1. (a) Uses and numerical criteria are established on a site-specific basis in Appendices A, D, amd E of §307.10 of this title (relating to Appendices A - E). Site-specific uses and numerical criteria may also be applied to unclassified waters in accordance with §307.4(h) of this title (relating to General Criteria) and §307.5(c) of this title (relating to Antidegradation). Site-specific criteria apply specifically to substances attributed to waste discharges or the activities of man. Site-specific criteria do not apply to those instances in which surface waters exceed criteria due to natural phenomena. The application of site-specific uses and criteria is described in §307.8 of this title (relating to the Application of Standards) and §307.9 of this title (relating to the Determination of Standards Attainment).

2. (b) Appropriate uses and criteria for site-specific standards are defined as follows.

   1. (1) Recreation. Recreational use consists of two categories--contact recreation waters and noncontact recreation waters. Classified segments are designated for contact recreation unless elevated concentrations of indicator bacteria frequently occur due to sources of pollution which cannot be reasonably controlled by existing regulations or contact recreation is considered unsafe for other reasons such as ship or barge traffic. In a classified segment where contact recreation is considered unsafe for reasons unrelated to water quality, a designated use of noncontact recreation may be assigned criteria normally associated with contact recreation. A designation of contact recreation is not a guarantee that the water so designated is completely free of disease-causing organisms. Indicator bacteria, although not generally pathogenic, are indicative of potential contamination by feces of warm blooded animals. The criteria for contact recreation are based on these indicator bacteria, rather than direct measurements of pathogens. Criteria are expressed as the number of "colony forming units" of bacteria per 100 milliliters (ml) of water. Even where the concentration of indicator bacteria is less than the criteria for contact recreation, there is still some risk of contracting waterborne diseases. Additional guidelines on minimum data requirements and procedures for evaluating standards attainment are specified in the latest approved version of the TNRCC Guidance for Screening and Assessing Texas Surface and Finished Drinking Water Quality Data.

      1. (A) Freshwater

         1. (i) Contact recreation. The geometric mean of E. coli should not exceed 126 per 100 ml. In addition, single samples of E. coli should not exceed 394 per 100 ml. Contact recreation applies to all bodies of freshwater except where specifically designated otherwise in §307.10 of this title.
         2. (ii) Noncontact recreation. The geometric mean of E. coli should not exceed 605 per 100 ml.

      2. (B) Saltwater.

         1. (i) Contact recreation. The geometric mean of Enterococci should not exceed 35 per 100 ml. In addition, single samples of Enterococci should not exceed 89 per 100 ml. Contact recreation applies to all bodies of saltwater, except where specifically designated otherwise in §307.10 of this title.
         2. (ii) Noncontact recreation. The geometric mean of Enterococci should not exceed 168 per 100 ml.

      3. (C) Fecal coliform bacteria. Fecal coliform bacteria can be used as an alternative instream indicator of recreational suitability until sufficient data are available for E coli or Enterococci. For segments designated as oyster waters in §307.10 of this title, fecal coliform can continue to be used as an indicator of recreational suitability because fecal coliform is used as the indicator for suitability of oyster water use as described in paragraph (3)(B) of this subsection. Fecal coliform can also continue to be used as a surrogate indicator in effluent limits for wastewater discharges. Fecal coliform criteria are the same for both freshwater and saltwater, as follows.

         1. (i) Contact recreation. The geometric mean of fecal coliform should not exceed 200 per 100 ml. In addition, single samples of fecal coliform should not exceed 400 per 100 ml.
         2. (ii) Noncontact recreation. Fecal coliform shall not exceed 2,000 per 100 ml as a geometric mean. In addition, single samples of fecal coliform should not exceed 4,000 per 100 ml.
      4. (D) Swimming advisory programs. For areas where local jurisdictions or private property owners voluntarily provide public notice or closure based on water quality, the use of any single-sample or short-term indicators of recreational suitability are selected at the discretion of the local managers of aquatic recreation. Guidance for single-sample bacterial indicators is available in the EPA document entitled Ambient Water Quality Criteria for Bacteria--1986. Other short-term indicators to assess water quality suitability for recreation--such as measures of streamflow, turbidity, or rainfall--may also be appropriate.

   2. (2) Domestic water supply.

      1. (A) Use categories. Domestic water supply consists of two use subcategories--public water supply and aquifer protection.

         1. (i) Public water supply. Segments designated for public water supply are those known to be used or exhibit characteristics that would allow them to be used as the supply source for public water systems, as defined by Chapter 290 of this title (relating to Water Hygiene).
         2. (ii) Aquifer protection. Segments designated for aquifer protection are capable of recharging the Edwards Aquifer. The principal purpose of this use designation is to protect the quality of water infiltrating into and recharging the aquifer. The designation for aquifer protection applies only to those portions of the segments so designated that are on the recharge zone, transition zone, or contributing zone as defined in Chapter 213 of this title (relating to the Edwards Aquifer). Chapter 213 of this title establishes provisions for activities in the watersheds of segments which are designated for aquifer protection.

      2. (B) Use criteria. The following use criteria apply to both domestic water supply use subcategories.

         1. (i) Radioactivity associated with dissolved minerals in the freshwater portions of river basin and coastal basin waters should not exceed levels established by drinking water standards as specified in Chapter 290 of this title unless the conditions are of natural origin.
         2. (ii) Surface waters utilized for domestic water supply shall not exceed toxic material concentrations that prevent them from being treated by conventional surface water treatment to meet drinking water standards as specified in Chapter 290 of this title.
         3. (iii) Chemical and microbiological quality of surface waters used for domestic water supply should conform to drinking water standards as specified in Chapter 290 of this title.

   3. (3) Aquatic life. The establishment of numerical criteria for aquatic life is highly dependent on desired use, sensitivities of usual aquatic communities, and local physical and chemical characteristics. Five subcategories of aquatic life use are established. They include limited, intermediate, high, and exceptional aquatic life and oyster waters. Aquatic life use subcategories designated for segments listed in Appendix A of §307.10 of this title recognize the natural variability of aquatic community requirements and local environmental conditions.

      1. (A) Dissolved oxygen.

         1. (i) The characteristics and associated dissolved oxygen criteria for limited, intermediate, high, and exceptional aquatic life use subcategories are indicated in Table 4.
            Attached Graphic
            
         2. (ii) The dissolved oxygen criteria and associated critical low-flow values in Table 5 apply to streams which have significant aquatic life uses, and to streams which are specifically listed in Appendix A or D of §307.10 of this title. The criteria in Table 5 apply to streams in Texas which are east of a line defined by Interstate Highway 35 and 35W from the Red River to the community of Moore in Frio County, and by U.S. Highway 57 from the community of Moore to the Rio Grande. The critical low-flow values in Table 5 (at the appropriate stream bedslope) will be utilized as headwater flows when the flows are larger than applicable 7Q2 flows, in order to determine discharge effluent limits necessary to achieve dissolved oxygen criteria. For streams which have bedslopes less than the minimum bedslopes in Table 5, the flows listed for the minimum bedslope of 0.1 m/km will be applicable. For streams which have bedslopes greater than the maximum bedslope in Table 5, the flows listed for the maximum bedslope of 2.4 m/km will be applicable. The required effluent limits will be those necessary to achieve each level of dissolved oxygen (as defined in clause (i) of this subparagraph, Table 4) at or below an assigned, designated, or presumed aquatic life use. Presumed aquatic life uses will be in accordance with those required by §307.4(h) of this title. The dissolved oxygen criteria in Table 5 do not apply to tidal streams.
            Attached Graphic
            
         3. (iii) The dissolved oxygen criteria in Table 5 are based upon data from the agency's least impacted stream study (Texas Aquatic Ecoregion Project). Results of this study indicate a strong dependent relationship for average summertime background dissolved oxygen concentrations and several hydrologic and physical stream characteristics--particularly bedslope (stream gradient) and stream flow. The dissolved oxygen criteria in Table 5 are derived from a multiple regression equation for the eastern portion of Texas as defined in clause (ii) of this subparagraph. Further explanation of the development of the regression equation and its application will be contained in the standards implementation procedures.
         4. (iv) The critical low-flow values in Table 5 may be adjusted based on site-specific data relating dissolved oxygen concentrations to factors such as flow, temperature, or hydraulic conditions in accordance with the standards implementation procedures. Site-specific, critical low-flow values require approval by the agency. EPA will review any site-specific, critical low-flow values that could affect permits or other regulatory actions that are subject to approval by EPA. Critical low-flow values which have been determined for particular streams are listed in §307.10 of this title when standards are revised.

      2. (B) Oyster waters.

         1. (i) A 1,000 foot buffer zone, measured from the shoreline at ordinary high tide, is established for all bay and gulf waters, except those contained in river or coastal basins as defined in §307.2 of this title (relating to Description of Standards). Recreational criteria for indicator bacteria, as specified in §307.10(b)(1) of this title, are applicable within buffer zones.
         2. (ii) Median fecal coliform concentration in bay and gulf waters, exclusive of buffer zones, shall not exceed 14 colonies per 100 ml, with not more than 10% of all samples exceeding 43 colonies per 100 ml.
         3. (iii) Oyster waters should be maintained so that concentrations of toxic materials do not cause edible species of clams, oysters, and mussels to exceed accepted guidelines for the protection of public health. Guidelines are provided by U. S. Food and Drug Administration Action Levels for molluscan shellfish.

   4. (4) Additional criteria.

      1. (A) Chemical parameters. Site-specific criteria for chloride, sulfate, and total dissolved solids are established as averages over an annual period for either a single sampling point or multiple sampling points.
      2. (B) pH. Site-specific numerical criteria for pH are established as absolute minima and maxima.
      3. (C) Temperature. Site-specific temperature criteria are established as absolute maxima.
      4. (D) Toxic materials. Criteria for toxic materials are established in §307.6 of this title (relating to Toxic Materials).
   5. (5) Additional uses. Other basic uses, such as navigation, agricultural water supply, industrial water supply, seagrass propagation, and wetland water quality functions will be maintained and protected for all water in the state in which these uses can be achieved.

Source Note:The provisions of this §307.7 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.