SITE INFORMATION AND CORRESPONDENCE_FILE 1

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IBJ �.► \" • 4 BP OIL t, BP Oil Company _ Environmental Remediation Management 295 SW 41st Street r }�, 12; 37 Renton,Washington 98055-4931 (425)251-0667 Fax No:(425)251.0736 December 30, 1997 San Joaquin County Public Health Services Environmental Health Division Attention Mr. M. Infurna, Jr., Senior REHS 304 E. Weber Ave., Third Floor P.O. Box 388 Stockton, CA 95201-0388 RE: BP Oil Site No. 11195 I-5 & Louise, SEQ 16500 S. I-5 Lathrop, CA Site Code:1554 Dear Mr. Infurna: Enclosed please find a report titled Groundwater Monitoring and Sampling Report, dated 10 December 1997. The report summarizes chemical data obtained from the groundwater monitoring wells since 1992, including the results associated with groundwater monitoring performed on 15 October 1997. A metal detector was used to attempt to locate Well MW-7, located in the public right-of- way, during this sampling event. I understand that you were present and observed Alisto's attempt to locate the well. Well MW-7 was not located by the field technicians, and I understand that the San Joaquim County Public Health Services Department considers the well to be abandoned. MTBE concentration data is now shown in Figure 3, replacing the dissolved oxygen measurements shown in past reports. You should note that the estimated MTBE concentrations for samples analyzed during 1993 and 1994 are also shown on Table I - Summary of Results of Groundwater Sampling. Prior laboratory documentation is appended to the enclosed report. I have no other information regarding the suspected or confirmed presence of MTBE other than the data summarized in this report. It is my understanding that PACE included MTBE in the gasoline standard used to determine the retention time of various gasoline components, however, MTBE was not included in the calibration standards used to calculate sample concentrations. This is why Pace refers to the MTBE concentrations for samples analyzed during 1993 and 1994 an estimates. It is noted that MTBE was reported to be present in samples obtained prior to the sale of the site to Tosco in 1994, however, concentrations detected since the introduction of "cleaner burning gasoline" in 1995 are significantly higher. It is noted that the UST system will require upgrading to comply with December 1998 requirements for leak detection and prevention. Information provided by Tosco indicates that the installation of containment sumps beneath the product dispensers and around the turbine pump risers, and spill buckets around the product fill pipes