The Upper and Lower Floridan (Boulder Zone) Aquifers, respectively, are roughly 1000 to 1800 ft and 2500 to 3000 ft below the surface of BNP. Historically, the aquifers are believed to be flowing slowly toward the shelf edge where they empty into the Florida Straits. Locally, these aquifers deepen eastward, and there is concern about leakage from the deep aquifer that is used for sewage disposal (McNeill, 2000). Regional changes in hydraulic head play the major role in flow of the Upper Floridan that has its recharge area in northwestern Florida. Lower Floridan flow is driven by an additional component of geothermal warming that causes warmer, lessdense water to rise beneath the Florida Platform and flow outward both on the Atlantic and Gulf of Mexico sides of the peninsula (Kohout, 1965). In Dade and Monroe Counties, artesian flow from wells drilled into these aquifers was encountered during exploratory well drilling. Natural springs and seeps from these aquifers are known to occur in north and central Florida as far south as 27° N, but not south of that latitude. Mud Hole Submarine Spring, believed to emanate from the Lower Floridan Aquifer, occurs in the Gulf of Mexico off Ft. Myers at 26° 15' 50" N (Fanning and others, 1981). No natural springs flowing from the Floridan Aquifer are known in Dade or Monroe Counties (Rosenau and others, 1998).