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Hydrogeology of the Surficial Aquifer System in Southwest Florida

Project Proposal for 1999

Continuing Project Workplan - FY 1999

Project Title: Hydrogeology of the Surficial Aquifer System in Southwest Florida
Geographic Area: Southwest Florida
Project Start Date: October 1, 1996
Project End Date: September 31, 1999

Project Chief: Suzanne D. Weedman
Region/Division/Team/Section: Eastern Region/Geologic Division/Eastern Region National Geologic Mapping Team/South Florida Mapping project
E-mail: sweedman@usgs.gov
Phone: 703-648-6379
Fax: 703-648-6953
Mail Address: MS 926A, 12201 Sunrise Valley Drive, Reston, Virginia 20192
Program Element(s)/Task(s): Ecological and Geological Studies of Southwest Florida, Task 5.1

Project Summary: The objective of this project is to describe the three-dimensional variations in the hydrologic properties of the surficial aquifer system within a geologic framework. The geologic and hydrologic data will be incorporated into hydrologic models that simulate ground-water and surface-water flow in the surficial aquifer system. Land and water managers will use these models to predict the consequences of ecosystem restoration plans and to evaluate their effectiveness. This study will provide essential hydrogeological data to extend existing and next-generation water management, natural system, and other models across southern Florida to the natural boundary of the southwest coast. Hydrologic models that simulate flow of ground and surface water will be used to predict consequences of many of the south Florida ecosystem restoration plans, as well as guide future land and water management decisions in a rapidly growing part of the state.

Project Objectives and strategy:
The major questions to be addressed are: 1) what is the lithology of the aquifers and the contining units of the system and how does that lithology change across the study area, 2) is the confining unit(s) within the aquifer system laterally continuous, 3) does the aquifer system thicken or thin across the study area, 4) how has depositional and diagenetic history of the rocks and sediments of the aquifer system controlled its transmissivity?

Over a four year period, approximately 21 coreholes will be drilled through the surficial aquifer system (averaging 200 feet depth) in Collier and Monroe Counties. In FY96 the study area was western Collier County where seven coreholes were drilled, in FY 97 and 98, the project study area was primarily in Big Cypress National Preserve, in eastern Collier and Monroe Counties, where subsurface data were previously unavailable. Ten coreholes -were drilled and logged in FY97, and four additional coreholes were drilled and logged in the Preserve in FY98. Drilling, permeability testing, hydrologic monitoring and testing, lithologic and geophysical logging, age determination, and interpretation will be accomplished by personnel of the U.S. Geological Survey and the Florida Geological Survey, in cooperation with the South Florida Water Management District. This project was combined, in FY98, with a project directed by Ron Reese, USGS-WRD, to assess the spatial extent of the gray limestone aquifer of the surficial aquifer system in south-central Florida. Coring and hydrogeological data collection are shared where the two study areas overlap, and are made available to the public as reports are completed. Field work is completed within the winter months each year,primarily January through March, and sample analysis begins in early April, with results available near the end of the fiscal year, and an open-file report completed by the end of each calendar year.

Continuous cores are drilled and examined for mineralogy, composition, texture, structures, and fossils to determine lithology, age, alteration, and porosity of the aquifer rocks, and to construct a depositional model that will aid in the extrapolation of subsurface data. Stratigraphic units are correlated between coreholes and their lithologic and hydrologic properties estimated where core data are absent. Permeability tests have been run on selected core samples by the FGS and integrated with hydrologic and geophysical logs to estimate transmissivities of lithofacies. Geophysical logs (natural gamma, caliper, resistivity, temperature, neutron, density, flowmeter, televiewer) will be run as holes are drilled. The geophysical investigation is the responsibility of USGS-WRD. The aquifer testing is coordinated by among GD and WRD personnel. Wells will be sampled for standard complete and nutrient analysis, and the phosphorous content compared from carbonate and siliciclastic aquifers. Seismic transacts are planned, pending the results of a pilot study, to image the large-scale structure of the aquifer system. Also, levelling and head measurements are being made at corehole sites to collect data to construct a potentiometric map of the study area. All data are being digitized and archived in GWSI and Geosys databases. Reports on the FY96 drilling and analyses are completed. A report summarizing 10 cores drilled in FY97 should be completed in summer 1998.

Potential Impacts and Major Products:
Critical, and probably quite controversial, decisions will be made in the next decade in southwest Florida that will probably include limitation of development, state purchase of private lands for restoration, rehydration of previously drained area, permitting of new well fields, diversion or blocking of canals, removal of exotic species, and restriction of access to ecologically sensitive areas. Local, state, and federal agencies need reliable, unbiased scientific information to justify their decisions on such controversial issues. Data from this project will support hydrologic models that can simulate the modified natural hydrologic system, and will be used to address several pressing problems in south Florida: 1) How can the needs of the growing population be met while also restoring and maintaining the wetland ecosystem? 2) How can fresh water be equitably allocated to the three primary users: the residents, agricultural businesses, and the ecosystem itself? 3) How and when should development be limited as it encroaches upon or affects the coastal ecosystem and the Big Cypress Swamp, which are now primarily under the management of state and Federal agencies?

We anticipate that the hydrogeologic data, available in both Professional Paper and GIS format, will be a significant tool for land and water management decisions. The primary final product of this study will be a comprehensive report of the lithology, sedimentology, geophysics, stratigraphy and hydrology of the surficial aquifer system, and will include an array of cross-sections of the surficial aquifer system in the study area which, when combined, will yield a three-dimensional database of the stratigraphy and both estimated and measured hydraulic conductivity of the system.


  1. Florida Geological Survey: Tom Scott and Harley Means have described our cores, sampled fossils, made formation picks, and performed permeability testing on selected core samples.
  2. South Florida Water Management District: Kevin Rohrer, David Demonstranti, and Peter Dauenhauer logged one of our coreholes and shared water conductivity data from that well with our project.
  3. National Park Service, Big Cypress National Preserve: Christine Bates have provided surface water quality data to us for our corehole sites for FY97 and 98.
  4. USGS, WRD-Miami: in FY97, Ron Reese has described cores and estimated permeability using grain size distributions, and in FY98 was included in our budget.
  5. Drs. Paul Wolfe and Benjamin Richard, and their students Laura R. Hite, Matthew I. Carlson, Erin Sesslar, and Steve Edlavitch of Wright State University have completed a four TDEM transects in our FY96 study area in Collier County.
  6. Dr. Sarah Kruse, University of South Florida, and students have completed a pilot seismic transect near the Bass core hole site demonstrating that their method can successfully image the shape of the siliciclastic unit that forms the base of the surficial aquifer system.

This project provides the data and interpretations for current and future hydrologic models being developed by the South Florida Water Management District (SFWMD), U.S Geological Survey-Water Resources Division (USGS/WRD), the National Park Service (NPS), and other research groups. There is also substantial interest in the hydrologic resources of south Florida from the Florida State Division of Parks and Recreation and the Division of Forestry. Over the course of the project we have worked with the Florida Geological Survey, Collier-Seminole State Park, Fakahatchee Strand State Preserve, Southern States Utilities, Big Cypress National Preserve, Everglades National Park (Gulf Coast) region, Calumet Oil Company, Florida Rock Incorporated, the Florida Department of Transportation, and the FAA and Dade-Collier Airport Authority.

  1. South Florida Water Management District: We have provided daily drilling logs to John Lukasiewiecz documenting the locations and depths of our coreholes and the nature of the aquifer system at each site during our drilling season FY98. The SFWMD is interested in monitoring both head and water quality.
  2. National Park Service, Big Cypress National Preserve: We have provided daily drilling logs to Christine Bates, hydrologist, documenting the locations and depths of our coreholes and the nature of the aquifer system at each site during our drilling season FY98. The park is interested in our data on the water table aquifer to monitor their efforts at restoration of sheet flow in the preserve.

Time Line:
October - December 1998 (personnel responsible)

  • Continue analysis of cores drilled in FY97 and FY98 including sedimentology, paleontology, geochemical analysis (Weedman, Wardlaw, Edwards).
  • Continue aquifer testing and monitoring (Weedman, Reese, Paillet)
  • Begin final report on drilling, core analyses, hydrologic testing (Weedman, Wardlaw, Edwards, Paillet, Reese)
  • Begin planning document for future research in southwest Florida (Paillet, Reese, Snyder, Levesque, Desmond)

January - March 1999
  • Continue aquifer testing and monitoring (Weedman, Reese, Paillet)
  • Continue analysis of surface geophysics surveys.
  • Continue sample analyses.
  • Continue compilation of final report.

March - October 1999
  • Complete analyses of cores, hydrologic, and, geophysical data.
  • Complete final synthesis report and planning document. All project members.
FY 1999 activities:
All core drilling is complete and sample analyses are nearing completion. The primary activity in FY99 will be completion of core descriptions, completion of core analyses, compiling stratigraphic, sedimentologic, and hydrologic data, analysis of aquifer test data, writing final reports.

FY 1999 deliverables/products:
We have completed two reports: one summarizes the lithology and geophysics of the coreholes drilled through the aquifer system, and the second summarizes the various analyses done on the cores. These reports are separate because descriptions and geophysical logs are completed as much as a year before some of the paleontological and chemical analyses. The third Open File Report on the lithology, geophysics, core analyses, and monitor-well installation, of the FY97 cores is currently underway.

The primary final product will be a USGS Professional Paper: The Hydrogeology of the Surficial Aquifer System in Southwest Florida. Anticipated completion. late 1999. Chapters and anticipated authors:

Sedimentology: Weedman and Wardlaw (USGS)
Lithostratigraphy: Scott (FGS)
Paleontology: Edwards and Wingard (USGS)
Sr-isotope gechronology: Edwards, Weedman, and Simmons (USGS)
Geophysics: Paillet (USGS)
Hydrology: Paillet, Reese, and Weedman (USGS)

This publication will include cross-sections of the surficial system with the stratigraphic and hydrologic framework shown. Hydraulic conductivities will be indicated where measured and estimated for other parts of the system. The data also will be available in digital form in a GIS format.

Other planned publications include:

  1. Sr-isotope stratigraphy of southwest Florida (Edwards, Weedman, and Simmons)
  2. Analysis of TDEM data from south Florida (Paillet, Wolf, Richards, Hite, Carlson, Sesslar, Edlavitch)
  3. Interdisciplinary planning document: guide to future activities in southwest Florida (Weedman, Wardlaw, Paillet, Reese, Desmond, Snyder)

New Directions, Expansion of Continuing Project (if applicable):
A planning document will be written for southwest Florida to summarize past research in the area, and to address future research needs in the areas of geology, hydrology, topography, and biology, and will be written by members of all four divisions of the USGS. Anticipated authors: S. D. Weedman and B. R. Wardlaw (GD-Reston), R. S. Reese (WRD-Miami); F. L. Paillet (WRD-Denver), G. B. Desmond (NMD-Reston), J. R. Snyder (BRD-Ochopee, FL), and V. Levesque (WRD-Tampa).

In FY98, we drilled and logged 4 coreholes in the Big Cypress National Preserve in Collier and Monroe Counties, Florida, drilled and logged holes along a TDEM transect to callibrate the geophysical soundings, and redrilled a that had collapsed in FY96 for geophysical logging. In addition, we contracted a group of geophysics students and professors from the Wright State University, who completed geophysical surveys along two transects across our study area, showing variability in water conductivity in the surficial aquifer system. Two theses have been completed and two more are in progress. Their results show the salt water intrusion near the southwest coast, the depth to the top of the brackish water interface (-100 feet depth), and its slightly upward slope to the north and perhaps east. Another student TDEM study is in progress (spring FY98), supervised by Ron Reese, to delineate changes in water salinity in the vicinity of a suspected fault within the surficial system.

Three multi-well and 8 single-well aquifer tests are planned this summer (FY98) for 8 sites in the study area, and are the primary responsibility of WRD-Miami. A seismic transect was accomplished as a pilot study near the Bass corehole. More extensive transacts will be run along Tamiami Trail, Alligator Alley, and State Road 29, and will be the responsibility a collaborating study funded by the mapping program of GD-Reston. These transects will delineate the top of the Arcadia Formation, and also the base of the extensive siliciclastic unit that forms the base of the surficial aquifer system. Leveling and sampling of all monitor wells will be completed by the end of FY98. An inventory of existing wells will be accomplished this summer by a student working with Miami-WRD.

We have developed abroad overview of the variability of lithology in the study area. In general, in the western part of the study area the aquifer system is compartmentalized into two zones of differing water salinity confining beds of low permeability. The upper zone is the water table aquifer (freshwater) and the lower zone is slight brackish to brackish water. Low permeabililty is due to poor sorting in the siliciclasitc units and by diagenetic cements in the carbonate units. As a consequence, the fresh-water lens is shallow and of limited extent, although the transmissivities in the upper aquifer are extremely high. Therefore, aquifer recharge is relatively rapid and changes in the surface water regime for restoration, such as reestablishment of sheet flow, should be effective in increasing aquifer recharge, enlarging the freshwater lens, and displacing salt water intrusion.

In contrast, in the east part of the study area, the aquifer system is largely fresh down to at least 200 feet, with no apparent salinity compartmentalization. In addition, the carbonate portion of the system, i.e., the upper 50 to 70 feet, is still unconsolidated, and has not undergone lithification. The lithification process enhances porosity and permeability. The poor sorting in the siliciclastic units causes them to be thick discontinuous confining zones, as in the west, but thicker siliciclastic units and the near absence of lithification of the carbonates, results in much lower estimated tranmissivities of the water table and shallow aquifers.

We have been asked to design a visitor center exhibit for the Big Cypress National Preserve, which will be designed and prepared near the end of the project.

FY 1998 deliverables, products completed:
During the field season, we provided daily logs of our drilling progress to the South Florida Water Management District, the Big Cypress National Preserve, the Florida Geological Survey, the Calumet Oil Company, and WRD-Miami. Upon completion of each hble, we have sent to the agencies listed above, initial core descriptions and photographs, geophysical logs, flow meter data, and a brief initial interpretation.

A fact sheet, two Open File Reports, a thesis, and paper are complete, to date, that summarize drilling, logging, surface geophysics, and analyses from western Collier County:

Weedman, S.D., 1996, Hydrogeology of the surficial aquifer system of southwest Florida, FS-158-96. Weedman, S.D., Paillet, F. L, Means, G. H., and Scott, T. M., 1997, Lithology and geophysics of the surficial aquifer sytem in western Collier County, U.S. Geological Survey Open File Report 97-436, 18 figures, 4 tables, 167 p.

Hite, L. R., 1997, Aquifer delineation in southwest Florida using time-domain electromagnetics, M.S. Thesis, Wright State University, Dayton, 77 p.

Edwards, L.E., Weedman, S.D., Simmons, K.R., Scott, T.M., Brewster-Wingard, G.L., Ishman, SE., and Carlin, N.M., 1998, Lithostratigraphy, petrography, biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifier system of western Collier County, U.S. Geological Survey Open File Report 98-205, 12 figures, 11 tables, 79 p. Also available on the WWW at http://pubs.usgs.gov/pdf/of/ofr98205.html.

Paillet, F.L., Hite, Laura, and Carlson, Matt, 1998, Integrating surface and borehole geophysics in ground water studies - an example from south Florida: Symposium on the Application of Geophysics to Environmental and Engineering Problems, Chicago, Illinois, March, 1998 [Proceedings], p. 349-358.

Meeting abstracts:
Paillet, F.. and Weedman, S.D., 1996, Using borehole logs and core to identify and characterize confining units in the surficial aquifer sytem of south Florida, Geological Society of America Abstracts with Programs, vol. 28, p. A25.

Weedman. S.D., Simmons, K.R., and Edwards, L.E., 1996, Episodic dolomitization of the Florida platform from late Oligocene to middle Miocene, Geological Society of America, Abstracts with Programs, vol. 28, A-336-337.

Weedman, S.D., Edwards, L.E., Simmons, K.R., Brewster-Wingard, G.L., Ishman, S.E., and Wardlaw, B.R., 1997, Geologic framework of the surficial aquifer system of southwest Florida, 2nd Annual USGS South Florida Ecosystem Meeting, Ft. Lauderdale, May 23, 1997, USGS Open-File Report 97-385.

Wardlaw, B.R., Weedman, S.D., and Carlin, N., 1997, Preliminary investigation of the "River of Sand": Fact and Fiction, 2nd Annual USGS South Florida Ecosystem Meeting, Ft. Lauderdale, May 23, 1997.

Weedman, S.D., Paillet, F.L., and Wardlaw, B.R., 1997, Sedimentologic and geophysical characterization of the surficial aquifer system under the wetlands of southwest Florida: Geological Society of America, Abstracts with Programs, vol. 29, A-176.

Paillet. F.L., and Weedman, S.D., 1998, Integrating surface and borehole measurements to develop a shallow ground-water flow model in southwest Florida, American Geophysical Union, Annual Meeting, 1998. Boston.

FY99 Names and expertise:
S.D. Weedman, Sedimentology
G. L. Wingard, Molluscan paleontology
F. L. Paillet, Borehole geophysics
B.R. Wardlaw, Stratigraphy and sedimentology
R.G. Stamm, Technician


Drilling capital(?)

Other required expertise for which no individual has been identified: None

Major equipment /facility needs: None

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