Saltwater can seep into the underground aquifers as "water from the Gulf of Mexico is pulled inland"
Protect our fragile aquifers from oil spill before too late, Sun-Sentinel (Ft. Lauderdale), June 20, 2010:
Millions of lives remain at risk of toxicity if the oil and dispersants seep into the groundwater and aquifers.
An aquifer is a water-bearing layer of rock, sediment or soil. While Florida is best known for its sunshine and beaches, its Floridan aquifer system is, according to the U.S. Geological Survey, one of the most productive aquifers in the world. The Floridan aquifer system and Biscayne aquifer are among only a few carbonate-rock aquifers in the United States. These aquifers supply drinking water to millions every day.
Yet, these massive carbonate rock aquifers are also most fragile and vulnerable. The Biscayne aquifer is surficial — that is, a shallow aquifer located close to the surface. Studies also define the Biscayne aquifer as, uniquely, an unconfined coastal aquifer that joins with the floor of Biscayne Bay and the Atlantic Ocean. Such features provide easy pathways for contaminants to flow due to the possibilities of saltwater intrusions and surface contaminations. ...
[T]he sources for numerous bottled waters available commercially in Florida — as an option to tap water — appear to be wells within close proximity to the Gulf of Mexico.
Assessing the Vulnerability of Public-Supply Wells to Contamination: Floridan Aquifer System Near Tampa, Florida, U.S. Geological Survey, September 14, 2009:
The well selected for study typically produces water at the rate of 700 gallons per minute from the Upper Floridan aquifer. ...
Samples of untreated water from the public-supply wellhead contained the undesirable constituents nitrate, arsenic, uranium, radon-222, volatile organic compounds (VOCs), and pesticides...
Roughly 50 percent of the simulated flow to the public-supply well consists of water less than about 10 years old, thus making the well vulnerable to contamination from human activities.
FARMS Program Conserves Water, Tampa Tribune, January 9, 2008:
Overuse of the aquifer means saltwater can seep into the underground freshwater. Water from the Gulf of Mexico is pulled inland as the aquifers recede.
Not all areas that use the Floridan for drinking water are at the same risk. Coastal regions are most vulnerable to seawater intrusion.
From the Summary of the Hydrology of the Floridan Aquifer System In Florida and In Parts of Georgia, South Carolina, and Alabama: "This figure shows the general distribution of dissolved-solids concentrations in water produced from wells that yield from the entire Upper Floridan... Higher concentrations are generally due to the presence of seawater in the system":