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Workplan for Additional Assessment and Feasibility Testing 3 7-Eleven,Inc Store No.21756 853 East Yosemite Avenue,Manteca CA October 17,2001 Selected soil samples from each borehole will be analyzed by a State-certified analytical laboratory for benzene,toluene, ethylbenzene and xylenes(BTEX),total petroleum hydrocarbons-as-gasoline (TPH-G) by EPA Method 8020/8015, and oxygenates MTBE,tert-butanol (TBA),diisopropyl ether(DIPE),ethyl-tert- butyl ether(ETBE),and tert-emylmethyl ether(TAME) by EPA Method 8260. Samples from the capillary fringe,significant lithologic changes, any areas of elevated PID readings, and total depth of drilling will be analyzed from the borings. All soil generated through drilling will be placed in Department of Transportation (DOT)-approved 55-gallon drums pending characterization and disposal. Water generated by steam cleaning will be temporarily stored on site in DOT-approved 55-gallon drums pending characterization and disposal. All waste will be disposed of as non-hazardous at a certified facility by a licensed hauling firm. Vertical Delineation Groundwater Sam lin The Siimulprobe device will be used to collect discrete groundwater samples at depths of 20, 30, and 40 feet below grade to identify vertical concentration changes with depth below grade. The samples will be collected into 40-milliliter volatile organics analysis(VOA)vials,filled to zero headspace, acidified and kept on ice until delivery to a state-certified laboratory for analysis. Groundwater samples will be analyzed for BTEX and TPH-G by EPA Methods 8020/8015 modified, and oxygenates MTBE,TBA, DIPE, ETBE, and TAME by EPA Method 8260. Well Construction/Development/Gaupina/Samplin The groundwater monitoring well will be constructed with 2-inch diameter Schedule 40 poly-vinyl-chloride (PVC)casings with flush threads and 0.020-inch-slot well screen from 10-25 feet below grade. Sand filter packing will be placed around the well screen to a maximum height of 2 feet above the top of the screen. The filter pack will be sealed with 2 feet of bentonite (hydrated in place to prevent bridging) overlain by neat cement to surface grade. The wellhead will be protected at the surface by locking, expandable caps and traffic-rated street boxes(with watertight bolted lid)set in concrete. Following installation,the monitoring well will be developed by hand bailing to remove fine-grained sediments from the well and filter pack. Water from the development process will be containerized and temporarily stored on site in DOT-approved 55-gallon drums. The top of casing of the well will be professionally surveyed relative to a mean sea level datum, and gauged and sampled during the next quarterly monitoring event following drilling. Groundwater samples from the new well will be analyzed by a State-certified analytical laboratory for BTEX and TPH-G by EPA methods 8020/8015 modified, and the oxygenates:TBA, MTBE, DIPE, ETBE,TAME by EPA Method 8260. 21756SAW.DOC