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Site Delineation and RAP Addendum Proposal April 16,2008 Former Canteen Facility—1500 Shaw Rd Page 5 Based on the analytical results presented above, Delta recommends two additional soil borings be installed to confirm the presence or absence of residual petroleum hydrocarbon impacts in the subsurface soil (see Figure 1). One boring, tentatively designated CB-13, will be located near the southeast end of the former UST field and the South Wall and Southeast Wall UST soil samples(this location is also close to where the most recent soil sample, SB-13D, was obtained). The second boring, tentatively designated CB-3, will be drilled just south (down-gradient)of the MW-3 series wells. The soil borings will be drilled to a depth of approximately 80 feet bgs. Continuous sampling will occur on 5-ft intervals during drilling for the entire depth of the borings. Up to four soil samples will be collected per boring for laboratory analyses, based on the following criteria: • Highest PID and/or just above encountered groundwater; • At the shallowest groundwater depth on record for that area; • At the deepest groundwater depth on record for that area; and, • Bottom of borehole(optional). Delta believes these borings are necessary for confirmation of remediated vadose zone concentrations in the two main site areas, which has been requested by the San Joaquin County Public Health Services (SJCPHS). Even if subsurface clean-up is not confirmed, these borings will provide useful information on other areas or depths that may require additional remediation, which will be addressed in the RAP addendum, if necessary. SCOPE OF WORK Details of our work scope are summarized below: Well Installation and Soil Sampling • Two soil borings will be installed to approximately 80 feet bgs. Continuous sampling on 5-ft intervals will be conducted for the entire depth of each boring. These borings will provide confirmation of soil clean-up and/or highlight specific areas and depths for continued remediation. • Two monitor wells, designated MW-14M and MW-14D, will be installed between the MW-3 and - 13 series wells. The groundwater sampling results from these well installations will indicate whether additional remediation focus is needed in this area. • Two monitor wells, designated MW-15M and MW-15D, will be installed down-gradient of MW-1 1, along Shaw Road. These wells will be used to monitor down-gradient concentrations of MTBE and 1,2-DCA, if present. A right-of-way permit from City of Stockton will be required for these well installations. • Wells MW-14D and MW-15D will be installed to a depth of approximately 85 feet bgs. Based upon past soil analytical results, no sampling will be conducted from 0 to 30 ft bgs. Continuous sampling on 5-ft intervals will be conducted from 30 feet to total depth of the boring. • Wells MW-14M and MW-15M shall be installed to a depth of approximately 70 feet bgs. Since sampling will be performed for the `D' wells, no soil sampling will be conducted for these two wells. • Any soil accumulated due to the drilling activities will be stored in sealed 55-gallon drums on-site. A composite soil sample will be collected from the drums for disposal characterization purposes.