The objective of this project was to evaluate approaches for quantifying ground-water seepage beneath Levee 30. The accounting of all significant hydrologic inflows and outflows to the Everglades ecosystem of the south Florida mainland is a key element of the South Florida Ecosystem Program.
A continuous geologic core from land surface to a depth of 78 feet was obtained during the drilling of a monitor well completed in February 1995. Permeability and porosity tests were performed on 10 plugs from the core. Of particular interest was a thin, very hard, impermeable limestone layer at 7 feet below land surface with a very low porosity (less than 5 percent) and very low permeability (less than 0.001 millidarcy). This layer is believed to be areally extensive and, therefore, would constitute a semiconfining layer retarding the seepage of water from Water Conservation Area 3B into the underlying Biscayne aquifer.
Geophysical logs were obtained from two monitor wells using electromagnetic induction and natural gamma tools. The resulting logs are useful for determining changes in rock types and water quality.
Discharge measurements were made in the Levee 30 canal under various hydrologic conditions at three locations: at the transect, 1 mile south of the transect, and 1 mile north of the transect. The differences in flow rates at these three sections are used to determine the rate at which water is seeping into or out of the canal from the aquifer, a critical input requirement for the ground-water flow models.
At two sites in the wetlands, seepage meters were used to directly measure the flux of water across the water-sediment interface. Measurements were made under varying hydrologic conditions.
U.S. Department of the Interior, U.S. Geological Survey, Center for
Coastal Geology
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