Upward migration of deep-well waste injection fluids in Floridan Aquifer, south Florida

Geochemical data from an industrial deep-well waste injection system southeast of Lake Okeechobee indicate a decrease in sulfate concentration concomitant with an increase in hydrogen sulfide concentration, a result of oxidation of injected organic waste by anaerobic bacteria. Subtle decreases in the sulfate-chloride ratio suggest that the waste migrated upward to a shallow monitor well about 27 mo after waste injection began and again within 15 mo of the resumption of waste injection after the injection well was deepened. The possibility of a hydraulic connection between the injection zone and overlying monitoring zone is implied. The decrease in the sulfate-chloride ratio appears to be a sensitive indicator of waste migration. Potential conflicts exist in the use of the Floridan aquifer for waste disposal and subsequent use as a natural resource.