A test well drilled for Southwest Florida Water Management District at Sun City Center in Hillsborough County, will serve to monitor the interface between freshwater in the aquifer and the underlying chloride water. The sulfate content of the water in the aquifer at the well site exceeds 250 mg/L below a depth of about 700 feet. Wells for domestic and public supply in the area bottom at less than 500 feet and are separated from the sulfate water by about 100 feet of poorly-permeable limestone. The freshwater-chloride water interface is quite sharp and occurs at a depth of 1,410 feet. The chloride water is similar in composition to seawater but nearly twice as saline. (Woodard-USGS).