SYSTEM 

The distribution of salinity and water temperature, isotopic analyses, and recent temporal changes in 

salinity in the study area are discussed in this section. 

Water-quality data are available mostly for wells open 

only in the Upper Floridan aquifer. Some wells, 

however, including some of those used for irrigation 

supply, were drilled to greater depths to increase yield 

and penetrate the Lower Floridan aquifer, and these 

wells are open to the upper part of the Lower Floridan 

aquifer in addition to the Upper Floridan aquifer.

Selected water-quality data used in this study 

and collected from numerous wells tapping the Floridan aquifer system are presented in appendix III. Wells 

M-1325, OK-9001/OK-9002, PB-1196, STL-255, and 

STL-335 are dual-zone monitoring wells in which 

water-quality samples were obtained from both zones. 

Sources of water-quality data given in appendix III 

include data collected during this study; from previous 

research by Lichtler (1960), Reece and others (1980), 

Lukasiewicz and Switanek (1995), Reese and Memberg (2000); and from consulting reports on deep 

wastewater injection well systems, previously collected 

USGS data stored in a USGS water-quality database 

(QWDATA), NRCS data, well abandonment files from 

the SFWMD, and Florida Department of Environmental Protection (FDEP) data from the Florida GroundWater Quality Network Program (Generalized Water 

Information System database − GWIS3). Major constituent and field characteristic water-quality data collected during this study are presented in appendix IV.

Classification and Characterization 

of Salinity

A salinity classification scheme based on 

dissolved-solids concentrations was used for the 

Floridan aquifer system in the study area. This scheme, 

modified from Fetter (1988), has three categories: 

• Brackish water—Dissolved-solids concentrations 

range from 1,000 to 10,000 mg/L,

• Moderately saline water—Dissolved-solids concentrations range from 10,000 to 35,000 mg/L, and

• Saline water—Dissolved-solids concentrations 

range from 35,000 to 100,000 mg/L.

In the scheme by Fetter (1988), saline water has a 

dissolved-solids concentration range from 10,000 

to 100,000 mg/L, and the moderately-saline-water 

category is not used. 

Table 3. Wells in production at Floridan aquifer system municipal water systems in the study area and their average 

withdrawals for system and aquifer(s) open 

Municipal water system

Number of

production 

wells

Year

Average daily

pumpage for year 

for system

(million gallons 

per day)

Aquifer(s) open 

in individual wells

Total In use Upper

Floridan

Upper 

and

Lower 

Floridan

Lower 

Floridan

Fort Pierce Utilities (blending) 3 2 2000 0.45 X

Fort Pierce Utilities (reverse osmosis) 1 6 0 2001 0 X

Joe's Point 2 1 1992 .03 X

Jupiter Water System 10 8 2000 5.2 X X

North Martin County Utilities

 (Jensen Beach) 4 3 2000 2.5 X X

Port St. Lucie Utilities 3 3 2000 3.6 X

Radnor 2 1 1996 .24 X

Sailfish Point 2 2 2000 .21 X

South Martin Regional Utilities

 (Hobe Sound) 1 2 0 2001 0 X

Tequesta 2 2 2001 1.5 X

1Not yet in production.
32 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

A well-defined relation between chloride and 

dissolved-solids concentrations in water from the Floridan aquifer system has been established for southeastern Florida (Reese, 1994), allowing these constituents 

to be interchanged in the characterization of salinity. 

This relation for the 73 samples collected during this 

study (fig. 18) is similar to that found by Reese (1994) 

for Miami-Dade and Broward Counties. In this report, 

chloride concentration is used to map the distribution 

of salinity.

The dominant water type present in ground 

water from the Upper Floridan aquifer in Martin and 

St. Lucie Counties, based on data plotted on trilinear 

diagrams, is the sodium-chloride type (Lukasiewicz 

and Switanek, 1995). Although both counties have 

sodium-chloride type water, interpretation of these 

plots by Lukasiewicz and Switanek (1995) based on a 

classification scheme by Frazee (1982) indicated that 

ground water from St. Lucie County is connate in 

nature, whereas Martin County has both connate and 

lateral intrusion (seawater invasion) signatures. The 

connate signature has a lower percentage of sodium 

plus potassium out of the combined major cations 

(sodium plus potassium, magnesium, and calcium) 

than the lateral intrusion signature. 

Comparison of the sulfate and chloride concentrations for the data collected in this study indicates 

some enrichment of sulfate as compared to that 

expected from mixing of freshwater with seawater, but 

only for samples with chloride concentration less than 

about 6,000 mg/L (fig. 19). This enrichment probably 

indicates that some dissolution of gypsum has 

occurred. Severe depletion of sulfate is evident for 

most samples with chloride concentration greater than 

6,000 mg/L, and this depletion is likely caused by 

sulfate reduction.

Figure 18. Relation between chloride and dissolved-solids concentrations for samples collected 

in this study.
Water Quality in the Floridan Aquifer System 33

Distribution of Salinity

On the basis of water-quality data and borehole 

geophysical log responses, the distribution of salinity 

within the Floridan aquifer system in the study area 

indicates that the system can be divided into the same 

three salinity zones, as used in earlier studies of southern Florida (Reese, 1994, 2000; Reese and Memberg, 

2000). These zones and their ranges in salinity, in order 

of increasing depth, are defined as follows: 

• Brackish-water zone—Dissolved-solids concentration less than 10,000 mg/L, and chloride concentration less than 5,330 mg/L;

• Salinity transition zone—Dissolved-solids concentration ranging from 10,000 to 35,000 mg/L, and 

chloride concentration ranging from 5,330 to 

19,500 mg/L; and

• Saline-water zone—Dissolved-solids concentration 

greater than 35,000 mg/L, and chloride concentration greater than 19,500 mg/L.

 Salinity increases rapidly with depth in the 

transition zone. The salinity within the saline-water 

zone is similar to that of seawater, which has a 

dissolved-solids concentration of about 36,000 mg/L 

(Nordstrom and others, 1979) and a chloride concentration of about 19,000 mg/L (Hem, 1989). As will be 

shown later in this report, the base of the brackishwater zone may or may not approximate a brackishwater/saltwater interface due to density equilibrium 

(same as a freshwater-saltwater interface).

A linear relation between specific conductance 

and chloride concentration less than 4,000 mg/L was 

established using samples collected during this study 

(fig. 20). The relation was used to estimate chloride 

concentration in samples for which specific conductance was determined but not chloride concentration 

(app. III). 

In mapping the distribution of salinity in the 

study area, it was assumed that salinity has not changed 

substantially since development of the aquifer system 

began in the 1930’s. As will be shown later, salinity in 

most wells in the study area has changed little during 

the last 40 to 50 years. 

Figure 19. Sulfate and chloride concentrations for samples collected in this 

study and relation to a pure water-seawater mixing line.
34 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Upper Floridan Aquifer 

The brackish-water zone encompasses the entire 

Upper Floridan aquifer in the Martin, St. Lucie, Palm 

Beach, and Okeechobee County study area. Although a 

number of distinct flow zones are present at various 

depths in the Upper Floridan aquifer, the salinity of 

water within the zones does not vary greatly (Lukasiewicz and Switanek, 1995). Salinity does increase 

with depth between the Upper and Lower Floridan 

aquifers in Martin and St. Lucie Counties (Lukasiewicz, 1992), Okeechobee County to the west (Bradner, 

1994), and Indian River County to the north (Schiner 

and others, 1988).

The areal distribution of chloride concentration 

in ground water from the Upper Floridan aquifer varies 

widely in the study area (fig. 21 and app. III). Figure 21 

was constructed using the most recently collected water 

sample at a specific well, which in many instances, was 

a sample collected during this study. In some cases, 

however, the only samples collected for certain wells 

were those collected as early as the 1940’s, especially 

in Martin County. Chloride concentrations in the study 

area range from 19 mg/L in Okeechobee County to 

8,000 mg/L in northeastern Palm Beach County. Three 

areas have been identified in which chloride concentrations exceed 1,000 mg/L: (1) an area at the northern 

end of Lake Okeechobee in Okeechobee County, (2) part 

of the inland area that extends northwest through northcentral Martin County and western St. Lucie County, 

and (3) part of the coastal area that trends parallel to the 

coast in Palm Beach County, eastern Martin County, 

and southeastern St. Lucie County. The maximum 

chloride concentration in each of these three areas is 

2,626, 1,670, and 8,000 mg/L, respectively. Chloride 

concentration is less than 500 mg/L in large geographic 

areas in Okeechobee County, northeastern St. Lucie 

County, and northwestern Martin County. 

Some of the wells used to map Upper Floridan 

aquifer chloride concentration are open to the upper 

part of the Lower Floridan aquifer (Lukasiewicz, 1992) 

as well as the Upper Floridan aquifer (fig. 21), and the 

chloride concentration in water from these wells can be 

higher than water from only the Upper Floridan aquifer. 

Figure 20. Relation between specific conductance and chloride concentration less than 

4,000 milligrams per liter for samples collected during this study.
Water Quality in the Floridan Aquifer System 35

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

FLORIDA’S TURNPIKE

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

1,000

2,000

4,000

6,000

2,000

1,000

2,000

750

450

1,220

1,400

1,040

1,790

900

885

940

800

810

950

2,150

913

685

600

400

420

540

600

470

1,200

545

575

1,100

1370

2,400

1,170

320 1,200

1,020

1,050

2,900

280

640 1,100 930

1,230 1,030

515

2,300

954

1,200

370

1,100

1,100

1,005

120

170

19

460

86

905

960

1,800

1,620

3,020

3,800

610

820

1,000

820

1,400

830

1,380

1,100

990

750

830 320

1,295

910

1,075

980

878

147

470

840

980

1,220

1,250

1,010

1,190

1,500

1,200

1,200

520

800

954

552

1,093

1,100

200

964 940

1,000

1,308

1215

1,290

1,317

1,333

337

318

700

330

1,282

1,300

280

810

970 1,200

1,400

1,350

1,520

325

778

828

957

733

1,341

799

940

1,010

420

708

1,770

530

420

967

510

373

811

1,270

1,422 885

695

1,734

1,098

275

375

435

410

1,125

1,040

410

610

775

665

1,188

573

512

403

517

1,210

836

742

327

468

330

877 1,670

1,130

1,110 2,070

276

1350

669

910

1,273

624 1,250

1,063

320

1,900

2,626

2,089

2,040

940

1,150 4,200

3,500

1,404

1,100

1,640

1,450

1140

1,850

1,530

8,000

1,400

2,100

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

940 WELL LOCATION AND CHLORIDE CONCENTRATION--

Concentration in milligrams per liter. See plate 2

for local well number. For wells with values shown in red,

open interval in well includes an upper part of the Lower

Floridan aquifer as mapped by Lukasiewicz (1992) in

addition to the Upper Floridan aquifer

Question mark (?) indicates total depth of well is unknown

LINE OF EQUAL CHLORIDE CONCENTRATION--In

milligrams per liter. Dashed where approximately located.

Contour interval is variable

1,000

?

?

?

?

?

?

?

?

?

?

?

?

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 21. Distribution of chloride concentration in the Upper Floridan aquifer.
36 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

This is because salinity, hydraulic head, and transmissivity 

can be higher in the Lower Floridan aquifer than in the 

Upper Floridan aquifer. Some of the northwesterly 

extensions where chloride concentration is greater than 

1,000 mg/L in the inland area in western St. Lucie 

County (fig. 21) could be due to wells open in the 

Upper Floridan aquifer that also penetrate the Lower 

Floridan aquifer. However, many of the wells that are 

open to both aquifers, particularly in the coastal area, 

do not contain water with higher chloride concentration 

when compared to nearby wells open only in the Upper 

Floridan aquifer.

Lower Floridan Aquifer

Only eight wells in the study area were open 

only to the Lower Floridan aquifer above the base of 

the brackish-water zone. These wells, the locations of 

which are all shown in figure 2, are M-1325 (upper 

monitoring zone), M-1353, OK-9002, PB-1170 (upper 

and lower monitoring zones), PB-1182 (packer test), 

PB-1196 (fig. 9, lower monitoring zone), STL-255 

(lower monitoring zone), and STL-380. Chloride 

concentration in water from these wells (nine samples) 

ranges from 510 to 3,050 mg/L (app. III). All of these 

wells, except for OK-9002 and STL-380, are in the 

coastal area.

Chloride concentration does not increase with 

depth between the Upper and Lower Floridan aquifers 

in the coastal area within the brackish-water zone. 

Chloride concentrations in sampled wells were compared with the depth of the sample in both inland and 

coastal areas (fig. 22). Only samples collected in this 

study and only one sample per well or monitoring zone 

were used. There seems to be no correlation in the 

coastal area (fig. 22B) between salinity and sample 

depth; however, some correlation exists in the inland 

area (fig. 22A). Chloride concentration seems to 

increase with well depth between the Upper and Lower 

Floridan aquifers in the inland area.

Reversals (decreases) in salinity with increasing 

depth between the Upper and Lower Floridan aquifers 

occur in the coastal area as indicated by monitoring 

wells that are completed at different depths at the same 

site. An example is shown by two samples collected 

from well PB-1196 (Jupiter RO Well Field) on July 17, 

2001: chloride concentration was 3,800 mg/L in water 

from the upper monitoring zone at a depth interval 

between 1,137 and 1,155 ft below land surface, and 

1,760 mg/L from the lower monitoring zone at a depth 

interval between 1,549 and 1,609 ft below land surface 

(figs. 9 and 22). Other examples include, from south 

to north, wells M-1034 (upper monitoring zone) and 

M-1353 (lower monitoring zone) at the Stuart WWTP 

site and well STL-255 (upper and lower monitoring 

zones) at the South Port St. Lucie WWTP site (fig. 22).

Similar reversals in salinity with depth within 

the brackish-water zone of the Floridan aquifer system 

were found in areas along the coast in Palm Beach and 

northern Broward Counties (Reese and Memberg, 

2000). An example of this salinity distribution, based 

on water-quality data and a resistivity geophysical log, 

is shown in three wells at the Coral Springs WWTP 

in northeastern Broward County (fig. 23), two of 

the which (CS-I1 and CS-M2) were sampled as part 

of this study. The Coral Springs site is classified within 

the coastal area due to the vertical distribution of salinity, location, and thickness (165 to 235 ft) of the 

basal Hawthorn/Suwannee unit (Reese and Memberg 

2000).

Salinity Zone Boundaries

The two boundaries of the three salinity zones in 

the Floridan aquifer system, the base of the brackishwater zone and the top of the saline-water zone, were 

determined in the study area principally using resistivity 

geophysical logs. The dual-induction resistivity log, the 

preferred log type for boundary delineation, includes 

three resistivity curves that are produced by the deepinduction, medium-induction, and shallow-focusing 

electrode devices all on the same logging tool. These 

devices are focused to different depths of investigation 

beyond the borehole wall and record deep, medium, 

and shallow formation resistivity measurements, 

respectively.

Calculations of true formation resistivity (using 

these three resistivity curves and correction charts for 

borehole and invasion effects) were made for a deep 

injection well in southeastern Florida in which salty 

drilling fluid had not invaded the formation (Reese, 

1994). The corrections between true formation resistivity 

and the deep induction resistivity values were shown to 

be small. Although these calculations were made for a 

well located in Miami-Dade County south of the study 

area, lithology and depth are similar to those in the 

study area. Therefore, it is reasonable to assume that 

deep-induction resistivity approximates true formation 

resistivity, provided extensive invasion with salty 

drilling fluid has not occurred.
Water Quality in the Floridan Aquifer System 37

Figure 22. Relation between well depth 

and chloride concentration less than 

4,000 milligrams per liter for (A) inland 

and (B) coastal areas. Sample depth 

used is bottom of completed open 

interval.
38 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Figure 23. Water-quality data, resistivity geophysical log, salinity zones, and hydrogeologic units for wells at the Coral Springs 

Wastewater Treatment Plant in northeastern Broward County (modified from Reese, 1994, fig. 14). Wells used at site include 

CS-I1, CS-I2, and CS-M2. Well CS-I1 is 750 feet south of well CS-I2, and well CS-M2 is 75 feet from well CS-I2.
Water Quality in the Floridan Aquifer System 39

The formation resistivity, Ro, for limestone was 

computed using an empirical formula (Archie, 1942) for 

the two threshold salinity values that define the top and 

base of the salinity transition zone for expected ranges in 

porosity, cementation factor, and formation temperature 

in the study area. The calculated average Ro values used 

to determine the boundaries are 6 ohm-m for a dissolvedsolids concentration of 10,000 mg/L and 2 ohm-m for a 

dissolved-solids concentration of 35,000 mg/L. These 

average Ro values were calculated using a porosity of 30 

to 35 percent, a cementation factor of 2.0, and a formation temperature of 27 °C. The methodology, relations, 

and assumptions (Reese, 1994, 2000; Reese and Memberg, 2000) used in this evaluation are believed to be 

valid for the Floridan aquifer system in all of southern 

Florida.

The depths of the salinity zone boundaries at the 

Coral Springs site, based primarily on a resistivity 

geophysical log, are shown in figure 23. Additionally, 

these boundaries are shown in well STL-332 at the Fort 

Pierce Wastewater Treatment Plant in northeastern 

St. Lucie County (fig. 24).

The approximate depths of the base of the brackish-water zone, and in most cases, the top of the salinewater zone, were determined at 13 wells in the study 

area (table 4). Three other wells (OK-9001/OK-9002, 

PB-1197 and STL-379) were drilled to sufficient 

depths to provide a minimum depth to the base of the 

brackish-water zone or an estimate of the depth, even 

though this boundary was not reached. A dual-induction log was used to determine both boundaries at 6 of 

the 13 wells; this log also was used to determine the top 

of the saline-water zone at 2 other wells (table 4). 

Placement of boundaries in all wells were in agreement 

with water-quality data collected from known intervals 

(packer test or completed intervals) in a well or at 

another well at the same site. Only water-quality data 

from known intervals were used at two wells to determine the base of the brackish-water zone. Use of waterquality data alone is often not as accurate as using 

geophysical logs to determine salinity zone boundaries 

because sampled intervals tend to be large, limited in 

number, or both.

The thickness of the salinity transition zone 

ranges from 70 to greater than 760 ft and averages about 

200 ft thick at seven sites; the thickness was 134 ft or 

less at four sites (table 4). South of the study area in 

Miami-Dade and Broward Counties, southeastern Florida, the average thickness of this zone was 143 ft with a 

range from 60 to 257 ft at 18 wells (Reese, 1994).

In the Martin, St. Lucie, Palm Beach, and 

Okeechobee County study area, the base of the brackish-water zone lies solely within the Lower Floridan 

aquifer. The depth to this boundary ranges from 1,525 

ft below NGVD of 1929 at well IR-1001 to 2,042 ft 

below NGVD of 1929 at well PB-1133, both of which 

are in the inland area (fig. 25). Generally, this boundary 

is deeper in the coastal area than in the inland area. The 

boundary is anomalously deep in the southern part of 

the coastal area where it seems to be greater than 1,900 

ft below NGVD of 1929 (fig. 25). At the Coral Springs 

site, the boundary is 2,017 ft below land surface or 

2,004 ft below NGVD of 1929 (fig. 23).

In central St. Lucie County, water samples 

collected from well STL-379 during drilling by the 

reverse-air rotary method indicate chloride concentration increases to 3,600 mg/L at a depth of 1,515 ft 

below NGVD of 1929 (Lukasiewicz and Switanek, 

1995). On this basis, the base of the brackish-water 

zone at this well is estimated to be at a depth ranging 

from 1,575 to 1,675 ft below NGVD of 1929 (table 4).

A state of equilibrium may exist between the 

brackish-water and saline-water zones. If so, then the 

base of the brackish water zone approximates a brackish-water/saltwater interface, and the depth to the base 

of the brackish-water zone can be estimated using the 

Ghyben-Herzberg approximation (Bear, 1979). This 

approximation assumes that pressure at the interface 

due to the column of overlying freshwater (brackish 

water) is balanced by the pressure due to a column of 

saltwater extending up to sea level. In southeastern 

Florida, south of the study area, the predicted shape of 

a saltwater interface based on the distribution of 

hydraulic head and the Ghyben-Herzberg relation 

generally conforms to the mapped base of the brackishwater zone (Reese, 1994; Reese and Memberg, 2000). 

The base of the brackish water zone is shallowest along 

the coast and dips inland to the west or northwest as 

head increases. 

In calculations of the altitudes of a saltwater 

interface using the Ghyben-Herzberg approximation in 

the study area, density of water in the Upper Floridan 

aquifer was estimated using an average chloride 

concentration of water within the aquifer and by 

assuming that a linear relation exists between chloride 

concentration and density from freshwater to seawater 

(table 5). Two values for head were used in the calculations, estimated predevelopment head (Bush and 

Johnston, 1988) and head as of May 2001 (fig. 15).
40 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

DEPTH, IN FEET BELOW LAND SURFACE

SALINE-WATER

ZONE

SALINITY

TRANSITION

ZONE

BRACKISH-WATER ZONE

OCALA

LIMESTONE AVON PARK FORMATION

UPPER FLORIDAN

AQUIFER MIDDLE CONFINING UNIT LOWER FLORIDAN AQUIFER

900

800

1,000

1,100

1,200

14,200

1,300

1,200 16,600

1,400

1,500

1,600

1,700

1,800

1,900

2,000

TOP OF LOG RUN INTERVAL

RESISTIVITY, IN OHM-METERS (LOG SCALE)

1 5 10 100

14,200

?

?

EXPLANATION

BOUNDARY BETWEEN

UNITS UNCERTAIN

MEDIUM

INDUCTION

WELL STL-332 DEEP

INDUCTION

WELL

STL-332

WATER-QUALITY DATA--Water

samples collected from completed

and packer test intervals. Number

is chloride concentration, in

milligrams per liter

PACKER TEST INTERVAL--Interval

is from 1,900 to 2,028 feet below

land surface in well STL-332

COMPLETED INTERVALS--In

monitoring well STL-333

?

SHALLOW FOCUSED

LATEROLOG 8

WELL STL-332

Figure 24. Water-quality data, 

resistivity geophysical log, salinity zones, and hydrogeologic 

units for twin wells STL-332 and 

STL-333 at the Fort Pierce 

Wastewater Treatment Plant in 

northeastern St. Lucie County. 

Lithology is limestone with various degrees of cementation 

throughout the interval shown.
Water Quality in the Floridan Aquifer System 41

These heads, recorded as freshwater heads, were 

corrected using the estimated density of water contained 

within the Upper Floridan aquifer at each well.

The position of the computed predevelopment 

Ghyben-Herzberg saltwater interface is comparable to 

the altitude of the base of the brackish-water zone in 

some wells and substantially different in other wells 

(table 5); the difference is 80 ft or less at 5 of 13 wells. 

In Miami-Dade and Broward Counties of southeastern 

Florida, this difference was 56 ft or less at five of eight 

wells (Reese, 1994). Differences between these two 

numbers can be attributed to the presence of the salinity 

transition zone rather than a sharp interface, a groundwater flow system that does not conform well to the 

assumptions of the Ghyben-Herzberg approximation 

(horizontal flow above the interface and no flow in the 

saltwater region), and the potential for upward movement of the interface from its predevelopment position in 

response to regional lowering of head prior to when a 

well was drilled. Additionally, an error in the estimated 

average chloride concentration in the Upper Floridan 

aquifer (table 5) could cause a significant error in the 

computed predevelopment saltwater interface. For 

example, decreasing the average chloride concentration 

in well PB-1182 (table 5) from 3,000 mg/L to 2,000 mg/L 

lessens the depth of the interface by 104 ft, from 2,087 ft 

to 1,983 ft below NGVD of 1929, and using the 

lower chloride concentration in this case gives better 

agreement of the computed predevelopment saltwater 

interface with the base of the brackish-water zone. 

Table 4. Depths to salinity zone boundaries in the Floridan aquifer system as determined in this study 

[Depths are below land surface. Annotations: SFWMD, South Florida Water Management District; USGS, U.S. Geological Survey; BWZ,

brackish-water zone; STZ, salinity transition zone; SWZ, saline-water zone. Methods: DIL, dual induction geophysical log (deep and medium 

induction and shallow focusing electrode devices); E, conventional electrical geophysical log (long and short normal devices); SPR, single 

point resistance geophysical log; completed interval, water-quality data collected from constructed well; DQW, water-quality data collected 

while drilling by reverse-air rotary method; packer test, water-quality data collected from packer test. Other annotations: ?, Depth uncertain 

because of formation contamination with salty drilling fluid; NR, not reached; <, less than the value; >, greater than the value]

USGS

well 

number

SFWMD number or 

other identifier

Total 

depth

(feet)

Land 

surface

elevation

(feet)

Depth to 

base of 

BWZ

(feet)

Depth to 

top of 

SWZ

(feet)

Thickness

of STZ

(feet)

Method

IR-1001 Hercules IW-1 3,005 25 1,550 <1,700 <150 For base of BWZ - SPR. DIL 

for top of SWZ

M-1352 Stuart IW-2 3,252 8.74 1,970 2,040 70 DIL

M-1358 North Martin IW-2 3,350 17.5 1,850 2,045 195 DIL

M-1360 MF-37 2,030 16 1,710 1,885 175 DIL

OK-100 OKF-100 2,030 15 <1,640 NR NR Packer test

OK-9001/

OK-9002

Lake Okeechobee 

ASR monitoring well 1,800 16 NR at 1,800 NR NR DQW and completed interval

PB-1133 Permit 235 11,010 38 2,080 2,230 150 E

PB-1166 Pratt & Whitney IW-1 3,310 25 1,830 2,010 180 DQW for base BWZ

E for top of SWZ

PB-1170 ENCON IW-1 3,505 18 2,040? >2,800 >760 DIL

PB-1182 Seacoast IW-1 3,320 21 1,880 2,550 670

Packer test and completed 

intervals. DIL for top of 

SWZ

PB-1197 Jupiter RO-5 1,900 17 NR at 1,900 NR NR DQW

STL-254 SPSL IW-1 3,418 9.5 1,840 1,916 76 E and packer tests in MW-1A

STL-332 FP IW-1 3,315 6 1,750 1,884 134 DIL

STL-334 NPSL IW-1 3,324 15 1,730 1,835 105 DIL

STL-379 SLF-73 1,540 25 NR, estimated at 

1,600 to 1,700 NR NR DQW

STL-386 SPSL MW-1A 1,960 9 1,870 Uncertain Uncertain E
42 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

1,700

1,600

1,700

2,000

1,900

1,800

2,000

1,900

TURNPIKE

IR-1001

M-1352

M-1358

M-1360

PB-1133

PB-1166

OK-100

OK-9001/

OK-9002

PB-1170

1,961

1,833

1,716

1,694

2,042

1,805

1,625 or

shallower

Not reached

at 1,784

Not reached at

1,515, estimated

to be 1,575 to 1,675

1,744

1,525

1,831

Not reached

at 1,883 2,022? (formation

contaminated with

salty drilling fluid)

PB-1197

STL-254

STL-332

STL-334 STL-379

PB-1182

1,859

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

M-1360

1,694

1,600

DEPTH OF BASE OF BRACKISH-WATER ZONE

AND LOCAL WELL NUMBER--Upper number is

altitude of base of brackish-water zone, in feet below

NGVD of 1929. Lower number is local well number

LINE OF EQUAL ALTITUDE OF THE BASE OF

THE BRACKISH-WATER ZONE--In feet below

NGVD of 1929. All contours approximately located.

Contour interval is 100 feet

70

60

710

441

FLORIDA’S

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 25. Altitude of the base of the brackish-water zone. NGVD of 1929 is National Geodetic Vertical Datum 

of 1929.
Water Quality in the Floridan Aquifer System 43

Table 5. Calculated altitudes of a saltwater interface using the Ghyben-Herzberg approximation and comparison with altitudes of the base o[Well locations are shown in figure 2. BWZ, brackish-water zone; NGVD of 1929, National Geodetic Vertical Datum of 1929; SFWMD, South Florida Water M

UFA, Upper Floridan aquifer; USGS, U.S. Geological Survey, NA, Not applicable]

USGS

well 

number

SFWMD or other 

identifier

Estimated

predevel

opment

head1

(feet above

NGVD of 

1929)

Estimated

average

chloride

 concentration

in UFA 

(milligrams 

per liter)

Estimated

density of

of water in 

UFA

(grams 

per cubic 

centimeter)

a b c (a × b) d (c - d) e 

Corrected

predevelopment

head

(feet above

NGVD of 

1929)

GhybenHerzberg

factor2

Calculated 

altitude of predevelopment 

of saltwater

interface3

(feet below 

NGVD of 

1929)

Altitude 

of base 

of BWZ4

(feet below

NGVD of 

1929)

Calculated 

predevelopment 

saltwater 

interface 

minus base 

of BWZ

 (feet)

Estimate

 head 

May 200

(feet abo

NGVD o

1929)

IR-1001 Hercules IW-1 48 1,000 1.0013 47.9 39.267 1,882 1,525 357 32 M-1352 Stuart IW-2 48 2,300 1.0030 47.9 42.143 2,017 1,961 56 48 M-1358 N.Martin IW-2 48 1,300 1.0017 47.9 39.908 1,912 1,833 80 44 M-1360 MF-37 59 500 1.0006 59.0 38.191 2,252 1,694 558 49 OK-100 OKF-100 62 Fresh 1.0000 62.0 37.313 2,313 1,625 688 47 PB-1133 Permit 235 54 1,000 1.0013 53.9 39.267 2,118 2,042 76 UnknowPB-1166 Pratt&Whitney IW-1 51 1,600 1.0021 50.9 40.571 2,065 1,805 260 UnknowPB-1170 ENCON IW-1 48 2,000 1.0026 47.9 41.430 1,983 2,022 -39 47 PB-1182 Seacoast 48 3,000 1.0038 47.8 43.643 2,087 1,859 228 47 STL-254 SPSL IW-1 49 1,500 1.0019 48.9 40.237 1,968 1,831 137 43 STL-332 FP IW-1 46 1,000 1.0013 45.9 39.267 1,804 1,744 59 28 STL-334 NPSL IW-1 48 1,000 1.0013 47.9 39.267 1,882 1,716 167 36 STL-379 SLF-73 51 1,000 1.0013 50.9 39.267 2,000 1,575 425 37 

1Predevelopment head from Bush and Johnston (1988) recorded as a freshwater head.2Ghyben-Herzberg factor equals ρf/(ρs-ρf), where ρf is the density of water in the Upper Floridan aquifer and ρs is the density of seawater. Uses 1.0268 grams per cub

(Parker and others, 1955).

3Corrected predevelopment head times Ghyben-Herzberg factor.4Altitude of the base of the brackish-water zone deterined in this study.5May 2001 head from Knowles (2001) recorded as a freshwater head.
44 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

In five inland wells, however, the difference between 

these two depths is greater than what would be 

expected for these factors; at wells IR-1001, M-1360, 

OK-100, PB-1166, and STL-379, the altitude of the 

base of the brackish-water zone was shallower than the 

calculated predevelopment interface by an amount 

ranging from 260 ft to 688 ft (table 5). 

Formation of a saltwater interface at its equilibrium position in much of the inland area may be 

prevented by confining units in the Lower Floridan 

aquifer. Downward movement of fresh to brackish 

water may be prevented by beds of very low permeability, such as dense dolomite. An alternate theory, 

however, for explaining this difference is that the 

hydraulic head in the saline-water zone is substantially 

greater than zero (sea level), which is assumed in the 

Ghyben-Herzberg approximation, due to possible heating and expansion of the water in the saline-water zone. 

Assuming equilibrium, increasing head in the salinewater zone to above sea level would cause the interface 

to move to a shallower position for the same head in the 

brackish-water zone.

The anomalous depth of the base of the brackishwater zone in the southern part of the coastal area could 

be related to the anomalous vertical distribution of 

salinity in the brackish-water zone in this same area. 

Anomalously high salinity occurs in this area in the 

Upper Floridan aquifer (fig. 21), and as previously 

discussed, there often is a reversal in salinity with 

depth.

Distribution of Water Temperature

The temperature of ground water withdrawn 

from the Floridan aquifer system was surveyed in the 

Martin, St. Lucie, Palm Beach and Okeechobee County 

study area. For the purpose of this analysis, it is 

assumed that the change in the temperature of water 

flowing up a well from the aquifer to the surface is 

minimal, and that the change is similar between adjacent wells or areas because the depth to the aquifer is 

similar. The greatest potential error in the latter 

assumption could be in comparison of areas with a 

large difference in depth to the top of the Upper 

Floridan aquifer, such as between north-central 

Martin County and northeastern Palm Beach County 

(fig. 11). 

The temperature of water withdrawn from the 

Upper Floridan aquifer varies considerably, ranging 

from 22.2 °C near the coast in northeastern Martin 

County to 32.0 °C inland in southern St. Lucie County 

(fig. 26). An area of high water temperature generally 

greater than 28 °C trends northwest from central 

Martin County to northwestern St. Lucie County. 

Temperatures within this northwest-trending area are 

greater than 30 °C and up to 32 °C in north-central 

Martin and south-central St. Lucie Counties. Water 

temperature in the coastal area is less than 28 °C, 

except for two small areas with temperatures greater 

than 28 °C that extend slightly from the inland area into 

the coastal area (figs. 12 and 26).

Water temperature and sample depth were 

compared in wells for the Upper and Lower Floridan 

aquifers (fig. 27), using only samples collected during 

the course of this study. No correlation exists for wells 

in the coastal area, whereas in the inland area, a very 

weak relation of increasing water temperature with 

depth may exist. Lichtler (1960) indicated a poor correlation of water temperature with depth in the northcentral Martin County part of the inland area.

Comparison of the maps showing the distribution 

of water temperature (fig. 26) and the distribution of 

chloride concentration (fig. 21) illustrates that the area 

of high water temperature trending northwest through 

western St. Lucie County coincides with the northwesttrending area of higher chloride concentration (greater 

than 1,000 mg/L). Plots of water temperature and chloride concentration using samples collected during this 

study suggest little correlation exists in the coastal 

area (fig. 28). A statistically significant correlation, 

however, has been identified between water temperature and chloride concentration in the inland area 

(R2 = 0.46).

Meyer (1989) mapped an area of elevated water 

temperature and salinity in the Upper Floridan aquifer 

in Martin County and extending northwest through 

western St. Lucie County. He used this anomaly as 

evidence in support of upwelling of saline water from 

the Boulder zone of the Lower Floridan aquifer and 

mixing with freshwater contained within the Upper 

Floridan aquifer. In accordance with this interpretation, 

Kohout (1965) theorized convective movement of 

ground water in southern Florida because of geothermal heating from below: cold seawater moves inland 

into the Boulder zone along the southeastern coast, 

upward through preferential vertical pathways within 

overlying confining units, and then coastward, mixing 

within the freshwater flow system in the upper part of 

the Floridan aquifer system.
Water Quality in the Floridan Aquifer System 45

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

24

24

24

26

26

28

30

32

28

28

26

28

28

28

26

26

26

26

26

26

?

?

?

?

?

?

?

?

?

?

?

?

28

26.7

25.5

28.9

28.3

25.0

25.0

25.6

24.4 25.0

23.9

23.9 24.4 22.2

23.9 24.4

26.1

28.3

27.0 24.5

27.0

27.5

27.5

27.8

26.5

30.8

29.4

29.4

25.0

28.0

28.2

24.5

24.4

26.1

26.2

24.0

27.2 30.1

27.2

27.2 24.4

27.8

26.5 25.5 27.2

25.0

27.8 25.8

26.5

24.9

27.6

23.8

28.9

29.1

24.9

25.8

25.8

25.8

26.5

26.0

26.2

28.4

27.8

27.6

23.5

24.9

23.3

23.1

25.0

24.0

27.7

27.5 27.9

27.6

27.9

28.4

26.9

27.8

28.6

25.1

32.0

26.0 23.8

27.8

26.4

25.3

27.6

29.2

30.7

24.0

30.5

28.8

28.5

24.9

27.1

26.9

27.2

24.6

24.4

24.3

24.7

29.5 24.4

27.8

27.7

26.3

28.3

24.9

24.9

24.6 30.4

31.0

29.3

27.9

25.4

27.8

27.8

27.0

27.1

28.8

26.4

26.2

27.6

25.6

23.9

29.2

26.1

26.4

28.9

27.2

26.1

27.8 25.3

27.8

27.8

27.8

24.7

29.4

24.9

26.6

26.3

26.0

28.3

26.4

26.9

26.6

25.6

27.2

28.3

27.1

26.4

27.8

26.3

31.1

27.2

27.6

25.9

24.9

24.8

27.7

EXPLANATION

WELL LOCATION AND WATER TEMPERATURE--Temperature

in degrees Celsius. See figures 1, 2, or 3 for local well number.

For wells with values shown in red, open interval in well includes

an upper part of the Lower Floridan aquifer as mapped by

Lukasiewicz (1992) in addition to the Upper Floridan aquifer.

Question mark (?) indicates total depth of well is unknown

LINE OF EQUAL WATER TEMPERATURE--In degrees

Celsius. Dashed where approximately located.

Contour interval is 2 degrees Celsius.

28.9

28

0

0

15 MILES

15 KILOMETERS

5 10

5 10

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

70

60

710

441

FLORIDA’S

1

1

95

95

95

TURNPIKE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 26. Distribution of water temperature in the Upper Floridan aquifer.
46 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

DEPTH, IN FEET BELOW LAND SURFACE DEPTH, IN FEET BELOW LAND SURFACE

A

B

y = 1.4x + 1,325

R2= 0

400

600

800

1,000

1,200

1,400

1,600

1,800

22 23 24 25 26 27 28 29 30

WATER TEMPERATURE, IN DEGREES CELSIUS

y = 37.6x - 43

Linear regression:

Linear regression:

R2 = 0.05

400

600

800

1,000

1,200

1,400

1,600

1,800

24 25 26 27 28 29 30 31 32

WATER TEMPERATURE, IN DEGREES CELSIUS

EXPLANATION

WELL OPEN ONLY TO UPPER FLORIDAN AQUIFER

WELL OPEN TO UPPER AND LOWER FLORIDAN AQUIFERS

WELL OPEN ONLY TO LOWER FLORIDAN AQUIFER

Figure 27. Relation between well depth 

and water temperature for (A) inland 

and (B) coastal areas. Depth used is 

bottom of completed open interval.
Water Quality in the Floridan Aquifer System 47

WATER TEMPERATURE, IN DEGREES CELSIUS WATER TEMPERATURE, IN DEGREES CELSIUS

A

B

y = -0.0004x + 25

Linear regression:

R2 = 0.10

22

24

26

28

30

32

0 1,000 2,000 3,000 4,000

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

y = 0.0018x + 26

Linear regression:

R2 = 0.46

22

24

26

28

30

32

0 1,000 2,000 3,000 4,000

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

EXPLANATION

WELL OPEN ONLY TO UPPER FLORIDAN AQUIFER

WELL OPEN TO UPPER AND LOWER FLORIDAN AQUIFERS

WELL OPEN ONLY TO LOWER FLORIDAN AQUIFER

Figure 28. Relation between water 

temperature and chloride concentration 

less than 4,000 milligrams per liter for 

(A) inland and (B) coastal areas. Samples are from completed open intervals 

in wells.
48 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Localized, warm, upwelling water in the 

Floridan aquifer system could result in higher hydraulic head than surrounding areas. An area of elevated 

hydraulic head in the Upper Floridan aquifer for 

September 1977 is indicated in north-central Martin 

County and south-central St. Lucie County that 

extends north-northwest (Brown and Reece, 1979, 

pl. 2). This area of elevated head (about 4 to 6 ft higher 

than surrounding areas) roughly coincides with the area 

of water temperature higher than 30 °C mapped in this 

study (fig. 26). 

Isotopic Analyses

Deuterium (δD), oxygen-18 (δ18O), the strontium-87 to strontium-86 ratio (87Sr/86Sr), and stable 

(δ13C) and radioactive (14C) carbon isotope data were 

collected during this study, and variations in these 

constituents were related to factors such as source aquifer, 

salinity, water temperature, and location (inland or 

coastal areas). Study of these ground-water isotopic 

variations can improve understanding of the flow 

system and the origin and age of water from different 

areas, water-bearing units, and depths. Isotopic data 

were collected from 55 completed open intervals in 49 

wells (table 6). 

Table 6. Isotopic data collected in this study 

[Well locations are shown in plate 2. Isotope annotations: δ18O, delta oxygen-18; δ2H, delta deuterium; 87Sr/86Sr, ratio of strontium-87 to 

strontium-86; δ13C, delta carbon-13; 14C, carbon-14. Other annotations: DIC, dissolved inorganic carbon; per mil, parts per thousand; PMC, 

percent modern carbon (unnormalized); BP, before present; --, not determined; ?, unknown]

Local

 well

number

Date

Depth top of 

open interval

(feet below 

land surface)

Depth bottom 

of open

 interval

(feet below land 

surface)

δ18O

(per mil)

δ2H

(per mil)

87Sr/86Sr

δ13C

of DIC

(per

mil)

14C

of DIC

(as PMC)

14C

apparent

age

(years BP)

CS-I1 09-13-2000 2,153 2,183 0.30 4.7 0.70791 -2.0 5.32 23,570

CS-M2 09-13-2000 1,000 1,110 -.80 -1.8 .70865 -2.2 4.35 25,180

09-13-2000 1,510 1,653 -1.42 -3.7 .70792 -2.5 4.16 25,530

G3-1 07-26-2001 ? ? -1.51 -4.3 .70777 -4.8 1.70 32,640

G205-5 07-26-2001 ? ? -1.65 -5.6 .70776 -6.6 4.00 25,810

M-255 06-08-2000 300 800 -1.64 -2.9 .70778 -- -- --

07-24-2001 300 800 -- -- -- -5.6 2.10 30,920

M-745 06-08-2000 360 810 -1.53 -2.9 .70776 -- -- --

07-24-2001 360 810 -- -- -- -5.7 2.30 30,490

M-1033 07-10-2000 2,027 2,093 .37 5.9 .70787 -.4 2.41 29,910

M-1034 07-10-2000 1,010 1,300 -1.14 -2.1 .70780 -4.2 4.77 24,440

M-1121 07-13-2000 543 1,020 -1.42 -4.4 .70785 -- -- --

07-18-2001 543 1,020 -- -- -- -3.7 2.10 31,180

M-1125 06-08-2000 456 1,120 -1.81 -4.1 .70781 -- -- --

M-1325 08-30-2001 1,715 1,757 -1.24 -3.5 .70782 -2.1 3.90 26,090

08-30-2001 2,177 2,212 .50 3.7 .70782 -3.4 10.40 18,220

M-1326 07-10-2000 844 1,091 -1.30 -3.5 .70785 -- -- --

M-1330 06-08-2000 400 1,250 -1.52 -3.6 .70774 -- -- --

07-17-2001 400 1,250 -- -- -- -3.7 1.60 33,490

M-1347 07-13-2000 400 1,320 -1.44 -5.0 .70781 -- -- --

M-1353 07-10-2000 1,600 1,650 -1.24 -2.9 .70784 -4.8 2.68 29,070

M-1356 08-30-2001 1,165 1,400 -1.22 -2.9 .70777 -2.9 2.30 30,260

OK-13 05-31-2000 600 1,200 -1.53 -4.7 .70780 -- -- --

OK-17 05-31-2000 538 986 -1.39 -4.4 .70777 -- -- --

OK-23 05-31-2000 496 925 -1.80 -6.3 .70777 -- -- --

OK-31 05-31-2000 ? 1,079 -1.71 -3.3 .70781 -- -- --

07-19-2001 ? 1,079 -1.80 -6.0 .70777 -3.3 1.60 33,340
Water Quality in the Floridan Aquifer System 49

OK-72 05-31-2000 500 800 -1.65 -3.3 .70776 -- -- --

07-19-2001 500 800 -- -- -- -3.3 .80 38,420

OK-9001 07-24-2001 990 1,075 -1.98 -7.4 .70777 -2.4 3.00 28,070

OK-9002 07-24-2001 1,275 1,700 -1.69 -5.6 .70776 -6.1 10.80 17,880

PB-1144 07-13-2000 1,020 1,038 -1.36 -3.0 .70791 -- -- --

PB-1196 06-05-2000 1,137 1,155 -1.09 -1.3 .70789 -- -- --

06-05-2000 1,549 1,609 -1.26 -1.4 .70784 -- -- --

07-17-2001 1,137 1,155 -- -- -- -1.1 .50 41,900

07-17-2001 1,549 1,609 -- -- -- -2.5 .80 39,280

PB-1774 08-29-2001 1,120 1,740 -1.19 -3.0 .70791 -2.6 1.00 36,650

STL-215 06-06-2000 310 1,106 -1.52 -2.9 .70781 -- -- --

07-25-2001 310 1,106 -- -- -- -7.6 2.10 30,860

STL-216 06-01-2000 482 993 -1.46 -2.8 .70780 -- -- --

STL-217 06-01-2000 263 1,058 -1.49 -2.7 .70779 -- -- --

10-19-2001 263 1,058 -- -- -- -3.9 1.10 36,250

STL-218 06-01-2000 224 946 -1.53 -6.3 .70773 -- -- --

STL-220 06-07-2000 318 1,286 -1.64 -4.6 .70775 -- -- --

07-18-2001 318 1,286 -- -- -- -5.6 0.90 38,160

STL-224 06-06-2000 156 707 -1.52 -4.0 .70777 -- -- --

STL-255 07-12-2000 898 1,268 -1.27 -2.5 .70779 -4.4 4.62 24,690

07-12-2000 1,610 1,663 -1.27 -1.9 .70784 -4.3 3.61 26,670

STL-335 07-12-2000 950 1,175 -1.35 -3.6 .70780 -7.4 5.20 23,740

07-12-2000 1,730 1,800 -.54 -.1 .70782 -.2 1.37 34,490

STL-342 06-01-2000 ? ? -1.46 -5.2 .70780 -- -- --

STL-346 06-01-2000 ? 786 -1.56 -3.1 .70780 -- -- --

STL-352 06-06-2000 ? 1,100 -1.48 -4.1 .70788 -- -- --

07-16-2001 ? 1,100 -- -- -- -2.4 2.30 30,200

STL-353 06-06-2000 850 1,230 -1.39 -2.8 .70779 -- -- --

STL-375 06-07-2000 420 866 -1.51 -2.6 .70777 -- -- --

STL-376 07-12-2000 ? 638 -1.52 -5.0 .70777 -- -- --

07-25-2001 ? 638 -- -- -- -3.6 3.20 27,700

STL-380 06-07-2000 1,070 1,450 -1.45 -3.6 .70778 -- -- --

07-18-2001 1,070 1,450 -- -- -- -4.6 1.00 36,760

STL-381 06-07-2000 480 700 -1.51 -3.6 .70779 -- -- --

07-18-2001 480 700 -- -- -- -4.7 1.20 35,300

STL-382 06-07-2000 790 860 -1.49 -3.0 .70775 -- -- --

STL-385 06-15-2000 500 880 -1.57 -4.1 .70780 -- -- --

07-25-2001 500 880 -- -- -- -3.6 2.80 28,750

STL-386 07-12-2000 1,887 1,960 -.28 3.4 .70785 -.5 1.22 35,400

STL-387 07-11-2000 ? 1,600 -1.39 -3.7 .70783 -6.2 4.52 24,870

STL-388 07-11-2000 650 1,350 -1.43 -4.0 .70780 -4.6 2.28 30,360

STL-389 07-11-2000 650 1,350 -1.41 -4.5 .70778 -- -- --

STL-391 07-11-2000 ? 900 -1.33 -4.4 .70779 -- -- --

07-18-2001 ? 900 -- -- -- -5.7 1.50 33,620

STL-392 07-11-2000 ? 900 -1.39 -3.6 .70783 -- -- --

Table 6. Isotopic data collected in this study (Continued)

[Well locations are shown in plate 2. Isotope annotations: δ18O, delta oxygen-18; δ2H, delta deuterium; 87Sr/86Sr, ratio of strontium-87 to 

strontium-86; δ13C, delta carbon-13; 14C, carbon-14. Other annotations: DIC, dissolved inorganic carbon; per mil, parts per thousand; PMC, 

percent modern carbon (unnormalized); BP, before present; --, not determined; ?, unknown]

Local

 well

number

Date

Depth top of 

open interval

(feet below 

land surface)

Depth bottom 

of open

 interval

(feet below land 

surface)

δ18O

(per mil)

δ2H

(per mil)

87Sr/86Sr

δ13C

of DIC

(per

mil)

14C

of DIC

(as PMC)

14C

apparent

age

(years BP)
50 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Deuterium and Oxygen-18

Values of δD and δ18O for each sample are 

typically plotted on a diagram, and the distribution 

of samples is related to a global meteoric water line 

(Craig, 1961). The position of data relative to this line 

can indicate important information on waters that have 

undergone evaporation, recharge during different climatic conditions, and mixing of waters from different 

sources, such as recharged downgradient ground water 

and saltwater. Most of the 56 samples from 55 separate 

open intervals collected in the study area (table 6) fall 

below the global meteoric water line (fig. 29). Data 

from the coastal area and the three samples from the 

Coral Springs WWTP plot along a saltwater mixing 

line. All six of the points along this line, with δ18O 

higher than -1 per mil, have a dissolved-solids concentration exceeding 10,000 mg/L. The extension and 

intersection of this saltwater mixing line with the global 

meteoric water line occurs approximately at δD equal 

to –6.5 per mil and δ18O equal to –2 per mil; this point 

compares favorably with isotope data described by 

Sacks and Tihansky (1996) as fresh “downgradient 

waters from the Upper Floridan aquifer” in southwestern 

Florida. Samples from the inland area are isotopically 

lighter (depleted in deuterium and 18O and values of 

δD and δ18O more negative) than samples from the 

coastal area and plot as a relatively separate nonlinear 

group. Some inland area data plot close to an extension 

of the saltwater mixing line fit to the coastal area data, 

whereas others plot on or near the global meteoric 

water line. Separation of the data from the two areas 

indicates that inland area ground water was recharged 

under different climatic conditions than coastal area 

ground water or has not mixed with saltwater or both.

Strontium-87/Strontium-86 and Stontium 

Concentration

Strontium concentration and 87Sr/86Sr can be 

useful indicators of ground-water movement and origin 

of salinity. The 87Sr/86Sr of marine carbonate rocks of 

Cenozoic age have been measured, and these data have 

shown strong variation during the late Cenozoic 

Erathem, providing a high-resolution dating tool during 

this time (Elderfield, 1986; Howarth and McArthur, 

1997). The Floridan aquifer system consists of marine 

carbonates of Cenozoic age that contain strontium 

derived from the seawater present during deposition. 

If the 87Sr/86Sr of ground water has equilibrated with 

the 87Sr/86Sr of the rock or sediment containing the 

water, then the source of the water can be determined, 

provided the age of potential source rocks are known. 

The time required for equilibration to occur, however, 

is uncertain.

Figure 29. Relation between delta deuterium and delta oxygen-18 in ground water in the study area.
Water Quality in the Floridan Aquifer System 51

For all of the samples collected in this study 

(app. IV), strontium concentration was compared to 

chloride concentration. All water samples had strontium concentrations that plotted considerably above the 

saltwater mixing line when strontium was graphically 

compared to chloride concentration (fig. 30). This 

suggests that dissolution of strontium from the carbonate aquifer matrix represents an important process. 

Samples from inland area wells generally exhibited a 

much higher concentration of strontium than coastal 

area wells, suggesting that inland area waters are older, 

allowing more time for dissolution.

The 87Sr/86Sr ratio was graphically compared to 

the inverse of strontium concentration and 87Sr/86Sr 

seawater age boundaries (fig. 31). Many of the 87Sr/

86Sr samples from coastal area wells indicate an early 

Oligocene seawater age, whereas inland area samples 

indicate an Eocene seawater age. This result suggests 

that the basal Hawthorn/Suwannee unit of Oligocene 

age, which thickens in the coastal area, contributes a 

greater portion of the water withdrawn in the coastal 

area wells (as compared to deeper formations) than in 

the inland area. Many of the samples indicating an 

early Oligocene age, however, were obtained from 

wells open exclusively or partially to the Lower Floridan aquifer of Eocene age. A more likely explanation 

is that Floridan aquifer system ground water in the 

coastal area may be younger than the host rock because 

equilibration with the host rock has not yet occurred. 

Perhaps much of the Floridan aquifer system in the 

coastal area was invaded with seawater during Pleistocene Epoch high sea-level stands, and flushing out 

this saline water has been incomplete. Saline water 

with a 87Sr/86Sr-derived Oligocene seawater age was 

collected within the Avon Park Formation of Eocene 

age near the coast in southwestern Florida. This age is 

attributed to the mixing of formation water with 

younger seawater introduced into the Floridan aquifer 

system (Sacks and Tihansky, 1996).

Stable and Radioactive Carbon Isotopes

Carbon-13 (δ13C) and carbon-14 (14C) of 

dissolved inorganic carbon are used together to date 

ground water and gain insight on the evolution of 

Figure 30. Relation between strontium and chloride concentrations in ground water in the study area.
52 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

ground water from recharge areas to confined downgradient areas. A laboratory-derived, apparent carbon14 age can be adjusted using geochemical models for 

reactions of the ground water with aquifer minerals. 

This adjusted sample age is younger that the apparent 

age due to dissolution of dead carbon (zero 14C) from 

the carbonate rocks in the Floridan aquifer system 

during downgradient movement from the recharge area 

in central Florida. In this study, however, adjusted ages 

were not determined, and the ages of samples, in terms 

of PMC, are used in a relative sense to compare the 

ages of samples. In a study of the intermediate aquifer 

system in southwestern Florida, adjusted carbon-14 

ages were determined for ground-water samples from 

the intermediate and Floridan aquifer systems (Torres 

and others, 2001), and a linear correlation between 

these ages and the apparent ages was evident (L.A. 

Sacks, U.S.Geological Survey, written commun., 

2003). Apparent ages were about 12,000 years older 

than adjusted ages.

Carbon-13 in ground water evolves to near zero 

per mil in deeply buried parts of the flow system as a 

result of confinement and dissolution of isotopically 

heavy (enriched in 13C) calcite and dolomite. Recently 

recharged water in the surficial aquifer system has the 

isotopically light (depleted in 13C) δ13C signature of 

soil-zone carbon dioxide (CO2). Soil-zone CO2 usually 

has a δ13C range of -25 to -20 per mil (Deines and 

others, 1974). Changes in δ13C in the confined Upper 

Floridan aquifer of southwestern Florida is attributed to 

dissolution or precipitation of dolomite (Sacks and 

Tihansky, 1996). 

The carbon-13 and carbon-14 analysis was 

performed on 38 samples collected in this study. 

Unnormalized 14C activity was reported as PMC and 

apparent age in years before present (table 6). The 

PMC values range from 0.50 to 10.80, and correspondingly apparent ages range from 41,900 to 17,880 years 

before present. The δ13C in the 38 samples range from 

-7.6 to -0.2 per mil (table 6).

Comparison of δ13C with PMC indicates that the 

evolution of ground water in inland and coastal areas is 

different (fig. 32). Inland area samples tend to group 

toward low PMC and lighter δ13C (-8 to-2.5 per mil); 

grouping is even more concentrated for inland area 

samples having a water temperature of 28 °C or higher 

(δ13C from -6 to -3 per mil). Coastal area samples tend 

to exhibit wide variability in both δ13C and PMC. 

Figure 31. Relation between ratio of strontium-87 to strontium-86 and the inverse of strontium 

concentration in ground water in the study area.
Water Quality in the Floridan Aquifer System 53

-8

-7

-6

-5

-4

-3

-2

-1

0

0 2 4 6 8 10 12

CARBON-14, IN PERCENT MODERN CARBON

INLAND

AREA

COASTAL

AREA

HIGH

SALINITY

TREND

M-1033

STL-335

lower

STL-386

PB-1196 upper

CS-I1 CS-M2

upper

CS-M2

lower

M-1325

upper

M-1325 lower

OK-9002**

STL-335 upper

STL-215

G205-5

STL-387

STL-255 upper

STL-255 lower M-1034

STL-220

STL-391

M-255

M-745

STL-380

STL-381

G3-1

STL-388

M-1353

STL-217

OK-72

M-1330

OK-31

M-1121

STL-385*

STL-376*

M-1356

STL-352

OK-9001**

COASTAL AREA WELL AND NUMBER With

dissolved-solids concentration less

than 10,000 milligrams per liter

−

INLAND AREA WELL AND NUMBER With water

temperature of 28 degrees Celsius or greater

−

INLAND AREA WELL AND NUMBER With

water temperature less than 28 degrees Celsius

−

OK-31

M-1356

OK-72

PB-1196 lower

PB-1774

COASTAL AREA WELL AND NUMBER With

dissolved-solids concentration greater

than 10,000 milligrams per liter

−

LOCATED CLOSE TO THE BOUNDARY Used

to separate the inland area from the coastal

area-see figure 12

−

LOCATED AT THE NORTHERN END OF

LAKE OKEECHOBEE Well away from the area

of elevated salinity and water temperature in

inland Martin and St. Lucie Counties

−

CS-I1

**

*

EXPLANATION

Figure 32. Relation between δ13C and carbon-14, in percent modern carbon in the study area.
54 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

However, samples containing dissolved-solids concentration exceeding 10,000 mg/L group in a separate 

trend that extends toward 0.0 per mil δ13C and 0.0 

PMC and has δ13C heavier than -3.5 per mil. The distribution of data indicates that ground water in the 

inland area has had a greater time of residence than 

ground water in much of the coastal area, particularly 

for samples from inland wells having water temperature of 28 °C or higher. Four notable exceptions are 

samples from wells STL-376, STL-385, OK-9001, 

and OK-9002. They are inland area samples that plot 

in the same area as coastal area samples in figure 32. 

However, both wells STL-376 and STL-385 are located 

close to the 100-ft thickness contour line for the basal 

Hawthorn/Suwannee unit used to separate the inland 

area from the coastal area (pl. 2 and fig. 12), and monitoring well OK-9001/OK-9002 at the northern end of 

Lake Okeechobee, may be in a different flow regime 

than most of the inland area. This well is located in a 

structurally low area (figs. 11 and 13) and well away 

from the area of elevated salinity and water temperature in inland Martin and St. Lucie Counties (figs. 21 

and 26). Of the five samples from the coastal area indicating an older age (less than 2 PMC), two have high 

salinity (greater than 10,000 mg/L dissolved-solids 

concentration), and the other three are from northeastern Palm Beach County − the farthest downgradient 

part of the study area (fig. 15, predevelopment potentiometric contours).

The δ13C values of inland area ground water 

could be influenced by dolomite dissolution, if the 

dolomite that is common in the Lower Floridan aquifer 

in the inland area formed in a brackish- to saline-water 

mixing zone associated with a saltwater interface. 

Some evidence supporting a mixing zone origin for the 

thick beds of dolomite has been described previously 

for the Lower Floridan aquifer in Palm Beach County 

(Reese and Memberg, 2000). Hanshaw and Back 

(1972) hypothesized that isotopically lighter dolomites 

in the Floridan aquifer system with δ13C ranging from 

–7.5 to –2.8 per mil formed in a saltwater mixing zone; 

this range is similar to that seen for inland area samples 

(fig. 32). The trend of coastal area samples with high 

salinity (greater than 10,000 mg/L dissolved-solids 

concentration) shown in figure 32 could indicate that 

dolomite precipitation is occurring in a saltwater 

mixing zone.

Temporal Changes in Salinity

Few salinity data are available for the study area 

prior to 1977, and the data that are available indicate 

minor, if any, change in the salinity of the Upper Floridan aquifer. Lichtler (1960) does not mention any 

increase in salinity in Martin County. Chloride concentration data indicate salinity in the Upper Floridan 

aquifer did not change substantially in the UEC Planning Area between 1957 and 1977 (Brown and Reece, 

1979). In Indian River County, however, a 22-percent 

increase on average in chloride concentration was 

observed between 1951 and 1984 in 26 Floridan aquifer system wells located mostly in the eastern half of 

the county (Schiner and others, 1988). 

Temporal salinity change in the Upper Floridan 

aquifer was studied at 18 monitoring wells in the UEC 

Planning Area between 1977 and 1990 (Lukasiewicz 

and Switanek, 1995). Salinity indicators, including 

chloride and dissolved-solids concentrations, exhibited 

change in only 4 of the 18 wells during this period. The 

increase in salinity indicated was considered to be inconclusive due to limited observations in only a few wells. 

Only minor seasonal variability in salinity was observed 

in most wells. At the Sailfish Point Well Field, however, 

average salinity for two wells increased 15 percent 

between 1982 and 1992 (table 1 and fig. 2). Combined 

water use for six wells at this well field for the same 

period of time increased by 250 percent to greater than 

1 Mgal/d (Lukasiewicz and Switanek, 1995).

In this study, additional Floridan aquifer system 

wells were identified that indicate increasing salinity 

with time. Based on current and historical water-quality data collected since 1977, salinity has increased 

substantially in 9 of 24 wells (table 2). All but one of 

these 24 wells are in the SFWMD Floridan aquifer 

system monitoring well network. In the nine wells indicating an increase, the increase was from 10 percent to 

as high as 207 percent based on linear regression. The 

periods over which these increases occurred ranged 

from 6 to 24 years. The percent increase and period for 

two of the wells in table 2, STL-220 and STL-224, was 

20 percent over 24 years and 4 percent over 10 years, 

respectively (fig. 16). 

Specific conductance data obtained from the 

NRCS monitoring program (45 wells in 16 groves 

since 1996) were used to assess salinity changes. Nine 

wells located in six groves exhibited a substantial 

increase in salinity over the last 5 to 6 years (1996-

2001). Specific conductance increased by 26 percent in 

G35-1 as indicated by linear regression (fig. 33) and by 
Sources of Salinity in the Floridan Aquifer System 55

11 to 72 percent for all nine wells. Some of the increase 

in these nine wells could be due to increased water use 

in the agricultural area during the 2000 and 2001 water 

years, as evidenced by the NRCS water-use data (fig. 17).

Production well chloride concentration data from 

the Jupiter Well Field indicate a temporal increase in 

salinity. Monthly withdrawals and average chloride 

concentration in eight wells were evaluated between 

1996 and 2001 (fig. 34); average chloride concentration increased 40 percent as indicated by linear regression of the data. Chloride concentration generally 

seems to correspond to the withdrawal rate; however, 

chloride concentration can increase during the latter 

part of the dry season before the withdrawal rate substantially increases. The temporal change in chloride 

concentration in individual wells is variable. In some 

wells, such as Jupiter RO-5 (fig. 9, well PB-1197), 

chloride concentration is not increasing, whereas in 

other wells the increase in chloride concentration is 

greater than average. Chloride concentration increased 

temporarily to 4,000 mg/L in Jupiter RO-2 and RO-3 in 

June 2000. Available data from other Floridan well 

fields in the study area did not indicate a substantial 

increase in salinity with time; although an increase at 

the Sailfish Point Well Field, as discussed above, was 

observed between 1982 and 1992 (Lukasiewicz and 

Switanek, 1995).

All of the wells or well fields that indicate an 

increase in salinity with time (those from the SFWMD 

and NRCS monitoring well networks, well OK-72, and 

the Jupiter and Sailfish Point Well Fields) were 

compared with the areal distribution of water temperature (fig. 35). Two-thirds of inland area wells are 

located within an area of higher ground-water temperature (greater than 28 °C).

SOURCES OF SALINITY IN THE 

FLORIDAN AQUIFER SYSTEM 

Four potential sources of high salinity and their 

origin were evaluated for this study: (1) the presence 

of incompletely flushed pockets of relict seawater, 

(2) upconing or upward movement of the saltwater 

interface, (3) lateral encroachment of the saltwater 

interface, and (4) upward leakage through structural 

deformities or dissolution features. Relict seawater 

involves the occurrence of high salinity ground water in 

the Upper Floridan aquifer well above the saltwater 

interface.

Figure 33. Water-use and specific conductance data for Natural Resources Conservation Service monitoring 

well G35-1, 1997-2001.
56 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

0

1

2

3

4

5

6

7

8

9

10

YEAR

AVERAGE MONTHLY WATER WITHDRAWAL,

IN MILLION GALLONS PER DAY

AVERAGE CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1996 1997 1998 1999 2000 2001

EXPLANATION

AVERAGE WATER WITHDRAWAL

LINEAR REGRESSION FIT OF CHLORIDE

CONCENTRATION DATA

AVERAGE CHLORIDE CONCENTRATION

Relict Seawater

High salinity in the Upper Floridan aquifer that 

occurs in the coastal area could have resulted from the 

influx of seawater during high sea-level stands in the 

Pleistocene Epoch. According to this theory, flushing 

of this saline water by the modern-day fresh groundwater flow system has been incomplete. A similar 

explanation was used to describe the occurrence of 

areas of high salinity in the Upper Floridan aquifer in 

coastal areas of southeastern Florida (Reese, 1994; 

Reese and Memberg, 2000).

During sea-level rise, the freshwater-saltwater 

interface in the Floridan aquifer system responded, 

seeking a new equilibrium position. During adjustment 

of the interface to a new equilibrium position within or 

above the Upper Floridan aquifer, lateral invasion of 

seawater into zones of higher permeability in both the 

Upper and Lower Floridan aquifers may have occurred. 

Invasion of the inland area may have been limited not 

only because of its greater distance from the coast but 

also because geologic contacts associated with flow 

zones generally occur at a shallower depth in the inland 

area than in the coastal area (figs. 5-8, 11, and 13). The 

reversal in salinity with depth within the brackishwater zone between the Upper Floridan aquifer and 

upper part of the Lower Floridan aquifer, common in 

the coastal area, could be explained by greater flushing 

of saline water from the Lower Floridan aquifer by 

upgradient recharged water. This greater flushing 

would have been facilitated by the higher permeability 

in the Lower Floridan aquifer. 

Isotopic data, presented earlier, support saltwater 

invasion of the coastal area during relatively recent 

geologic times. Both 87Sr/86Sr and 14C data indicate 

that Floridan aquifer system ground water in the 

coastal area generally is younger than in the inland area.

Figure 34. Average monthly total water withdrawals and average chloride concentrations for eight production 

wells at the Jupiter Well Field, January 1996 to July 2001.
Sources of Salinity in the Floridan Aquifer System 57

FLORIDA’S TURNPIKE

24

24

24

26

26

28

30

32

28

28

28

26

28

28

26

26

26

26

26

26

28

1

0

0

15 MILES

15 KILOMETERS

5 10

5 10 EXPLANATION

WELL LOCATION AND NUMBER--Shows well

with increasing chloride concentration over time

LINE OF EQUAL WATER TEMPERATURE--In

degrees Celsius.Dashed where approximately

located. Contour interval is 2 degrees Celsius.

Well control used is shown on Figure 24

AREA WITH WATER TEMPERATURE

GREATER THAN 28 DEGREES CELSIUS

WELL FIELD LOCATION AND NAME--Shows

well fields with increasing chloride concentration

over time

28

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY FAULT MAPPED BY BARNETT (1975)

70

60

710

441

FLORIDA’S

1

95

95

95

TURNPIKE

U D

M-1121

M-1326

OK-72 STL-215

STL-217

STL-218

STL-220

STL-225

STL-215

STL-356

G2-2

G2-3

G3-1

G5-1

G29-14

G29-15

G35-1

G36-1 G36-2

JUPITER

JUPITER

SAILFISH POINT

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27

Figure 35. Location of monitoring wells and well fields with increasing salinity over time and distribution of water 

temperature in the Upper Floridan aquifer.
58 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Apparently, an exception occurs in the southern part of 

the coastal area in northeastern Palm Beach County 

near wells PB-1196 and PB-1774. The apparent 14C 

age for the three samples from these two wells is as old 

as ground water from the inland area wells (fig. 32). 

The 87Sr/86Sr data, however, still indicate a younger 

age for ground water from these wells than from inland 

area wells (fig. 31). An early Oligocene age is indicated 

even though the open intervals for all three samples are 

in Eocene-aged rocks (fig. 9, Ocala Limestone and 

Avon Park Formations).

High salinity water of relict origin in the Upper 

Floridan aquifer in the coastal area could impact withdrawals through lateral flow. For example, Port St. 

Lucie Well Field RO production wells STL-388 and 

STL-389 (fig. 2) are open in both the Upper and Lower 

Floridan aquifers; movement of higher salinity ground 

water in the Upper Floridan aquifer from the south or 

southeast (fig. 21) could result in increased salinity in 

the production wells. The current direction of Upper 

Floridan aquifer ground-water flow in the area of this 

well field is from the south (fig. 15).

Upward Movement of the Saltwater 

Interface

Diffuse upward movement of the brackish-water/

saltwater interface is possible in some parts of the study 

area. Such movement implies that water in the salinewater zone below the interface is free to move and is 

open to large-scale circulation. Two 14C samples were 

collected from the saline-water zone during this study, 

including (1) the deep monitoring zone of well M-1325 

(North Martin County WWTP), and (2) well M-1033 

(Stuart WWTP). The PMC was 10.40 for M-1325 and 

2.41 for M-1033 (fig. 32). Because the saltwater in the 

saline-water zone is substantially younger at the North 

Martin County site than at the Stuart site, the North 

Martin County site could be more open to groundwater circulation of saltwater from the coast below the 

interface. 

Currently, a large potential for upward movement 

of the saltwater interface is apparent in some parts of 

the study area. The depth of the Ghyben-Herzberg saltwater interface also was calculated using May 2001 

head data, and the depth of the base of the brackishwater zone was subtracted from these calculated values 

(table 5). A negative number resulting from this difference indicates wells where currently there is potential 

for upward movement of the interface. Two inland area 

wells have a significant negative difference; they are 

IR-1001 (268 ft) and STL-379 (122 ft). All of the 

coastal wells, except for M-1352 and PB-1182, have a 

negative difference, but the two wells with the greatest 

difference (STL-332 with 645 ft and STL-334 with 

302 ft) are in the northern part of the coastal area.

Lateral Encroachment of the Saltwater 

Interface

Lateral encroachment of the saltwater interface 

along the coast into the Upper Floridan aquifer is not 

likely to occur because of the depth of the saltwater 

interface along the coast and the extent of the aquifer 

offshore. The submarine outcrop of the top of the 

Upper Floridan aquifer is estimated to range from 17 

to 32 mi offshore in the UEC Planning Area (Lukasiewicz, 1992). However, municipal wells open in the 

Lower Floridan aquifer (table 3) could experience this 

problem, particularly in the northern part of the coastal 

area because: (1) the depth of the saltwater interface is 

shallower than in the southern part of the coastal area, 

and (2) the potential for upward (and lateral) movement 

is much greater based on current head data in the Upper 

Floridan aquifer. 

Upward Leakage through Structural 

Deformities or Dissolution Features

Upward leakage of water through structural 

deformities, such as faults and fracture zones or associated dissolution features, is indicated as occurring (or 

has the potential to occur) in the inland area. The 

evidence for this leakage comes from multiple sources 

and includes:

• Coincidence of northwest-trending areas of higher 

salinity (fig. 21), water temperature (fig. 26), and 

head (Brown and Reece, 1979) in north-central 

Martin and western St. Lucie Counties.

• Structural features that coincide with areas of higher 

salinity and water temperature including a previously mapped, inferred, northwest-trending basement fault (fig. 10) and, based on detailed 

mapping completed in this study, an apparent 

southeast-trending trough (figs. 11 and 13).

• Significant correlation of water temperature and 

chloride concentration in the inland area (fig. 28), 

but poor to nonexistent correlation of water temperature with depth (fig. 27), suggesting localized 

upward leakage.
Areas of Highest Potential for Increasing Salinity 59

• Simulation of ground-water flow that indicates 

recharge to the Upper Floridan aquifer is dominated by upward leakage from the Lower Floridan 

aquifer (Lukasiewicz, 1992).

Upward leaking high-salinity water in the inland 

area could originate from the upper permeable unit of 

the Lower Floridan aquifer in the lower part of the 

brackish-water zone or deeper in the saline-water zone. 

The older nature of this water is indicated by high 

concentration of strontium compared to chloride 

concentration (fig. 30) and old apparent age based on 

14C data (fig. 32). The occurrence of “old” ground 

water does not support the geothermal convection cell 

theory; Kohout (1965) theorized that the water invading the Boulder zone and leaking upward into the 

Upper Floridan aquifer is relatively recent seawater.

AREAS OF HIGHEST POTENTIAL FOR 

INCREASING SALINITY 

As withdrawals continue or increase, the Upper 

Floridan aquifer in the inland area seems to be more 

susceptible to salinity increase than the coastal area due 

to: (1) greater apparent structural deformation, (2) higher 

salinity in the Lower Floridan aquifer relative to the 

Upper Floridan aquifer, (3) greater water withdrawals, and 

(4) a Ghyben-Herzberg potential for upward movement 

of the saltwater interface in some areas (table 5, wells 

IR-1001 and STL-379). The inland areas that seem to 

have the highest potential for increasing salinity include: 

• Areas of structural deformation as indicated by 

detailed mapping and high water temperature 

(figs. 11, 13, and 26),

• Areas of greatest decline in hydraulic head in the 

Upper Floridan aquifer since predevelopment time 

(fig. 15 and table 2),

• Areas where agricultural water withdrawals have 

been, and continue to be, high (figs. 2 and 17; 

Lukasiewicz, 1992, fig. 22), and 

• Areas where monitoring wells have shown salinity 

to be increasing (fig. 35).

Some of these areas overlap, indicating a greater potential for increasing salinity. Refined geologic and hydrogeologic mapping studies could better identify areas of 

high potential by detailing areas of deformation. Future 

mapping efforts could be conducted by using new well 

control, by geophysical logging of existing wells, and 

by using surface-geophysical methods such as reflection seismic profiling.

The Lower Floridan aquifer could be affected by 

increasing salinity in the northern part of the coastal 

area due to the potential for upward or lateral movement of the saltwater interface. The Fort Pierce and 

Port St. Lucie Well Fields could be affected by such 

movement (fig. 2). Both well fields are located near 

deep injection well sites in eastern St. Lucie County 

where currently there is potential for substantial 

upward movement of the saltwater interface due to 

regional decline in hydraulic head in the Upper Floridan aquifer. The May 2001 Ghyben-Herzberg altitude 

of the saltwater interface at well STL-332 at the Fort 

Pierce WWTP is about 1,100 ft below NGVD of 1929 

(table 5). This depth is substantially above the base of 

the open interval at well STL-422 at the nearby Fort 

Pierce Well Field (1,240 ft below NGVD of 1929).

Depending on lithology, however, upward movement of the saltwater interface in the coastal area could 

be retarded by low vertical permeability. For example, 

a resistivity geophysical log and lithologic description 

of well STL-332 indicate that the lithology from the 

base of the brackish-water zone at 1,750 ft below land 

surface up to 1,360 ft is poorly cemented limestone 

(fig. 24). This limestone is probably fine grained or 

micritic in nature and of relatively low permeability, 

which is a lithology common in the Avon Park Formation.

An area of low salinity (less than 1,000 mg/L 

chloride concentration) was mapped in the Upper 

Floridan aquifer in northeastern St. Lucie County 

(fig. 21), and much of this area is within or borders the 

northern part of the coastal area (fig. 12). Available 

data did not indicate increasing salinity with time in 

this area of lower salinity. The low and apparently 

stable salinity in this area could be related to a low 

degree of structural deformation, its high structural 

position (figs. 11 and 13), or distribution of dolomite in 

the middle confining unit and Lower Floridan aquifer. 

As previously discussed, dolomite grades out west to 

east from the inland area to the coastal area (for example, 

see figs. 5 and 7). Because dolomite is more prone to 

fracturing than limestone, this loss of dolomite might 

have prevented the formation of vertical fractures 

acting as conduits in the middle confining unit and 

Lower Floridan aquifer in this area.

The potential for increasing salinity in the southern part of the coastal area (fig. 12) due to upward or 

lateral movement of the saltwater interface seems to be 

substantially less than in the northern part. In the southern part of the coastal area, the depth to the base of the 

brackish-water zone is greater, and little change in 
60 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

hydraulic head compared to predevelopment conditions 

is apparent (fig. 15). Additionally, some evidence was 

found that indicates low vertical permeability and poor 

vertical mixing in the lower part of the brackish-water 

zone and salinity transition zone in the northeastern 

Palm Beach County part of the coastal area (Reese and 

Memberg, 2000). This evidence, also found in other 

coastal areas of Palm Beach County, includes: (1) a 

base of the brackish-water zone that is deeper than 

expected given the location of these coastal areas, (2) a 

thickness of the salinity transition zone that is much 

greater than normal, and (3) a sulfate concentration of 

ground water that is depleted relative to chloride 

concentration, which could be due to prolonged sulfate 

reduction. Two wells in the southern part of the coastal 

area, PB-1170 and PB-1182, have a thickness of the 

salinity transition zone that is 670 ft or greater (table 4).

The increasing salinity at the Jupiter Well Field 

suggests that upward movement of saltwater can occur 

locally in the southern part of the coastal area. This 

upward movement could result from hydraulic head 

drawdown at the well field due to well field withdrawals and to regional lowering of head in the Upper Floridan aquifer near the end of dry season caused by 

agricultural withdrawals to the north. Structural deformation may have occurred at the Jupiter site, and 

upward movement or leakage of saline water could be 

through localized fractures resulting from this deformation. The basement fault mapped by Barnett (1975) 

extends to the southeast through or close to the Jupiter 

site (fig. 35). Additionally, mapping completed in this 

study indicates deformation could be present. Over 

100 ft of offset in the altitude of the top of the basal 

Hawthorn/Suwannee unit is present between well 

PB-1197 at the Jupiter Well Field and well PB-652 

located only 1.3 mi northeast of well PB-1197 (fig. 11).

SUMMARY 

The Floridan aquifer system is considered to be a 

valuable source for agricultural and municipal water 

supply in Martin and St. Lucie Counties, despite the 

brackish nature of its water. Municipal supply withdrawals are increasing, however, and this could 

threaten the quality of withdrawn water because of 

increasing salinity. Flow mechanisms that could 

provide sources of higher salinity water and affect 

withdrawals need to be identified and described 

through a better understanding of the hydrogeologic 

framework and flow system history.

Two geologic units in the Upper Floridan aquifer 

were mapped using all wells with a gamma-ray geophysical log available. The top of the uppermost unit, 

referred to as the “basal Hawthorn/Suwannee unit,” 

approximates the top of the Upper Floridan aquifer and 

is also the base of a marker unit in the Hawthorn 

Group; the basal Hawthorn/Suwannee unit includes 

what has been previously mapped as the Suwannee 

Limestone along the coast. The top and base of the 

Ocala Limestone were also determined and the top was 

mapped. A southeast-trending trough on top of the 

basal Hawthorn/Suwannee unit and Ocala Limestone is 

apparent in south-central St. Lucie County. This trough 

coincides in position and trend with a northwest-trending basement fault previously mapped.

Mapping the thickness of the basal Hawthorn/

Suwannee unit indicates an area where substantial eastward thickening begins along the coast. This area is 

approximately defined by the 100-ft-thickness contour 

line that runs subparallel to the coast, and this line is 

used to divide the study area into inland and coastal 

areas. The unit is as thick as 310 ft in the coastal area 

and as thin as 15 ft in the inland area. The Ocala Limestone also thickens in the coastal area.

The Floridan aquifer system consists of limestone, dolomitic limestone, and dolomite and is divided 

into three hydrogeologic units: the Upper Floridan 

aquifer, a middle confining unit, and the Lower Floridan aquifer. The upper permeable unit of the Lower 

Floridan aquifer, about 400 ft thick in central St. Lucie 

County, is composed mostly of dolomite and contains 

two cavernous dolomite flow zones in the inland area. 

In the coastal area, however, the unit can contain very 

little dolomite.

A comparison of the May 2001 Upper Floridan 

aquifer potentiometric surface with the predevelopment 

potentiometric surface indicates that decline in heads in 

eastern Martin and northeastern Palm Beach Counties 

have been minimal, but the decline indicated in central 

and northern St. Lucie County and Okeechobee County 

ranges from about 15 to 20 ft. Apparently, decline has 

continued during recent years; eight monitoring wells 

in central and northwestern St. Lucie County indicate a 

decline of 2 to 4 ft within the last 15 years. 

The most intense agricultural water use is in the 

inland area, whereas all municipal well fields are in the 

coastal area. Agricultural water use is about 80 to 90 

percent of the total use based on a survey conducted in 

1990, but municipal water-supply withdrawals are 

increasing as new wells and well fields are constructed. 
Summary 61

All of the municipal well fields that produce at higher 

rates have wells open to both the Upper and Lower 

Floridan aquifers or only to the Lower Floridan aquifer.

The distribution of salinity in the Upper Floridan 

aquifer was mapped using chloride concentration data. 

One area having an elevated chloride concentration 

(greater than 1,000 mg/L) exists in the inland area and 

trends northwest through north-central Martin County 

and western St. Lucie County. Another area of elevated 

concentration is in the southern part of the coastal area 

(eastern Martin County south of the St. Lucie River and 

northeastern Palm Beach County) where chloride 

concentration is more than 2,000 mg/L and as great as 

8,000 mg/L. Salinity shows a reversal with depth in 

most of the coastal area, decreasing from the Upper 

Floridan aquifer to the upper part of the Lower Floridan 

aquifer. In the inland area, however, salinity is greater 

in the Lower Floridan aquifer than in the Upper Floridan 

aquifer.

A dissolved-solids concentration of less than 

10,000 mg/L defines the brackish-water zone, the base 

of which can approximate the brackish-water/saltwater 

interface in the Floridan aquifer system. Below the 

brackish-water zone and separated from it by a salinity 

transition zone is the saline-water zone, within which 

the dissolved-solids concentration is greater than 

35,000 mg/L. The base of the brackish-water zone and 

top of the saline-water zone, which are present in the 

Lower Floridan aquifer, were determined at 13 wells, 

mostly using resistivity geophysical logs. The depth of 

the base of the brackish-water zone ranged from 1,525 

to 2,042 ft below NGVD of 1929; generally, the base 

increases in depth to the south and east. The depth of 

the saltwater interface was calculated using the 

Ghyben-Herzberg approximation and estimated predevelopment hydraulic heads in the Upper Floridan aquifer, and comparisons of this depth to that of the base of 

the brackish-water zone were made. In five of six 

inland area wells, the depth to the base of the brackishwater zone was substantially shallower than the calculated predevelopment interface (260 ft or greater), 

whereas in five of the seven coastal wells, this difference was not great (about 140 ft or less). Confining 

units in the inland area, such as dense dolomite, may 

prevent an interface from forming at its equilibrium 

position.

The temperature of withdrawn water from the 

Upper Floridan aquifer ranges from as low as 22.2 °C 

near the coast to as high as 32.0 °C inland. An area of 

high water temperature (generally greater than 28 °C) 

trends from central Martin County to the northwest 

through northwestern St. Lucie County. Correlation of 

water temperature with well depth is poor to nonexistent, but correlation of water temperature with chloride 

concentration for data from the inland area gives a 

statistically significant positive correlation.

Isotopic data collected during this study provide 

evidence for differences in the Floridan aquifer system 

ground-water geochemistry and its evolution between 

inland and coastal areas. In a graphical comparison of 

isotopic ratios of deuterium and oxygen-18 for 56 

samples collected in the study area, samples from the 

coastal area plot as a somewhat separate group and 

define a saltwater mixing line. The ratio of strontium-87 

to strontium-86 for many of the samples from the 

coastal area give an apparent source rock age that is 

younger than the rocks from which the seawater is 

derived, indicating that the coastal area was intruded 

with seawater during relatively recent geologic time. 

A plot of 38 sample analyses for stable and radioactive 

carbon indicates that water from the inland area is older 

than water from much of the coastal area, particularly 

for samples from inland area wells having a water 

temperature of 28 °C or higher. Exceptions in the 

coastal area are two samples with high salinity from 

below the base of the brackish-water zone and samples 

from the northeastern Palm Beach County part of the 

coastal area. The strontium-87 to strontium-86 ratio 

data, however, indicate a younger age for water from 

the wells in northeastern Palm Beach County than for 

the inland area. The comparison of strontium concentration to chloride concentration also suggests that 

inland area water is older than coastal area water. 

Potential sources of high salinity include relict 

seawater, upward or lateral movement of the saltwater 

interface, and high salinity water leaking upward 

through structural deformities or dissolution features. 

Areas of high salinity in the Upper Floridan aquifer 

that are present in the coastal area could have resulted 

from the influx of seawater into the Upper Floridan 

aquifer during high sea-level stands in the Pleistocene 

Epoch and incomplete flushing by the modern-day 

ground-water flow system.

High potential exists in much of the study area 

for upward or lateral movement of the saltwater interface because of large declines in hydraulic head since 

predevelopment. The depth of the saltwater interface 

from the Ghyben-Herzberg approximation, calculated 

using estimated May 2001 water levels in the Upper 

Floridan aquifer, was compared with the depth to the 
62 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

base of the brackish-water zone determined in this 

study. Based on two wells, the interface in the inland 

area in central to northern St. Lucie County has the 

potential to move up as much as about 270 ft. Based 

on four wells, the interface in the northern part of the 

coastal area has a potential to move up as much as 640 ft. 

Upward movement of the saltwater interface, particularly in the coastal area, however, could be retarded by 

low vertical permeability. The potential of increasing 

salinity in the southern part of the coastal area due to 

upward or lateral movement of the saltwater interface 

seems to be less than in the northern coastal area 

because the base of the brackish-water zone is deeper 

by several hundred feet and postdevelopment declines 

in head have been minimal.

Upward leakage of high salinity water through 

structural deformities, such as faults and fracture zones 

or associated dissolution features, is indicated as occurring (or has the potential to occur) in some inland areas. 

An upward trend in salinity is indicated in 16 monitoring wells in the inland area, and agricultural withdrawals are probably causing these increases. Most of these 

16 wells are located in areas of higher Upper Floridan 

aquifer ground-water temperature (greater than 28 °C). 

The upward leakage could originate from the upper 

permeable unit of the of the Lower Floridan aquifer in 

the lower part of the brackish-water zone or from 

deeper in the saline-water zone. The evidence for this 

leakage comes from multiple sources and includes: 

(1) coincidence of northwest-trending areas of higher 

salinity, water temperature, and head in north-central 

Martin and western St. Lucie Counties; (2) structural 

features mapped in this study and previously that coincide with the areas of higher salinity and water temperature; (3) correlation of water temperature and chloride 

concentration in the inland area, but a weak to nonexistent correlation of water temperature with depth, indicating that upward leakage is localized; and (4) groundwater flow modeling conducted in a previous study that 

indicates recharge to the Upper Floridan aquifer is 

dominated by upward leakage from the Lower Floridan 

aquifer.

The Upper Floridan aquifer has the greatest 

potential for increasing salinity in areas of structural 

deformation in the inland area. Areas with higher water 

temperature (greater than 28 °C) seem to indicate 

greater potential for increasing salinity, and these areas 

probably correlate with areas of greater deformation 

based on the correlation of water temperature anomalies with structural features. More detailed mapping of 

the altitude of the top of the uppermost geologic units 

comprising the aquifer could better identify areas of 

greater potential by better defining areas of deformation. This mapping could be done through additional 

well control, by geophysical logging of existing wells, 

or by using surface-geophysical methods such as 

reflection seismic profiling.

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Appendix I 65

APPENDIX I 

Inventory of Wells Used in this Study

Well locations are shown on plates 1 or 2 or in figure 2, except for wells CS-I1 and CS-M2, which are shown in 

figure 23. Altitude of measuring point commonly is land surface. All depths are below measuring point. 

Local well number:

G Grove

IR Indian River County

M Martin County

OK Okeechobee County

PB Palm Beach County

STL St. Lucie County

WA SFWMD well abandonment program

Other well identifier or owner:

NRCS National Resources Conservation Service

IW Wastewater injection well

W Well number assigned by the Florida Geological Survey

MW Monitoring well

RO Reverse-osmosis production well

ASR Aquifer storage and recovery well

SPSL South Port St. Lucie

NPSL North Port St. Lucie

PSL Port St. Lucie

SFWMD South Florida Water Management District

ddmmss.s is degrees, minutes, and seconds

Asterisk (*) next to local well number indicates horizontal coordinate information is referenced to the North 

American Datum of 1983.

Dashes (--) indicate data unknown or not determined.
66 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Appendix I. Inventory of wells used in this study

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)

CS-I1* Coral Springs IW-1 261438080154801 261439 801550 13 125 42 3,500 

 995 34 2,300 22 3,006 12.75

CS-M2* Coral Springs 261445080154802 261446.4 801547.7 13 170 24 1,650 

MW-2 1,000 16 

1,510 6.63

G1-1* NRCS 272123.5 802807.8 -- 296 8 825 G2-1* STL- 394, NRCS 272404080310401 272447.7 803142.4 20 260 6 823 G2-2* NRCS 272447.5 803124.2G2-3* NRCS 272441.4 803102.9G2-4* NRCS -- --G2-5* NRCS -- --G3-1* STL- 395, NRCS 272002080313301 272002.2 803133.1 -- -- -- -- G3-2* NRCS 271949.3 803133.4G3-3* NRCS 271937.5 803133.3G4-1* NRCS 271237.6 803224.2 -- -- -- -- G5-1* NRCS 272148.6 802837.2G6-1* NRCS 272610.1 803312.4 -- -- -- -- G6-2* NRCS 272542.1 803312.9G7-1* STL- 401, NRCS 272533080293501 272533.1 802935.8 20 278 8 878 G7-2* NRCS 272559.2 802935.9G7-3* NRCS 272624.9 802935.9G8-1* NRCS 272644.1 802237.7G8-2* NRCS 272644.2 802241.7G8-3* NRCS 272633.8 802242.7G8-4* NRCS 272625.8 802242.2

G11-1* NRCS 272857.5 802418.2 -- 120 6 893 G12-1* NRCS 272920.7 802346.2 20 345 6 917 G13-1* NRCS 271300.1 803224.4 -- -- -- -- G14-1* NRCS 272901.3 802341.0 -- -- -- -- 
Appendix I 67

G29-1A* NRCS -- -- -- -- -- -- 

G29-1B* NRCS 273119.4 802736.7 -- -- -- -- 

G29-2* NRCS 273144.3 802750.3G29-3* NRCS 273211.1 802750.1G29-4* NRCS 273143.9 802730.4G29-5* NRCS 273211.1 802720.6G29-6* NRCS 273212.6 802735.3G29-7* NRCS 273237.4 802736.0G29-8* STL- 410, NRCS 273237080273001 273237 802730.5 22 278 6 890 G29-9* NRCS 273237.2 802720.2

G29-10* NRCS 273237.1 802705.1G29-11* NRCS 273304.7 802703.1G29-12* NRCS 273303.2 802706.7G29-13* NRCS 273303.5 802734.4G29-14* NRCS 273303.6 802735.7G29-15* NRCS 273315.9 802719.8

G35-1* NRCS 271829.4 803048.1 -- -- -- -- G35-2* NRCS 271815.5 803053.8G36-1* NRCS 271353.1 803224.4G36-2* NRCS 271323.4 803001.7 -- -- -- -- 

G121-1* STL- 415, NRCS 272705080293601 272751.8 802936 -- 316 6 804 G205-5* STL- 421, NRCS 273119080372601 273119.3 803726.6 -- -- -- -- 

IR-1001 Hercules IW-1 273505080285701 273505 802857 23 116 42 3,005 

 462 301,680 202,378 10

M-27 270305080173001 270311 801736 22 430 4 1,000M-29 270912080382001 270904 803825 31 -- 4 1,100 M-30 270300080301801 270300 803018 41 450 6 1,100 M-32 270306080301201 270306 803012 42 -- 4 1,100 M-43 270847080191101 270847 801911 22 -- 4 800 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
68 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida M-47 270938080193601 270938 801936 21 -- 3 500 

M-64 271522080115001 271520 801152 10 -- 4 600 M-65 271317080130801 271317 801308 21 -- 4 500 M-86 271336080124701 271336 801247 10 -- 6 1,200 M-88 271130080120001 271136 801151 12 -- 5 1,180 M-95 271102080112301 271102 801123 15 748 5 1,058 

M-106 271036080120301 271036 801203 11 698 3 1,020 M-110 MF-30 271006080121201 271006 801212 7.5 -- 6 1,379 M-113 270916080131601 270916 801316 17.5 -- 5 960 M-143 271055080205501 271055 802055 20 272 6 958 M-145 270428080303701 270428 803037 42 425 6 1,485 M-146 W-2800 270653080342201 270653 803422 36 437 5 1,155 M-150 270608080122701 270608 801227 15 740 6 1,315 M-168 270507080334801 270507 803348 32 500 5 1,080 M-169 270916080343501 270916 803435 39 500 5 1,080 M-170 270832080341401 270832 803414 38 500 5 1,080 M-171 270742080341201 270742 803412 37 500 5 1,080 M-173 270546080335801 270546 803358 32 500 5 1,080 M-186 MF-1 271208080291001 271208 802910 29 373 5 835 M-189 270409080292701 270409 802927 49 400 8 1,000 M-192 270236080291901 270236 802919 41 400 5 1,000 M-244 270508080154001 270508 801540 14 350 6 900 M-254 270725080290201 270725 802902 28 -- 5 840 

M-255* MF-2 270935080300001 270940.7 803003.1 28 300 6 800 

M-306 270548080124401 270548 801244 15 688 6 1,170 M-443 271118080163201 271118 801632 12 275 6 951 M-582 271104080153601 271104 801536 2.5 -- -- 700 M-602 271200080205601 271200 802056 22 418 6 939 M-655 271116080144601 271116 801446 -- -- -- M-657 271122080143101 271122 801431 15 -- 4 125 M-740 MF-10 270426080171401 270426 801714 21 240 5.5 990 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix I 69

 474 4.25

M-741 270444080180401 270444 801804 22 500 6 890 M-742 270401080175001 270401 801750 21 500 6 1,003 M-744 MF-6 270940080350801 270940 803508 35 162 3.5 1,052 

 400 4.25

M-745* MF-9 270941080275901 271015.2 802807.3 30 360 6 810 

M-747 271041080321401 271041 803214 26 -- 6 825 M-748 271022080181601 271022 801816 16 397 6 773 M-841 271004080144601 271004 801446 12 454 4 1,057 M-901 270413080305801 270413 803058 38 490 8 1,110 M-911 270153080290801 270153 802908 37 -- 6 1,000 M-919 270104080331501 270104 803315 26 636 8 950 M-920 270249080341301 270249 803413 26 448 5 1,033 M-922 270120080282301 270120 802823 36 -- 6 800 M-926 271105080173201 271105 801732 41 -- 6 950 M-927 271038080303101 271028 803031 28 -- 6 792 M-940 271058080093801 271058 800938 13.5 435 6 1,150 

 948 4

M-1033* Stuart DMW-1 271146080150202 271146.7 801454.5 10 310 24 3,024 

1,200 162,027 8.63

M-1034* Stuart IW-1 271146080150201 271145.4 801459.2 10 319 36 3,305 

1,010 24 2,000 16 2,670 10

M-1076 MF-20 270917080365701 270917 803657 32 450 8 1,200 M-1118 Well no. 1 271417080113801 271417 801138 5 880 5 1,705 

M-1121* MF-3 271246080104801 271247.2 801046.9 3 543 8 1,025 M-1125* MF-23 270425080334701 270428.6 803348.1 32 170 5.5 1,119 

 456 4.25

M-1127 MF-4 271104080094301 271104 800943 9 658 6 1,525 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
70 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida M-1324* Jensen Beach 271423080154201 271427.4 801544.4 -- 62 48 3,505 

IW-1 173 38 850 30 1,683 20 M-1325* Jensen Beach 271423080154202 271427.3 801543.8 -- 59 24 2,212 

MW-1 178 18 

 850 12 M-1326* MF-31 270847080103801 270857.8 801026.4 13.55 844 6 1,091 

M-1328 MF-33 270742080352501 270742 803525 35.26 420 -- 1,200 M-1329 MF-34 271053080172501 271053 801725 12 -- 6 800 

M-1330* MF-35 270010080290001 270009.1 802858.3 28.94 400 10 1,340 

M-1331 MF-36B 270907080114501 270907 801145 20 225 6 1,021 M-1332 MF-37 270232080304501 270232 803045 20 400 10 1,260 M-1335 MF-40, W-5441 270558080392701 270558 803927 18 441 4 1,006 M-1346 MF-51 270344080231201 270344 802312 -- 600 10 1,380 

M-1347* MF-52 270512080230801 270506.6 802308.2 -- 400 10 1,320 

M-1349 MF-54, well 6 271034080101201 271034 801012 -- 300 1,040 

M-1352* Stuart IW-2 271146080145401 271146.4 801453.6 8.74 172 54 3,252 

 840 442,105 342,890 24

M-1353* Stuart MW2-2 271146080145402 271146.4 801453.6 10 175 20 1,650 

 840 141,600 6.63

M-1356* North Martin RO-3 271449080154901 271449.1 801549.7 17 140 16 1,400 

 202 301,165 12

M-1357* North Martin RO-4 271448080152801 271448.1 801528.4 17.8 140 16 1,375 

 199 30 893 181,065 12

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix I 71

M-1358* North Martin IW-2 271427080154501 271427.3 801545.3 17.5 179 50 3,350 

 858 422,230 362,811 202,830 26

M-1359 Hobe Sound RO-1 270307080072701 270307 800727 42.8 200 16 1,495 

South Martin 239 30

 970 181,228 12

M-1360* MF-37 265928080361601 265928.8 803616.5 16 74 24 2,046 

Port Mayaca ASR 170 18

test 765 12

M-1362 MF-25 270228080325301 270228 803253 28 400 8 1,220 M-1363 W-5442 270122080380401 270122 803804 15 -- -- 1,012 M-1364 MT-23 270316080342801 270316 803428 25 112 5 1,013 

 446 4

M-1365 MF-27 271025080125501 271025 801255 13 600 8 991 M-1366 MF-28 271147080115701 271147 801157 25 725 5 1,086 

OK-1 OKF-1 272815 804254 -- -- -- -- OK-2 OKF-2 273238080424201 273238 804242 28 218 6 686 OK-3 OKF-3 271140 804222 -- 700 -- 1,300 OK-5 OKF-5 271855080482501 271855 804825 30 440 8 1,180 OK-7 OKF-7 272158080470901 272158 804709 61.98 412 -- 963 

OK-13* OKF-13 273043080440001 273042.8 804356.2 -- 600 -- 1,200 OK-17* OKF-17 272011080550701 272011 805507 -- 538 -- 986 

OK-23 OKF-23 271514080511601 271514 805116 34.44 496 6 925 OK-29 OKF-29 272630080503001 272630 805030 65 336 6 1,040 OK-31 OKF-31 271343080504001 271343 805040 25.72 -- -- 1,079 OK-71 OKF-71 273120 804430 -- 500 -- 800 

OK-72* OKF-72 273030080440501 273009 804404 -- 500 -- 800 

OK-73 OKF-73 271900 804824 -- 500 -- 1,000 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
72 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida OK-74 OKF-74 271804 804714 -- 500 -- 1,000 

OK-100* OKF-100 270917080521701 270917.4 805216.5 13 80 24 2,048 

Kissimmee River 207 18 ASR test 565 12 OK-201 W-5405 270755080413701 270755 804137 17.2 266 4 1,008 

OK-202 OK0005 273311080421601 273311 804216 25 -- -- 939 OK-203 OK0006 273154080522001 273154 805220 70 -- -- 720 

OK-9000 Lake Okeechobee ASR1 271416080471101 271416 804711 16 65 42 1,710 

ASR-1 271416080471101 271416 804711 16 200 34

1,268 24

OK-9001* Lake Okeechobee 271421080471001 271420.7 804707.5 16 82 24 1,800 

SMW-1 200 12 

 990 61,270 1.5

OK-9002* Lake Okeechobee 271421080471002 271420.7 804707.5 16 1,270 1.5 1,800 

DMW-1

PB-215 S399, field 11 265008080353801 265008 803542 18 850 6 958 PB-652 265642080072301 265642 800723 7 826 6 1,385 

PB-747* PB- 733 265604080082601 265606.5 800824.5 13 400 20 1,280 

 990 12

PB-1133 Permit 235, Amerada 265146080253501 265152 802513 38 1,032 4,219 13.38 9.63 11,010 

PB-1144* PBF1 265800080051301 265809.1 800512.4 13 250 12 1,165 

1,021 6

PB-1166 Pratt&Whitney IW-1 265404080181701

265404 801817

25 165

 9701,8652,728

40302010

3,310 

PB-1167 Pratt & Whitney 265404080181702 265404 801817 25 165 24 2,050 

MW-1 1,000 16 

1,958 6

PB-1170 Loxahatchee 265515080082501 265528 800827 18 115 52 3,505 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix I 73

ENCON IW-1 923 44 

1,997 34 2,839 24

PB-1182 Seacoast IW-1 265118080075501 265118 800755 20.52 200 54 3,320 

 990 442,020 342,750 24

PB-1183 Seacoast MW-1 265118080075502 265118 800755 20.23 200 24 2,020 

 995 16 1,965 6.63

PB-1196 Jupiter DZMW 265522080092401 265522 800924 300 18 1,609 

 137 10 1,549 4

PB-1197 Jupiter RO-5 265523080092301 265523 800923 17 150 16 1,900 

1,024 121,451 8

PB-1774* Tequesta RO-1 265801080052901 265801.2 800529.1 14.2 325 30 1,740 

1,120 161,191 16

STL-47 272645080311201 272645 803112 24 287 5 745 STL-71 SLF-28 272023080163201 272023 801632 31.38 200 4 883 

STL-215* SLF- 3 272927080261601 272958.3 802610.6 21 310 16 1,106 STL-216* SLF- 4 272823080290201 272825 802902 27.5 482 9.25 993 STL-217* SLF- 9 272650080265001 272650 803525 24 263 10 1,058 STL-218* SLF-11 273212080351101 273214 803459 22.5 224 8 946 

STL-219 SLF-13 272412080364801 272412 803648 25 344 12 1,238 

STL-220* SLF-14 272014080341801 272016 803417.1 24 318 7.75 1,286 

STL-221 SLF-15 272000080341801 272000 803418 24 -- -- -- STL-222 SLF-17 271934080341801 271934 803418 24 320 10 1,286 STL-223 SLF-20 272604080404001 272604 804040 28 311 5 896 

STL-224* SLF-21 272537080240901 272542 802407 20 156 3.5 707 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
74 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida STL-225 SLF-23 271311080281101 271311 802811 28 350 6 894 

STL-228 SLF-26 272323080183901 272323 801839 2.5 382 3.25 1,000 STL-229 SLF-27 272322080304901 272322 803049 22 -- 8 900 STL-230 SLF-31 271614080235001 271614 802350 23 136 3.5 1,008 

 818 4 STL-242 SLF-5, SL00033 273000080275201 273000 802752 12 355 12 1,231 

STL-243 SLF- 6 272445080241501 272445 802415 18 142 3 596 STL-244 SLF- 7 272912080315801 272912 803158 24 257 10 1,040 STL-245 SLF-16 271953080341701 271953 803417 28 328 6.5 1,239 STL-246 SLF-18 271645080331601 271645 803316 29 330 12 1,240 STL-247 SLF-25 273050080185101 273050 801851 2.5 -- 4 STL-248 SLF-32 271311080240001 271311 802400 27.5 -- 4 1,007 STL-250 SLF-35 272823080300701 272823 803007 22.5 -- -- -- STL-253 SLF-38 272405080354501 272405 803545 24 -- -- -- STL-254 SPSL IW-1 271500080175701 271500 801757 9.5 30 54 3,418 

 175 42 840 321,876 222,715 12

STL-255* SPSL DZMW-1 271500080175702 271500.4 801757.2 9.50 30 34 1,663 

 175 24  898 161,610 6

STL-332 Fort Pierce IW-1 272720080182701 272720 801827 5.56 45 60 3,315 

 180 54 810 441,800 342,770 24

STL-333 Fort Pierce MW-1 272720080182702 272720 801827 -- 180 26 1,920 

 900 16 1,850 6

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix I 75

STL-334 NPSL IW-1 272009080210301 272009 802103 15 40 54 3,324 

 195 42 850 321,950 222,750 12

STL-335* NPSL DZMW-1 272009080210302 272014.6 802105.9 -- 40 36 1,800 

 193 24  950 161,730 6.63

STL-342* SLF-36 272747080305401 272746 803050 24.5 -- -- -- STL-346* SLF-40 272503080295701 272519 802934 22 -- -- 786 

STL-347 SLF-41 271425080371701 271425 803717 42.71 -- -- 1,272 STL-348 SLF-42 273054080184701 273054 801847 5 630 6 1,060 STL-349 SLF-43 271710080125501 271710 801255 3 650 6 866 STL-350 SLF-44 271707080125501 271707 801255 3 620 6 876 STL-351 SLF-45 273145080190001 273145 801900 5.27 -- -- 1,100 

STL-352* SLF-46 273007080182501 273042.5 801830.7 6.71 -- -- 1,100 

STL-353 SLF-47 271938080135201 271938 801352 5.66 850 6 1,230 STL-354 SLF-48 271752080252601 271752 802526 26.33 -- -- 800 STL-355 SLF-49 272019080295501 272019 802955 25.09 560 -- 893 STL-356 SLF-50 272017080295301 272017 802953 31.75 600 -- 1,000 STL-357 SLF-51 272017080295302 272017 802953 25.56 600 -- 775 STL-359 SLF-53 272640080324001 272640 803240 25 330 -- 911 STL-360 SLF-54 271456080401501 271456 804015 25 450 10 1,304 STL-367 SLF-61, Duda 22 271604080262201 271604 802622 -- 350 -- 695 STL-368 SLF-62 271725080281001 271725 802810 -- 480 -- 935 STL-369 SLF-63 272853080362401 272853 803624 -- 250 10 1,040 STL-370 SLF-64 273044080373101 273044 803731 -- 246 10 1,080 STL-371 SLF-65, Well 1 273213080382901 273213 803829 -- 240 10 1,020 STL-373 SLF-67 272230080392101 272230 803921 -- 300 6 -- STL-374 SLF-68, well 3 272608080414901 272608 804149 -- -- 6 -- 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
76 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida STL-375* SLF-69 272146080263701 272149.2 802639.3 -- 420 -- 866 

STL-376 SLF-70 273157080241301 273157 802413 -- -- -- 638 STL-377 SLF-71 272055080193001 272055 801930 -- -- -- 820 

STL-379* SLF-73 272016080292601 272016 802926 25 540 14 1,540 

W-16543 1,070 8 STL-380* SLF-74 272015080292401 272015.9 802923 -- 1,068 8 1,450 

STL-381* SLF-75 272015080292402 272015.9 802923 -- 480 4 700 STL-382* SLF-76 272015080292403 272015.9 802923 -- 790 4 860 STL-385* FB-2 272631080211301 272631.3 802112.9 -- 500 12 880 STL-386* SPSL MW-1A 271500080175703 271500.3 801759 9 36 36 1,960 

 175 24 839 161,887 6.63

STL-387* PSL RO DMW 271829080203101 271828.5 802031.2 -- -- -- 1,600 STL-388* PSL RO-1 271828080203501 271827.5 802035.1 -- -- -- 1,350 STL-389* PSL RO-2 271816080202301 271815.7 802022.9 -- -- -- 1,350 STL-391* SLF-62B 271841080264601 271841.3 802646.3 -- 480 6 935 STL-392* Duda by pool 271542080255801 271542.4 802558.3 -- -- 16 900 STL-422* Fort Pierce FA-8 272727080212801 272727.2 802128.6 20 135 26 1,500 

 500 16

WA-117 SFWMD 271721 803534 -- -- -- 750 WA-119 SFWMD 271235 803201 -- -- -- 950 WA-546 SFWMD 270637 803638 30 442 7.5 1,038 WA-547 SFWMD 272308 803453 25 364 6 820 WA-561 SFWMD 271835 802251 25 -- -- 620 WA-562 SFWMD 271825 802455 28 270 5.8 1,018 WA-565 SFWMD 271801 802336 25 -- -- WA-580 SFWMD 271845 802324 25 476 5.8 1,136 WA-582 SFWMD 271841 802445 25 -- -- -- WA-611 SFWMD 271710 802242 -- -- -- 750 WA-612 SFWMD 271627 802414 -- -- -- 870 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix I 77

WA-625 SFWMD 271236 802014 -- -- -- 1,012 WA-699 SFWMD 272504 802306 25 376 6 1,156 WA-708 SFWMD 272603 802007 10 274 4 957 WA-727 SFWMD 273300 802620 -- -- -- 1,000 WA-815 SFWMD 272658 801930 -- 460 8 995 WA-820 SFWMD 272329 802624 20 328 8 922 WA-823 SFWMD 272827 802937 20 -- -- -- WA-825 SFWMD 272534 802233 -- -- -- -- WA-829 SFWMD 271951 802746 -- 342 5 741 WA-875 SFWMD 272427 802949 20 300 4 704 WA-877 SFWMD 272645 802249 20 -- -- 740 WA-878 SFWMD 272410 803192 20 -- -- 766 WA-879 SFWMD 272610 802225 -- -- -- 903 WA-887 SFWMD 272616 802206 17 -- -- -- 

WA-1001 SFWMD 272134 802815 20 326 4 829 WA-1003 SFWMD 272122 802807 20 822 WA-1005 SFWMD 272145 802507 -- 4 830 WA-1006 SFWMD 272146 802838 20 -- -- 930 WA-1009 SFWMD 272935 802346 20 -- -- WA-1016 SFWMD 272236 802640 20 -- -- 876 WA-1031 SFWMD 273201 802416 20 -- -- WA-1032 SFWMD 272956 801747 20 -- -- 1,020 WA-1033 SFWMD 273131 802402 -- -- -- WA-1082 SFWMD 272330 802908 -- -- -- 1,324 WA-1083 SFWMD 272303 802813 20 -- -- 646 WA-1085 SFWMD 272628 803831 20 -- -- 784 WA-1087 SFWMD 272417 803813 20 -- -- 624 WA-1107 SFWMD 272208 802826 26 -- -- 636 WA-1111 SFWMD 272448 803916 25 -- -- 1,108 WA-1113 SFWMD 272149 802847 -- 308 4.9 827 WA-1119 SFWMD 272448 803916 25 280 4.9 673 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
78 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida WA-1121 SFWMD 272323 803012 -- -- 6 798 

WA-1134 SFWMD 273030 802412 -- -- -- -- WA-1136 SFWMD 272222 802942 20 264 -- 674 WA-1139 SFWMD 273040 802450 20 286 -- 987 WA-1140 SFWMD 272222 802942 20 290 4 792 WA-1143 SFWMD 272905 802511 -- 296 5 903 WA-1144 SFWMD 271831 803427 20 -- -- -- WA-1146 SFWMD 272903 802300 -- 330 4 814 WA-1147 SFWMD 271144 802716 25 -- -- 891 WA-1148 SFWMD 270716 803726 -- 340 4 742 WA-1151 SFWMD 272401 802654 20 352 6 849 WA-1155 SFWMD 272657 802371 20 198 5 1,176 WA-1158 SFWMD 272522 802204 20 -- -- 840 WA-1179 SFWMD 272808 801947 -- 113 3 700 WA-1183 SFWMD 272048 802912 -- 376 4 880 WA-1186 SFWMD 272030 802935 10 480 6 824 WA-1188 SFWMD 272048 802912 -- 298 5 628 WA-1192 SFWMD 272030 802935 20 -- -- 739 

Appendix I. Inventory of wells used in this study (Continued)

Local

well

number

Other well identifier or 

owner

U.S. Geological 

Survey site

identification

number

Latitude

(ddmmss.s)

Longitude

(ddmmss.s)

Altitude of

measuring

 point

(feet)

Depth

bottom of

casing

 (feet)

Casing

 diameter

 (inches)

Depth

 drilled

 (feet)
Appendix II 79

APPENDIX II 

Boundaries of Geologic Units in Selected Wells Penetrating the Floridan 

Aquifer System as Determined for this Study

Well locations are shown on plate 1. Altitude of measuring point is usually land surface. All depths are below 

measuring point. Gamma-ray logs were available on all wells and were used in determining tops. Lithologic 

descriptions were also available for some wells and were used. Dashes (--) indicate well not deep enough or 

inadequate data available.

Local well number:

G Grove

IR Indian River County

M Martin County

OK Okeechobee County

PB Palm Beach County

STL St. Lucie County

WA SFWMD well abandonment program

Other well identifier or owner:

NRCS National Resources Conservation Service

IW Wastewater injection well

W Well number assigned by the Florida Geological Survey

MW Monitoring well

RO Reverse-osmosis production well

SPSL South Port St. Lucie

NPSL North Port St. Lucie

SFWMD South Florida Water Management District
80 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Appendix II. Boundaries of geologic units in selected wells penetrating the Floridan aquifer system as determined for 

this study

Local

well

number

Other well

identifier or owner

Altitude of 

measuring 

point

(feet)

Depth to top of 

basal Hawthorn/

Suwannee unit 

(feet)

Depth to top 

of Ocala 

Limestone

(feet)

Depth to top of 

Avon Park 

Formation

(feet)

Depth drilled 

or total depth 

reached by

geophysical

log

(feet)

G2-1 STL-394, NRCS 20 445 505 580 823

G7-1 STL-401, NRCS 20 455 520 585 878

G29-8 STL-410, NRCS 22 435 495 600 890

G121-1 NRCS 20 490 570 620 917

IR-1001 Hercules IW-1 23 440 520 600 3,005

M-110 MF-30 8 742 917 -- 1,349

M-186 MF-1 29 627 710 790 835

M-740 MF-10 21 622 665 810 990

M-744 MF-6 35 663 727 782 1,052

M-745 MF-9 30 540 623 742 880

M-1076 MF-20 32 653 693 742 1,200

M-1118 Well no. 1 5 875 1,080 1,230 1,705

M-1121 MF-3 3 700 880 -- 1,025

M-1125 MF-23 32 745 800 865 1,119

M-1127 MF-4 9 755 1,040 1,200 1,525

M-1326 MF-31 14 800 983 -- 1,092

M-1328 MF-33 35 680 730 810 1,200

M-1329 MF-34 12 578 718 -- 800

M-1330 MF-35 29 690 750 868 1,340

M-1331 MF-36B 20 762 919 -- 1,021

M-1332 MF-37 20 700 748 863 1,260

M-1335 MF-40, W-5441 18 675 715 775 1,006

M-1353 Stuart MW2-2 10 710 883 1,050 1,650

M-1357 North Martin RO-4 18 670 835 1,100 1,375

M-1359 Hobe Sound RO-1 43 860 1,045 1,225 1,495

M-1360 MF-37 16 715 820 892 2,046

M-1363 W-5442 15 695 740 775 1,012

M-1364 MT-23 25 755 805 840 1,013

M-1365 MF-27 13 720 890 -- 1,000

M-1366 MF-28 25 790 935 -- 1,086

OK-2 OKF-2 28 368 400 465 690

OK-5 OKF-5 30 570 620 740 1,181

OK-7 OKF-7 62 638 670 800 963

OK-29 OKF-29 65 435 465 600 1,040

OK-100 OKF-100 13 528 610 748 2,048

OK-201 OE-1 17 640 670 765 1,008

OK-202 OK0005 25 368 412 462 939

OK-203 OK0006 70 380 410 520 720
Appendix II 81

OK-9000 OKF-77 16 682 733 835 1,710?

PB-652 7 890 1,200 -- 1,385

PB-747 PB-733 13 840 1,050 1,200 1,280

PB-1144 PBF-1 13 835 1,020 -- 1,165

PB-1197 Jupiter RO-5 17 973 1,110 1,246 1,900

STL-71 SLF-28 31 595 760 880 883

STL-216 SLF-4 28 460 523 570 993

STL-217 SLF-9 24 465 510 580 1,058

STL-218 SLF-11 23 412 440 490 946

STL-220 SLF-14 24 555 640 740 1,286

STL-222 SLF-17 24 560 650 765 1,297

STL-223 SLF-20 28 490 543 650 896

STL-224 SLF-21 20 460 530 600 707

STL-225 SLF-23 28 568 655 763 894

STL-228 SLF-26 3 600 741 875 1,000

STL-230 SLF-31 23 625 721 800 1,030

STL-242 SLF-5 12 475 522 635 1,231

STL-243 SLF-6 18 475 540 -- 596

STL-245 SLF-16 28 570 660 773 1,239

STL-332 Fort Pierce IW-1 6 570 750 970 3,315

STL-334 NPSL IW-1 15 550 700 815 3,324

STL-346 SLF-40 22 448 511 575 790

STL-348 SLF-42 5 585 780 945 1,062

STL-349 SLF-43 3 632 822 -- 866

STL-350 SLF-44 3 643 844 878

STL-351 SLF-45 5 600 800 918 1,104

STL-352 SLF-46 7 620 812 960 1,100

STL-353 SLF-47 6 800 1,000 1,190 1,230

STL-354 SLF-48 26 560 630 700 800

STL-355 SLF-49 25 639 719 795 894

STL-356 SLF-50 32 600 677 765 1,000

STL-359 SLF-53 25 540 595 665 911

STL-360 SLF-54 25 735 750 865 1,304

STL-379 SLF-73 25 513 590 655 1,540

STL-386 SPSL MW-1A 9 625 813 970 1,960

STL-422 Fort Pierce FA-8 20 480 550 830 1,500

WA-546 SFWMD 30 710 770 810 1,038

WA-547 SFWMD 25 590 642 735 820

WA-561 SFWMD 25 610 -- -- 620

Appendix II. Boundaries of geologic units in selected wells penetrating the Floridan aquifer system as determined for 

this study (Continued)

Local

well

number

Other well

identifier or owner

Altitude of 

measuring 

point

(feet)

Depth to top of 

basal Hawthorn/

Suwannee unit 

(feet)

Depth to top 

of Ocala 

Limestone

(feet)

Depth to top of 

Avon Park 

Formation

(feet)

Depth drilled 

or total depth 

reached by

geophysical

log

(feet)
82 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

WA-562 SFWMD 28 535 607 682 1,018

WA-565 SFWMD 25 580 675 750 763

WA-580 SFWMD 25 563 680 753 1,136

WA-582 SFWMD 25 553 637 702 930

WA-699 SFWMD 25 515 600 662 1,156

WA-708 SFWMD 10 580 705 815 957

WA-820 SFWMD 20 452 539 592 922

WA-823 SFWMD 20 420 496 540 640

WA-875 SFWMD 20 495 550 613 704

WA-877 SFWMD 20 448 518 645 740

WA-878 SFWMD 20 470 515 605 766

WA-887 SFWMD 17 470 540 680 894

WA-1001 SFWMD 20 525 580 650 829

WA-1003 SFWMD 20 495 555 620 822

WA-1006 SFWMD 20 498 550 625 930

WA-1009 SFWMD 20 420 490 590 904

WA-1016 SFWMD 20 500 575 640 876

WA-1031 SFWMD 20 402 480 638 686

WA-1032 SFWMD 20 708 920 -- 1,020

WA-1083 SFWMD 20 470 535 583 646

WA-1085 SFWMD 20 470 527 590 784

WA-1087 SFWMD 20 475 530 595 624

WA-1107 SFWMD 26 480 545 -- 636

WA-1111 SFWMD 25 568 630 736 1,108

WA-1119 SFWMD 25 462 525 625 673

WA-1136 SFWMD 20 450 505 575 674

WA-1139 SFWMD 20 390 450 550 987

WA-1140 SFWMD 20 465 520 590 792

WA-1144 SFWMD 20 450 515 638 891

WA-1147 SFWMD 25 540 640 745 891

WA-1151 SFWMD 20 605 700 792 849

WA-1155 SFWMD 20 698 750 800 1,176

WA-1158 SFWMD 20 537 605 662 840

WA-1186 SFWMD 10 570 730 -- 824

WA-1192 SFWMD 20 530 600 725 739

Appendix II. Boundaries of geologic units in selected wells penetrating the Floridan aquifer system as determined for 

this study (Continued)

Local

well

number

Other well

identifier or owner

Altitude of 

measuring 

point

(feet)

Depth to top of 

basal Hawthorn/

Suwannee unit 

(feet)

Depth to top 

of Ocala 

Limestone

(feet)

Depth to top of 

Avon Park 

Formation

(feet)

Depth drilled 

or total depth 

reached by

geophysical

log

(feet)
Appendix III 83

APPENDIX III 

Selected Water-Quality Data Collected from Known Intervals in Wells in the 

Floridan Aquifer System

Well locations are shown on plate 2, except for wells CS-I1 and CS-M2, which are shown in figure 23. Depths are 

given in feet below measuring point, which commonly is land surface. Measuring points are given in appendix I. 

Dashes (--) indicate data unknown or not determined, asterisk (*) indicates under source - packer test, and double 

asterisk (**) indicates chloride concentration calculated from specific conductance from equation in figure 20.

Local well number:

CS Coral Springs (Broward County)

G Grove

M Martin County

OK Okeechobee County

PB Palm Beach County

STL St. Lucie County

WA South Florida Water Management District well abandonment program

Source:

 1 Lichtler (1960)

 2 Reece and others (1980)

 3 Lukasiewicz and Switanek (1995)

 4 Lukasiewicz and Switanek (1995) - abandonment wells

 5 U.S. Geological Survey data collected prior to this study

 6 Reese and Memberg (2000)

 7 Natural Resources Conservation Service monitoring program

 8 Well-construction report from consulting firm

 9 Abandonment well files from South Florida Water Management District

10 Ambient network data (GWIS3)

11 Collected during this study

12 Collected by South Florida Water Management District
84 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)

CS-I1 11 09-13-2000 2,153 2,183 45,900 17,000 29,674 25.9

CS-M2 11 09-13-2000 1,000 1,110 17,770 5,700 11,206 23.3

11 09-13-2000 1,510 1,653 9,530 2,800 5,830 22.3

G1-1 7 02-29-96 296 825 4,235 1,670 3,269 --

G2-1 7 03-05-96 260 823 3,094 1,190 2,317 --

G3-1 11 07-26-2001 -- -- 4,830 1,350 3,210 29.3

G4-1 7 02-29-96 -- -- 2,875 1,130 2,051 --

G6-1 7 03-05-96 -- -- 2,930 1,110 2,044 --

G7-1 7 02-29-96 278 878 5,240 2,070 3,640 --

G11-1 7 12-98 120 893 1,900 **420 -- --

G13-1 7 02-29-96 -- -- 3,532 1,350 2,422 --

G14-1 7 03-05-96 -- -- 1,990 669 1,365 --

G29-1B 7 12-98 -- -- 3,770 **990 -- --

G35-1 7 12-98 -- -- 4,840 **1,300 -- --

G36-2 7 12-98 -- -- 2,928 **730 -- --

G205-5 11 07-26-2001 -- -- 5,740 1,520 3,760 27.9

M-27 1 07-03-46 430 1,000 -- 1,640 -- 26.7

M-29 4 -- -- 1,100 3,325 750 -- 25.5

M-30 5 03-25-58 450 1,100 2,020 450 1,126 28.9

M-32 1 01-25-57 -- 1,100 -- 1,220 -- 28.3

M-43 4 -- -- 800 4,800 1,400 -- 25.0

M-47 5 06-07-46 -- 500 -- -- -- 25.0

5 07-07-46 -- 500 3,950 1,040 -- --

M-64 5 07-18-46 -- 600 5,990 1,790 -- 25.6

M-65 1 07-19-46 -- 500 -- 890 -- 24.4

M-86 5 07-23-46 -- 1,200 3,410 885 -- 25.0

M-88 5 07-23-46 -- 1,180 3,570 940 -- 23.9

M-95 5 07-24-46 748 1,060 3,190 800 -- 23.9

M-106 5 05-28-57 698 1,020 3,150 **800 1,950 24.4

1 08-13-46 698 1,020 -- 810 -- 23.9

M-110 1 08-13-46 -- 1,379 -- 950 -- 23.9

M-113 1 08-13-46 -- 960 -- 2,150 -- 23.9

1 05-3-57 -- 960 -- 1,600 -- 24.4

M-143 5 10-24-61 272 958 3,780 913 2,110 26.1

M-145 1 02-05-53 425 1,485 -- 685 -- 28.3

M-146 4 -- 437 1,155 2,660 600 -- 27.0

M-150 4 -- 740 1,315 13,300 4,200 -- 24.5

M-168 5 07-16-80 500 1,080 1,830 400 -- 27.0

M-169 4 -- 500 1,080 2,000 420 -- 27.5

M-170 4 -- 500 1,080 2,400 540 -- 27.5

M-171 1 02-19-53 500 1,080 -- 600 -- 27.8

M-173 4 -- 500 1,080 2,180 470 -- 26.5
Appendix III 85

M-186 2 12-30-77 377 837 4,060 1,150 2,480 30.8

4 -- 377 843 4,240 1,200 -- 24.0

M-189 1 03-02-53 400 1,000 -- 545 -- 29.4

M-192 1 04-16-57 400 1,000 -- 575 -- 29.4

M-244 1 03-23-53 350 960 -- 1,450 -- 25.0

M-254 4 -- -- 840 4,540 1,150 -- 28.0

M-255

2 12-30-77 300 800 3,640 1,060 2,300 28.2

3 05-18-90 300 800 3,920 1,034 2,177 27.8

11 06-08-2000 300 800 3,920 1,100 2,348 29.1

11 07-24-2001 300 800 3,930 1,020 2,430 29.2

M-306 4 -- 688 1,170 12,000 3,500 -- 24.5

M-443 1 04-23-57 275 951 -- 1,370 -- 24.4

M-582 1 01-10-55 -- 700 -- 2,400 -- --

M-602 1 11-16-53 418 939 -- 1,170 -- 26.1

M-740 2 05-24-78 474 993 3,350 1,140 2,570 26.2

M-741 4 -- 500 890 6,550 1,850 -- 24.0

M-742 1 12-16-55 460 1,003 -- 1,530 -- --

M-744 2 05-10-79 400 1,052 1,620 320 1,000 27.2

M-745

3 05-30-90 342 680 4,280 1,288 2,514 29.8

11 06-08-2000 360 810 4,440 1,200 2,667 30.1

11 07-24-2001 360 810 4,470 1,210 2,850 30.3

M-747 1 12-16-55 -- 825 -- 1,020 -- 27.2

M-748 1 04-23-57 397 773 -- 1,050 -- 27.2

M-841 5 09-04-57 454 1,060 9,380 **2,700 6,080 24.4

1 09-04-57 454 1,057 -- 2,900 -- --

M-901 5 05-29-57 490 1,110 1,310 **230 778 27.8

1 09-21-56 490 1,110 -- 280 -- 27.8

M-911 5 07-16-80 -- 1,000 2,800 640 -- 26.5

M-919 4 -- 636 950 4,025 1,100 -- 25.5

M-920 1 03-07-57 448 1,033 -- 490 -- --

M-922 1 03-07-57 -- 800 -- 930 -- 27.2

M-926 1 04-23-57 -- 950 -- 1,230 -- 25.0

M-927 5 10-23-61 -- 792 3,870 1,030 2,130 27.8

M-940 5 08-31-59 948 1,150 2,210 515 1,250 --

M-1033 11 07-10-2000 2,027 2,093 46,900 18,000 31,096 26.6

M-1034 11 07-10-2000 1,010 1,300 8,000 2,300 4,784 25.8

M-1076 5 11-18-75 450 1,200 3,900 **1,000 2,030 26.5

M-1121

3 05-31-90 543 980 3,750 1,048 2,153 24.1

11 07-13-2000 543 1,025 4,330 1,200 2,560 24.9

11 07-18-2001 543 1,020 4,290 1,100 2,560 24.7

M-1125

2 12-05-77 456 1,119 1,600 390 1,130 26.1

3 05-17-90 456 1,119 1,760 363 1,025 --

11 06-08-2000 170 1,119 1,830 370 1,078 27.6

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
86 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

M-1324 8 07-30-87 2,917 3,505 44,000 18,800 34,260 --

M-1325

8 10-20-87 1,715 1,757 2,700 904 2,550 25.9

8 11-10-87 2,177 2,212 44,000 19,740 50,000 25.8

11 08-30-2001 1,715 1,757 3,600 940 2,100 27.1

11 08-30-2001 2,177 2,212 52,500 19,670 36,400 26.9

M-1326

3 11-19-85 844 1,091 3,510 930 2,010 24.0

10 08-02-90 844 1,091 3,940 942 2,145 23.9

10 07-22-97 844 1,091 4,128 940 -- 23.8

11 07-10-2000 844 1,091 4,050 1,100 2,377 23.7

M-1328 10 10-19-89 420 1,200 701 31 449 24.4

M-1330

3 05-17-90 400 1,250 3,870 1,045 2,132 --

11 06-08-2000 400 1,250 3,850 1,100 2,266 28.9

11 07-17-2001 400 1,250 3,870 1,020 2,370 29.4

M-1346 3 05-17-90 400 1,250 5,600 1,404 3,121 --

M-1347 11 06-08-2000 400 1,320 3,990 -- -- 28.7

11 07-13-2000 400 1,320 4,000 1,100 2,393 29.1

M-1349 3 05-31-90 300 1,111 3,710 1,005 2,156 22.2

M-1353 8 09-02-97 1,600 1,650 3,400 730 2,100 29.0

11 07-10-2000 1,600 1,650 3,540 910 2,148 24.7

M-1356 11 08-30-2001 1,165 1,400 4,570 1,250 2,610 24.9

M-1360

12* 11-13-2001 765 900 2,973 **750 -- 27.0

12* 11-01-2001 1,241 1,288 1,140 **180 -- 27.7

12* 10-30-2001 1,610 1,657 10,161 **2,970 -- 28.7

12* 10-26-2001 1,496 1,543 6,434 **1,820 -- 28.0

12* 10-23-2001 1,782 1,850 33,067 **10,100 -- 29.7

12* 10-16-2001 1,992 2,046 49,941 **15,300 -- 30.0

OK-1 2 11-29-77 -- -- 830 120 540 25.8

OK-2 2 09-19-78 218 686 880 170 670 25.8

OK-3 3 05-17-90 700 1,300 4,050 1,063 2,321 --

OK-7 10 07-15-87 412 963 532 20 332 24.9

10 07-23-97 412 963 486 19 -- 25.8

OK-13 10 06-27-88 600 1,200 2,330 588 1,364 27.4

11 05-31-2000 600 1,200 2,090 460 1,238 26.5

OK-17

10 07-16-90 538 986 946 106 444 27.2

10 07-10-97 538 986 961 100 -- 26.0

11 05-31-2000 538 986 909 86 548 25.8

OK-23

10 07-15-87 496 925 1,647 339 991 26.2

3 05-17-90 496 925 1,641 322 -- --

10 07-10-97 496 925 1,671 350 -- 26.2

11 05-31-2000 496 925 1,620 320 982 26.3

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
Appendix III 87

OK-31

3 09-19-84 -- 1,079 1,841 416 1,146 26.4

10 06-29-88 -- 1,079 6,631 1,992 3,993 26.8

3 05-17-90 -- 1,079 7,560 2,306 4,520 --

11 05-31-2000 -- 1,079 7,110 1,900 4,254 28.4

11 07-19-2001 -- 1,079 2,220 480 1,330 27.1

OK-71 3 05-22-90 500 800 3,900 905 2,213 --

OK-72

3 05-22-90 500 800 1,732 358 989 --

11 05-31-2000 500 800 3,850 960 2,294 27.8

11 07-19-2001 500 800 4,480 1,180 2,930 27.4

OK-73 3 05-18-90 500 1,000 8,410 2,626 5,170 --

OK-74 3 05-18-90 500 1,000 6,940 2,089 4,186 --

OK-100

12* 12-17-2001 1,640 1,700 20,590 **6,200 Not 

measured

29.2

12* 12-14-2001 1,790 1,850 16,696 **4,990 Not 

measured

33.1

12* 12-6-2001 1,955 2,030 23,100 **6,970 Not 

measured

29.3

OK-9000 5 04-17-91 1,270 1,700 -- 3,000 7,120 35.0

OK-9001 5 04-17-91 990 1,075 -- 210 820 27.5

11 07-24-2001 990 1,075 1,070 150 676 27.5

OK-9002 5 04-17-91 1,275 1,700 -- 2,200 5,230 27.0

11 07-24-2001 1,275 1,700 7,580 2,040 4,970 27.6

PB-215 5 09-12-41 850 958 3,590 940 -- --

PB-652 6 02-23-73 826 1,385 21,500 **6,500 -- --

PB-747 5 06-19-74 990 1,280 6,400 1,800 4,060 23.5

PB-1144

2 12-5-77 250 1,038 4,370 1,380 3,180 25.9

3 05-31-90 250 1,038 4,600 1,489 2,600 23.3

2 12-05-77 250 1,038 4,370 1,380 3,180 25.9

11 07-13-2000 1,021 1,038 5,130 1,400 3,062 24.9

PB-1167 8 12-07-94 1,000 1,237 -- 1,620 2,990 --

PB-1170 8 09-08-94 1,501 1,532 5,130 1,380 2,790 --

8 09-08-94 1,840 1,870 5,800 1,900 3,610 --

PB-1182 8* 1988 1,814 1,837 8,500 3,050 5,950 --

PB-1183 8 09-29-88 995 1,103 -- 3,020 6,280 --

PB-1196

8 09-24-93 1,137 1,155 -- 4,000 -- --

8 09-24-93 1,549 1,609 -- 2,020 -- --

11 06-05-2000 1,137 1,155 12,890 3,800 7,942 23.3

11 06-05-2000 1,549 1,609 6,110 1,700 3,484 23.3

11 07-17-2001 1,137 1,155 13,000 3,800 8,290 22.9

11 07-17-2001 1,549 1,609 6,350 1,760 3,890 23.0

PB-1774 11 08-29-2001 1,120 1,740 7,450 2,100 4,310 23.1

STL-47 5 07-16-80 287 745 2,410 610 -- 25.0

STL-71 5 07-16-80 200 883 3,130 820 -- 24.0

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
88 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

STL-215

2 03-30-78 310 1,106 2,710 690 1,490 27.4

3 05-23-90 310 1,106 3,450 941 1,893 26.1

11 06-06-2000 310 1,106 3,680 1,000 2,182 27.7

11 07-25-2001 310 1,106 3,800 1,020 2,380 28.1

STL-216

2 05-23-78 482 993 2,540 840 1,970 28.2

3 05-23-90 482 993 3,390 902 1,858 25.0

11 06-01-2000 482 993 3,220 820 1,900 27.9

STL-217

2 09-26-77 263 1,058 3,530 1,110 2,480 26.9

2 05-08-79 263 1,058 4,360 1,200 2,600 26.6

3 11-28-84 256 1,058 5,705 732 2,872 26.4

10 08-15-88 263 1,058 4,860 1,538 3,247 27.1

10 10-17-96 263 1,058 5,058 1,700 -- 26.8

11 06-01-2000 263 1,058 5,200 1,400 3,082 27.5

11 07-19-2001 263 1,058 5,170 1,420 3,480 27.4

11 10-19-2001 263 1,058 5,010 1,380 3,150 27.4

STL-218

2 01-30-78 224 946 2,650 620 1,500 26.5

3 05-24-90 224 946 2,830 690 1,648 25.8

11 06-01-2000 224 946 3,300 830 1,960 27.6

STL-219 2 01-30-78 344 1,238 5,670 1,380 3,370 27.9

STL-220

2 12-01-77 318 1,286 3,200 940 1,990 26.0

11 06-07-2000 318 1,286 4,150 1,100 2,601 28.4

11 07-18-2001 318 1,286 4,310 1,150 2,890 28.4

STL-221 2 04-27-77 -- -- -- 990 2,200 26.9

STL-222 2 09-20-78 320 1,286 2,090 750 1,820 27.8

STL-223 2 03-28-78 311 896 3,550 830 2,200 28.6

STL-224

2 05-22-78 156 700 1,210 310 930 25.1

10 10-18-90 156 707 1,383 316 901 25.6

10 03-20-96 156 707 1,530 330 -- 25.1

11 06-06-2000 156 707 1,610 320 969 25.4

STL-225 2 05-24-78 350 894 3,720 1,170 2,640 32.0

3 05-30-90 350 894 1,940 1,295 2,437 30.2

STL-228 2 05-09-79 382 958 3,760 910 2,260 23.8

STL-229 2 12-27-77 -- 900 3,510 1,060 2,470 26.0

3 05-23-90 -- 900 3,870 1,075 2,224 26.9

STL-230 2 09-29-77 818 1,008 3,470 980 2,190 27.8

STL-242 2 07-27-77 355 1,227 -- 610 1,490 27.0

4 -- 355 1,227 3,680 **970 -- 26.4

STL-243 4 -- 142 596 1,518 **300 -- 25.3

STL-244 2 09-26-77 257 1,040 1,890 470 1,050 27.6

STL-245 2 04-27-77 328 1,239 -- 840 1,940 29.2

STL-246 2 05-23-78 330 1,240 3,010 980 2,260 30.7

STL-247 2 07-27-77 -- -- -- 1,220 2,600 24.0

STL-248 2 09-29-77 -- 1,007 4,230 1,250 2,510 30.5

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
Appendix III 89

STL-250 2 06-29-77 -- -- -- 1,010 2,120 28.8

STL-253 2 03-29-77 -- -- -- 1,190 2,830 28.5

STL-254 5 11-02-82 2,715 3,418 53,000 20,000 35,300 25.5

STL-255

8 12-09-82 898 1,268 5,100 1,480 2,880 24.4

8 12-01-82 1,610 1,663 2,530 598 1,360 24.4

11 07-12-2000 898 1,268 5,430 1,500 3,046 24.9

11 07-12-2000 1,610 1,663 2,290 510 1,335 24.8

STL-332 8* 09-29-92 1,900 2,028 38,100 16,600 31,500 --

8 02-01-93 2,770 3,315 ... 19,000 36,700 --

STL-333 8 05-24-93 900 1,019 -- 1,200 2,130 --

8 05-24-93 1,850 1,920 -- 14,200 25,000 --

STL-334 8 08-18-87 2,750 3,324 50,000 19,400 -- --

STL-335

8 08-30-87 950 1,175 3,400 1,000 2,060 --

8 08-30-87 1,730 1,800 20,500 9,000 14,900 --

11 07-12-2000 950 1,175 4,140 1,200 2,425 27.1

11 07-12-2000 1,730 1,800 27,100 10,000 17,468 27.3

STL-342

2 07-27-77 -- -- -- 650 1,470 27.9

3 05-30-90 -- -- 3,220 811 1,851 26.0

11 06-01-2000 -- -- 2,250 520 1,326 26.9

STL-346 3 05-23-90 -- 786 2,970 782 1,640 24.0

11 06-01-2000 -- 786 3,130 800 1,888 27.2

STL-348 4 -- 630 1,060 3,900 **1,000 -- 24.6

STL-350 4 -- 620 876 2,712 **670 -- 24.4

STL-351 4 -- -- 1,100 4,310 **1,200 -- 24.3

STL-352

4 -- -- 1,100 3,754 **990 -- 24.3

11 06-06-2000 -- 1,100 4,170 1,100 2,475 24.7

11 07-16-2001 -- 1,100 4,210 1,120 2,540 24.4

STL-353

3 05-31-90 850 1,230 1,239 243 713 23.7

10 08-15-88 850 1,230 1,195 208 696 24.3

10 08-05-93 850 1,230 1,250 216 -- 24.4

11 06-06-2000 850 1,230 1,228 200 701 24.1

STL-355 10 08-31-87 560 893 1,915 964 2,008 29.5

STL-356 3 05-23-90 600 775 1,719 431 911 22.0

10 03-20-96 600 775 2,570 700 -- 28.4

STL-357 10 08-5-93 600 775 3,470 940 1,904 28.6

STL-359 4 -- 330 906 -- 1,000 -- 27.8

STL-367 3 05-25-90 350 695 4,340 1,308 2,334 25.6

STL-368 3 05-25-90 480 935 4,150 1,215 2,251 21.0

STL-369 3 05-30-90 250 1,040 4,390 1,290 2,544 26.0

STL-370 3 05-30-90 246 1,080 5,060 1,317 3,000 26.6

STL-371 3 05-30-90 240 1,020 4,210 1,333 2,602 27.3

STL-373 3 05-24-90 300 -- 1,622 337 903 27.2

STL-374 3 05-24-90 -- -- 1,618 318 922 26.9

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
90 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

STL-375 3 05-23-90 420 866 1,990 679 1,420 25.2

11 06-07-2000 420 866 2,710 700 1,562 27.7

STL-376

3 05-23-90 -- 638 1,611 336 903 25.6

11 07-12-2000 -- 638 1,560 330 917 26.3

11 07-25-2001 -- 638 1,610 330 951 26.9

STL-377 3 05-31-90 -- 820 4,550 1,282 2,774 23.0

STL-380 11 06-07-2000 1,070 1,450 6,550 2,000 3,866 30.1

11 07-18-2001 1,070 1,450 6,860 2,060 4,660 30.7

STL-381 11 06-07-2000 480 700 3,560 960 2,125 27.2

11 07-18-2001 480 700 3,530 940 2,220 29.0

STL-382 11 06-07-2000 790 860 4,330 1,300 2,634 28.3

STL-385 11 06-15-2000 500 880 1,570 280 918 24.9

11 07-25-2001 500 880 1,580 280 924 25.0

STL-386 11 07-12-2000 1,887 1,960 35,900 13,000 24,276 24.7

STL-387 11 07-11-2000 ? 1,600 4,750 1,300 2,766 24.8

STL-388 11 07-11-2000 650 1,350 3,260 810 1,949 24.9

STL-389 11 07-11-2000 650 1,350 3,750 970 2,207 24.6

STL-391 11 07-11-2000 480 935 4,270 1,200 2,729 30.4

11 07-18-2001 480 900 4,480 1,260 3,010 29.9

STL-392 11 07-11-2000 -- 900 4,810 1,400 3,026 31.0

WA-117 4 -- -- 750 1,512 325 -- 25.4

WA-119 4 -- -- 950 3,138 778 -- 27.8

WA-546 9 07-31-85 442 1,038 2,484 828 -- 27.8

WA-547 4 08-01-85 364 820 2,870 957 -- 27.0

WA-562 9 11-13-85 270 1,018 3,120 733 -- 27.1

WA-580 9 01-27-86 476 1,136 5,014 1,341 -- 28.8

WA-611 4 -- -- 750 3,582 940 -- 26.2

WA-612 4 -- -- 870 1,590 799 -- 26.4

WA-625 4 -- -- 1,012 4,060 1,010 -- 27.6

WA-699 4 11-25-86 376 1,156 1,910 420 -- 25.6

WA-708 4 12-29-86 274 957 1,496 708 -- 23.9

WA-727 4 -- -- 1,000 6,010 1,770 -- 29.2

WA-815 4 06-25-87 460 995 2,982 530 -- 26.1

WA-820 4 07-27-87 328 922 1,260 420 -- 26.4

WA-829 4 08-05-87 342 741 3,050 967 -- 28.9

WA-875 4 08-18-87 300 704 2,080 510 -- 27.2

WA-877 9 08-19-87 -- 740 1,500 373 -- 26.1

WA-878 4 08-25-87 -- 766 3,050 811 -- 27.8

WA-879 9 08-26-87 -- 903 1,270 1,270 -- 25.3

WA-1001 9 11-03-87 326 829 2,580 1,422 -- 27.8

WA-1005 4 -- -- 830 2,975 885 -- 27.8

WA-1016 4 -- -- 876 2,838 695 -- 27.8

WA-1032 4 -- -- 1,020 6,270 1,734 -- 24.7

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
Appendix III 91

WA-1082 4 -- -- 1,324 4,558 1,098 -- 29.4

WA-1083 4 -- -- 646 612 275 -- 24.9

WA-1085 4 -- -- 784 1,780 375 -- 26.6

WA-1087 4 -- -- 624 2,046 435 -- 26.3

WA-1107 4 -- -- 636 2,012 410 -- 26.0

WA-1111 4 -- -- 1,108 4,500 1,125 -- 28.3

WA-1113 9 04-14-88 308 827 3,930 1,040 -- 26.4

WA-1119 9 04-15-88 280 673 2,052 410 -- 26.9

WA-1121 9 05-02-88 -- 798 2,774 610 -- 26.6

WA-1136 4 05-05-88 264 674 3,110 775 -- 25.6

WA-1139 4 05-06-88 286 987 2,764 665 -- 27.2

WA-1140 4 05-16-88 290 792 4,500 1,188 -- 28.3

WA-1143 9 05-18-88 296 903 2,530 573 -- 27.1

WA-1146 9 05-18-88 330 814 2,210 512 -- 26.4

WA-1147 4 -- -- 891 2,080 403 -- 27.8

WA-1148 9 05-20-88 340 742 2,116 517 -- 26.3

WA-1151 9 06-07-88 352 849 5,086 1,210 -- 31.1

WA-1155 9 06-09-88 198 1,176 3,600 836 -- 27.2

WA-1158 4 -- -- 840 3,218 742 -- 27.6

WA-1179 9 07-19-88 113 700 1,674 327 -- 25.9

WA-1183 9 07-20-88 376 880 1,927 468 -- 24.9

WA-1186 4 07-20-88 480 824 1,928 330 -- 24.8

WA-1188 9 07-21-88 298 628 3,705 877 -- 27.7

Appendix III. Selected water-quality data collected from known intervals in wells from the Floridan aquifer system (Continued)

Local

well

number

Source Date

Depth

base of

casing

(feet)

Depth to 

bottom of 

open interval 

or depth of 

well

(feet)

Specific

conductance

(microsiemens 

per centimeter 

at 25 degrees 

Celsius)

Chloride

(milligrams 

per liter)

Dissolved

solids

(milligrams 

per liter)

Temperat

ure

(degrees

Celsius)
92 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida
Appendix IV 93

APPENDIX IV 

Major Constituent and Field Characteristic Water-Quality Data Collected 

from Floridan Aquifer System Wells in this Study

Depths are given in feet below measuring point, which commonly is land surface. Measuring points are given in 

appendix I.

Annotations:

pH Field, whole sample, in standard units

SC Specific conductance, field, in microsiemens per centimeter at

25 degrees Celsius

T Temperature, in degrees Celsius

Ca Calcium, dissolved, in milligrams per liter

Mg Magnesium, dissolved, in milligrams per liter

K Potassium, dissolved, in milligrams per liter

Na Sodium, dissolved, in milligrams per liter

Sr Strontium, dissolved, in milligrams per liter

CaCO3 Alkalinity, dissolved, total, field, in milligrams per liter

ANC Acid neutralizing capacity, unfiltered, field, in milligrams per liter

as CaCO3

Br Bromide, dissolved, in milligrams per liter

Cl Chloride, dissolved, in milligrams per liter

F Fluoride, dissolved, in milligrams per liter

SiO2 Silica, dissolved, in milligrams per liter

SO4 Sulfate, dissolved, in milligrams per liter

DS Dissolved solids, at 180 degrees Celsius, in milligrams per liter
94 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida

Appendix IV. Major constituent and field parameter water-quality data collected from Floridan aquifer system wells in this study

Local

well

number

Date

Depth 

top

 of open

 interval

 (feet)

Depth

bottom 

of

 open

 interval

(feet)

pH SC

T Ca Mg

K Na Sr CaCO3 ANC Br Cl 

CS-I1 09-13-2000 2,153 2,183 7.30 45,900 25.9 460 906 240 9,000 37.002 154.0 -- 53.0 17,000 CS-M2 09-13-2000 1,000 1,110 7.93 17,770 23.3 240 335 140 3,300 13.872 151.4 -- 18.0 5,700 

09-13-2000 1,510 1,653 7.74 9,530 22.3 150 195 69 1,400 14.656 122.8 -- 9.0 2,800 

G3-1 07-26-2001 -- -- 7.30 4,830 29.3 164 112 15 640 32.560 144.5 -- 6.4 1,350 G205-5 07-26-2001 -- -- 7.28 5,740 27.9 206 123 19 800 35.500 115.7 -- 6.4 1,520 M-255 06-8-2000 300 800 7.48 3,920 29.1 110 82 17 540 21.782 140.0 -- 3.6 1,100 

07-24-2001 300 800 7.38 3,930 29.2 116 85 17 550 21.740 141.8 -- -- 1,020 

M-745 06-8-2000 360 810 7.44 4,440 30.1 130 94 19 630 20.019 141.0 -- 3.9 1,200 

07-24-2001 360 810 7.35 4,470 30.3 129 95 17 630 19.700 142.9 -- -- 1,210 

M-1033 07-10-2000 2,027 2,093 8.08 46,900 26.6 370 981 320 9,300 27.431 174.0 -- 60.0 18,000 M-1034 07-10-2000 1,010 1,300 7.81 8,000 25.8 110 143 50 1,300 17.312 181.0 -- 8.3 2,300 M-1121 07-13-2000 543 1,020 7.61 4,330 24.9 90 102 25 650 7.600 166.0 -- 4.4 1,200 

07-18-2001 543 1,020 7.59 4,290 24.7 92 98 24 640 7.480 169.9 -- -- 1,100 

M-1125 06-8-2000 456 1,120 7.73 1,830 27.6 65 52 9.3 210 12.190 126.0 -- 1.4 370 M-1325 08-30-2001 1,715 1,757 7.66 3,600 27.1 75 100 20 480 10.780 162.7 -- 4.0 940 

08-30-2001 2,177 2,212 7.93 52,500 26.9 415 1270 430 11,230 22.680 141.5 -- 83.0 19,670 

M-1326 07-10-2000 844 1,091 7.68 4,050 23.7 86 80 25 600 6.200 191.0 -- 4.4 1,100 M-1330 06-08-2000 400 1,250 7.42 3,850 28.9 97 80 17 540 20.604 141.0 -- 3.9 1,100 

07-17-2001 400 1,250 7.49 3,870 29.4 102 84 17 560 20.810 138.9 -- -- 1,020 

M-1347 07-13-2000 400 1,320 7.44 4,000 29.1 110 89 19 580 11.863 164.0 -- 4.4 1,100 M-1353 07-10-2000 1,600 1,650 7.54 3,540 24.7 82 79 21 520 9.100 161.0 -- 3.2 910 M-1356 08-30-2001 1,165 1,400 7.34 4,570 24.9 96 102 22 650 10.090 163.4 -- 5.1 1,250 OK-13 05-31-2000 600 1,200 7.62 2,090 26.5 82 56 7.8 240 15.665 -- 137 1.5 460 OK-17 05-31-2000 538 986 8.67 909 25.8 16 20 10 130 10.271 -- 178 0.2 86 OK-23 05-31-2000 496 925 7.66 1,620 26.3 56 41 7.8 190 15.907 -- 116 0.9 320 OK-31 05-31-2000 -- 1,079 7.35 7,110 28.4 230 148 26 1,100 37.608 -- 99 6.3 1,900 

07-19-2001 -- 1,079 7.72 2,220 27.1 70 48 11 300 17.000 105.2 -- 2.0 480 

OK-72 05-31-2000 500 800 7.47 3,850 27.8 140 90 12 500 30.030 -- 122 3.0 960 

07-19-2001 500 800 7.37 4,480 27.4 165 101 15 600 32.970 111.9 -- -- 1,180 

OK-9001 07-24-2001 990 1,075 7.90 1,070 27.5 51 47 5.5 84 17.000 113.5 -- 0.7 150 OK-9002 07-24-2001 1,275 1,700 7.38 7,580 27.6 291 165 26 1,070 37.430 100.9 -- 8.3 2,040 
Appendix IV 95

PB-1144 07-13-2000 1,020 1,038 7.61 5,130 24.9 100 103 28 800 6.900 164.0 -- 5.3 1,400 PB-1196 06-05-2000 1,137 1,155 7.88 12,890 23.3 190 256 70 2,300 17.536 160.0 -- 13.0 3,800 

06-05-2000 1,549 1,609 7.68 6,110 23.3 120 122 36 1,000 13.381 160.0 -- 6.1 1,700 07-17-2001 1,137 1,155 7.53 13,000 22.9 190 264 67 2,080 17.460 161.2 -- -- 3,800 07-17-2001 1,549 1,609 7.50 6,350 23.0 124 131 36 1,010 13.630 155.1 -- -- 1,760 

PB-1774 08-29-2001 1,120 1,740 7.31 7,450 23.1 151 157 39 1,150 8.700 164.1 -- 8.9 2,100 STL-215 06-06-2000 310 1,106 7.67 3,680 27.7 120 86 14 470 15.047 160.0 -- 3.5 1,000 

07-25-2001 310 1,106 7.40 3,800 28.1 124 92 14 500 15.290 147.5 -- -- 1,020 

STL-216 06-01-2000 482 993 7.40 3,220 27.9 110 77 12 410 14.180 -- 140 2.6 820 STL-217 06-01-2000 263 1,058 7.35 5,200 27.5 160 112 17 730 32.421 -- 143 4.8 1,400 

07-19-2001 263 1,058 7.34 5,170 27.4 162 110 17 720 30.710 142.5 -- -- 1,420 10-19-2001 263 1,058 7.28 5,010 27.4 154 114 16 710 30.450 148.0 -- -- 1,380 

STL-218 06-01-2000 224 946 7.39 3,300 27.6 130 77 11 420 21.781 -- 168 2.6 830 STL-220 06-07-2000 318 1,286 7.34 4,150 28.4 150 92 13 540 34.700 129.0 -- 3.6 1,100 

07-18-2001 318 1,286 7.32 4,310 28.4 155 94 14 580 32.860 130.4 -- -- 1,150 

STL-224 06-06-2000 156 707 7.61 1,610 25.4 52 44 10 200 8.700 172.0 -- 1.1 320 STL-255 07-12-2000 898 1,268 7.90 5,430 24.9 83 100 32 810 15.290 168.0 -- 5.5 1,500 

07-12-2000 1,610 1,663 7.64 2,290 24.8 63 60 14 300 7.500 171.0 -- 1.7 510 

STL-335 07-12-2000 950 1,175 7.64 4,140 27.1 110 94 20 600 11.738 151.0 -- 4.2 1,200 STL-335 07-12-2000 1,730 1,800 7.91 27,100 27.3 450 472 140 4,800 54.398 127.0 -- 38.0 10,000 STL-342 06-01-2000 -- -- 7.45 2,250 26.9 77 54 9.8 280 11.387 -- 168 1.5 520 STL-346 06-01-2000 -- 786 7.41 3,130 27.2 110 76 11 390 15.823 -- 160 2.7 800 STL-352 0606-2000 -- 1,100 7.59 4,170 24.7 80 102 30 590 12.511 158.0 -- 3.6 1,100 

07-16-2001 -- 1,100 7.71 4,210 24.4 82 102 29 600 12.220 159.2 -- -- 1,120 

STL-353 060-6-2000 850 1,230 7.80 1,230 24.1 37 35 14 150 5.700 161.0 -- 0.8 200 STL-375 060-7-2000 420 866 7.64 2,710 27.7 87 65 11 340 11.762 154.0 -- 2.4 700 STL-376 07-12-2000 -- 638 7.53 1,560 26.3 54 48 9.3 170 9.000 163.0 -- 1.2 330 

07-25-2001 -- 638 7.53 1,610 26.9 55 49 9.4 190 9.320 173.3 -- -- 330 

STL-380 06-07-2000 1,070 1,450 7.30 6,550 30.1 220 151 19 880 32.789 135.0 -- 7.5 2,000 

07-18-2001 1,070 1,450 7.18 6,860 30.7 244 162 19 940 32.520 135.4 -- -- 2,060 

Appendix IV. Major constituent and field parameter water-quality data collected from Floridan aquifer system wells in this study (Continu

Local

well

number

Date

Depth 

top

 of open

 interval

 (feet)

Depth

bottom 

of

 open

 interval

(feet)

pH SC T Ca Mg K Na Sr CaCO3 ANC Br Cl 
96 Hydrogeology, Water Quality, and Distribution and Sources of Salinity in the Floridan Aquifer System, 

Martin and St. Lucie Counties, Florida STL-381 06-07-2000 480 700 7.37 3,560 27.2 110 77 15 470 15.760 144.0 -- 3.2 960 

07-18-2001 480 700 7.31 3,530 29.0 114 81 15 480 15.490 141.4 -- -- 940 

STL-382 06-07-2000 790 860 7.29 4,330 28.3 150 102 15 560 23.172 140.0 -- 4.4 1,300 STL-385 06-15-2000 500 880 7.72 1,570 24.9 48 39 13 200 8.000 181.0 -- < 0.05 280 

07-25-2001 500 880 7.54 1,580 25.0 49 41 13 210 7.950 175.7 -- -- 280 

STL-386 07-12-2000 1,887 1,960 7.83 35,900 24.7 530 695 190 6,400 59.420 142.0 -- 56.0 13,000 STL-387 07-11-2000 -- 1,600 7.49 4,750 24.8 110 104 23 670 13.557 151.0 -- 5.0 1,300 STL-388 07-11-2000 650 1,350 7.54 3,260 24.9 77 69 19 480 13.101 163.0 -- 2.7 810 STL-389 07-11-2000 650 1,350 7.47 3,750 24.6 93 79 21 550 12.724 156.0 -- 3.8 970 STL-391 07-11-2000 -- 900 7.27 4,270 30.4 140 101 16 590 16.845 144.0 -- 4.4 1,200 

07-18-2001 -- 900 7.24 4,480 29.9 142 101 17 600 17.160 143.5 -- -- 1,260 

STL-392 07-11-2000 -- 900 7.21 4,810 31.0 140 102 21 670 13.193 148.0 -- 5.0 1,400 

Appendix IV. Major constituent and field parameter water-quality data collected from Floridan aquifer system wells in this study (Continu

Local

well

number

Date

Depth 

top

 of open

 interval

 (feet)

Depth

bottom 

of

 open

 interval

(feet)

pH SC T Ca Mg K Na Sr CaCO3 ANC Br Cl 
M-1330

B B ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

OKEECHOBEE

COUNTY

0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

WELL LOCATION AND NUMBER

WELL LOCATION AND NUMBER ON LINE

OF HYDROGEOLOGIC SECTION

LINE OF HYDROGEOLOGIC SECTION

G2-1

G7-1

G29-8

G121-1

M-110

M-745

M-1127

M-1326

M-1328

M-1331

M-1335

M-1357

M-1359

M-1363

M-1364 M-1332

M-1365

M-1366

OK-7

OK-201

PB-747

STL-222

STL-228

STL-230

STL-242

STL-243

STL-245

STL-346

STL-348

STL-349

STL-350

STL-351

STL-355

STL-359

STL-360

STL-386

WA-546

WA-547

WA-561

WA-562

WA-565

WA-582

WA-699

WA-708

WA-820

WA-823

WA-878 WA-875

WA-877

WA-1001 WA-1006 WA-1003

WA-1009

WA-1016

WA-1032

WA-1083

WA-1085

WA-1087

WA-1111

WA-1119

WA-1136

WA-1139

WA-1140

WA-1144

WA-1147

WA-1151

WA-1155

WA-1158

WA-1186

WA-1192

PB-652

WA-1107

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

A

B

C

D

E

D ́

E ́

A ́

B ́

C ́

70

60

710

441

FLORIDA’S TURNPIKE

FLORIDA’S

1

1

95

95

95

TURNPIKE

NORTHERN BOUNDARY

OF STUDY AREA

STL-356

M-1353

STL-379

M-740

M-1125

M-1330

M-1360

PB-1144

PB-1197

M-186

M-1076 M-744

M-1118

M-1121

M-1329

OK-100

OK-100

OK-9000

STL-225

OK-5

STL-71

STL-220 STL-334

STL-353

STL-354

WA-580

OK-29

STL-216

STL-217

STL-223

STL-224

STL-332

STL-352

STL-422

WA-887

IR-1001

OK-2

OK-202

OK-203

STL-218 WA-1031

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

WATER-RESOURCES INVESTIGATIONS REPORT 03-4242

Location of wells used for geologic mapping in the study and hydrogeologic section lines--PLATE 1

Reese, Ronald S. 2004, Hydrogeology, water quality, and distribution and sources

of salinity in the Floridan aquifer system, Martin and St. Lucie Counties, Florida

PLATE 1. LOCATION OF WELLS USED FOR GEOLOGIC MAPPING IN THE STUDY AND HYDROGEOLOGIC SECTION LINES

By

Ronald S. Reese

2004

SOUTH FLORIDA WATER MANAGEMENT DISTRICT

PREPARED IN COOPERATION WITH THE

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27
0

0

15 MILES

15 KILOMETERS

5 10

5 10

EXPLANATION

WELL LOCATION AND NUMBER

80°45 ́ 80°30 ́ 80°15 ́ 80°00 ́

27°30 ́

27°00 ́

27°15 ́

LAKE

OKEECHOBEE

ATLANTIC OCEAN

MARTIN COUNTY

MARTIN COUNTY

ST. LUCIE COUNTY

ST. LUCIE COUNTY

OKEECHOBEE

COUNTY

INDIAN RIVER COUNTY

PALM BEACH COUNTY

70

60

710

441

FLORIDA’S TURNPIKE

FLORIDA’S

1

1

95

95

95

TURNPIKE

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

WATER-RESOURCES INVESTIGATIONS REPORT 03-4242

Location of wells with water-quality data used in the study--PLATE 2

Reese, Ronald S. 2004, Hydrogeology, water quality, and distribution and sources

of salinity in the Florida aquifer system, Martin and St. Lucie Counties, Florida

PLATE 2. LOCATION OF WELLS WITH WATER-QUALITY DATA USED IN THE STUDY

By

Ronald S. Reese

2004

SOUTH FLORIDA WATER MANAGEMENT DISTRICT

PREPARED IN COOPERATION WITH THE

M-27

M-29

M-30

M-32

M-43

M-47

M-64

M-65

M-86

M-88 M-95

M-106

M-110

M-113

M-143

M-145

M-146 M-150

M-168

M-169

M-170

M-171

M-173

M-186

M-189

M-192

M-244

M-254

M-255

M-306

M-443 M-582

M-602

M-740

M-741

M-742

M-744 M-745

M-747

M-748

M-841

M-901

M-911

M-919

M-920

M-922

M-926

M-927

M-940

M-1033

M-1034

M-1076

M-1121

M-1125

M-1324

M-1325

M-1326

M-1328

M-1330

M-1346

M-1347

M-1349

M-1353

M-1356

M-1360

M-1360

OK-1

OK-2

OK-3

OK-7

OK-13

OK-17

OK-23

OK-31

OK-71

OK-72

OK-73

OK-74

OK-100

OK-9000

OK-9001

OK-9002

PB-215

PB-652

PB-747

PB-1144

PB-1167

PB-1170

PB-1182

PB-1183

PB-1196

PB-1774

STL-47

STL-71

STL-215

STL-216

STL-217

STL-218

STL-219

STL-220

STL-221

STL-222

STL-223

STL-224

STL-225

STL-228 STL-229

STL-230

STL-242

STL-243

STL-244

STL-245

STL-246

STL-247

STL-248

STL-250

STL-253

STL-254

STL-255

STL-332

STL-333

STL-334

STL-335

STL-342

STL-346

STL-347

STL-348

STL-350

STL-351

STL-352

STL-353 STL-355

STL-356

STL-357

STL-359

STL-367

STL-368

STL-369

STL-370

STL-371

STL-373

STL-374

STL-375

STL-376

STL-377

STL-380

STL-381

STL-382

STL-385

STL-386

STL-387

STL-388

STL-389

STL-391

STL-392

G3-1

G205-5

WA-117

WA-119

WA-546

WA-547

WA-562

WA-580

WA-611

WA-612

WA-625

WA-699

WA-708

WA-727

WA-815

WA-820

WA-829

WA-875

WA-877

WA-878

WA-879

WA-1001

WA-1005

WA-1016

WA-1032

WA-1082

WA-1083

WA-1085

WA-1087

WA-1107

WA-1111

WA-1113

WA-1119

WA-1121

WA-1136

WA-1139

WA-1140

WA-1143

WA-1146

WA-1147

WA-1148

WA-1151

WA-1155

WA-1158

WA-1179

WA-1183

WA-1186

WA-1188

G1-1

G2-1

G4-1

G6-1 G7-1

G11-1

G13-1

G14-1

G29-1B

G35-1

G36-2

Base from U.S. Geological Survey digital data, 1972

Universal Transverse Mercator projection, Zone 17, Datum NAD 27