Delineate: To indicate or represent by drawn lines.
Florida's extensive ground water resources serve as the drinking water source for 90% of the stateís 14 million people and 42 million annual visitors. These water resources are vulnerable to contamination because large areas are characterized by well-drained sandy soils overlying porous limestone. A shallow water table and high rainfall increase the potential for contamination to reach the ground water. These factors in combination exacerbate the threat of contamination to the quality of ground water resources and, in turn, to the quality and safety of drinking water.
Map Direct is a GIS web based application that can be used to search by location for delineated areas of ground water contamination as well as many other search capabilities. A quick tutorial to assist you with using this application is also available.
Human activities result in the production of a large number and variety of contaminants, including those associated with urban stormwater runoff and agricultural activity. From 1962 to mid 1983, for example, the Florida Department of Agriculture and Consumer Services conducted widespread field application of a soil fumigant, ethylene dibromide (EDB), to control nematodes in citrus groves. EDB was also used by private citizens on golf courses and on crops such as peanuts and soybeans. EDB is a carcinogenic compound determined by the U.S. Environmental Protection Agency to have the potential to produce adverse health affects from prolonged consumption. It is a potential threat to public health when present in drinking water. The primary drinking water standard for EDB is 0.02 micrograms per liter (parts per billion).
Discovery of EDB in drinking water wells in other states prompted Florida to test drinking water wells in 1983, and EDB was found to be present. To date, over 2,400 drinking water wells across Florida have been identified as being contaminated with EDB. Contaminated wells are typically remediated by granular activated carbon filter installation or connection to a municipal water system.
Because of the EDB in drinking water wells, the 1988 Legislature directed the Department of Environmental Protection to implement water well construction and water testing standards within areas of known ground water contamination. These actions were taken to protect public health and ground water resources, and to promote cost-effective remediation of contaminated potable water supplies [s. 373.309(1)(e), F.S.]. While areas have been delineated based on detection's of solvents and gasoline, EDB, detected in 38 counties statewide, has been the primary contaminant serving as the basis for the 427,897 acres delineated under Chapter 62-524 of the Florida Administrative Code.
The DEPís primary responsibility in the implementation of chapter 62-524 has been the delineation of areas of ground water contamination and the corresponding development of maps identifying those areas. The first step in producing a delineation map is reviewing ground water data from a variety of sources to determine where state ground water quality standards have been violated. The data are also reviewed to determine whether they were compiled under appropriate quality assurance procedures. The next step is assessing the spatial extent of the ground water contamination. If sufficient data are available, the extent of contamination is estimated using a geo-statistical tool called variogram analysis. Where data are incomplete, a 1000-foot protective setback is placed around the contaminated site or well to estimate the extent of the contaminated plume. The contaminated sites and associated plumes are plotted on maps and each plume is labeled with a unique identifier that can be used to determine the contaminants contained therein. A well permitted in a delineated area must be tested for the contaminants for which the area was delineated before it can be cleared for use.
Additionally, the DEP has delineated areas of Florida where EDB was historically applied but for which little or no ground water quality data exist. The available water quality data near EDB application sites suggest it is likely that contamination also would be found at EDB application sites where no wells (and, thus, no data) currently exist. Delineation of these areas will protect public health if future development occurs.
All delineation maps undergo rigorous internal review, and are adopted under chapter 120, F.S., rulemaking procedures, including public meetings and approval by the Environmental Regulation Commission. The latest maps produced by the DEP were approved in 1994.
Delineated areas are typically drawn within a 1000-foot setback from a contaminated site or well. Many EDB soil application sites are linear features termed "buffers." Setbacks around contaminated wells or buffers can range from 1000 to 5000 feet based on the distribution and movement of ground water contamination within specific regions or soil types. These setbacks are determined statistically to ensure that contaminated plumes are contained within calculated distances. Contaminated wells within 2000 feet of one another commonly result in overlapping delineated areas. Areal clusters containing many contaminated wells around known EDB application sites are found in many parts of Florida. This occurrence generates complex overlapping delineated areas. In Jackson County, for example, areas situated between setbacks in the northeast portion of the county were included in the delineation at the request of county officials and the Northwest Water Management District to simplify of the program.
Implementation of the delineation rule has been a cooperative effort among the DEP, the Department of Health, and the water management districts. After the DEP delineates areas of ground water contamination, the water management districts implement stricter well-construction standards through permitting requirements. Each permit application for a new well is reviewed to determine the wellís location relative to delineated areas. If the well is located in a delineated area, the water management district will either require more rigorous well construction standards or connection to a public water system. The Department of Health is responsible for the collection and testing of water samples.
Last updated: January 30, 2013
2600 Blair Stone Road M.S. 3500
Tallahassee, Florida 32399
850-245-8336 (phone) / 850-245-8356 (fax)