Texas Administrative Code
Title 30 - ENVIRONMENTAL QUALITY
Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
Chapter 307 - TEXAS SURFACE WATER QUALITY STANDARDS
Section 307.6 - Toxic Materials
Universal Citation: 30 TX Admin Code § 307.6
Current through Reg. 49, No. 52; December 27, 2024
(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.
(2)
Numerical criteria are based on ambient water quality criteria documents
published by the 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
documents entitled Guidelines for Deriving Numerical Site-specific
Water Quality Criteria (EPA 600/3-84-099) and Revised Deletion
Process for the Site-Specific Recalculation Procedure for Aquatic Life
Criteria (EPA-823-R-13-001). 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. Site-specific criteria may be based on either a WER or a biotic
ligand model. The WER 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 WER multiplier or biotic
ligand model result is only applicable to those portions of a water body that
are adequately addressed by site-specific data. The biotic ligand model is
based on the dissolved portion of copper, and the freshwater equation is not
used in this case. As WER multipliers and criteria based on biotic ligand
models 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 WER multiplier or biotic
ligand model result 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 WER multiplier or
biotic ligand model result 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.
(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 §
307.10 of this
title or as a sole-source surface drinking water supply in Appendix B of §
307.10 of this
title. (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 IRIS database; EPA's
National Recommended Water Quality Criteria: 2002, Human Health
Criteria Calculation Matrix (EPA-822-R-02-012); EPA inputs for
calculating the 2015 updated national recommended human health criteria; EPA
Health Effects Assessment Summary Tables (HEAST); Assessment Tools for the
Evaluation of Risk (ASTER); EPA's QSAR Toxicity Estimation Software Tool,
version 4.1; 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 carcinogens and noncarcinogens 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, unless otherwise specified in
Table 2 of paragraph (1) of this subsection.
(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).
(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 effluent and are
not listed in Table 1 of subsection (c)(1) of this section or that are in
source waters.
(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 agency and the EPA is also acceptable. Toxicity
tests must be conducted using representative, sensitive aquatic organisms as
approved by the agency, and any such testing must adequately determine if
toxicity standards are being attained.
(D) If toxicity biomonitoring results
indicate that a discharge is not sufficiently controlled to preclude acute or
chronic toxicity as described in this subsection, then the permittee will be
required to eliminate sources of toxicity and may be required to conduct a
toxicity reduction evaluation (TRE) in accordance with the permitting
procedures of the commission. In accordance with the standards implementation
procedures (RG-194), permits are amended to include appropriate provisions to
eliminate toxicity. Such provisions may include total toxicity limits,
chemical-specific limits, best management practices, or other actions (such as
moving a discharge location) designed to reduce or eliminate toxicity. Where
sufficient to attain and maintain applicable numeric and narrative state water
quality standards, a chemical-specific limit, best management practices, or
other actions designed to reduce or eliminate toxicity rather than a total
toxicity limit may be established in the permit. Where conditions may be
necessary to prevent or reduce effluent toxicity, permits must include a
reasonable schedule for achieving compliance with such additional
conditions.
(E) Discharge permit
limits based on total toxicity may be established in consideration of
site-specific factors, but the application of such factors must not result in
impairment of an existing, attainable, presumed, 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, or
other necessary information as determined by the agency. Factors that may
justify a temporary variance or site-specific standards amendment include the
following:
(i) background toxicity of
receiving waters;
(ii) persistence
and degradation rate of principal toxic materials that are contributing to the
total toxicity of the discharge;
(iii) site-specific variables that may alter
the impact of toxicity in the discharge;
(iv) indigenous aquatic organisms that may
have different levels of sensitivity than the species used for total toxicity
testing; and
(v) technological,
economic, or legal limits of treatability or control for specific toxic
material.
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