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

(a) Application. The toxic criteria set forth in this section apply to surface water in the state and specifically apply to substances attributed to waste discharges or human activity. With the exception of numeric human health criteria, toxic criteria do not apply to those instances where surface water, solely as a result of natural phenomena, exhibit characteristics beyond the limits established by this section. Standards and procedures set forth in this section are 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).

(b) General provisions.

  (1) Water in the state must not be acutely toxic to aquatic life in accordance with §307.8 of this title.

  (2) Water in the state with designated or existing aquatic life uses of limited or greater must not be chronically toxic to aquatic life, in accordance with §307.8 of this title.

  (3) Water in the state must 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. Water in the state with sustainable fisheries or public drinking water supply uses must not exceed applicable human health toxic criteria, in accordance with subsection (d) of this section and §307.8 of this title.

  (4) Water in the state must be maintained to preclude adverse toxic effects on aquatic life, terrestrial life, livestock, or domestic animals, resulting from contact, consumption of aquatic organisms, consumption of water, or any combination of the three.

(c) Specific numerical aquatic life criteria.

  (1) Numerical criteria are established in Table 1 of this paragraph for those specific toxic substances where adequate toxicity information is available and that have the potential for exerting adverse impacts on water in the state.

Attached Graphic

  (2) Numerical criteria are based on ambient water quality criteria documents published by the United States Environmental Protection Agency (EPA). EPA guidance criteria have been appropriately recalculated to eliminate the effects of toxicity data for aquatic organisms that 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) and Appendix B of the EPA draft guidance document entitled Interim Guidance on the Determination and Use of Water-Effect Ratios for Metals (EPA-823-B-94-001). Additional EPA guidelines that may be used to establish aquatic life criteria are detailed in the guidance documents.

  (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) Ammonia and chlorine toxicity are addressed by total toxicity (biomonitoring) requirements in subsection (e) of this section.

  (5) Specific numerical aquatic life criteria for metals and metalloids in Table 1 of paragraph (1) of this subsection apply to dissolved concentrations where noted. Dissolved concentrations 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 standards implementation procedures (RG-194) as amended. Specific numerical aquatic life criteria for non-metallic substances in Table 1 of paragraph (1) of this subsection apply to total recoverable concentrations unless otherwise noted.

  (6) Specific numerical acute criteria for toxic substances are applicable to all water in the state except for small zones of initial dilution (ZIDs) at discharge points. Acute criteria may be exceeded within a ZID and below extremely low streamflow conditions (one-fourth of critical low-flow conditions) in accordance with §307.8 of this title. There must be no lethality to aquatic organisms that move through a ZID, and the sizes of ZIDs are limited in accordance with §307.8 of this title. Specific numerical chronic criteria are applicable to all water in the state with designated or existing aquatic life uses of limited or greater, except inside mixing zones and below critical low-flow conditions, in accordance with §307.8 of this title.

  (7) For toxic materials where specific numerical criteria are not listed in Table 1 of paragraph (1) of this subsection, 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 are applied in accordance with this section and §307.8 of this title. The LC50 data used in the subsequent calculations are typically obtained from traditional laboratory studies; however, if LC50 data are unavailable or incomplete, other methodologies (such as quantitative structure-activity relationships) may be used:

    (A) acute criteria are calculated as 0.3 of the LC50 of the most sensitive aquatic species; LC50 × (0.3) = acute criteria;

    (B) concentrations of nonpersistent toxic materials must not exceed concentrations that are chronically toxic as determined from appropriate chronic toxicity data obtained in accordance with procedures in the EPA guidance document entitled Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Life and Their Uses (EPA 822-R-85-100) or calculated as 0.1 of acute LC50 values to the most sensitive aquatic species; LC50 × (0.1) = chronic criteria;

    (C) concentrations of persistent toxic materials that do not bioaccumulate shall not exceed concentrations that are chronically toxic as determined from appropriate chronic toxicity data obtained in accordance with procedures in the EPA guidance document entitled Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Life and Their Uses (EPA 822-R-85-100) or calculated as 0.05 of LC50 values to the most sensitive aquatic species; LC50 × (0.05) = chronic criteria; and

    (D) concentrations of toxic materials that bioaccumulate must not exceed concentrations that are chronically toxic as determined from appropriate chronic toxicity data obtained in accordance with procedures in the EPA guidance document entitled Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Life and Their Uses (EPA 822-R-85-100) or calculated as 0.01 of LC50 values to the most sensitive aquatic species; LC50 × (0.01) = chronic criteria.

  (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. Site-specific values for each segment are given in the standards implementation procedures (RG-194) as amended.

  (9) Criteria for most metals are multiplied by a water-effect ratio (WER) in order to incorporate the effects of local water chemistry on toxicity. The WER is assumed to be equal to one except where sufficient site-specific data are available to determine the WER for a particular water body or portion of a water body. A WER is only applicable to those portions of a water body that are adequately addressed by site-specific data. WERs that have been determined for particular water bodies are listed in Appendix E of §307.10 of this title (relating to Appendices A - G) when standards are revised. A site-specific WER that affects an effluent limitation in a wastewater discharge permit, and that has not been incorporated into Appendix E of §307.10 of this title, must be noted in a public notice during the permit application process. An opportunity for public comment must be provided, and the WER may be considered in any public hearing on the permit application.

  (10) Freshwater copper aquatic-life criteria include a multiplier (m) to incorporate effects of local water chemistry on toxicity. This multiplier may be based on either a WER or a biotic ligand model. The multiplier is assumed to be equal to one except where sufficient site-specific data are available to determine the multiplier for a particular water body or portion of a water body. The multiplier is only applicable to those portions of a water body that are adequately addressed by site-specific data. As multipliers are determined for particular water bodies they are listed in Appendix E of §307.10 of this title when standards are revised. A site-specific multiplier that affects an effluent limitation in a wastewater discharge permit, and that has not been incorporated into Appendix E of §307.10 of this title, is noted in a public notice during the permit application process. An opportunity for public comment must be provided, and the multiplier may be considered in any public hearing on the permit application.

  (11) Additional site-specific factors may indicate that the numerical criteria listed in Table 1 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 (relating to Description of Standards). The application of a site-specific standard must not impair an existing, attainable, or designated use. 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, additive, or antagonistic interactions of toxic substances with other toxic or nontoxic materials;

    (D) measurements of total effluent toxicity;

    (E) indigenous aquatic organisms, which may have different responses to particular toxic materials;

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

    (G) bioavailability of specific toxic substances of concern, as determined by WER tests or other analyses approved by the commission; and

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

(d) Specific numerical human health criteria.

  (1) Numerical human health criteria are established in Table 2 of this paragraph.

Attached Graphic

  (2) Categories of human health criteria:

    (A) concentration criteria to prevent contamination of drinking water, fish, and other aquatic life to ensure that they are safe for human consumption. These criteria apply to surface waters that are designated or used for public drinking water supplies, including all water bodies identified as having a public drinking water supply use in Appendix A of this chapter or as a sole-source surface drinking water supply in Appendix B of this chapter. (Column A in Table 2 of paragraph (1) of this subsection);

    (B) concentration criteria to prevent contamination of fish and other aquatic life to ensure that they are safe for human consumption. These criteria apply to surface waters that have sustainable fisheries and that are not designated or used for public water supply or as a sole-source surface drinking water supply (Column B in Table 2 of paragraph (1) of this subsection);

  (3) Specific assumptions and procedures (except where noted in Table 2 of paragraph (1) of this subsection).

    (A) Sources for the toxicity factors to calculate criteria were derived from EPA's Integrated Risk Information System (IRIS); EPA's National Recommended Water Quality Criteria: 2002, Human Health Criteria Calculation Matrix (EPA-822-R-02-012); EPA Health Effects Assessment Summary Tables (HEAST); Assessment Tools for the Evaluation of Risk (ASTER); and the computer program, CLOGP3.

    (B) For known or suspected carcinogens (as identified in EPA's IRIS database), an incremental cancer risk level of 10-5 (1 in 100,000) was used to derive criteria. An RfD (reference dose) was determined for noncarcinogens and for carcinogens where the EPA has not derived cancer slope factors.

    (C) Consumption rates of fish and shellfish were estimated as 17.5 grams per person per day.

    (D) Drinking water consumption rates were estimated as 2.0 liters per person per day.

    (E) For carcinogens, a body-weight scaling factor of 3/4 power was used to convert data on laboratory test animals to human scale. Reported weights of laboratory test animals are used, and an average weight of 70 kilograms is assumed for humans.

    (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).

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