The Clean Water Act (CWA) requires states to identify all impaired waterbodies and include them on the Section 303(d) list during a biennial update to their Integrated Report.
The CWA also requires states to establish a priority ranking for impaired waters and to develop and implement a Total Maximum Daily Load (TMDL) for each §303(d)-listed impairment. Regulations at 40 CFR 130.7(c)(1) further require that “[e]ach State shall establish TMDLs for the water quality limited segments identified” in its Integrated Report. A TMDL is the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. It is defined as the sum of the individual waste load allocations (WLAs) for point sources and load allocations (LAs) for nonpoint sources, plus natural background (40 CFR §130.2). The purpose of a TMDL is to identify the pollutant load reductions needed to return a waterbody to attainment with water quality standards, thereby supporting the designated uses of the waterbody.
Practically speaking, a TMDL typically consists of identifying the pollutant of concern, estimating the waterbody’s assimilative capacity, estimating the existing pollutant loads from sources in the watershed, determining the allowable loading from the sources and the reductions needed to meet water quality standards, and allocating the pollutant load among the sources.
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The Clean Water Act (CWA) requires states to identify all impaired waterbodies and include them on the Section 303(d) list during a biennial update to their Integrated Report.
The CWA also requires states to establish a priority ranking for impaired waters and to develop and implement a Total Maximum Daily Load (TMDL) for each §303(d)-listed impairment. Regulations at 40 CFR 130.7(c)(1) further require that “[e]ach State shall establish TMDLs for the water quality limited segments identified” in its Integrated Report. A TMDL is the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. It is defined as the sum of the individual waste load allocations (WLAs) for point sources and load allocations (LAs) for nonpoint sources, plus natural background (40 CFR §130.2). The purpose of a TMDL is to identify the pollutant load reductions needed to return a waterbody to attainment with water quality standards, thereby supporting the designated uses of the waterbody.
Practically speaking, a TMDL typically consists of identifying the pollutant of concern, estimating the waterbody’s assimilative capacity, estimating the existing pollutant loads from sources in the watershed, determining the allowable loading from the sources and the reductions needed to meet water quality standards, and allocating the pollutant load among the sources.
Contact Information
*Indicates Required Fields