API PUBL 4756-2006 pdf download.Interim Permitting Manual— Navigating NPDES Permit Issues on Impaired Waters.
Water quality standards serve as the foundation of the listing process for impaired waters (also called the 303(d) process), because waters can only be listed if they are not meeting the state’s water quality standards. If the standards applicable to your receiving water are not appropriate, the basis of any impairment determination will be flawed. The Clean Water Act (CWA) sets forth the components of water quality standards as follows: … Such revised or new water quality standard shall consist of the designated uses of the navigable waters involved and the water quality criteria for such waters based upon such uses. … 1 Water quality standards therefore include designated uses and specific water quality criteria necessary to protect those uses. As discussed in more detail below, criteria may be numeric or narrative (e.g., “no toxics in toxic amounts”). In addition, the state’s antidegradation policy is considered to be part of its water quality standards. 2 States are required to adopt water quality standards applicable to waters within their jurisdictions, and to evaluate those waters to determine whether the standards are being met. As discussed in more detail below, waters that are not meeting standards will be considered impaired, and generally will be scheduled for TMDL development.
(1) Naturally occurring pollutant concentrations prevent the attainment of the use; or (2) Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State or Tribal water conservation requirements to enable uses to be met; (3) Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; (4) Dams, diversions or other types of hydrological modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in the attainment of a use; (5) Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or (6) Controls more stringent than those required by Sections 301(b) and 306 of the Act would result in substantial and widespread economic and social impact.
Criteria to Support Designated Uses Water quality criteria are established to protect designated uses, and must be scientifically sound: States must adopt those water quality criteria that protect the designated use. Such criteria must be based on sound scientific rationale and must contain sufficient parameters or constituents to protect the designated use. For waters with multiple use designations, the criteria shall support the most sensitive use. 25 Waters are evaluated for listing purposes based on whether they meet the state’s water quality standards, which include the designated use classifications and the criteria necessary to support those classifications. Waters that do not meet a criterion for a specific pollutant—or that do not meet the statutory thermal requirements—must be included on the state’s 303(d) List, and will be scheduled for TMDL development, with a few limited exceptions. The process a state must follow to assess waters in comparison to water quality criteria, including listing methodologies and data quality requirements, is discussed in more detail later in this manual. Federal regulations set forth the procedures a state must follow to adopt criteria for toxic pollutants: Toxic Pollutants. States must review water quality data and information on discharges to identify specific water bodies where toxic pollutants may be adversely affecting water quality or the attainment of the designated water use or where the levels of toxic pollutants are at a level to warrant concern and must adopt criteria for such toxic pollutants applicable to the water body sufficient to protect the designated use. Where a State adopts narrative criteria for toxic pollutants to protect designated uses, the State must provide information identifying the method by which the State intends to regulate point source discharges of toxic pollutants on water quality limited segments based on such narrative criteria.