Pennsylvania Code › Title 25 - ENVIRONMENTAL PROTECTION › Part I - Department of Environmental Protection › Subpart A - Preliminary Provisions › Article II - Statements of Policy › Chapter 16 - WATER QUALITY TOXICS MANAGEMENT STRATEGY-STATEMENT OF POLICY › Subchapter A - GUIDELINES FOR DEVELOPMENT OF CRITERIA FOR TOXIC SUBSTANCES AND WATER QUALITY CRITERIA FOR TOXIC SUBSTANCES › GUIDELINES FOR DEVELOPMENT OF AQUATIC LIFE CRITERIA › Section 16.24 - Metals criteria

Current through Register Vol. 54, No. 28, July 13, 2024
(a) Metals
						  criteria are established to control the toxic portion of a substance in the
						  water column. Depending upon available data, aquatic life criteria for metals
						  are expressed as either dissolved or total recoverable. As information
						  develops, the chemical identifiers for the toxic portion may be added, changed
						  or refined. The criteria form one of the bases for water quality-based effluent
						  limitations, which are expressed as total recoverable metal. When calculating
						  equation-based metals criteria for determining effluent limitations, the
						  criteria must be developed in accordance with §
													93.8c (relating to human health
						  and aquatic life criteria for toxic substances).
(b) Chemical translators are used to convert
						  dissolved criteria into effluent limitations which are required by Federal
						  regulations to be expressed as total recoverable metal. The default chemical
						  translator used by the Department is the reciprocal of the conversion factor
						  (listed in the Conversion Factors Table located in §
													93.8b (relating to metals
						  criteria)) that was used to determine the dissolved criterion. If an NPDES
						  discharger performs a chemical translator study for a dissolved criterion, the
						  study of this site-specific translator should be conducted in accordance with
						  the EPA's "The Metals Translator: Guidance for Calculating a Total Recoverable
						  Permit Limit from a Dissolved Criterion" (June 1996), as amended and
						  updated.
(c) NPDES dischargers may
						  request alternate effluent limitations by using site-specific water quality
						  characteristics in a request to modify an existing water quality criterion, in
						  accordance with §
													93.8d (relating to development of
						  site-specific water quality criteria). This may be accomplished through one or
						  more of the following methods:
(1)
						  Recalculating a water quality criterion in accordance with the EPA's "Interim
						  Guidance on the Determination and Use of Water-Effect Ratios for Metals,
						  Appendix B: The Recalculation Procedure" (February 1994), as amended and
						  updated. The Recalculation Procedure accounts for corrections, update and
						  additions to the original criterion dataset to create an appropriate dataset to
						  calculate the site-specific criterion. If the optional deletion process is used
						  to evaluate the taxonomic composition, this process should follow the EPA's
						  "Revised Deletion Process for the Site-Specific Recalculation Procedure for
						  Aquatic Life Criteria" (April 2013).
(2) Developing a water quality criterion by
						  performing a Water Effect Ratio (WER) study, which is a factor that expresses
						  the difference between the measures of the toxicity of a substance in
						  laboratory water and the toxicity in site water. The WER provides a mechanism
						  to account for that portion of a metal which is toxic under certain physical,
						  chemical or biological conditions. WERs are applicable only to certain metals,
						  which are listed by the EPA in "Interim Guidance on the Determination and Use
						  of Water-Effect Ratios for Metals" (February 1994), as amended and updated.
						  WERs should not be used for the development of site specific criteria for
						  copper.
(3) Developing a water
						  quality criterion by performing a Biotic Ligand Model (BLM) study for copper in
						  freshwater systems. The BLM is a metal bioavailability model that uses
						  receiving water body characteristics and monitoring data to develop
						  site-specific water quality criteria. The BLM is used in evaluating the
						  differences in the bioavailability and toxicity of metals. These differences
						  occur as a result of variation in local water chemistry. The BLM may be used to
						  derive site-specific criteria for copper in freshwater systems. The BLM
						  incorporates the best available science for determining site-specific water
						  quality criteria for copper and is therefore preferred by the Department. The
						  Department will require use of BLM for copper in freshwater systems. Subject to
						  Departmental approval of the testing and its results, the Department will
						  evaluate the use of the BLM to establish alternate site-specific criteria. In
						  the absence of available site data to run the BLM, estimates for missing water
						  quality parameters may be developed using EPA's guidance, "Draft Technical
						  Support Document: Recommended Estimates for Missing Water Quality Parameters
						  for Application in EPA's Biotic Ligand Model," (March 2016), as amended and
						  updated.
(4) Developing a water
						  quality criterion using other guidance approved by the Department, which is
						  based on other EPA-approved or scientifically defensible
						  methodologies.