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' 10 June 1999 . AGE-NC Project No 97-0290 ' Page 2 of 26 According to the Geologic Map of California, published in 1977 by the State of California ' Department of Mines and Geology, the subject site is underlain by Pleistocene and Holocene alluvium composed of unconsolidated to semi-consolidated alluvial,playa, lake and terrace deposits 23 PRELIMINARY SITE ASSESSMENT ACTIVITIES ' Additional background information is summarized in the Preliminary Site Assessment Report, dated 16 February 1999, prepared by AGE Procedures and findings for the installation of wells MW-8, ' VW-1, SWI and SW2 and the April 1999 quarterly ground water monitoring event will be summarized in a quarterly report, currently in preparation by AGE Analytical data is summarized in the included tables The following is a summary of preliminary site assessment field activities ' conducted at the site Four USTs and one 55-gallon drum were removed from the site on 21 September 1987 The ' USTs ranged in volume from 250 to 2,000 gallons and were used to store gasoline and waste oil Petroleum hydrocarbons were detected in soil samples collected beneath the USTs at ' concentrations as high as 1,300 ppm On 25 February 1989, impacted soil was excavated from the former UST area The excavation reportedly encompassed an area of approximately 40 feet by 40 feet and extended ' to a depth of approximately 22 feet below surface grade(bsg) The excavation was backfilled to grade with sandy loam ' - On 13 October 1989, soil was excavated at the southeast corner of the property to confirm the removal of impacted soil during the February 1989 excavation The second excavation addressed an area approximately 8 feet by 12 feet and extended to a depth of 26 feet bsg One ' sample was collected from the second excavation Field observations indicated that petroleum-hydrocarbons were present in soil samples collected from the excavation Laboratory analyses of the soil samples were not available to AGE - In November 1989, one soil boring was advanced to a depth of 40 feet bsg Hydrocarbon odor was noted in the bonng, however analysis of soil samples was not performed Drilling ' was aborted and the boring was backfilled with grout Between October 1998 and April 1999, eighteen soil borings were advanced at the site ' Organic vapor was detected in 12 of the 18 borings advanced at the site Organic vapor was not detected in soil samples collected from borings MW3, MWS, MW6, MW7, MWS or B5 PID data is summarized on Table I ' - TPH-g was detected at concentrations as high as 11,000 parts per million (ppm, reported as • milligrams per kilogram) in 26 of the 47 soil samples analyzed Benzene was detected in 15 r4d►ancedGeoEnr►ronmental,Inc