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Mr Harlan Knoll August 9, 2001 Page 2 of 7 In July 1999 five direct push soil borings were advanced along the penmeter of the UST excavation to investigate the vertical and Iateral extent of soil and groundwater contamination, and four hand augured soil borings were advanced to investigate the lateral extent of shallow soil contamination Total petroleum hydrocarbons as gasoline (TPHg) and total petroleum I hydrocarbons as diesel (TPHd) were detected in the soil at low to moderate levels Benzene and methyl tert butyl ether (MTBE) were detected only in one boring in the immediate vicinity of the former USTs Elevated levels of benzene, toluene, ethylbenzene xylenes (BTEX), TPHg, TPHd, and MTBE were detected in grab groundwater samples collected during drilling The data suggested that the vertical extent of soil contamination did not exceed 15 feet below ground surface (bgs) and occurred within a relatively limited area near the former USTs fBased on the results of the investigations, source removal excavation and supplemental groundwater removal and disposal were proposed in an Interim Corrective Action Workplan dated February 15, 2000 Approximately 3,700 cubic yards of soil was excavated from the area immediately surrounding the former USTs in March 2000 The excavation proceeded to a depth of approximately 15 feet bgs where subjective analysis and field PID readings suggested the vertical extent of contamination had been reached Approximately 1,100 cubic yards of soil was classified as uncontaminated and was utilized as backfill material Approximately 2,600 cubic yards of low to moderately impacted soil remained stockpiled on site Confirmation soil samples collected from the sidewalls and floor of the excavation confirmed that virtually all contaminated soil was excavated The approximate limits of the excavation are shown on Figure 2 i I Approximately 60,000 gallons of contaminated groundwater was pumped from the excavation, treated through ex-situ air-sparging to reduce contaminant concentrations, and subsequently transported to the Sacramento County Regional Wastewater Treatment Plant for disposal under a I temporary discharge permit Analytical results from groundwater samples collected on the first day of excavating and after interim remedial measures were completed indicated that petroleum hydrocarbon constituents were reduced via intenm remedial measures by approximately 97- 99 9%, except for MTBE, which was reduced by approximately 80% 2.0 WELL INSTALLATION AND SAMPLING METHODS ` 2.1 Permitting and Protocols Prior to initiating fieldwork, well installation permits were obtained from PHS/EHD All fieldwork was performed in accordance with Ground Zero's Site Safety Plan and Quality Assurance/Quality Control Plan IG1Data1GROLNDZE18amyard-ManseraeportslWELLRPT doe