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TITLE 30ENVIRONMENTAL QUALITY
PART 1TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
CHAPTER 307TEXAS SURFACE WATER QUALITY STANDARDS
RULE §307.6Toxic Materials

    (F) Childhood exposure was considered for all noncarcinogens. Consumption rates for fish and shellfish were estimated as 5.6 grams per child per day, and drinking water consumption rates were estimated as 0.64 liters per child per day. A child body weight was estimated at 15 kilograms. Both the water consumption rate and body weight are age-adjusted for a six-year-old child. The consumption rate for fish and shellfish for children is from Table 10-61 of EPA's 1997 Exposure Factors Handbook (EPA/600/P-95/002Fa-c).

    (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); Guidance Manual for Assessing Human Health Risks from Chemically Contaminated Fish and Shellfish (EPA/503/8-89-002); and Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) (EPA-822-B-00-004).

    (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 2 of paragraph (1) of this subsection) was greater than the applicable maximum contaminant level (MCL) in Chapter 290 of this title (relating to Public Drinking Water), then the MCL was used as the criterion.

    (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) Human health criteria for additional toxic materials are adopted by the commission as appropriate.

  (5) Specific human health concentration criteria for water are applicable to water in the state that has sustainable fisheries or designation or use as a public drinking water supply or as a sole-source drinking water supply except within mixing zones and below stream flow conditions as specified in §307.8 of this title. The following waters are considered to have sustainable fisheries:

    (A) all designated segments listed in Appendix A of §307.10 of this title, unless specifically exempted;

    (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);

    (C) lakes and reservoirs greater than or equal to 150 acre-feet or 50 surface acres;

    (D) all bays, estuaries, and tidal rivers; and

    (E) any other waters that potentially have sufficient fish production or fishing activity to create significant long-term human consumption of fish.

  (6) Waters that are not considered to have a sustainable fishery, but that have an aquatic life use of limited or greater, are considered to have an incidental fishery. Consumption rates assumed for incidental fishery waters are 1.75 grams per person per day. Therefore, numerical criteria applicable to incidental fishery waters are ten times the criteria listed in Column B in Table 2 of paragraph (1) of this subsection.

  (7) Specific human health criteria are applied as long term average exposure criteria designed to protect populations over a life time. Attainment measures for human health are addressed in §307.9 of this title.

  (8) For toxic materials of concern where specific human health criteria are not listed in Table 2 of paragraph (1) of this subsection, the following provisions apply:

    (A) For known or suspected carcinogens (as identified in EPA's IRIS database), a cancer risk of 10-5 (1 in 100,000) is applied to the most recent numerical criteria adopted by the EPA and published in the Federal Register. If an MCL or equivalent agency guideline for protection of drinking water sources is less than the resulting criterion, then the MCL applies to public drinking water supplies in accordance with paragraph (3)(H) of this subsection.

    (B) For toxic materials not defined as carcinogens, the most recent numerical criteria adopted by the EPA and published in the Federal Register are applicable. If an MCL or equivalent agency guideline for protection of drinking water sources is less than the resulting criterion, then the MCL applies to public drinking water supplies in accordance with paragraph (3)(H) of this subsection.

    (C) In the absence of available criteria, numerical criteria may be derived from technically valid information and calculated in accordance with the provisions of paragraph (3) of this subsection.

  (9) Numerical criteria for bioconcentratable pollutants are derived in accordance with the general procedures in the EPA guidance document entitled Assessment and Control of Bioconcentratable Contaminants in Surface Water (March 1991). The commission may develop discharge permit limits in accordance with the provisions of this section.

  (10) Numerical human health criteria are expressed as total recoverable concentrations for nonmetals and selenium and as dissolved concentrations for other metals and metalloids.

  (11) Additional site-specific factors may indicate that the numerical human health criteria listed in Table 2 of paragraph (1) of this subsection are inappropriate for a particular water body. These factors are applied as a site-specific standards modification in accordance with §307.2(d) of this title. The application of site-specific criteria must not impair an existing, attainable, presumed, or designated use or affect human health. Factors that may justify a temporary variance or site-specific standards amendment include the following:

    (A) background concentrations of specific toxics of concern in receiving waters, sediment, or indigenous biota;

    (B) persistence and degradation rate of specific toxic materials;

    (C) synergistic or antagonistic interactions of toxic substances with other toxic or nontoxic materials;

    (D) technological or economic limits of treatability for specific toxic materials;

    (E) bioavailability of specific toxic substances of concern;

    (F) local water chemistry and other site-specific conditions that may alter the bioconcentration, bioaccumulation, or toxicity of specific toxic substances;

    (G) site-specific differences in the bioaccumulation responses of indigenous, edible aquatic organisms to specific toxic materials;

    (H) local differences in consumption patterns of fish and shellfish or drinking water, but only if any changes in assumed consumption rates are protective of the local population that frequently consumes fish, shellfish, or drinking water from a particular water body; and

    (I) new information concerning the toxicity of a particular substance.

(e) Total toxicity.

  (1) Total (whole-effluent) toxicity of permitted discharges, as determined from biomonitoring of effluent samples at appropriate dilutions, must be sufficiently controlled to preclude acute total toxicity in all water in the state with the exception of small ZIDs at discharge points and at extremely low streamflow conditions (one-fourth of critical low-flow conditions) in accordance with §307.8 of this title. Acute total toxicity levels may be exceeded in a ZID, but there must be no significant lethality to aquatic organisms that move through a ZID, and the sizes of ZIDs are limited in accordance with §307.8 of this title. Chronic total toxicity, as determined from biomonitoring of effluent samples at appropriate dilutions, must be sufficiently controlled to preclude chronic toxicity in all water in the state with an existing or designated aquatic life use of limited or greater except in mixing zones at discharge points and at flows less than critical low-flows, in accordance with §307.8 of this title. Chronic toxicity levels may be exceeded in a mixing zone, but there must be no significant sublethal toxicity to aquatic organisms that move through the mixing zone.

  (2) General provisions for controlling total toxicity.

    (A) Dischargers whose effluent has a significant potential for exerting toxicity in receiving waters as described in the Procedures to Implement the Texas Surface Water Quality Standards (RG-194) as amended are required to conduct whole effluent toxicity biomonitoring at appropriate dilutions.

    (B) In addition to the other requirements of this section, the effluent of discharges to water in the state must not be acutely toxic to sensitive species of aquatic life, as demonstrated by effluent toxicity tests. Toxicity testing for this purpose is conducted on samples of 100% effluent, and the criterion for acute toxicity is mortality of 50% or more of the test organisms after 24 hours of exposure. 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, or carbonate) that are in the Cont'd...

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