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y V S ECOR - - - - - -- 3.4 RISK-BASED CORRECTIVE ACTION METHODOLOGY In this section, reporting criteria to achieve a no further action required (NFAR)by the RWQCB (RWQCB, 2004a), including a discussion of water quality objectives and the RBCA methodology, are presented. 3.1 RWQCB JURISDICTION—WATER QUALITY OBJECTIVES Typically in California, the Basin Plan requirements and Resolution No. 88-63 (Source of Drinking Water Policy) (RWQCB, 2004b) states in part "All surface and ground waters of the State are considered to be suitable, or potentially suitable, for municipal or domestic water supply and should be so designated by the Regional Boards, with the exception of surface and ground waters where: • The total dissolved solids (TDS) exceed 3,000 milligrams per liter (mg/L) and it is not reasonably expected by the Regional Boards to supply a public water system, or • There is contamination, either by natural processes or by human activities (unrelated to a specific pollution incident), that cannot reasonably be treated for domestic use using either Best Management Practices or best economically achievable treatment practices, or • The water source does not provide sufficient water to supply a single well capable of producing an average, sustained yield of 200 gallons per day." Since no data exists regarding the TDS levels in groundwater at the Site and the average shallow aquifer production rate, the shallow groundwater at the Site must conservatively be assumed to be a potentially potable source. In this case, chemical concentrations in the shallow groundwater at the Site must first be compared to applicable water quality objectives for potentially potable water(RWQCB, 2004a), which are California's primary or secondary MCLS (California Office of Administrative Law, 2006), public health goals (PHGs) (RWQCB, 2004a; Cal-EPA, 2006a), or California Department of Health Services (DHS) notification levels(NLs), (known as action levels(ALs]through 2004) (Cal-EPA, 2006b). A chemical-specific MCL is the maximum permissible level of a contaminant in water which is delivered to the free flowing outlet of the ultimate user of a public water system (tap water). Not all primary MCLs are risk-based; even if they are risk-based, they may not be based on the same target excess cancer risk (ECR). Primary MCLs can reflect other factors relating to technologic and economic feasibility of attainment and monitoring in a water distribution system and at the tap; and these factors may not be relevant for the water resources (RWQCB, 2004a). As such, MCLs for some volatile organic compounds (VOCs) may be at the practical quantitation limits (PQLs), or reflect concentrations associated with an ECR much below one in a million (1E-06) due to the relatively simple removal of VOCs from the water distribution system. PHGs, derived by Cal-EPA Office of Environmental Health and Hazard Assessment (OEHHA)following the requirements of the Calderon-Sher California Safe Drinking Water Act of 1996, are concentrations of chemicals in drinking water that are not anticipated to produce adverse health effects following long-term exposures. For cancer-causing chemicals, PHGs are based on a target ECR of 1E- 06 and adults' water consumption rate of 2 liters per day (Qday) and 70 kilograms (kg) of body weight. 5