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STATE OF CALIFORNIA-Environmental Pr&n Agency • PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD c "Who <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A e l <br /> Sacramento, CA 95827-3098 <br /> PHONE: (916) 255-3000 <br /> FAX: (916) 255-3015 03 <br /> 12 March 1997 <br /> Mr. Nick Nickerson <br /> Unocal ERS <br /> 2000 Crow Canyon Place, Suite 400 <br /> San Ramon,.CA 94583 <br /> REVIEW OF WORK CONDUCTED TO DATE AT 1905 N. BROADWAY AVENUE, STOCKTON <br /> I have recently reviewed the document „Evaluation of Alternatives for Remediation of 1,2- <br /> Dichloropropane in Groundwater” for the former PureGro/Brea Ag facility at 1905 N. Broadway, <br /> Stockton. As stated in the document, Unocal believes that groundwater remediation is not necessary <br /> at this site. My review of the document is found in the enclosed memo; I consulted both State and <br /> Regional Board policy (Amended Resolution No. 92-49 and the Basin Plan, both enclosed) in my <br /> review. To summarize, the Board's policies will not allow staff to accept Unocal's conclusion that <br /> there is no practical and cost-effective method for removing 1,2-DCP from the groundwater. <br /> After reviewing the remedial alternatives document, I realized that this would be an appropriate time <br /> to complete a comprehensive review of the status of this site's environmental characterization and <br /> remediation. Accordingly, I reviewed the files and reports, and summarized the information in the <br /> second enclosed memo. <br /> Based on the information in the two memos and on the guidance given in the State and Regional <br /> Board policies, I have developed the following list of actions which need to be accomplished at this <br /> site: <br /> 1. MODIFY THE GROUNDWATER ANALYTICAL SCHEME TO INCLUDE ANALYSIS FOR 1,2,3- <br /> TRICHLOROPROPANE (EXPANDED EPA 601 OR 8010 SCAN) AND DBCP (EPA METHOD 504). <br /> This is necessary because the US EPA detected 1,2,3-TCP when they split samples in May <br /> 1993, and because DBCP was found in one of the wells in March 1996. Both chemicals were <br /> found at concentrations significantly exceeding their water quality levels of concern. The <br /> March 1996 sampling event should include these chemicals. <br /> 2. FULLY CHARACTERIZE THE ON-SITE soiLs. Although extensive sampling and remediation has <br /> been completed in several areas (the oil-water separator, dry wells, new tank farm, and two <br /> evaporation ponds), there remains other areas of the site which appear to contain excess <br /> concentrations of contaminants. A soil investigation is needed for the paint booth area, drum <br /> storage area, PureGro tank farm, northern side of the PureGro warehouse, and washrack area. <br /> 3. COMPLETE A HUMAN HEALTH RISK ASSESSMENT. Because there are multiple contaminants in <br /> the groundwater, a site-wide human health risk assessment is needed to determine groundwater, <br /> and possibly soil, cleanup levels. The risk assessment must follow the attached guidance, which <br /> states that the discharger has the option of conducting a screening-level or a site-specific risk <br />