1. (a) Application. The general criteria set forth in this section apply to surface water in the state and specifically apply to substances attributed to waste discharges or the activities of man. General criteria do not apply to those instances in which surface water, as a result of natural phenomena, exhibit characteristics beyond the limits established by this section. General criteria are superseded by specific exemptions stated in this section or in §307.8 of this title (relating to the Application of Standards), or by site-specific water quality standards for classified segments. Provisions of the general criteria remain in effect in mixing zones or below critical low-flow conditions unless specifically exempted in §307.8 of this title (relating to the Application of Standards).

2. (b) Aesthetic parameters.

   1. (1) Concentrations of taste and odor producing substances shall not interfere with the production of potable water by reasonable water treatment methods, impart unpalatable flavor to food fish including shellfish, result in offensive odors arising from the waters, or otherwise interfere with the reasonable use of the water in the state.
   2. (2) Surface water shall be essentially free of floating debris and suspended solids that are conducive to producing adverse responses in aquatic organisms or putrescible sludge deposits or sediment layers which adversely affect benthic biota or any lawful uses.
   3. (3) Surface waters shall be essentially free of settleable solids conducive to changes in flow characteristics of stream channels or the untimely filling of reservoirs, lakes, and bays.
   4. (4) Surface waters shall be maintained in an aesthetically attractive condition.
   5. (5) Waste discharges shall not cause substantial and persistent changes from ambient conditions of turbidity or color.
   6. (6) There shall be no foaming or frothing of a persistent nature.
   7. (7) Surface waters shall be maintained so that oil, grease, or related residue will not produce a visible film of oil or globules of grease on the surface or coat the banks or bottoms of the watercourse; or cause toxicity to man, aquatic life, or terrestrial life in accordance with §307.4(d) of this title (relating to General Criteria).
3. (c) Radiological parameters. Radioactive materials shall not be discharged in excess of the amount regulated by Chapter 336 of this title (relating to Radiation Rules).
4. (d) Toxic parameters. Surface waters will not be toxic to man from ingestion of water, consumption of aquatic organisms, or contact with the skin, or to terrestrial or aquatic life. Additional standards requirements for toxic materials are specified in §307.6 of this title (relating to Toxic Materials).
5. (e) Nutrient parameters. Nutrients from permitted discharges or other controllable sources shall not cause excessive growth of aquatic vegetation which impairs an existing, attainable, or designated use. Site-specific nutrient criteria, nutrient permit limitations, and/or separate rules to control nutrients in individual watersheds will be established where appropriate after notice and opportunity for public participation and proper hearing.
6. (f) Temperature. Consistent with §307.1 of this title (relating to General Policy Statement) and in accordance with state water rights permits, temperature in industrial cooling lake impoundments and all other surface water in the state shall be maintained so as to not interfere with the reasonable use of such waters. Numerical temperature criteria have not been specifically established for industrial cooling lake impoundments, which in most areas of the state contribute to water conservation and water quality objectives. With the exception of industrial cooling impoundments, temperature elevations due to discharges of treated domestic (sanitary) effluent, and designated mixing zones, the following temperature criteria, expressed as a maximum temperature differential (rise over ambient) are established: freshwater streams -5 degrees Fahrenheit; freshwater lakes and impoundments--3 degrees Fahrenheit; tidal river reaches, bay and gulf waters--4 degrees Fahrenheit in fall, winter, and spring, and 1.5 degrees Fahrenheit in summer (June, July, and August). Additional temperature criteria (expressed as maximum temperatures) for classified segments are specified in Appendix A of §307.10 of this title (relating to Appendices A-E).

7. (g) Salinity.

   1. (1) Estuarine salinity criteria have not been established, despite the recognition that proper salinity gradient maintenance is important for the continuation of balanced and desirable populations of estuarine dependent marine life, because weather is the dominant factor influencing salinity gradients.
   2. (2) Absence of numerical salinity criteria shall not preclude evaluations and regulatory actions based on estuarine salinity, and careful consideration will be given to all activities which may detrimentally affect salinity gradients in estuarine waters.
   3. (3) Concentrations and the relative ratios of dissolved minerals such as chlorides, sulfates, and total dissolved solids will be maintained such that attainable uses will not be impaired.

8. (h) Dissolved oxygen and aquatic life uses.

   1. (1) Dissolved oxygen criteria for unclassified waters with aquatic life uses will be sufficient to support appropriate aquatic life use categories, in accordance with §307.7 of this title (relating to Site-specific Uses and Criteria). Perennial streams, rivers, lakes, bays, estuaries, and other appropriate perennial waters which are not specifically listed in Appendix A or D of §307.10 of this title are presumed to have a high aquatic life use and corresponding dissolved oxygen criteria. In accordance with results from statewide ecoregion studies, unclassified perennial streams in southeast and northeast Texas are assigned dissolved oxygen criteria as indicated in §307.7(b)(3)(A)(ii) of this title. Higher uses will be maintained where they are attainable.
   2. (2) Intermittent streams which are not specifically listed in Appendix A or D of §307.10 of this title will maintain a 24-hour dissolved oxygen mean of 2.0 mg/L and an absolute minimum dissolved oxygen concentration of 1.5 mg/L. For intermittent streams with seasonal aquatic life uses, dissolved oxygen concentrations commensurate with the aquatic life uses will be maintained during the seasons in which the aquatic life uses occur. Unclassified intermittent streams with significant aquatic life uses created by perennial pools are presumed to have a limited aquatic life use and corresponding dissolved oxygen criteria. Additional definitions of significant aquatic life, perennial pools, and seasonal uses will be developed in the standards implementation procedures. Higher uses will be maintained where they are attainable.
9. (i) Bacteria. A fecal coliform criterion of not more than 200 bacteria per 100 ml shall apply to all water bodies not specifically listed in Appendix A of §307.10 of this title (relating to Appendices A-E). Application of this criterion shall be in accordance with §307.7(b)(1) of this title.
10. (j) Antidegradation. Nothing in this section shall be construed or otherwise utilized to supersede the requirements of §307.5 of this title (relating to Antidegradation).
11. (k) Assessment of unclassified waters. Waters which are not specifically listed in Appendices A or D of §307.10 of this title are designated for the specific uses that are attainable or characteristic of those waters. Upon administrative or regulatory action by the commission which affects a particular unclassified waterbody, the characteristics of the affected waterbody will be reviewed to determine which aquatic life uses are appropriate. Additional uses so determined shall be indicated in public notices for discharge applications. Uses which are not applicable throughout the year in a particular unclassified waterbody will be assigned and protected for the seasons in which such uses are attainable. Initial determinations of use shall be considered preliminary, and in no way preclude redeterminations of use in public hearings conducted by the commission under the provisions of the Texas Water Code. For unclassified waters where the presumed minimum uses or criteria specified in this section are inappropriate, site-specific standards may be developed in accordance with §307.2(d) of this title (relating to Modification of Standards). Uses and criteria will be assigned in accordance with this section and with §307.7(3) of this title. Procedures for assigning uses and criteria are described in the standards implementation procedures.

Source Note:The provisions of this §307.4 adopted to be effective July 10, 1991, 16 TexReg 3400; amended to be effective July 13, 1995, 20 TexReg 4701; amended to be effective April 30, 1997, 22 TexReg 3712.