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Ski ., S E C 0 R NEW� 7-Eleven Store #32262 Work Plan for Additional Site Assessment and Interim Remediation March 19, 2004 Page 5 conducting subsurface work at the site, Underground Service Alert (USA) will be contacted to delineate subsurface piping near the site with surface markings In addition, a private utility locator service will be contracted to clear the area surrounding the proposed monitoring well locations WELL INSTALLATION Soil Boring, Soil Sampling and Analysis SECOR will supervise the drilling of three groundwater monitoring wells (MW-7, MW-8 and MW-9), one groundwater extraction well (EX-1), one oxygen infection well (S-1), and two CPT borings (CPT- 1 and CPT-2), at the locations shown on Figure 5 The wells will be drilled using a truck-mounted drilling rig equipped with 8-inch diameter hollow-stem augers (HSAs) (for the monitoring and Infection wells) and 10-inch HSAs (for the extraction well) to the total depths shown In Table 3 Soil samples will be collected continuously from 10 to 17 feet bgs In wells MW-7, MW-8 and MW-9 using a split spoon sampler lined with 2-inch diameter by 6-inch-long brass sample tubes (Table 4) Continuous soil samples will also be collected from EX-1 from 5 to 25 feet bgs Since S-1 is located within 5 feet of EX-1 and 10 feet from MW-5, S-1 will be installed without collection of soil samples Down hole drilling equipment will be steam cleaned before drilling each borehole, and sampling equipment will be cleaned between each sampling interval Each soil sample will be screened for hydrocarbon vapors using a portable photojonization detector (PID) Soils encountered during drilling will be logged using the Unified Soil Classification System by a SECOR field geologist working under the supervision of a California registered geologist SECOR will supervise the drilling of two CPT soil borings, CPT-1 and CPT-2, to an assumed depth of 80 feet bgs (Figure 5) The CPT soil borings will be advanced using a direct push CPT rig to log soil stratigraphy Immediately adjacent to each CPT borehole, a second direct-push borehole will be advanced to collect a depth-discrete grab groundwater sample at approximately 80 feet bgs The exact sample Interval will be adjusted based on review of the CPT logs Depth discrete grab groundwater samples will be collected using a modified HydroPunch®sampler The sampler will be driven to approximately 3 feet below the desired sampling depth and retracted 3 feet to expose the disposable schedule 20 polyvinyl chloride (PVC) screen and allow groundwater to enter the HydroPunch® sampler The depth discrete water samples will be collected by lowering a 3/4"- diameter stainless steel bailer through the drive rods to groundwater The groundwater will be bailed from the drive rods, decanted from the bailer into 40-ml volatile organic analysis (VOA) vials, and capped Each VOA vial will be checked to ensure no bubbles are present, labeled, placed on ice, and transported to the laboratory under chain-of-custody documentation The drive rods will be retracted, leaving the disposable drive tip and 4 foot length of PVC well screen In the hole Downhole drilling equipment will be steam cleaned before drilling each borehole The down-hole sampling equipment will be washed In a tri-sodium phosphate or AlconoxTM solution between each sampling effort The soil borings will be abandoned by tremie grouting back to grade using neat cement Soil generated through drilling will be placed In Department-of-Transportation (DOT) approved 55- gallon drums on site pending characterization and disposal Water generated by steam cleaning will be contained in a steam-clean trailer and temporarily stored on site in DOT approved 55-gallon drums Soil samples collected using 2-Inch diameter by 6-inch-long brass sample tubes will be sealed with Teflon® sheeting and plastic caps, then labeled and placed on ice in an insulated container for 32262 Offsite well install and interim remediation workplan doc SECOR Intematlonal Incorporated