1. (a) Application. Standards and procedures set forth in this section shall be applied in accordance with §307.8 of this title (relating to Application of Standards) and §307.9 of this title (relating to Determination of Standards Attainment).

2. (b) General provisions.

   1. (1) Water in the state shall not be acutely toxic to aquatic life in accordance with §307.8 of this title (relating to Application of Standards).
   2. (2) Water in the state with designated or existing aquatic life uses shall not be chronically toxic to aquatic life, in accordance with §307.8 of this title (relating to Application of Standards).
   3. (3) Water in the state shall be maintained to preclude adverse toxic effects on human health resulting from contact recreation, consumption of aquatic organisms, consumption of drinking water, or any combination of the three. Waters in the state with sustainable fisheries and/or public drinking water supply uses will not exceed applicable human health toxic criteria, in accordance with subsection (d) of this section and §307.8 of this title (relating to Application of Standards).
   4. (4) Water in the state shall be maintained to preclude adverse toxic effects on aquatic and terrestrial wildlife, livestock, or domestic animals, resulting from contact, consumption of aquatic organisms, consumption of water, or any combination of the three.

3. (c) Specific numerical aquatic life criteria.

   1. (1) Numerical criteria are established in Table 1 for those specific toxic substances for which adequate toxicity information is available, and which have the potential for exerting adverse impacts on water in the state.
      Attached Graphic
      
   2. (2) Numerical criteria are based on ambient water quality criteria documents published by EPA. EPA guidance criteria have been appropriately recalculated to eliminate the effects of toxicity data for aquatic organisms which are not native to Texas, in accordance with procedures in the EPA guidance document entitled Guidelines for Deriving Numerical Site-specific Water Quality Criteria (EPA 600/3-84-099).
   3. (3) Specific numerical acute aquatic life criteria are applied as 24-hour averages, and specific numerical chronic aquatic life criteria are applied as seven-day averages.
   4. (4) Ammonia and chlorine toxicity will be addressed by total toxicity biomonitoring requirements in subsection (e) of this section.
   5. (5) Specific numerical aquatic life criteria for metals and metalloids in Table 1 apply to dissolved concentrations (unless otherwise stated), which can be estimated by filtration of samples prior to analysis, or by converting from total recoverable measurements in accordance with procedures approved by the commission in the latest revision of the standards implementation procedures. Specific numerical aquatic life criteria for non-metallic substances in Table 1 apply to total recoverable concentrations unless otherwise noted.
   6. (6) Specific numerical acute criteria for toxic substances are applicable to all waters in the state except for small zones of initial dilution (ZIDs) at discharge points. Acute criteria may be exceeded within a ZID, but there shall be no lethality to aquatic organisms which move through a ZID, and the sizes of ZIDs are limited in accordance with §307.8 of this title (relating to Application of Standards). Specific numerical chronic criteria are applicable to all waters in the state with designated or existing aquatic life uses, except inside mixing zones and below critical low-flow conditions, in accordance with §307.8 of this title.

   7. (7) For toxic materials for which specific numerical criteria are not listed in Table 1, the appropriate criteria for aquatic life protection may be derived in accordance with current EPA guidelines for deriving site-specific water quality criteria. When insufficient data are available to use EPA guidelines, the following provisions shall be applied in accordance with this section and §307.8 of this title:

      1. (A) acute criteria will be calculated as 0.3 of the LC[sub]50[/sub] of the most sensitive aquatic organism; LC[sub]50[/sub] x (0.3) = acute criteria;
      2. (B) concentrations of non-persistent toxic materials shall not exceed concentrations which are chronically toxic (as determined from appropriate chronic toxicity data or calculated as 0.1 of acute LC[sub]50[/sub] values) to the most sensitive aquatic organisms; LC[sub]50[/sub] x (0.1) = chronic criteria;
      3. (C) concentrations of persistent toxic materials that do not bioaccumulate shall not exceed concentrations which are chronically toxic (as determined from appropriate chronic toxicity data or calculated as 0.05 of LC[sub]50[/sub] values) to the most sensitive aquatic organisms; and
      4. (D) concentrations of toxic materials that bioaccumulate shall not exceed concentrations that are chronically toxic (as determined from appropriate chronic toxicity data or calculated as 0.01 of LC[sub]50[/sub] values) to the most sensitive aquatic organisms.
   8. (8) For toxic substances where the relationship of toxicity is defined as a function of pH or hardness, numerical criteria are presented as an equation based on this relationship. Appropriate pH or hardness values for such criteria are listed for each basin in Table 2. The indicated pH and hardness values (Table 2) for each basin will be assumed unless sufficient data are available to derive segment specific pH and hardness values.
      Attached Graphic
      

   9. (9) Additional site-specific factors may indicate that the numerical criteria listed in Table 1 are inappropriate for a particular waterbody. These factors are applied as a site-specific standards modification in accordance with §307.2(d) of this title (relating to Modification of Standards). The application of a site-specific standard must not impair an existing, attainable, or designated use. Factors which may justify a temporary variance or site-specific standards amendment include the following:

      1. (A) background concentrations of specific toxics of concern in receiving waters, sediment, and/or indigenous biota;
      2. (B) persistence and degradation rate of specific toxic materials;
      3. (C) synergistic, additive, or antagonistic interactions of toxic substances with other toxic or nontoxic materials;
      4. (D) measurements of total effluent toxicity;
      5. (E) indigenous aquatic organisms, which may have different responses to particular toxic materials;
      6. (F) technological or economic limits of treatability for specific toxic materials;
      7. (G) bioavailability of specific toxic substances of concern, as determined by water-effect ratio tests or other analyses approved by the commission; and
      8. (H) new information concerning the toxicity of a particular substance.

4. (d) Specific numerical human health criteria.

   1. (1) Numerical human health criteria are established in Table 3.
      Attached Graphic
      

   2. (2) Categories of human health criteria:

      1. (A) concentration criteria in freshwaters to prevent contamination of drinking water, fish, and other aquatic life to ensure that they are safe for human consumption. These criteria apply to freshwaters which are designated or used for public drinking water supplies (Column A in Table 3);
      2. (B) concentration criteria in freshwaters to prevent contamination of fish and other aquatic life to ensure that they are safe for human consumption. These criteria apply to freshwater which have sustainable fisheries, and which are not designated or used for public water supply (column B in Table 3);
      3. (C) concentration criteria in marine waters to prevent contamination of fish and other aquatic life to ensure that they are safe for human health consumption. These criteria apply to marine waters which have sustainable fisheries (Column C in Table 3).

   3. (3) Specific assumptions and procedures (except where noted in Table 3).

      1. (A) Criteria were derived from information on toxicity in EPA's Integrated Risk Information Systems (IRIS) for both cancer potency slopes (q1*) and reference doses for non-carcinogens (Rfd). The values in Table 3 reflect values found in IRIS as of January 1994.
      2. (B) For known or suspected carcinogens (Types A, B, B[sub]2[/sub], or C in IRIS), an incremental cancer risk level of 10[sup]-5[/sup] (1 in 100,000) was used to derive criteria. An RfD (reference dose) was determined for noncarcinogens and for carcinogens for which EPA has not derived cancer slope factors.
      3. (C) Consumption rates of fish and shellfish were estimated as 10 grams per person per day for people living inland, and 15 grams per person per day for people living near the coast.
      4. (D) Drinking water consumption rates were estimated as 2.0 liters per person per day.
      5. (E) The ratio of average body weights was used to convert data on laboratory test animals to human scale. When the weight of test animals was not specified, the average weights were considered to be 0.35 kilograms for rats, 0.03 kilograms for mice, and 70 kilograms for humans.
      6. (F) Bioconcentration factors were obtained from the quantitative structure activity relationships database (EPA) and corrected to an average lipid concentration in fish tissue of 3.0%.
      7. (G) Numerical human health criteria were derived in accordance with the general procedures and calculations in the EPA guidance documents entitled Technical Support Document for Water Quality-based Toxics Control (EPA/505/2-90-001); and Guidance Manual for Assessing Human Health Risks from Chemically Contaminated Fish and Shellfish (EPA/503/8-89-002).
      8. (H) If a calculated criterion to prevent contamination of drinking water and fish to ensure they are safe for human consumption (column A in Table 3) was greater than the applicable maximum contaminant level (MCL) in Chapter 290 of this title (relating to Water Hygiene), then the maximum contaminant level was used as the criterion. MCLs were updated February 1993.
      9. (I) If the concentration of a substance in fish tissue used for these calculations was greater than the applicable United States Food and Drug Administration action level for edible fish and shellfish tissue, then the acceptable concentration in fish tissue was lowered to the action level for calculation of criteria.
   4. (4) Human health criteria for additional toxic materials will be adopted by the Commission as appropriate.

   5. (5) Specific human health concentration criteria for water are applicable to waters in the state which have sustainable fisheries, and/or designation or use as a public drinking water supply, except within mixing zones and below harmonic mean stream flows, in accordance with §307.8 of this title. The following waters are considered to have sustainable fisheries:

      1. (A) all designated segments listed in Appendix A of §307.10 of this title (relating to Appendices A-E), unless specifically exempted;
      2. (B) perennial streams and rivers with a stream order of three or greater, as defined in §307.3 of this title (relating to Definitions and Abbreviations);
      3. (C) lakes and reservoirs greater than or equal to 150 acre-feet and/or 50 surface acres;
      4. (D) all bays, estuaries, and tidal rivers; and
      5. (E) any other waters which potentially have sufficient fish production or fishing activity to create significant long-term human consumption of fish.
   6. (6) Waters which are not considered to have a sustainable fishery, but which have an aquatic life use, will be considered to have an incidental fishery. Consumption rates assumed for incidental fishery waters are 1.0 grams per person per day for inland waters, and 1.5 grams per person per day for marine waters. Numerical criteria applicable to incidental fishery waters are therefore 10 times the criteria listed in Columns B and C of Table 3.
   7. (7) Specific human health criteria are applied as long-term average exposure criteria designed to protect populations over a lifetime (70 years). Attainment measures for human health are addressed in §307.9 of this title (relating to Determination of Standards Attainment).

   8. (8) For toxic materials of concern for which specific human health criteria are not listed in Table 3, the following provisions shall apply:

      1. (A) for known or suspected carcinogens (Types A, B, B[sub]2[/sub], or C in IRIS), a cancer risk of 10[sup]-5[/sup] (1 in 100,000) shall be applied to the numerical criteria published in 57 FedReg 60848 December 22, 1992;
      2. (B) for toxic materials not defined as carcinogens, the numerical criteria in 57 FedReg 60848 shall directly apply;
      3. (C) in the absence of available criteria, numerical criteria may be developed from information available in IRIS and Quantitative Structure Activity Relationships Database (QSAR) and calculated in accordance with the provisions of paragraph (3) of this subsection.
   9. (9) Numerical criteria for bioconcentratable pollutants will be derived in accordance with the general procedures in the EPA guidance document entitled Assessment and Control of Bioconcentratable Contaminants in Surface Waters (March 1991). The commission may develop discharge permit limits in accordance with the provisions of this section.
   10. (10) Numerical human health criteria are expressed as total recoverable concentrations for nonmetals, and for mercury, and as dissolved concentrations for other metals and metalloids.

   11. (11) Additional site-specific factors may indicate that the numerical human health criteria listed in Table 3 are inappropriate for a particular waterbody. These factors are applied as a site-specific standards modification in accordance with §307.2(d) of this title (relating to Modification of Standards). The application of site-specific criteria shall not impair an existing, attainable, or designated use or affect human health. Factors which may justify a temporary variance or site-specific standards amendment include the following:

       1. (A) background concentrations of specific toxics of concern in receiving waters, sediment, and/or indigenous biota;
       2. (B) persistence and degradation rate of specific toxic materials;
       3. (C) synergistic or antagonistic interactions of toxic substances with other toxic or nontoxic materials;
       4. (D) technological or economic limits of treatability for specific toxic materials;
       5. (E) bioavailability of specific toxic substances of concern;
       6. (F) local water chemistry and other site-specific conditions which may alter the bioconcentration, bioaccumulation, or toxicity of specific toxic substances;
       7. (G) site-specific differences in the bioaccumulation responses of indigenous, edible aquatic organisms to specific toxic materials;
       8. (H) local differences in consumption patterns of fish and shellfish or drinking water, but only if any changes in assumed consumption rates will be protective of the local population that frequently consumes fish, shellfish, or drinking water from a particular waterbody; and
       9. (I) new information concerning the toxicity of a particular substance.

5. (e) Total toxicity.

   1. (1) Total (whole-effluent) toxicity of permitted discharges, as determined from biomonitoring of effluent samples at appropriate dilutions, will be sufficiently controlled to preclude acute total toxicity in all water in the state with the exception of small zones of initial dilution at discharge points (ZIDs). Acute total toxicity levels may be exceeded in a ZID, but there shall be no lethality to aquatic organisms which move through a ZID, and the sizes of ZIDs are limited in accordance with §307.8 of this title (relating to Application of Standards). Chronic total toxicity, as determined from biomonitoring of effluent samples, will be precluded in all water in the state with existing or designated aquatic life uses except in mixing zones and at flows less than critical low-flows, in accordance with §307.8.

   2. (2) General provisions for controlling total toxicity.

      1. (A) Dischargers whose effluent has a significant potential for exerting toxicity in receiving waters will be required to conduct whole effluent toxicity biomonitoring at appropriate dilutions.
      2. (B) In addition to the other requirements of this section, the effluent of discharges to waters in the state shall not be acutely toxic to sensitive species of aquatic life, as demonstrated by effluent toxicity tests. Toxicity testing for this purpose shall be conducted on samples of 100% effluent, and the criterion for acute toxicity shall be mortality of 50% or more of the test organisms after 24 hours of exposure. These observations for acute toxicity may be conducted during either acute or chronic toxicity tests, which are described in the standards implementation procedures. This provision does not apply to mortality that is a result of an excess, deficiency, or imbalance of dissolved inorganic salts (such as sodium, calcium, potassium, chloride, carbonate) which are in the effluent and are not listed in Table 1 in subsection (c) of this section or which are in source waters.
      3. (C) The latest revisions of the following EPA publications provide methods for appropriate biomonitoring procedures: Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Marine and Estuarine Organisms, and the Technical Support Document for Water Quality-based Toxics Control. The use of other procedures approved by the commission is also acceptable. Toxicity tests must be conducted using representative, sensitive aquatic organisms as approved by the commission, and any such testing must adequately determine if toxicity standards are being attained.
      4. (D) If toxicity biomonitoring results indicate that a discharge is exceeding the restrictions on total toxicity in this section, then the permittee shall conduct a toxicity identification evaluation and toxicity reduction evaluation in accordance with permitting procedures of the commission. As a result of a toxicity reduction evaluation, additional conditions may be established in the permit. Such conditions may include total toxicity limits, chemical specific limits, and/or best management practices designed to reduce or eliminate toxicity. Where sufficient to attain and maintain applicable numeric and narrative state water quality standards, a chemical specific limit rather than a total toxicity limit may be established in the permit. Where conditions may be necessary to prevent or reduce effluent toxicity, permits shall include a reasonable schedule for achieving compliance with such additional conditions.

      5. (E) If a permittee demonstrates, using the toxicity identification evaluation and toxicity reduction evaluation procedures, that diazinon is the primary cause of total toxicity, and that diazinon is ubiquitous within the wastewater system, the toxicity will be addressed in clauses (i) and (ii) of this subparagraph. If diazinon is not the primary cause of total toxicity, or if the permittee does not proceed with due diligence in controlling and investigating toxicity, or if diazinon is not ubiquitous within the wastewater system, the toxicity may be addressed in accordance with subparagraph (D) of this paragraph:

         1. (i) the permittee will be required to implement a public education and awareness campaign designed to control the introduction of diazinon into the wastewater system, and the permittee will be required to conduct an investigation into the sources of diazinon; and
         2. (ii) the permittee will be required to monitor for diazinon.

      6. (F) Discharge permit limits based on total toxicity may be established in consideration of site-specific factors, but the application of such factors shall not result in impairment of an existing, attainable, or designated use. These factors are applied as a site-specific standards modification in accordance with §307.2(d) of this title. A demonstration that uses are protected may consist of additional effluent toxicity testing, instream monitoring requirements, and/or other necessary information as determined by the commission. Factors which may justify a temporary variance or site-specific standards amendment include the following:

         1. (i) background toxicity of receiving waters;
         2. (ii) persistence and degradation rate of principal toxic materials which are contributing to the total toxicity of the discharge;
         3. (iii) site-specific variables which may alter the impact of toxicity in the discharge; and
         4. (iv) indigenous aquatic organisms, which may have different levels of sensitivity than the species used for total toxicity testing; and
         5. (v) technological, economic, or legal limits of treatability or control for specific toxic materials.

Source Note:The provisions of this §307.6 adopted to be effective July 10, 1991, 16 TexReg 3400; amended to be effective July 13, 1995, 20 TexReg 4701.