(a) Application. The antidegradation policy and implementation procedures set forth in this section apply to actions regulated under state and federal authority that would increase pollution of the water in the state. Such actions include authorized wastewater discharges, total maximum daily loads (TMDLs), waste load evaluations, and any other miscellaneous actions, such as those related to man-induced nonpoint sources of pollution, that may impact the water in the state.
(b) Antidegradation policy. In accordance with the Texas Water Code, §26.003, the following provisions establish the antidegradation policy of the commission.
  (1) Tier 1. Existing uses and water quality sufficient to protect those existing uses must be maintained. Categories of existing uses are the same as for designated uses, as defined in §307.7 of this title (relating to Site-Specific Uses and Criteria).
  (2) Tier 2. No activities subject to regulatory action that would cause degradation of waters that exceed fishable/swimmable quality are allowed unless it can be shown to the commission's satisfaction that the lowering of water quality is necessary for important economic or social development. Degradation is defined as a lowering of water quality by more than a de minimis extent, but not to the extent that an existing use is impaired. Water quality sufficient to protect existing uses must be maintained. Fishable/swimmable waters are defined as waters that have quality sufficient to support propagation of indigenous fish, shellfish, terrestrial life, and recreation in and on the water.
  (3) Tier 3. Outstanding national resource waters are defined as high quality waters within or adjacent to national parks and wildlife refuges, state parks, wild and scenic rivers designated by law, and other designated areas of exceptional recreational or ecological significance. The quality of outstanding national resource waters must be maintained and protected.
  (4) Discharges that cause pollution that are authorized by the Texas Water Code, the Federal Clean Water Act, or other applicable laws must not lower water quality to the extent that the Texas Surface Water Quality Standards are not attained.
  (5) Anyone discharging wastewater that would constitute a new source of pollution or an increased source of pollution from any industrial, public, or private project or development is required to provide a level of wastewater treatment consistent with the provisions of the Texas Water Code and the Clean Water Act (33 United States Code, §§1251 et seq.). As necessary, cost-effective and reasonable best management practices established through the Texas Water Quality Management Program are achieved for nonpoint sources of pollution.
  (6) Application of antidegradation provisions does not preclude the commission from establishing modified thermal discharge limitations consistent with the Clean Water Act, §316(a) (33 United States Code, §1326).
(c) Antidegradation implementation procedures.
  (1) Implementation for specific regulatory activities.
    (A) For TPDES permits for wastewater, the process for the antidegradation review and public coordination is described in the standards implementation procedures.
    (B) For federal permits relating to the discharge of fill or dredged material under Federal Clean Water Act, §404, the antidegradation policy and public coordination is implemented through the evaluation of alternatives and mitigation under Federal Clean Water Act, §404(b)(1). State review of alternatives, mitigation, and requirements to protect water quality may also be conducted for federal permits that are subject to state certification, as authorized by Federal Clean Water Act, §401 and conducted in accordance with Chapter 279 of this title (relating to Water Quality Certification).
    (C) Other state and federal permitted and regulated activities that increase pollution of water in the state are also subject to the provisions of the antidegradation policy as established in subsections (a) and (b) of this section.
  (2) General provisions for implementing the antidegradation policy.
    (A) Tier 1 reviews must ensure that water quality is sufficiently maintained so that existing uses are protected. All pollution that could cause an impairment of water quality is subject to Tier 1 reviews. If the existing uses and criteria of a potentially affected water body have not been previously determined, then the antidegradation review must include a preliminary determination of existing uses and criteria. Existing uses must be maintained and protected.
    (B) Tier 2 reviews apply to all pollution that could cause degradation of water quality where water quality exceeds levels necessary to support propagation of fish, shellfish, terrestrial life, and recreation in and on the water (fishable/swimmable quality). Guidance for determining water bodies that exceed fishable/swimmable quality is contained in the standards implementation procedures. For dissolved oxygen, analyses of degradation under Tier 2 must utilize the same critical conditions as are used to protect instream criteria. For other parameters, appropriate conditions may vary. Conditions for determining degradation are commensurate with conditions for determining existing uses. The highest water quality sustained since November 28, 1975 (in accordance with EPA Standards Regulation 40 Code of Federal Regulations Part 131) defines baseline conditions for determinations of degradation.
    (C) Tier 3 reviews apply to all pollution that could cause degradation of outstanding national resource waters. Outstanding national resource waters are those specifically designated in this chapter.
    (D) When degradation of waters exceeding fishable/swimmable quality is anticipated, a statement that the antidegradation policy is pertinent to the permit action must be included in the public notice for the permit application or amendment. If no degradation is anticipated, the public notice must so state.
    (E) Evidence can be introduced in public hearings, or through the public comment process, concerning the determination of existing uses and criteria; the assessment of degradation under Tier 1, Tier 2, and Tier 3; the social and economic justification for lowering water quality; requirements and conditions necessary to preclude degradation; and any other issues that bear upon the implementation of the antidegradation policy.
    (F) Interested parties are given the opportunity to provide comments and additional information concerning the determination of existing uses, anticipated impacts of the discharge, baseline conditions, and the necessity of the discharge for important economic or social development if degradation of water quality is expected under Tier 2.
    (G) The antidegradation policy and the general provisions for implementing the antidegradation policy apply to the determination of TMDLs and to waste load evaluations that allow an increase in loading. If the TMDL or waste load evaluation indicates that degradation of waters exceeding fishable/swimmable quality is expected, the public hearing notice must so state. Permits that are consistent with an approved TMDL or waste load evaluation under this antidegradation policy are not subjected to a separate antidegradation review for the specific parameters that are addressed by the TMDL or waste load evaluation.

Source Note: The provisions of this §307.5 adopted to be effective July 10, 1991, 16 TexReg 3400; amended to be effective July 13, 1995, 20 TexReg 4701; amended to be effective August 17, 2000, 25 TexReg 7722; amended to be effective July 22, 2010, 35 TexReg 6294