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ARARs and TBCs for SuAd Sites -8- • 17 May 1991 <br /> water quality limits using conservative assumptions regarding the attenuation of the <br /> constituents and/or environmental fate analysis. This methodology could be used at <br /> CERCLA sites to determine the classification of wastes and contaminated soils proposed <br /> to be left on-site. Therefore, the staff report would be a chemical-specific, action-specific, <br /> and location-specific TBC. <br /> According to EPA's CERCLA Compliance with Other Laws Manual, "ARARs (and TBCs <br /> necessary for protection), pertaining both to contaminant levels and to performance or <br /> design standards, should generally be attained at all points of potential exposure, or at <br /> the point specified by the ARAB itself. CERCLA requires, to the maximum extent <br /> practicable, the use of permanent solutions... Restrictions on use or access should not be <br /> a substitute for remediation to appropriate...levels." The Designated Level Methodology is <br /> also used by the Regional Board to determine the degree to which contaminated soils <br /> should be cleaned so that they do not threaten to adversely impact existing and probable <br /> future beneficial uses of waters of the state. Soil cleanup levels determined by this <br /> methodology are based on water quality objectives and,in the case of narrative <br /> objectives, numerical limits taken from the Water Quality Goals staff report. The basis of <br /> the methodology is similar to CERCLA risk assessment, except that the waters of the state <br /> act as the receptor. In California, this is necessary because Porter-Cologne requires the <br /> Regional Boards to restore or maintain beneficial uses throughout an affected or <br /> potentially affected body of water. The Designated Level Methodology could be used at <br /> CERCLA sites to determine soil cleanup levels and resulting remedial actions and, <br /> therefore, would be a chemical-specific, action-specific, and location-specific TBC. <br /> ,fit/RJY <br /> Attachment <br /> cc: Regional Board Federal Superfund Program Managers <br /> John Adams, Division of Clean Water Programs, State Water Resources Control Board <br /> Betsy Jennings, Office of the Chief Counsel, State Water Resources Control Board <br /> Frances McChesney, Office of the Chief Counsel, SWRCB <br />