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hydrogeology of
surficial aquifer systems in south florida >
1998 proposal
Program: FRAGILE ENVIRONMENTS CLIENTS: 1. South Florida Water Management District: We have provided daily drilling logs to Keith Smith and John Lukasiewiecz documenting the locations and depths of our coreholes and the nature of the aquifer system at each site during our drilling season FY97. The SFWMD is interested in monitoring both head and water quality. PARTNERS: BACKGROUND NARRATIVESProject 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 data will be incorporated into hydrologic models that simulate ground-water and surface-water flow in the aquifer system. Land and water managers will use these models to predict the consequences of ecosystem restoration plans and to evaluate their effectiveness. Project Justification: 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. 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 currently are 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. The first two years we have worked closely with Collier- Seminole State Park, Fakahatchee Strand State Preserve, and Southern States Utilities, Big Cypress National Preserve. Everglades National Park. Gulf Coast region, Dade-Collier Airport and FAA. Project Objectives: Over a four year period, approximately 30 coreholes will be drilled through the surficial aquifer system (averaging 200 feet depth) in Collier and Monroe Counties. Drilling, monitor well installation, aquifer testing, core permeability 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. Coring and hydrogeological tasks and data are shared between the Reston and Miami USGS offices, and data will be made available to the public as reports are completed. Field work will be completed within the winter months, January through March, and sample analysis of cores drilled then will begin 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. Overall Strategy, Study Design, and Planned Major Products: Continuous cores will be 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 will be correlated between coreholes and their lithologic and hydrologic properties estimated where core data are absent. Permeability tests will be run on lithified core samples 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 and monitor well installation will be coordinated by both GD and WRD personnel. Major questions to be addressed are: 1) what is the lithology of the aquifer and the confining units of the system and how does that lithology change from west to east, 2) is the confining unit(s) within the aquifer system laterally continuous to the east, 3) does the aquifer system thicken or thin to the east, 4) how is the aquifer architecture controlled by the depositional and diagenetic history of the rocks and sediments of the aquifer system? WORK PLANOverall: Over a four year period, approximately 30 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, in FY 97 and 98, the project study area will be primarily in Big Cypress National Preserve, in eastern Collier and Monroe Counties, where subsurface data is largely unavailable. Ten coreholes were drilled in FY97, and five additional coreholes will be 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 is combined, in FY98, with a project directed by Ron Reese, USGS-VA?,D, to assess the spatial extent of the gray limestone aquifer of the surficial aquifer system in south-central Florida. Coring and hydrogeological data collection will be shared where the two study areas overlap, and will be made available to the public as reports are completed. Field work should be completed within the winter months each year, primarily January through March, and sample analysis should begin 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 will be 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 will be correlated between coreholes and their lithologic and hydrologic properties estimated where core data are absent. Permeability tests will be 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 will be coordinated by both 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 transects are planned, pending the results of a pilot study, to image the large-scale structure of the aquifer system. Also, levelling and head measurements will be made at corehole sites to collect data to construct a potentiometric map of the study area. All data will be digitized and archived in GWSI and Geosys databases. There will be yearly reports on all drilling done in each year. The first year's report will cover all seven cores drilled in FY96 and it is near completion. A report summarizing all 10 cores drilled in FY97 should be completed by December 1997. The primary 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. Timeline:
January - March 1998
March - October 1998
October 1998 - October 1999
Planned Deliverables/Products: During the past drilling season, we keep several interested agencies supplied with daily logs of our progress and give them preliminary descriptions, core photographs, geophysical logs, and a preliminary analysis, immediately after completion of each corehole. For each year we will complete two reports: one will summarize the lithology and geophysics of the coreholes drilled through the aquifer system, and the second will summarize the varied analyses done on the cores. These reports are separate because descriptions and geophysical logs are complete as much as a year before some of the paleontological and chemical analyses. The work done on all cores for a given field season will be combined. The first Open-File Report is nearly complete and will be available by early summer 1997. The second Open File Report on the analysis of the FY96 cores is currently in preparation and will be completed when analyses are complete, which is anticipated in the Fall of 1998. Work for the third Open File Report on the lithology and geophysics of the FY97 cores is currently underway. The final product will be a USGS Professional Paper The Hydrogeology of the Surficial Aquifer System in Southwest Florida. Anticipated completion, late 1999. This publication will include fold-out cross-sections of the surficial system with the stratigraphic and hydrologic framework shown. Hydraulic conductivities will be estimated for rock and sediment types in the system. Prior Accomplishments in Proposed Area of Work: New Directions, Expansion of Continuing Project (if applicable): In FY98, we will be collaborating more formally with Ron Reese from WRD/Miami. He and his assistants will take primary responsibility for hydrologic testing and monitoring of wells at our corehole sites. See extension attached for staffing and budget. There are several elements that we are incorporating into the extension of this project. The division responsible for planning each effort is indicated, however, these elements will be collaborative efforts of mutual benefit, and will cross the boundaries of the two studies. 1. Aquifer tests will be conducted at 5 sites and will be the responsibility of WRD-Miami.
4. We will make an inventory of existing wells and their use for sampling, aquifer testing and head measurements. This work will be done by WRD-Miami. ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACHAccomplishments and Outcomes, Including Outreach: We drilled and logged 10 coreholes in the Big Cypress National Preserve in Collier and Monroe Counties, Florida. 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 1996 study area, showing variability in water conductivity in the surficial aquifer system. Two theses were completed this spring and will be presented at the annual Ecosystem Meeting in Ft. Lauderdale, FL, in August. Their results show graphically 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. We now have developed a broad 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 permeability is due to poor sorting in the siliciclastic 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 sicliciclastics 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 transmissivities of the water table and shallow aquifers. A major goal of the FY98 drilling and testing is to now quantify hydraulic conductivity across the study area. We are planning visitor center exhibits with the Big Cypress National Preserve park ranger staff, which will be designed and prepared near the end of the project. 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 FAA and Dade-Collier Airport, and WRD-Miami. Upon completion of each hole, we sent to each of the agencies listed above initial core descriptions and photographs, geophysical logs, flow meter data, and a brief initial interpretation. The first Open File Report is in review that summarizes drilling and logging from last year, and will be available within FY97: Weedman, S.D., Paillet, F. L, Means, G. H., and Scott, T. M., 1997, Lithology and geophysics of the surficial aquifer system in western Collier County, US. Geological Survey Open File Report 97-XXX, 18 figures, 4 tables, 178 ms pages. NEEDSMajor Equipment/Facility Needs: None
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U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology This page is: http://sflwww.er.usgs.gov/proposals/1998/surficialp98.html Comments and suggestions? Contact: Heather Henkel - Webmaster Last updated: 11 October, 2002 @ 09:31 PM (KP) |
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