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• 7-Eleven,Inc Store No 14117,Stockton,California July 9,2001 Workplan for Further Subsurface Investigation Page 2 GROUNDWATER MONITORING WELL INSTALLATION/SAMPLING Additional groundwater monitoring wells will be drilled using a drilling ng equipped with an 8-tnch diameter hollow-stem augers All dniling equipment will be steam cleaned pnor to drilling each boring, and sampling equipment will be washed In a non-phosphate solution and rinsed with water between sampling intervals All soil and rinse water generated during the drilling will be placed in labeled Department of Transportation (DOT)-approved 55-gallon drums and left on the site pending transportation and disposal Sod samples will be collected dunng drilling at 5-foot intervals to total depth using a split-spoon sampler lined with 2-inch-diameter by 6-inch-long brass sample tubes The sample tubes will be sealed with Teflon pads, plastic caps and tape,labeled,placed on ice in an insulated container, and submitted for analyses under chain- of-custody manifest to a state-certified laboratory for analysis Sod samples will be field screened for hydrocarbon vapors using a flame-ionization detector (FID) Soil will be logged using the Unified Soil Classification System by an IT Corporation field geologist working under the supervision of a California registered geologist Selected soil samples will be analyzed for BTEX,MTBE, and TPH-G by EPA methods 8020/8015 modified, and for oxygenates MTBE, TBA, DIPE, ETRE, and TAME using EPA method 8260 o �2 . The groundwater monitoring wells will be constructed of 10-foot long 2-Inch-diameter, Schedule 40 polyvinyl chloride casing with flush threads,and 0 020-inch-slot well screen Sand will occupy the annular spaces from the bottom to about two feet above the top of the well screens The sand packs will be sealed with about 2 feet of bentonite pellets saturated in place with neat-cement grout to about 10 inches below grade The wellheads will be protected at grade by locking, water-tight well caps and traffic-rated street boxes (with watertight bolted lads) set in concrete The top of casing and rim of the new well boxes will be surveyed by a professional surveyor for horizontal position and elevation relative to mean sea level datum The groundwater monitoring wells will be gauged and sampled in accordance with normal protocol during the next quarterly monitoring event following Installation, unless otherwise directed by the SJCPHS Groundwater samples will be analyzed for BTEX and TPH-G using EPA Methods 8020/modified 8015, and for TBA, MTBE, DIPE, ETBE, and TAME by EPA Method 8260 SCHEDULE AND REPORTING Findings from additional assessment will be submitted with the next quarterly groundwater monitoring data following well installation or within six weeks of fieldwork completions Fieldwork Is scheduled to be completed by the end of 2001,pending written regulatory approval of this scope of work and obtainment of the appropriate permits(including encroachment permits)