THE SANDSTONE AQUIFER OF SOUTHWEST FLORIDA: INTERMEDIATE AQUIFER SYSTEM OR SURFICIAL AQUIFER SYSTEM?

The Sandstone Aquifer occurs within at least 5 Southwest Florida counties, underlying more than 6500 square kilometers of area. This predominantly freshwater aquifer has been placed into the Intermediate Aquifer System within the hydrostratigraphic nomenclature of Florida. Within the stratigraphic framework, the aquifer lies within the Peace River Formation of the Hawthorn Group and some of the overlying Pliocene and Pleistocene sediments. It is in direct hydraulic contact with the Surficial Aquifer System in Glades, Charlotte, and parts of Lee and Collier counties. The pressure in the aquifer is atmospheric and the aquifer is unconfined in southern Glades County and in a 35 square kilometer area of Collier County. In southern Lee County, the aquifer merges with the Lower Tamiami Aquifer of the Surficial Aquifer System in the Bonita Springs area. Recharge to the aquifer occurs through direct entry of rainfall into the aquifer or by leakage from the overlying water-table aquifer through a subregional, semi-confining unit. Based on the direct connection to the Surficial Aquifer System and on the recharge characteristics of the aquifer, it should be classified as being in the Surficial System of Florida, not the Intermediate Aquifer System. The complex stratigraphic and hydraulic relationships between aquifers in Southwest Florida make classification a real challenge.