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k4easibility Testing Work Plan Jimco Truck Plaza C A M B R I A 1022 Frontage Road Ripon, California May 18, 2005 S site. As such,defining the lateral extent of the dissolved-phase contaminantsnsouthwest of the USTs will complete the delineation of the dissolved-phase plume related to the former USTs. I 4.2 Vertical Extent of Contamination Soil Contamination:The release of fuel from the former UST system is presumed to have occurred prior to September 1998, whereupon the USTs and its associated fuel dispensers and piping were removed from the site. As noted previously in Section 2.4,groundwater levels have dropped over 10 feet since 1998. The steady drop in groundwater levels at the site has effectively left the majority of impacted soil above the current groundwater table. Soil beneath the former USTs has been investigated to 40 feet bgs. Soil data from soil boring B17 indicates that impacted soil is present primarily at 20 ft bgs and does not appear to extend to 40 ft bgs. The vertical extent of impacted soil appears to be adequately characterized �a.a✓ Groundwater Contamination:A water-bearing zone consisting of poorly graded sand appears to exist from approximately 20 to 30 ft bgs beneath the former USTs. Hydrocarbons and fuel oxygenates have j been detected within the water-bearing zone in wells screened from 10 to 30 ft bgs. TPHg, ethylbenze, xylenes and MTBE were detected at approximately 42 feet bgs in a grab groundwater sample collected from boring B 17.'Due to the potential for cross contamination during the groundwater sampling method and the lack of any detected concentrations in soil at 40 ft bgs, the , presence of impacted groundwater at 42 to 46 ft bgs remains uncertain.The vertical extent of any impacted groundwater is adequate and likely attenuates quickly with depth, consistent with the soil P � q Y sample results. I I'I 5.0 PROPOSED SCOPE OF WORK The objective of the proposed scope of work is to assess the feasibility of SVE and air sparging(AS) as a potential remedial technology. To meet these objectives, Cambria will conduct the following: f • Install one air sparge well (AS-1) downgradient of the former USTs to assist with the 1 feasibility testing(Figure 3); and, i • Conduct a SVE test and a combined SVE/AS test using the new air sparge well(AS-1)and existing wells(EW-1,MW-1, and MW-9)in the vicinity of the former USTs. / I 6