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that the cleanup goal (100 mg/kg for TPH) was attained at the excavation sidewalls and bottom or until building structures prevented further excavation A total of 12 soil confirmation samples were collected The ' approximate volume of soil removed from Site #1 during excavation activities was 444 cubic yards ' Prior to backfilling, the saturated bottom of the excavation was stabilized by placing a 4-foot-thick rock base, consisting of 1- to 2-inch-diameter rock, over a geotextile fabric liner The remainder of the excavation was ' then backfilled with clean fill dirt and compacted using construction equipment The backfill area was subsequently paved with asphalt cover 2.41 Soil Aeration ' Excavated soil was stockpiled on site for aeration The aeration pile was covered with 6 mil polyethylene sheeting at all times, except when adding or removing soil The aeration pile was secured inside a padlocked fence ' A conventional tractor with disc-tilling attachment was used to aerate the soil for a total of 16 days at a rate of 60 cubic yards per day The aerated soil was sampled for post treatment confirmation on 13 December 1993 by ' ERM personnel under San Joaquin County supervision Twelve confirmation samples were analyzed to confirm that the cleanup goals (100 pprn for TPH-g and 1 ppm for total BTEX) were attained and no further aeration was needed A letter describing the soil aeration process and the post treatment confirmation data was prepared by ERM and sent ' to the Unified Air Pollution Control District on 29 December 1993 After laboratory analyses confirmed that all chemical concentrations were ' below applicable detection limits, the treated soil was spread along the northeast corner of the property as proposed in the Final Remediation ' Plan (ERM, September 1993) ' 25 ADDITIONAL CHARACTERIZATION After the remedial alternative selected for soil (excavation and on-site aeration) was completed, PHS/EHD expressed concern that the hydrocarbon.-containing soil at each site may not have been adequately ' remediated Specifically, PHS/EHD was concerned that residual concentrations of hydrocarbon-containing soil could remain in areas underlying the former excavations and the existing buildings at both ' former tank sites In September 1994, on behalf of Catellus, ERM conducted additional soil sampling within the former excavation footprint and underneath the existing building Three borings (S1-B1 through S1-- 133) were completed to a maximum depth of 18 feet, and soil was analyzed ERM 10 CA MLL VS/2996 10-11/13/99