Section 16.24. Metals criteria

(a) The 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.

(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.

(c) NPDES dischargers may request alternate effluent limitations by using site-specific water quality characteristics. This is accomplished by performing a site-specific chemical translator study for a dissolved criterion. A water effect ratio (WER) study may also be conducted, based on either total recoverable or dissolved criteria, depending on the form of the criterion.

(d) A WER 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. At this time, WERs are applicable only to certain metals, which are listed by the EPA in ‘‘Guidance on the Determination and Use of Water-Effect Ratios for Metals’’ (February 1994), as amended and updated. Subject to Departmental approval of the testing and its results, the Department will use the WER to establish an alternate site-specific criterion.

(e) Chemical translator studies must be conducted in accordance with the EPA’s interim final document, ‘‘The Metals Translator: A Guidance for calculating a total recoverable permit limit from a dissolved criterion’’ (June 1996), as amended and updated.

(f) Final reports on the studies shall be submitted to the Department within 60 days of completion. Upon approval of the study results, the Department will use the chemical translator or WER, or both, to determine revised effluent limitations.

The provisions of this § 16.24 adopted November 17, 1995, effective November 18, 1995, 25 Pa.B. 5067; amended November 17, 2000, effective November 18, 2000, 30 Pa.B. 6111; amended February 11, 2005, effective February 12, 2005, 35 Pa.B. 1223; corrected June 23, 2006, effective February 12, 2005, 36 Pa.B. 3117; amended May 15, 2009, effective May 16, 2009, 39 Pa.B. 2543. Immediately preceding text appears at serial pages (320513) to (320514).