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ARARs and TBCs for Superfund Sites -8- 17 Mav 1991 (updated 10 October 1991) values. In conjunction with the Basin Plans, this document could be used at CERCLA sites to determine ground water and surface water cleanup levels and corresponding remedial actions. Therefore, the staff report would be a chemical-specific and location- specific TBC. The Designated Level Methodology for Waste Classification and Cleanup Level Determination The Designated Level Methodology staff report offers guidance on how to classify wastes under the definitions contained in the Chapter 15, Waste Discharge to Land, regulations so as to select appropriate disposal practices protective of beneficial uses of waters of the state. The classification of a waste as a "designated waste" is based on concentrations of extractable waste constituents as they relate to water quality objectives or numerical values selected from the Water Quality Goals staff report. Waste constituent-specific and site-specific concentration limits called "Designated Levels" are calculated from numeric water quality limits using conservative assumptions regarding the attenuation of the constituents and/or environmental fate analysis. This methodology could be used at CERCLA sites to determine the classification of wastes and contaminated soils proposed to be left on-site. Therefore, the staff report would be a chemical-specific, action-specific, and location-specific TBC. According to EPA's CERCLA Compliance with Other Laws Manual, "ARARs (and TBCs necessary for protection), pertaining both to contaminant levels and to performance or design standards, should generally be attained at all points of potential exposure, or at the point specified by the ARAR itself CERCLA requires, to the maximum extent practicable, the use of permanent solutions... Restrictions on use or access should not be a substitute for remediation to appropriate...levels." The Designated Level Methodology is also used by the Regional Board to determine the degree to which contaminated soils should be cleaned so that they do not threaten to adversely impact existing and probable future beneficial uses of waters of the state. Soil cleanup levels determined by this methodology are based on water quality objectives and, in the case of narrative objectives, numerical limits taken from the Water Quality Goals staff report. The basis of the methodology is similar to CERCLA risk assessment, except that the waters of the state act as the receptor. In California,this is necessary because Porter-Cologne requires the Regional Boards to restore or maintain beneficial uses throughout an affected or potentially affected body of water. The Designated Level Methodology could be used at CERCLA sites to determine soil cleanup levels and resulting remedial actions and, therefore, would be a chemical-specific, action-specific, and location-specific TBC. _N/RJY Attachment cc: Regional Board Federal Superfund Program Managers John Adams, Division of Clean Water Programs, State Water Resources Control Board Betsy Jennings, Office of the Chief Counsel, State Water Resources Control Board Frances McChesney, Office of the Chief Counsel, SWRCB