WHAT ARE SOURCE WATER PROTECTION AREAS AND HOW ARE THEY DELINEATED?
A Source Water Protection Area defines the zone through which contaminants, if present, are likely to migrate and reach a drinking water well or surface water intake. Every public water system obtains its water from either a ground water source (aquifer) or a surface water source (stream, river, reservoir or lake). Delineation of source water protection areas is based on the source of the water supply.
Delineation for Ground Water Systems
For assessment and protection of ground water supplied public water systems, the Arbitrary Fixed Radius Method of delineation will be used. The Arbitrary Fixed Radius Method is the established method for the State's U.S. EPA approved Wellhead Protection Program, a protection program for ground water systems implemented since 1991. This method is most appropriate for Louisiana due to the highly variable nature of river laid deposits across the state and the lack of site-specific hydrogeologic data (aquifer data). Radius sizes based on vulnerability of the well in order of priority are as follows:
- A one-mile fixed radius for wells screened above 1000 feet.
- A half-mile fixed radius for wells screened below 1000 feet and completed before Louisiana Department of Transportation and Development (LDOTD) regulations promulgated November 1, 1985.
- A 1000-foot radius for wells screened below 1000 feet and completed after LDOTD regulations were promulgated.
- A half-mile radius for transient non-community wells in the Terrace Aquifer.
- A 1000-foot radius for all other transient non-community wells.
Delineation for Surface Water Systems
Delineation of Source Water Protection Areas for surface water bodies will include the entire watershed upstream of the public water supply intake structure up to the boundary of the state borders. However, for the purpose of assessment, a database assessment will be done for potential sources of contamination over the portion of the watershed contributing to the water intake that is outside of the field assessment area, the non-critical area. The field assessment will be conducted in the critical area which is defined as the upstream portion of the watershed within 5 miles of the intake.