SITE INFORMATION AND CORRESPONDENCE_CASE 1

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BP OIL BP Oil Company Environmental Resources Management Building 13,Suite N 2955W 41st Street Renton,Washington 9805SA931 (206)251-0667 Fax No:(206)251-0736 December 10, 1996 San Joaquin County Public Health Services Attention Mr. Harlin Knoll - Environmental Health Division P.O. Box 2009 Stockton, CA 95201 RE: Former BP Oil Site No. 11194 m1 2375 Tracy Boulevard Tracy, CA -� Dear Mr. Knoll: Enclosed find Groundwater Monitoring-and Sampling Report, dated August 30, 1996. The report includes a summary of chemical data collected since groundwater monitori% rte', activities began during 1990. Upon review of the report, you will note that aromatic o, ' petroleum hydrocarbons were;detected in three of the wells sampled this quarter. The highest benzene concentration was reported in well MW-4, where 160 ug/l was reported. Based on the data collected since 1990, we plan to alter the groundwater sampling regime. The proposed modification and attendant rationale is as follows: MW-1: Discontinue sampling; continue gauging groundwater elevations. Rationale: Petroleum hydrocarbons have never been detected. MW-2: Sample on a semi-annual basis. Rationale: While the aromatic hydrocarbon concentrations have either declined or stabilized, MTBE has been detected since BP sold the site. MW-3: Install a product recovery canister and sample on a semi-annual basis. Rationale: The highest benzene concentration reported since September, 1991 is 9 ug/l. While liquid petroleum hydrocarbon (LPH) has been measured, the LPH appears to be extensively weathered with very low residual concentrations of aromatic petroleum hydrocarbons. Nearby wells MW-5 and AMW-6 show that the LPH is isolated in occurrence, and that aromatic hydrocarbon concentrations are very low. MW-4: Sample on a semi-annual basis. Rationale: While the aromatic hydrocarbon concentrations have either declined or stabilized, MTBE has been detected on one occasion since BP sold the site.