Home Abstract Introduction Hydrogeology of S. Florida Ground-Water Movement >Subsurface Storage - Oil Field Brine - Liquid Wastes - Freshwater Storage Summary and Conclusions References PDF Version

Subsurface Storage in the Floridan Aquifer System in Southern Florida

Subsurface storage is the practice of emplacing fluids in permeable underground rocks (aquifers) by gravity flow or pressure-induced injection through wells. The receiving rocks must have sufficient confinement, porosity, and permeability to accept the fluids without endangering underground sources of drinking water. In most cases the fluids are nontoxic liquid wastes that cannot easily be disposed of at the surface. In some cases, however, the fluids are valuable and are temporarily emplaced underground for later recovery. The subsurface storage practice is commonly referred to as "underground injection," "deep disposal," and "deep-well injection."

The practice of injecting nontoxic liquid wastes into saline parts of the Floridan aquifer system began in 1943 at an oil field in Collier County (fig. 28, site 1); oil field brine was injected into the cavernous, saltwater-filled Boulder Zone of the Lower Floridan aquifer (Vernon, 1970). The injection of treated municipal wastewater into brackish zones of the Upper Floridan aquifer began in 1959 at a wastewater-treatment plant (fig. 28, site 14) in Broward County (McKenzie and Irwin, 1984). Injection of treated municipal wastewater into the saltwater-filled Boulder Zone began in 1971 at a wastewater-treatment plant (fig. 28, site 16) in Dade County (Meyer, 1974). Injection of industrial liquid wastes (chiefly acetic acid) into brackish zones of the Upper Floridan aquifer began in 1966 at a furfural plant (fig. 28, site 15) in Palm Beach County (Kaufman and McKenzie, 1975).

Figure 28. Location of oil fields, municipal and industrial deep-well injection systems, and freshwater injection pilot projects, southern Florida. [larger version]

Prior to 1970, regulation of injection wells was a principal function of the Florida State Board of Health (chapter 170C-3, Florida Administrative Code), and permits were issued as though the injection well were a drainage well. The criterion for issuing the permit was that the receiving rocks contain water that was nonpotable and salty (water having a chloride concentration of 1,500 mg/L or more). Subsequent assignment of the permitting function to the Florida Department of Pollution Control in about 1970 led to more stringent regulation, and permits were issued only after thorough review by the Florida Department of Natural Resources, the State Board of Health, and the local Water Management District in consultation with the U.S. Geological Survey.

As injection wells proliferated in the early 1970's, the Federal Government became increasingly concerned about the impact of deep-well disposal practices on drinking-water supplies. In 1974, Congress passed the Safe Drinking Water Act (Public Law 93-523, as amended by Public Law 95-190), which required the U.S. Environmental Protection Agency (EPA) to develop and publish regulatory and minimum requirements to control underground injection. The regulations, called UIC (underground injection control) regulations, were published in the Congressional Federal Register on June 24, 1980 (chapter 40, parts 122 and 146). Responsibility for development and enforcement of the UIC regulations along the lines established by the EPA, for all but Class II injection wells, was delegated to the Florida Department of Environmental Regulation in 1983. The regulation of injection wells associated with oil and gas production, Class II injection wells, is administered by the Florida Bureau of Geology, Florida Department of Natural Resources (chapter 377, Florida Statutes and Rules 16C-2 and 16C-26 through 16C-30, Florida Administrative Code), and by the EPA.

All injection wells other than those associated with oil and gas production are regulated by the Florida Department of Environmental Regulation (chapter 17-28, Florida Administrative Code). The purposes of the UIC regulations are to protect the quality of the State's underground sources of drinking water and to prevent degradation of the quality of other aquifers adjacent to the injection zone. They regulate the location, construction, operation, and monitoring of injection wells so that the injection does not interfere with any designated use of ground water or cause violations of water-quality standards for underground sources of drinking water. An underground source of drinking water is defined by the State as an aquifer or its portion that supplies drinking water for human consumption, or is classified by rule 17-3.403, Florida Administrative Code, as Class G-I or G-II water, and is not an exempted aquifer. In general, ground water having a dissolved solids concentration of 10,000 mg/L or less is protected by the UIC regulations.

This section of the report is concerned with Class I injection wells, those that are used to inject municipal and industrial wastewater, Class II injection wells, those that are used to inject oil field brine, and Class V, Group 2, injection wells, those that are used to inject freshwater for storage.