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I , <br /> 1 y f Y <br /> 1 <br /> K <br /> APPENDIX A - SITE BACKGROUND INFORMATION <br /> WEST CLAY PROPERTIES <br /> ` 639 West Clay Street, Stockton, California t <br /> J <br /> I <br /> Two areas of concern related to former underground storage tanks (USTs)'have been identified at <br /> the site The former UST No 3 area is located in the southern portion of the property and the former <br /> Cluster UST area,is located in the north portion of the property Following is a brief history of <br /> _ n 4, li <br /> environmental assessment and remediation <br /> UST No. 3 Location (South Area) <br /> 1990 to 1993 - It is AGE'S understanding that one 1,000-gallon UST was removed from the site in u <br /> May 1990;and the product line from the former UST to the dispenser was removed in October 1993 <br /> Subsequently, approximately 550 cubic yards of hydrocarbon-Impacted soil was removed from the <br /> former UST area, the soil was excavated to a depth of approximately 38 feet below surface grade <br /> (bsg) Total petroleum hydrocarbons quantified as gasoline (TPH-g) was encountered in one <br /> excavation bottom sample at a concentration of 5,200 milligrams per kilogram (mg/kg) and inone 4 <br /> sidewall sample at 2,100 mg/kg, however, the lateral and vertical extent of contamination was not <br />' assessed ' <br /> 1 <br /> Following excavation, fouF soil bonngs (B-1 through B-4) were advanced at the site as part of <br /> • environmental assessment related to the former UST Three borings were completed as monitoring <br /> wells (MW-1 through MW-3) Ground water was determined to be impacted and additional <br /> assessment was required by the San Joaquin County Environmental Health Department (EHD) to <br />' define the lateral and vertical extent of impacted soil and ground water` The excavation was not <br /> backfilled until April 1997 <br /> June 1996 - AGE begins working on project <br /> ! 1 <br /> 1 November 1996 - Four soil borings (B-5 through B-8) were advaiiced'at the'site Relatively low <br /> concentrations of,BTEX constituents were detected in the soil sample collected at 30 feet bsg in soil <br /> boring 4-7, analytes of concern were not detected in the soil samples collected and analyzed from <br /> borings B-5, B-6 and B-8 Xylenes and total petroleum hydrocarbons quantified as diesel (TPH-d) <br /> were detected'in grab ground water samples collected from borings B-6 and B-8 <br /> May 1997- Monitoring wells MW-4 and MW-5 were installed at the site Target'analytes were not <br />' r detected above laboratory reporting limits in soil samples collected and analyzed from the pilot <br /> ` borings Relatively low concentrations of various target analytes were detected in ground water <br /> samples collected during the preliminary ground water mn nitonng and sampling event ; <br /> August 1998-Five monitoring wells(MW-6", MW-7 and MW-8A/B)were installed at the site <br />' Relatively low concentrations of benzene and xylenesrwere'detected in the soil sample collected at <br /> 45 feet bsg from pilot boring MW-8 Analytes of concern were not detected in'the soil samples <br /> • collected and analyzed from pilolt,bonngs MW-6 and MW-7 , <br /> R' 1' <br /> L <br /> i <br /> f r Advanced GeoEnvironmental,Inc <br /> 3 r 1 <br /> y r A <br /> i <br />