§ 125.62 Attainment or maintenance of water quality which assures protection of public water supplies; assures the protection and propagation of a balanced indigenous population of shellfish, fish, and wildlife; and allows recreational activities.

(a) Physical characteristics of discharge. (1) At the time the 301(h) modification becomes effective, the applicant's outfall and diffuser must be located and designed to provide adequate initial dilution, dispersion, and transport of wastewater such that the discharge does not exceed at and beyond the zone of initial dilution:

(i) All applicable water quality standards; and

(ii) All applicable EPA water quality criteria for pollutants for which there is no applicable EPA-approved water quality standard that directly corresponds to the EPA water quality criterion for the pollutant.

(iii) For purposes of paragraph (a)(1)(ii) of this section, a State water quality standard “directly corresponds” to an EPA water quality criterion only if:

(A) The State water quality standard addresses the same pollutant as the EPA water quality criterion and

(B) The State water quality standard specifies a numeric criterion for that pollutant or State objective methodology for deriving such a numeric criterion.

(iv) The evaluation of compliance with paragraphs (a)(1) (i) and (ii) of this section shall be based upon conditions reflecting periods of maximum stratification and during other periods when discharge characteristics, water quality, biological seasons, or oceanographic conditions indicate more critical situations may exist.

(2) The evaluation under paragraph (a)(1)(ii) of this section as to compliance with applicable section 304(a)(1) water quality criteria shall be based on the following:

(i) For aquatic life criteria: The pollutant concentrations that must not be exceeded are the numeric ambient values, if any, specified in the EPA section 304(a)(1) water quality criteria documents as the concentrations at which acute and chronic toxicity to aquatic life occurs or that are otherwise identified as the criteria to protect aquatic life.

(ii) For human health criteria for carcinogens: (A) For a known or suspected carcinogen, the Administrator shall determine the pollutant concentration that shall not be exceeded. To make this determination, the Administrator shall first determine a level of risk associated with the pollutant that is acceptable for purposes of this section. The Administrator shall then use the information in the section 304(a)(1) water quality criterion document, supplemented by all other relevant information, to determine the specific pollutant concentration that corresponds to the identified risk level.