Site Specific Water Quality Criteria Development
Water quality-based effluent limitations are routinely derived from
national ambient water quality criteria for the protection of aquatic
life or “ALC”. NPDES permit limits do not usually consider actual
site conditions, so U.S. EPA allows ALC to be adjusted to local water
conditions through site-specific water quality criteria, which are often
less costly to meet than federal or state water quality standards.
GLEC is a national leader in developing site-specific water quality
criteria using several approaches, including:
- Determination of mixing zones - In mixing zones, the level of
toxic pollutants is allowed to be higher than in the surrounding
waters. GLEC researchers are experienced in defining mixing
zones through mathematical modeling or dye studies for toxic
substances and thermal impacts.
- Recalculation Procedure - ALC are typically derived from toxicity
databases for select representative test species. Federal regulations
permit criteria recalculation at specific sites based on the
presence of test species. GLEC regularly assists clients with
recalculation methods and with updating toxicity databases for
- Site Assessments – GLEC assesses water and sediment samples
at permitted sites to adjust residue-based limits of toxic
residues based on actual site conditions.
Biological Translator – GLEC researchers utilize this method
to compare effluent toxicity testing results to laboratory dilution
water results in order to predict the impact of a specific pollutant
in a given water body.
- Chemical Translator - Chemical translators convert dissolved
metal criteria back to a total metal concentration for use in permit
waste load limit calculations. GLEC researchers determine
translators for specific sites which reflect local conditions and
may result in less stringent limits than permits based on federal
or state default translators.
- Water Effect Ratio - The WER process recognizes that some
chemicals are not fully bioavailable and are thus less toxic to
aquatic life. GLEC researchers assist industrial clients and state/
federal regulators by measuring toxicity in both laboratory and
site water to adjust site-specific ALC.
Contact: Tyler Linton, Principal Research Scientist
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