SALTWATER INTRUSION AND QUALITY OF WATER IN THE …

1 SALTWATER INTRUSION AND QUALITY OF WATER IN THE FLORIDAN aquifer system , northeastern florida By Rick M. Spechler GEOLOGICAL SURVEY WATER -Resources Investigations Report 92-4174 Prepared in cooperation with the CITY OF JACKSONVILLE and the ST. JOHNS RIVER WATER MANAGEMENT DISTRICT Tallahassee, Flo rida 1994 DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secr etary GEOLOGICAL SURVEY Robert M. Hirsch, Act ing Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the Geological Survey. For additional in formatio n writ e to: District Chief Geologic al Surv ey Suite 3015 227 N.

2 Bronough Stre et Tall ahas see, FL 32301 Copies of this report can be purchased from: Geological Survey Bra nch of Informat io n Serv ic es Box 25286 Denver, CO 80225-0286 800-ASK-USGS Additional information about WATER resources in florida is available on the World Wide Web at CONTENTS 1 Introduction .. 1 Purpose and Scope .. 2 Previous 2 Acknowledgments .. 2 Well-Numbering system .. 4 WATER .. 4 Hydrogeologic Framework .. 6 Hydrogeology .. 11 Surficial aquifer system .. 11 Intermediate Confining 15 Floridan aquifer system .. 15 Hydraulic Characteristics .. 16 Ground- WATER Flow system .. 17 Long-Term WATER -Level Trends .. 17 Head 19 Sub-Floridan Confining 22 QUALITY of Ground WATER .

3 27 Wells Tapping the Upper Floridan aquifer .. 28 Specific Conductance .. 28 Sulfate .. 32 Chloride .. 32 Ionic Composition .. 32 Multiaquifer Wells Tapping the Upper Floridan and the Upper Zone of the Lower Floridan aquifer .. 34 Wells Tapping the Upper Zone of the Lower Floridan aquifer .. 37 Wells Tapping the Fernandina Permeable Zone .. 37 SALTWATER INTRUSION and Trends in Chloride 43 Mechanisms of SALTWATER INTRUSION .. 47 Relict Seawater .. 47 Lateral Encroachment .. 47 Upconing .. 49 Upward Leakage through Wells .. 49 Upward Leakage through Structural 49 WATER Management Considerations .. 53 Summary and Conclusions .. 56 Selected References.

4 58 Appendix I--Chemical and physical analyses of WATER from the Floridan aquifer system in Nassau, Duval, St. Johns, and northeastern Clay 63 Appendix 11--Records of wells completed in the Floridan aquifer system in Nassau, Duval, St. Johns, and northeastern Clay Counties .. 71 PLATE Map showing altitude of the top of the Ocala back pocket FIGURES 1. Map showing location of study 3 2. Graph showing total ground- WATER use, 1965-88 .. 4 3. Diagram showing total ground- WATER use by category for 1988 .. 5 4. Diagram showing generalized geology and hydrogeology of northeastern 7 Conte nts iii 5. Map showing location of hydrogeologic 8 6-8.

5 Hydrogeologic sections: 6. A-A and B-B .. 9 7. C-C .. 10 8. D-D .. 10 9. Map showing altitude of the top of the Avon Park 12 10. Map showing major structural features in (A) northern florida and (B) the study 13 11. Diagram showing summary of historical nomenclature applied to aquifer systems in the study area .. 14 12-15. Maps showing: 12. Potentiometric surface of the Upper Floridan aquifer in north-eastern florida , September 18 13. Estimated predevelopment potentiometric surface of the Upper Floridan 20 14. Approximate decline in potentiometric surface of the Upper Floridan aquifer from about 1880 (prior to development to September 1989.)

6 21 15. Locations of monitoring wells used for the collection of WATER -level and chloride-concentration 23 16. Hydrographs showing WATER levels in selected wells tapping the Upper Floridan 24 17. Hydrographs showing WATER levels in well D-262 tapping the upper zone of the Lower Floridan 25 18. Graph showing WATER levels in drill s tem and annulus during drilling of monitoring wells D-3060, D-2386, and SJ-150 .. 26 19. Diagram showing limiting concentrations of chloride recommended for plants, animals, public-supply, and industrial use 27 20-24. Maps showing: 20. Location of wells sampled in Nassau 28 21. Location of wells sampled in Duval and northern Clay Counties.

7 29 22. Location of wells sampled in St. Johns and northeastern Clay Counties .. 30 23. Distribution of specific conductance in WATER from the Upper Floridan aquifer and in selected wells tapping both the Upper Floridan and the upper zone of the Lower Floridan aquifers .. 31 24. Distribution of sulfate concentrations in WATER from the Upper Floridan aquifer and in selected wells tapping both the Upper Floridan and the upper zone of the Lower Floridan aquifers .. 33 25. Graph showing relation of sulfate-chloride equivalent concentration ratio to sulfate concentrations in WATER from the Floridan aquifer system .. 34 26. Map showing distribution of chloride concentrations in WATER from the Upper Floridan aquifer and in selected wells tapping both the Upper Floridan and the upper zone of the Lower Floridan aquifers.

8 35 27. Trilinear diagram showing chemical composition of WATER from selected wells tapping the Upper Floridan aquifer .. 36 28. Trilinear diagram showing chemical composition of WATER from selected wells tapping both the Upper Floridan and the upper zone of the Lower Floridan aquifers .. 38 29. Diagram showing chloride concentrations in WATER samples obtained through the drill stem and annulus during drilling of monitoring wells D-3060, D-2386, SJ-150, and N-1l7 39 30. Diagram showing specific conductance of WATER samples obtained through the drill stem and annulus during drilling of monitoring wells D-3060, D-2386, and SJ-150 40 31. Map showing chemical analyses of WATER from selected wells tapping the Fernandina permeable zone.

9 41 32. Trilinear diagram showing chemical composition of WATER from selected wells tapping the Fernandina permeable zone .. 42 33-35. Graphs showing: 33. Chloride concentrations in WATER from selected wells tapping the Upper Floridan aquifer .. 44 34. Chloride concentrations in WATER from selected wells tapping both the Upper Floridan aquifer and the upper zone of the Lower Floridan 45 35. Chloride concentrations in WATER from selected wells tapping the upper zone of the Lower Floridan aquifer .. 46 36. Diagram showing inferred position of the SALTWATER -freshwater 48 37. Diagram showing simplified model of the Floridan aquifer system in northeastern florida .

10 51 38. Seismic record showing collapse features along an approximate 4,000-foot section of the St. Johns River near Dames Point in Duval 52 39. Graph showing temperature log of monitoring well 53 40. Map showing distribution of chloride concentrations in WATER from selected wells tapping the Upper Floridan aquifer on Fort George Island .. 54 iv Contents 41. Graph showing WATER levels and chloride concentrations of WATER in well D-164,tapping the Upper Floridan aquifer on Fort George Island, 1930-90 .. 55 42. Graph showing chloride concentrations in WATER from selected wells tapping the Upper Floridan aquifer on Fort George Island, 1924-90 .. 55 TABLES 1.