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r • 20 March 1996 r AGE-NC Project No 95-0139 Page 2 of 6 rBetween 1988 and 1993, no regularly scheduled ground water monitoring program was in place Monitoring wells were sampled in June 1988, January 1990 and September 1990 During each sampling, hydrocarbons were detected in MW-1, north of the tank cavity It is uncertain if any additional field work was performed between September 1990 and February 1993 A quarterly monitoring program was initiated by Geological Audit Services, Inc (GAS) in February 1993 Since 1988, the depth to ground water at the site has fluctuated from 8 5 to 12 feet below surface r grade (bsg) Ground water flow direction has remained between N 8° W to N 28° W This flow ' direction is consistent with regional trends tr24 SOIL EXCAVATION In January 1990, additional hydrocarbon-impacted soils were removed to a depth of 14 feet from the tank cavity Ground water was encountered during excavation procedures and the excavation was dewatered The water was placed in an 8,000-gallon above ground tank and stored on-site Between March and May 1990, all of the previously excavated soil was returned to the excavation, bringing the surface of the excavation to 7 feet below grade Subsequently, additional soil was imported and used to backfill the excavation to surface grade The water stored on-site in the above ground tank ' was released to the area of the former excavation The backfilling and discharge of purged ground water were done without notification of the PHS-EHD, and therefore, no official documentation was available Approximately 1,000 cubic yards of soil were excavated from the former UST area in August 1993 Of the soil removed, 700 cubic yards were placed into "contaminated" stockpiles and transported under non-hazardous waste manifest to Forward, Inc Landfill in Manteca, California The remaining 300 cubic yards were placed into"clean' stockpiles and were used to partially backfill the excavation Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH,d) were detected in the north and east walls of the excavation Details of the excavation were included in a Quarterly Report for October 1993 prepared by GAS 25 UST INSTALLATION In January 1995, excavation for the installation of two new USTs at the subject site was initiated by SEMCO of Modesto, California Hydrocarbon-impacted soil was encountered during excavation Therefore, the FHS-EHD was notified All impacted soil was transported to Forward under non- hazardous waste manifest and disposed The procedures for the installation of the USTs were E' described in the report prepared by AGE titled Quarterly Repor t -June 1993 E