1. (a) Uses and numerical criteria are established on a site-specific basis for classified segments in Appendix A 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 limits 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 subcategories--contact recreation waters and noncontact recreation waters. Classified segments will be designated for contact recreation unless elevated fecal coliform bacteria concentrations frequently occur due to sources of pollution which cannot be reasonably controlled by the 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 the fecal coliform 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. Fecal coliform 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 pathogenic bacteria. Even where the concentration of fecal coliform is below the criteria for contact recreation, there is still some risk of contracting waterborne diseases.

      1. (A) Contact recreation waters.

         1. (i) Fecal coliform content shall not exceed 200 colonies per 100 ml as a geometric mean based on a representative sampling of not less than five samples collected over not more than 30 days.
         2. (ii) Fecal coliform content shall not equal or exceed 400 colonies per 100 ml in more than 10% of all samples, but based on at least five samples, taken during any 30-day period. If 10 or fewer samples are analyzed, no more than one sample shall exceed 400 colonies per 100 ml.

      2. (B) Noncontact recreation waters.

         1. (i) Fecal coliform content shall not exceed 2,000 colonies per 100 ml as a geometric mean based on a representative sampling of not less than five samples collected over not more than 30 days.
         2. (ii) Fecal coliform content shall not equal or exceed 4,000 colonies per 100 ml in more than 10% of all samples, but based on at least five samples, taken during any 30-day period. If 10 or fewer samples are analyzed, no more than one sample shall exceed 4,000 colonies per 100 ml.

   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 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.

      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 definitions 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 unclassified streams which have significant aquatic life uses, and to streams which are specifically listed in Appendix D of §307.10 of this title. The criteria in Table 5 apply to all parts of 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 to determine discharge effluent limits necessary to achieve dissolved oxygen criteria. 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 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 or streams which are specifically listed in Appendix A of §307.10 of this title.
         3. (iii) The dissolved oxygen criteria in Table 5 are based upon data from the commission'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.
            Attached Graphic
            

      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). Fecal coliform content in buffer zones shall not exceed 200 colonies per 100 ml as a geometric mean of not less than five samples collected over not more than 30 days or equal or exceed 400 colonies per 100 ml in more than 10% of all samples taken during a 30-day period.
         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 United States 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 or this title (relating to Toxic Materials).
   5. (5) Additional uses. Other basic uses, such as navigation, agricultural water supply, and industrial water 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.