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California Ronal Water Quality *ntrol Board <br /> Central Valley Region w� <br /> Peter M.Rooney <br /> Sacramento Main Office Ed J.Schnabel <br /> Secretaryfor Internet Address: http://www.swmb.m.gov/-mgcb5/home.html Chair <br /> Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Protection Phone(916)255-3000•FAX(916)255-3015 <br /> TO: Wendy L. Cohen FROM: Wendy Wyels <br /> Senior Engineer Site Cleanup Unit <br /> DATE: 29 September 1998 SIGNATURE: ' k'M y" <br /> SUBJECT: REVIEW OF HEALTH RISK ASSESSMENT WORK PLAN, WESTERN FARM <br /> SERVICE(FORMER PUREGRO), STOCKTON <br /> I have reviewed the 26 March 1998 Risk Assessment Work Plan for the former PureGro/Brea Ag facility <br /> at 1905 N. Broadway in Stockton. Board staff submitted this document to the Office of Environmental <br /> Health Hazard Assessment (OEHHA) for review, and received a 29 June review memorandum from <br /> OEHHA. I have also reviewed this work plan. Due to concerns expressed in a recent meeting about this <br /> site,I met with Dr. Julio Salinas of OEHHA to discuss the work plan and his review. My comments are <br /> as follows: <br /> 1. In order to provide the information needed by the Board to set cleanup levels, the conceptual site <br /> model needs to include the following exposures/receptors: ingestion of groundwater for the <br /> current on-site worker, ingestion of groundwater for the current off-site resident, and inhalation of <br /> groundwater vapor for the current off-site resident. In addition,I believe that the fugitive dust <br /> pathway is a current exposure route for the on-site worker and off-site resident. <br /> 2. An interim submittal should be data summary tables for all Tentatively Identified Compounds <br /> (TICS). Separate tables should be completed for soil and groundwater results, and each table <br /> should include the name of the chemical, the total number of samples collected,the total number <br /> of detections, the range of detected concentrations, the range of detection limits, and whether the <br /> chemical is considered a Chemical of Potential Concern (COPC). <br /> 3. I have contacted Nancy Bishop of Western Farm Service to obtain a copy of the sampling report <br /> which her company prepared as part of the Unocal claims process. These sampling results need to <br /> be included in the data summary. <br /> 4. I am concerned about the proposal to use only the most recent 12 months of groundwater <br /> concentration data. I strongly agree with Dr. Salinas that before this suggestion will be <br /> considered,Unocal must complete a data analysis of both trends over time and the distribution of <br /> contaminants among the wells. Alternatively,Unocal may propose to follow either the DTSC <br /> Preliminary Endangerment Assessment (PEA) guidance in which the maximum concentration of <br /> each contaminant is used as the exposure point concentration, or the USEPA guidance in which <br /> the 95% UCL for each contaminant is used. <br /> California Environmental Protection Agency <br /> er1 Recycled Paper <br />