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Subsurface Investigation Report,Tosco(Former BP) Service Stat]onNO 11 192 June 8,2001 contained 101 and 1 06 ppb (respectively) of MTBE by EPA Method 8020, but were non-detectable for MTBE by EPA Method 8260 Sample B-4 contained xylenes (0 948 ppb) and MTBE (11 ppb) Sample CPT-1, from the CPT boring, contained xylenes (1 24 ppb), MTBE(120 ppb) and 1,2 DCA (23 ppb) 5.0 WELL SEARCH AND SENSITIVE RECEPTOR SURVEY GR conducted a search of the California Department of Water Resources (DWR) files to identify domestic and municipal wells within 112-mile of the subject site (Figure 2) The well search was performed by DWR personnel at the DWR office in Sacramento, California At the time of our visit, DWR personnel indicated that the files were approximately four years out of date Based on available DWR Well Completion Reports, three municipal wells were identified within one-half mile of the subject site The closest well is located approximately 1000 feet north- northwest of the site These three wells are the only water-producing wells located in the study area, according to the DWR records The depths of the three wells all exceed 550 feet bgs with screened intervals beginning at least 350 feet bgs Wells No 1 and No 2 are present on a map of the study area generated by the GeoTracker internet site (http Ilgeotracker2 arsenaultlegg corn) The well locations are shown on the attached Figure 2 The well search data is presented in Table 3 A neap of the Geotiacker search is presented in Appendix C A visual reconnaissance of the area within 500 feet of the site was conducted to look for evidence of water wells, such as overhead power lines, pump houses or pressure tanks No water wells or other receptors were found during the visual inspection In addition, wells No 2 and No 3 could not be located during the reconnaissance A Sensitive Receptor Survey (SRS) was performed for the area within 500 feet of the subject site The SRS consisted of distributing questionnaires seeking information about potential receptors and performing a site reconnaissance The area within 500 feet of the site is shown on Figure 3 During May 2001, questionnaires were distributed by mail in the study area, using ownership records obtained from the San Joaquin County Assessor's office A total of 141 questionnaires with stamped and addressed envelopes for replies were distributed A sample questionnaire is enclosed As of the date of this report, a total of 36 questionnaires were returned to GR The questionnaires returned did not identify any wells within 500 feet of the site 6.0 RECOMMENDATIONS The analytical results of grab groundwater samples from the Geoprobes B-1,B-2, and B-4 show very low concentrations of MTBE are present offsite to the north and northeast of the site The analytical results of Geoprobes B-5 through B-8 indicate no MTBE impact to groundwater in the east and 144245 03-1 6 5