1. (a) Contents of the Texas Surface Water Quality Standards.

   1. (1) Section 307.1 of this title (relating to General Policy Statement) contains the general standards policy of the commission.
   2. (2) This section lists the major sections of the standards, defines basin classification categories, and describes justifications for standards modifications.
   3. (3) Section 307.3 of this title (relating to Definitions and Abbreviations) defines terms and abbreviations used in the standards.
   4. (4) Section 307.4 of this title (relating to General Criteria) lists the general criteria, which are applicable to all surface waters of the state unless specifically excepted in §307.8 of this title (relating to Application of Standards) or §307.9 of this title (relating to Determination of Standards Attainment).
   5. (5) Section 307.5 of this title (relating to Antidegradation) describes the antidegradation policy and implementation procedures.
   6. (6) Section 307.6 of this title (relating to Toxic Materials) establishes criteria and control procedures for specific toxic substances and total toxicity.
   7. (7) Section 307.7 of this title (relating to Site-specific Uses and Criteria) defines appropriate water uses and supporting criteria for site-specific standards.
   8. (8) Section 307.8 of this title (relating to Application of Standards) sets forth conditions under which portions of the standards do not apply--such as in mixing zones or below critical low-flows.
   9. (9) Section 307.9 of this title (relating to Determination of Standards Attainment) describes sampling and analytical procedures to determine standards attainment.

   10. (10) Section 307.10 of this title (relating to Appendices A-E) lists site-specific standards and supporting information for each classified segment (Appendices A-C), partially classified waterbodies (Appendix D), and site-specific criteria that may be derived for any waters in the state (Appendix E). Specific appendices are as follows:

       1. (A) Appendix A--Water Uses and Numerical Criteria;
       2. (B) Appendix B--Low Flow Criteria;
       3. (C) Appendix C--Segment Descriptions;
       4. (D) Appendix D--Site-specific Receiving Water Assessments.
       5. (E) Appendix E--Site-specific Criteria.
2. (b) Applicability. The Texas Surface Water Quality Standards apply to surface waters in the state--including wetlands.

3. (c) Classification of surface waters. The major surface waters of the state are classified as segments for purposes of water quality management and designation of site-specific standards. Classified segments are aggregated by basin, and basins are categorized as follows:

   1. (1) river basin waters. Surface inland waters comprising the major rivers, their tributaries, including listed impounded waters, and the tidal portion of rivers to the extent that they are confined in channels;
   2. (2) coastal basin waters. Surface inland waters, including listed impounded waters but exclusive of paragraph (1) of this subsection, discharging, flowing, or otherwise communicating with bays or the gulf, including the tidal portion of streams to the extent that they are confined in channels;
   3. (3) bay waters. All tidal waters, exclusive of those included in river basin waters, coastal basin waters, and gulf waters;
   4. (4) gulf waters. Waters which are not included in or do not form a part of any bay or estuary but which are a part of the open waters of the Gulf of Mexico to the limit of the state's jurisdiction.

4. (d) Modification of standards.

   1. (1) The commission reserves the right to amend these standards following the completion of special studies.
   2. (2) Any errors in water quality standards resulting from clerical errors or errors in data may be corrected by the commission through amendment of the affected standards. Water quality standards not affected by such clerical errors or errors in data remain valid until changed by the commission.
   3. (3) The narrative provisions, designated uses, and numerical criteria of the Texas Surface Water Quality Standards may be amended for a specific waterbody to account for local conditions. A site-specific standard is an explicit amendment to this title, Chapter 307 (Texas Surface Water Quality Standards), and adoption of a site-specific standard requires the procedures for public notice and hearing established under the Texas Water Code, §26.024 and §26.025. An amendment which establishes a site-specific standard will require a use-attainability analysis which demonstrates that reasonably attainable water-quality related uses will be protected. Upon adoption, site-specific amendments to the standards will be listed in §307.10 of this title.
   4. (4) When preliminary evidence indicates that a site-specific standards amendment is appropriate, the commission may allow a temporary variance to the water quality standards. A temporary variance is only applicable to an existing discharge facility. A permittee may apply for a temporary variance prior to or during the permit application process. The temporary variance request shall be included in the public notice for the permit application, and the request may be considered in any public hearing on the permit application. The temporary variance must have the approval of the Texas Natural Resource Conservation Commission before issuance of a final permit. A temporary variance for an NPDES permit will also require approval by the U.S. Environmental Protection Agency. The permit shall contain interim limits based upon the variance approval, and final limits based upon existing water quality standards. A variance shall not exceed a time period of three years. A temporary variance may be extended to allow additional time for a site-specific standard to be adopted in this title. This extension can be granted only after a site-specific study that supports a standards change has been completed. If the commission adopts the proposed site-specific standard prior to the expiration of the variance period, then the permit may be amended to meet the revised water quality standards. If the commission does not adopt the proposed site-specific standard prior to the expiration of the variance period, then the final effluent limits based on existing water quality standards will remain in effect, but the permit may be amended to include a permit schedule to meet standards in accordance with subsection (f) of this section.
   5. (5) Factors which may justify the development of site-specific standards are described in §307.4 of this title (relating to General Criteria), §307.6 of this title (relating to Toxic Materials), §307.7 of this title (relating to Site-specific Uses and Criteria), and §307.8 of this title (relating to Application of Standards).
5. (e) Implementation procedures. Provisions for implementing the water quality standards are described in a document entitled Implementation of the Texas Natural Resource Conservation Commission Standards via Permitting.
6. (f) Permit schedules to meet standards. Upon permit amendment or permit renewal, the commission may establish interim discharge limits to allow a permittee time to modify effluent quality in order to attain final effluent limits. The duration of any interim limit may not be longer than three years from the effective date of the permit issuance. An interim limit may be extended to allow additional time for a site-specific standard to be adopted in this title. This extension can be granted only after a site-specific study that supports a standards change has been completed, and the extension will only be granted for effluent limits that are affected by the site-specific standard under consideration.

Source Note:The provisions of this §307.2 adopted to be effective July 10, 1991, 16 TexReg 3400; amended to be effective July 13, 1995, 20 TexReg 4701.