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r <br /> 23 May 1996 <br /> AGE-NC Project No 95-0139 <br /> Page 2 of 4 f <br /> sampling event, hydrocarbons were detected in MW-1, located north of the tank cavity It is uncertain <br /> if any additional field work was performed between September 1990 and February 1993 A`quarterly <br /> ,monitoring program was initiated by Geological Audit Services, Inc (GAS) in February 1993 <br /> - <br /> Since 1988, the depth to ground water at the site has fluctuated from 8 5 to 12 feet below surface <br /> grade (bsg) Ground water flow direction has remained between N 8°W to N 28° W, a flow direction <br /> consistent with regional trends <br /> r <br /> r <br /> 24 SOIL EXCAVATION <br /> In January 1990, additional hydrocarbon=impacted soil was removed to a depth of 14 feet bsg from <br /> I° the tank cavity Between March and May 1990, all of the previously excavated soil was returned to <br /> the excavation, bringing the surface of the excavation to 7 feet below grade Subsequently, additional <br /> soil was imported and used to backfill the excavation to surface grade The backfilling was done <br /> without notification to the PHS-EHD, and therefore, no official documentation was available <br /> Approximately 1,000 cubic yards of soil were excavated from the former UST area in August 1993 <br /> Of the soil removed, 700 cubic yards were placed into "contaminated" stockpiles and transported <br /> under non-hazardous waste manifest to Forward, Inc Landfill in Manteca, Califorrua The remaining <br />' 300 cubic yards were placed into"clean" stockpiles and were used to partially backfill the excavation <br /> Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) were detected <br />' in the north and east was of the excavation Details of the excavation were included in the Quarterly <br /> Report for October 1993 prepared by GAS <br /> 25 UST INSTALLATION <br />' In January 1995, excavation for the installation of two new USTs at the subject site was initiated by <br /> SEMCO of Modesto, Cahforrua Hydrocarbon-impacted soil was encountered during excavation and <br /> the PHS-EHD was notified All impacted soil was transported to Forward under non-hazardous waste <br />' manifest and disposed The procedures for the installation of the USTs were'described in the report <br /> prepared by AGE titled Quarterly Report,-June 1995 <br /> i <br /> 26 GEOPROBE INVESTIGATION <br /> 1 Five probe borings were advanced on 22 January 1996, using a Geoprobe 5400 probing unit Probe <br /> borings were advanced to depths between 13 5 feet to 15 5 bsg and soil samples were collected One <br /> grab ground water sample was collected from probe boring B9 TPH-g was detected in soil samples <br />