CATEGORY 4b - A REGULATORY ALTERNATIVE TO TMDLs

Section 303(d) of the Clean Water Act and the US Environmental Protection Agency’s (USEPA’s) supporting regulations in 40 CFR Part 130.7 require states to develop lists of waterbodies impaired by a pollutant and needing a Total Maximum Daily Load (TMDL) (i.e., the Section 303(d) list) and to prepare a TMDL for each waterbody/pollutant combination. USEPA’s regulations also recognize that other pollution control requirements may obviate the need for a TMDL. These alternatives to TMDLs are commonly referred to as Category 4b waters as described in USEPA’s Integrated Reporting Guidance for Sections 303(d), 305(b), and 314 of the Clean Water Act. A survey was conducted in July 2006 to assess the extent to which states have successfully employed TMDL alternatives to address impaired waters and assigned these waters to Category 4b. This paper presents the results of the survey and summarizes several examples of impaired waters assigned to Category 4b in the State of Washington based on alternatives to TMDLs.