ANTI-BACKSLIDING.

SEC. 404. ANTI-BACKSLIDING. (a) General Rule.—Section 402 is amended by adding at the end thereof the following new subsection: “(o) Anti-Backsliding.— “(1) General prohibition.—In the case of effluent limitations established on the basis of subsection (a)(1)(B) of this section, a permit may not be renewed, reissued, or modified on the basis of effluent guidelines promulgated under section 304(b) subsequent to the original issuance of such permit, to contain effluent limitations which are less stringent than the comparable effluent limitations in the previous permit. In the case of effluent limitations established on the basis of section 301(b)(1)(C) or section 303 (d) or (e), a permit may not be renewed, reissued, or modified to contain effluent limitations which are less stringent than the comparable effluent limitations in the previous permit except in compliance with section 303(d)(4). “(2) Exceptions.—A permit with respect to which paragraph (1) applies may be renewed, reissued, or modified to contain a less stringent effluent limitation applicable to a pollutant if— “(A) material and substantial alterations or additions to the permitted facility occurred after permit issuance which justify the application of a less stringent effluent limitation; 101 STAT. 68 “(B)(i) information is available which was not available at the time of permit issuance (other than revised regulations, guidance, or test methods) and which would have justified the application of a less stringent effluent limitation at the time of permit issuance; or “(ii) the Administrator determines that technical mistakes or mistaken interpretations of law were made in issuing the permit under subsection (a)(1)(B); “(C) a less stringent effluent limitation is necessary because of events over which the permittee has no control and for which there is no reasonably available remedy; “(D) the permittee has received a permit modification under section 301(c), 301(g), 301(h), 301(i), 301(k), 301(n), or 316(a); or “(E) the permittee has installed the treatment facilities required to meet the effluent limitations in the previous permit and has properly operated and maintained the facilities but has nevertheless been unable to achieve the previous effluent limitations, in which case the limitations in the reviewed, reissued, or modified permit may reflect the level of pollutant control actually achieved (but shall not be less stringent than required by effluent guidelines in effect at the time of permit renewal, reissuance, or modification). Subparagraph (B) shall not apply to any revised waste load allocations or any alternative grounds for translating water quality standards into effluent limitations, except where the cumulative effect of such revised allocations results in a decrease in the amount of pollutants discharged into the concerned waters, and such revised allocations are not the result of a discharger eliminating or substantially reducing its discharge of pollutants due to complying with the requirements of this Act or for reasons otherwise unrelated to water quality. “(3) Limitations.—In no event may a permit with respect to which paragraph (1) applies be renewed, reissued, or modified to contain an effluent limitation which is less stringent than required by effluent guidelines in effect at the time the permit is renewed, reissued, or modified. In no event may such a permit to discharge into waters be renewed, reissued, or modified to contain a less stringent effluent limitation if the implementation of such limitation would result in a violation of a water quality standard under section 303 applicable to such waters.”. (b) Limitations on Revision of Certain Effluent Limitations.— Section 303(d) of the Act is amended by adding at the end thereof the following new paragraph: “(4) Limitations on revision of certain effluent limitations.— “(A) Standard not attained.—For waters identified under paragraph (1)(A) where the applicable water quality standard has not yet been attained, any effluent limitation based on a total maximum daily load or other waste load allocation established under this section may be revised only if (i) the cumulative effect of all such revised effluent limitations based on such total maximum daily load or waste load allocation will assure the attainment of such water quality standard, or (ii) the designated use which is 101 STAT. 69not being attained is removed in accordance with regulations established under this section. “(B) Standard attained.—For waters identified under paragraph (1)(A) where the quality of such waters equals or exceeds levels necessary to protect the designated use for such waters or otherwise required by applicable water quality standards, any effluent limitation based on a total maximum daily load or other waste load allocation established under this section, or any water quality standard established under this section, or any other permitting standard may be revised only if such revision is subject to and consistent with the antidegradation policy established under this section.”. (c) Study.—The Administrator shall study— (1) the extent to which States have reviewed, revised, and adopted water quality standards in accordance with section 24 of the Municipal Wastewater Treatment Construction Grant Amendments of 1981; and (2) the extent to which modifications of permits issued under section 402(a)(1)(B) of the Federal Water Pollution Control Act for the purpose of reflecting any revisions to water quality standards should be encouraged or discouraged. The Administrator shall submit a report on such study, together with recommendations, to Congress not later than 2 years after the date of the enactment of this Act. (d) Conforming Amendment.—Section 402(a)(1) is amended by inserting “(A)” after “either” and by inserting “(B)” after “this Act, or”.