SITE INFORMATION AND CORRESPONDENCE

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STATE OF CALIFORNIA PETE WILSON. Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION p 3443 ROUTIER ROAD, SUITE A SACRAMENTO, CA 958273098 1 PHONE'. !91613615600 SEP 1 2 1352 FAX_ 19161 361-5686 WNVIRONVIENTAL HEALTH gLMIT/5CIIVI"�4 10 September 1992 Mr. James Wang Mr. Rick Sisk Diamond Properties Unocal Corporation 2546 Derby Drive P.O. Box 5155 San Ramon, CA 94538 San Ramon, CA 94583 CLEANUP AND ABATEMENT ORnER NO. 90-700 (CSA), DIAMOND PROPERTIES, 701 WEST 11TH STREET, TRACY, SAN JOAQUIN COUNTY In August 1990, four composite soil samples were analyzed for "Priority Metals" analysis using method 6010 (ICP - Inductively Coupled Plasma) . All four samples contained levels of barium, chromium, lead, and/or nickel above Soluble Threshold Limit Concentrations (STLC) . The soil containing the metals had been treated by aeration on a portion of the site (no map of the treatment area has been provided) . Because the STLC levels were exceeded, I requested, by letter on 30 April 1992, that (1) background samples be collected and Waste Extraction Test (WET) analyses be performed, (2) a work plan showing sample locations be submitted by 15 May 1992, and (3) the sample results be submitted by 15 July 1992. We received a report, dated 14 August 1992, from Mittelhauser Corporation, a consultant for Unocal , containing results of soil samples collected at 701 West 11th Street in Tracy. No work plan was submitted, therefore the sample locations could not be reviewed by Board staff, and the results were submitted late. While we now know the background samples do not contain metals exceeding the STLC, the results cannot be compared to the sample results from August 1990. The samples collected in August 1990 were from the contaminated area, no WET analyses were performed, and the results were reported in mg/kg. While the samples collected in August 1992 may be considered background samples, no "Priority Metals" analyses were conducted and the results were reported in mg/1 . In order to resolve the analytical discrepancies it will be necessary to collect samples from the soil disposal area and analyze using the WET, collect samples from the background area and analyze them for "Priority Metals", and collect and analyze any other samples necessary to completely define the contaminated soil . By 15 October 1992, submit sample results with a map showing sample location and the soil treatment/disposal area. Once we have the results from these analyses we can reevaluate your recommendation for closure of the site. If STLC levels are exceeded in the soil treatment/disposal area it may be necessary to perform additional soil remediation. We have not received a quarterly ground water monitoring report since April 1992. By 15 October 1992, submit a quarterly report as required by the C&A and revision letter dated 24 July 1990. Until this site has been closed and the C&A rescinded, quarterly reports must be submitted.