| 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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| 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; amended to be effective August 17, 2000, 25 TexReg 7722; amended to be effective July 22, 2010, 35 TexReg 6294; amended to be effective March 6, 2014, 39 TexReg1450; amended to be effective March 1, 2018, 43 TexReg 1102 |
