Nonmechanical dewatering of the regional Floridan Aquifer system
Nonmechanical dewatering of the regional Floridan Aquifer system (in Perspectives on karst geomorphology, hydrology, and geochemistry; a tribute volume to Derek C. Ford and William B. White, Russell S. Harmon (editor) and Carol M. Wicks (editor))
Special Paper - Geological Society of America (2006) 404: 219-234
The regional Floridan aquifer system has been dewatered and otherwise altered extensively throughout much of Florida and coastal Georgia by groundwater pumpage (mining). An increasing threat to this karst aquifer system is structural mining of aquifer formations, primarily to produce fertilizers, titanium products, construction materials, and pet food supplements. These excavations often include mechanical dewatering to facilitate shallow and deep extraction of the aquifer formations. All include reduced aquifer levels, dewatering of the aquifer system, and altered hydroperiods at and surrounding the excavated pits, due to increased void space and evapotranspirative losses (nonmechanical dewatering). Only mechanical dewatering is considered by regulatory agencies during evaluations of applications for structural mining of the aquifer system. Despite refuting data, open pits resulting from these excavations increasingly are portrayed as subsurface "reservoirs" that create new or enhanced sources of water in areas where natural groundwater supplies have been depleted. Four permits and sites were evaluated for excavated and proposed pits in SE, NW, SW, and east-central Florida's natural areas used for groundwater supply. The combined surface area for pits under those four permits will result in approximately 237,000 m (super 3) /d ( approximately 62.7 million gallons per day [Mgd]) of induced discharge from the regional Floridan aquifer system due to nonmechanical dewatering. This volume is more than twice the reported pumpage from the combined three municipal supply wells at the Miami-Dade West Well Field. The approximately 123 ha ( approximately 308 ac) SW Florida mine, most recently excavated in an area designated as critical habitat for the federally listed Florida panther, will result in induced aquifer discharge of approximately 1505 m (super 3) /d (0.4 Mgd) due to nonmechanical dewatering. This loss is equivalent to approximately 5% of all water used by domestic supply wells in that county in 1990. That recently initiated excavation in SW Florida revealed environmental damage extending beyond the mine boundaries, to surrounding private property,and is the first documented case of such damage solely from aquifer formation mining and nonmechanical dewatering of the aquifer system. A federal court ruled on 22 March 2006 that the U.S. Army Corps of Engineers and U.S. Fish and Wildlife Service had failed to carry out their duty to protect the federal wetlands and protected species by issuing permits for mining in the SE case-study area.