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. h URS Ms. Robert McClellon September 13,2004 Page 2 The information collected during this investigation will be used to describe the nature and extent of the methane plume in the remediation plan. Our goal is to satisfy the regulatory requirement for controlling the methane from leaving the site boundary. We expect that additional phases of effort will need to be completed to meet this goal. After the extent of the methane plume has been established, we expect to complete the additional two phases of effort to achieve this goal: pilot test phase and full-scale phase. SCOPE OF WORK URS proposes to install 4 additional borings along the northern property boundary near probe VW-4 (Figure 1). We propose to install one boring 75 feet east and and one boring 75 feet west of probe VW- 4. We propose to advance each boring to a depth of 20.5 feet below the ground surface(bgs)using a truck-mounted drill rig equipped with hollow-stem augers. (We understand that from Mr.Tasiopoulos that the bottom of the landfill at the site was estimated to be 15 feet bgs. To assess whether the landfill bottom is deeper than 15 feet bgs, we have proposed to install a probe with a screened interval at a depth greater than 15 feet bgs.) Soil samples will be collected from all borings using a clean California modified split-spoon sampler fitted with brass liners. Soil samples will be collected at 5-foot intervals or at changes in lithology. The field geologist will log the soil from each boring using the Unified Soil Classification System. After each boring has been advanced to the desired depth, two gas-migration monitoring probes (deep and shallow) will be constructed within the boring. We plan to install the screened interval of each probe within a permeable layer. We expect that the deep probe will be screened from 15 feet to 20 feet bgs and that the shallow probe will be screened from 6 feet to 11 feet bgs. However, if we observe that the permeable layer is not located within the planned screened interval,we will change the depth of the screened interval based on field conditions encountered at the site. The probes will be constructed using a 1-inch polyvinyl chloride(PVC)pipe. Following the in a lation of these gas-migration monitoring probes, landfill gases will be measured within each probe. If methane is not measured within any of the probes, we propose to install one boring 25 feet west of probe VW-4 and one boring 25 feet east of probe VW-4. If methane is measured within both of the newly installed probes,we propose to install one boring 125 feet east of probe VW-4 and one boring 125 feet west of probe VW-4. If methane is measured within one of the probes, we propose to install one boring 125 feet away from probe VW-4 and the other boring 25 feet away from probe VW-4. The boring located 125 feet away will be1ocated on the same side(east or west of probe VW-4)of the newly installed probe where methane was found. Before initiating the probe installation,we will complete a utility survey.If utilities are located at or near any of the proposed probe locations,requiring the probes to be relocated,the probes will be relocated to an area along the property boundary within 10 feet of the approved location without seeking SJCEHD