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Mr.Nuel Henderson,Jr. • October 15,2002 ARCO Station 6100 Project No.U 6100 Work Plan Page 7 above and 10 feet below first encountered groundwater (similar in construction to well MW-1). The bottom of the screen interval will be placed to intersect the contact between Sand 2 and the underlying silty unit. A filter pack of#3 sand will be placed in the annular space around the well screen. The sand will be placed to a maximum of 4 feet above the top of the well screen. If groundwater is present in the well boring, the well will be surged for a minimum of 10 minutes to seat the filter pack prior to installing a sanitary seal. A maximum of four feet of bentonite pellets will be placed on top of the filter pack to provide a sanitary seal for the well. Cement grout will be placed in the space around the well from the top of the bentonite seal to the ground surface. A watertight locking cap will be installed over the top of the well casing and a traffic rated vault box will be mounted over the well. Well Development, Sampling, and Survey The monitoring wells will be allowed to stand a minimum of 72 hours after installation, then will be developed using a surge block and groundwater pumping. Development will continue, to the extent practical, until the development water runs clean and pH and conductivity measurements stabilize. After well development and stabilization of the water levels, water levels and the quantity of well volumes removed from the well will be recorded. A minimum of 48 hours after the monitoring wells are developed, the wells will be purged and a groundwater sample will be collected. Samples will be collected using a disposable bailer, transferred to laboratory supplied glass vials, and placed in an ice-chilled cooler. Samples will be forwarded to a California state- certified analytical laboratory for chemical analysis. Strict chain-of-custody procedures will be followed from the time the sample is collected until the time the sample is relinquished to the laboratory. The elevation of the top of each well casing will be surveyed to the nearest 0.01 vertical feet under the direction of a California licensed surveyor. Task 2b: Destruction of Well VW-15 Well VW-15 will be overdrilled to approximately 91 feet bgs using 8-inch diameter hollow stem augers. Once the well materials been removed from the borehole, the boring will be backfilled to ground surface with neat cement containing approximately 5%bentonite powder. The neat cement will be place by tremie pipe and pump in one continuous pour, as required by SJC/EHD regulations. The boring will be completed to match the surrounding surface. Task 3: LABORATORY ANALYSIS Soil and groundwater samples will be analyzed for TPHG using USEPA Method 8015/8020 DHS LUFT, and for BTEX, methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), 1,2-dichloroethane (1,2-DCA), ethanol, and ethylene dibromide (EDB) using USEPA Method 826013. A California-certified analytical laboratory will perform the proposed analyses. P:\Bp-Arco for URS\6100\Work Plans\6100 workplan-l.doc