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kilograms (ppm)) to 10200 mg/kg Toluene, ethylbenzene, and xylenes were also <br /> detected in high concentrations ranging from 240 ug/kg to 220,000 ug/kg - toluene, <br /> 880 ug/kg to 180,040 ug/kg - ethylbenzene, and 10600 ug/kg to 1020000 ug/kg - <br /> xylenes Benzene and EDB were non-detect in all samples Total lead was detected <br /> in three (3) samples (1 E 0 14 5', 2E Ca 14 5', and 3E Ca 15 5') and represents <br /> background concentrations Sample 3W C& 15.5' , collected on the west side of tank <br /> #3 was non-detect for all analytes The petroleum hydrocarbon concentrations, as <br /> reported from the samples collected beneath the east and west sides of tank 1 and <br /> tank 2 and the east side of tank 3, are in excess of State and County Guidelines <br /> Based on these results, additional site characterization has been requested by the <br /> San Joaquin County Environmental Health Department (County) <br /> A letter has been issued by the County stating that the vertical and lateral extent <br /> of contaminants beneath the underground storage tanks must be fully assessed before <br /> final closure can be issued. <br /> Crisp Construction contracted with AquaGeosc fences, Inc to prepare this <br /> workplan and implement a site characterization study. <br /> 30 Work Pian <br /> AquaGeosciences, Inc proposes to assess and define the lateral and vertical <br /> • extent of gasoline impacted soil <br /> 3 1 Soil Boring Depths and Locations <br /> Six (6) soil borings will be advanced to a depth of approximately 50 feet Soil <br /> samples will be collected at five foot intervals beginning at five feet and continuing <br /> until ten feet of unimpacted soil or groundwater is encountered Please Note <br /> Pursuant to information supplied to us by San Joaquin County, the average depth to <br /> groundwater in the vicinity of the site is estimated to be 20 feet below ground surface. <br /> The proposed locations are shown on Exhibit 2. The locations have been <br /> chosen to provide lateral and vertical definition in the vadose zone Boring TH-1 will <br /> be advanced between Tank #1 and Tank #2 on the east side where the highest <br /> concentrations were detected, to assess the vertical limits Boring TH-2 will be <br /> advanced east of TH-1 approximately 20 feet to assess the lateral migration to the <br /> east Boring TH-3 will be advanced south of TH-1 and the south side of Tank #1 to <br /> assess the lateral migration to the south Boring TH-4 will be advanced west of TH-1 <br /> approximately 50 feet and west of Tank #1 and Tank #2 to determine the extent of <br /> lateral migration to the west Boring TH-5 will be advanced north of TH-1 to assess <br /> the extent of lateral migration to the north Boring TH-6 will be advanced northeast of <br /> TH-1 to assess the extent of lateral migration to the northeast. <br /> 4of12 <br />