| (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 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 Cont'd... |
