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Ms. Vicki McCartney July 19, 2047 CONESTOGA-ROVERS &ASSOCIATES • We propose drilling three soil borings (SB-10, SB-11, and SB-12) south of the site along the southern edge of East Charter Way to assess the southern extent of 1,2-DCA in groundwater. • Shell considered installing monitoring wells in the proposed boring locations mentioned above, but due to the presence of overhead power lines along the south side of East Charter Way, we cannot safely install wells in this area. We also considered installing wells on the private property further south, but we wanted to avoid the delays typically encountered with obtaining access to private property, and therefore decided to drill soil borings as proposed. • Since previous investigations have shown that I,2-DCA is present primarily in the shallow groundwater, we propose collecting groundwater samples during this investigation from the bottom of the first saturated coarse-grained zone (approximately 50 feet below grade). Work Tasks Permits:CRA will obtain the required drilling permit. We will also obtain an encroachment permit from the City of Stockton for drilling in the public right of way. Site Safety Plan: CRA will prepare a health and safety plan to protect site workers. The plan will be reviewed and signed by each site worker and kept on the site during field activities. Utility Clearance: CRA will mark the proposed drilling locations and will clear the locations through Underground Service Alert and a private utility locator prior to drilling. Site Investigation. Assuming the absence of subsurface and overhead obstructions, CRA will use cone penetration testing(CPT) drilling equipment to drill three soil borings at the approximate locations shown on Figure 2. The borings will be drilled to approximately 60 feet below grade (fbg), depending on field conditions, and will be electronically logged using CPT logging techniques. We 41 collect groundwater samples from the bottom of the first saturated coarse-grained zone (approximately 50 fbg) for chemical analysis. Soil samples will be collected at 10 and 30 fbg to evaluate vadose soil quality south of the site. Soil and groundwater samples will be collected in separate borings at each boring location to minimize the potential for cross contamination during sampling activities. Soil and groundwater samples will be collected in appropriate sample containers, labeled, entered onto a chain-of-custody record, and placed into a cooler with ice for transport to a State of California certified laboratory for analysis. Chemical Analyses: Soil and groundwater samples will be analyzed for total petroleum hydrocarbons as gasoline, and benzene, toluene, ethylbenzene, xylenes, fuel oxygenates, and lead scavengers (1,2-DCA and ethylene dibromide)using appropriate EPA laboratory methods. 1 kn-r$,�'1 0i Pt- i Tari 2415[[ 2 Worldwide Engineering, Environmental,Construction,and IT Services