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STATE OF CALIFORNIA - Environmental Pron Agency PETE WILSON, Governor CALIFORNIA REGIONAL WATER QUTLITY CONTROL BOARD �d CENTRAL VALLEY REGION 3443 Routier Road, Suite A 7 Sacramento, CA 95827-3098 PHONE: (916) 255-3000 FAX: (916) 255-3015 29 July 1993 To: Interested Parties HEALTH RISK ASSESSMENTS Background In June 1992, the State Water Resources Control Board adopted Resolution No. 92-49, the Policies and Procedures for Investigation and Cleanup and Abatement of Discharges Under Water Code Section 13304. Finding No. III, Section F.2 (page 10) of the resolution states that the Regional Boards shall require that cleanup and abatement activities "implement the applicable provisions of Chapter 15, Division 3, Title 23, California Code of Regulations, to the extent feasible". Section 2550.4, subsections (c), (d)(1)(G), (d)(2)(H) and (g) of the Chapter 15 discusses the setting of concentration limits, or cleanup levels. Sites which threaten water quality must be cleaned up to background levels, unless this is technologically and economically infeasible to achieve. In that case, Chapter 15 requires that the cleanup level be set at a value that will not pose a hazard to human health or to the environment, and at the lowest concentration which is technologically and economically achievable. The cleanup level must also be consistent with all applicable standards and must take into account the additivity of any carcinogens. Sites which are not a threat to water quality must be cleaned up to human health standards. Based on the above policy and regulations, staff must now require that sites either be cleaned up to background levels, or that cleanup levels be set according to human health considerations as well as water quality limitations. Staff have had extensive discussions with the Department of Toxic Substance Control (DTSC) in regard to conducting a health risk assessment. The following information is provided to help facilitate the development of health risk assessments acceptable to both the Regional Board and to DTSC. Health Risk Assessment Health risk assessments shall follow the procedures found in th ised Screening Procedure TanU Ry for the Preliminary Endangerment Assessment, a : - memorandum by the DTSC (copy attached). Please note that a full Preliminary Endangerment Assessment (PEA) is not required, just the health risk assessment portion of a PEA. The health risk assessment should be conducted initially for all chemicals found at the site. The results will show which chemicals are present at health-based levels of concern, and therefore must be remediated. The Discharger should then propose health-based cleanup levels, and rerun the risk assessment using these numbers (to show that the proposed levels will protect human health). The final cleanup levels will be based on the lowest of the