SITE INFORMATION AND CORRESPONDENCE

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� I contamination distribution. Recommendations by consultant to further define site: 1996 4/25/96 2"d PSA workplan approved by PHS/EHD after three amendments by RP's consultant. Primary focus is fate and transport evaluation/risk assessment. ; Consultant interested in computerized model to predict risk. 6/17-18/96 The second intrusive subsurface investigation was completed consisting of three hollow stem auger boreholes completed, logged, and sampled to total, depths of 100' bgs (SB-5,6,7 100'bgs) then destroyed by tremie grouting. Boreholes were installed on 6/17-18/96. 10/11/96 Soil Boning Installation Report by Geological Technics completed: TPH - G, and BTEX contaminant distribution documented from 20-60" bgs. See a copy. of data Table 2 by Geological Technics attached for soil contamination distribution. Conclusions by the consultant suggest that contaminant mass is significant (10,050 lbs of fuel hydrocarbons in subsurface) and groundwater impact is likely over some undefined time interval. Recommendations by the consultantinclude a remedial action effort to reduce the mass of contaminants. 1997 5/13/97 Soil Vapor Extraction workplan approved by PHS/EHD. 9/18/97 A soil vapor extraction ,(SVE) system installation was .completed consisting of four hollow stem :auger boreholes completed as vapor extraction and air recharge wells, logged, and sampled to total depths 46' bgs (VEW-1, AR-1,2,3. Boreholes completed as remediation wells were installed on 9/18/97. The SVE Treatment Plant was installed and tested on 4 November 14, 1997 witnessed by SJVUAPCD. The system was operated in reverse flow for one week producing very low influent concentrations then returned to proper flow direction still producing low influent concentrations until shutdown on January 14. 1998 at the request of PHS/EHD. PHS/EHD requests a recalculation of contaminant mass in the next report. i E i i . E i N I 4