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w , Mr. Kyle Christie Project 20805-146.006 August 5, 1996 Page 9 EMCON conducted daily aeration monitoring events to determine progress. Soil samples collected from the aeration piles were placed in Ziploc`�' bags to allow volatilization of petroleum hydrocarbon vapors, and a PID was used to measure petroleum hydrocarbon vapors. If PID readings and odors indicated petroleum hydrocarbons were still present, aeration continued. Once field observations indicated petroleum hydrocarbons were not present, confirmation soil samples were collected at a frequency of four samples per 50 cubic yards. Soil samples were submitted, along with chain-of-custody documentation, to a state- certified analytical laboratory. The laboratory composited the samples four to one by quadrant and tested the samples for TPHG and BTEX. Analytical results indicated soil contained an average TPHG concentration of 3.5 mg/kg (see Table 2). SJCPHS granted approval to use the soil as backfill material after reviewing the analytical reports. EXCAVATION BACKFILL PROCEDURES ACES backfilled the UST excavation on February 14, and 15, 1996. Imported gravel was used to backfill the potholes excavated to determine the vertical extent of impacts. Native soils and backfill material excavated from the former UST complex were used to backfill the tank complex to within approximately 5 feet of surface grade. ACES placed and compacted the soil in accordance with the contract specifications. ACES personnel performed compaction testing using a compaction curved prepared using the stockpiled on-site soils (see Appendix Q. Soil generated during piping and dispenser area overexcavation activities and aerated on site, and an additional 160 cubic yards of soil imported to replace the UST volume, were placed as backfill on June 3 through June 5, 1996. The aerated and imported soils were placed to within 1 foot of grade, and AB was imported and placed for the asphalt base. After backfilling activities concluded, ACES placed an asphalt cap over the site. CONCLUSIONS The lateral extent of soil impacts appears to be restricted to the former UST complex and the vicinity of the former product piping trenches and dispenser island locations. Former UST complex soil samples indicate the impacts are distributed along the southern part of the former UST complex (TS-1, TS-2, and TS-6). Detected TPHG concentrations range from 1,100 to 3,600 mg/kg. Soil samples collected from the northern part of the former SACIN:\P30TI180M8051460.6[)S-()5\-cjb:3