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Mr. James Barton February 15,2007 Page 3 Well Decommissioning Prior to well decommissioning, ENSR will measure depth to water and verify the total well depth to confirm that it is not obstructed. Any obstructions will be removed prior to well abandonment. Following a review of the soil and historical groundwater analytical data for well MW-15,the SJCEHD approved pressure grouting as the method to decommission the well by email on January 4,2007. ENSR will oversee decommissioning by pressure grouting using 5%bentonite cement. Prior to grouting, a 21-inch diameter excavation will be cleared around the monitoring well to a depth of five feet below ground surface by air knifing. Subcontractor personnel will remove the well box and cut the well casing six inches above the bottom of the excavation. A one-inch tremie pipe will be placed to the bottom of the well and cement pumped to the top of the pipe. The volume of grout pumped into the well will exceed the calculated screen interval volume, including filter pack, by approximately 20%. The grout will be mixed and pumped mechanically. The driller will allow the grout to overfill the pipe and fill it for a thickness of one foot and form a"cap"that has the diameter of at least 20 inches. Once the grout has settled, the remaining four feet of the hole will be backfilled with clean sand or native soil and a neat asphalt patch will be placed at the surface. The well removal depth and backfilling method is preferred to accommodate construction activities associated with the planned expansion of Pacific Avenue over the area currently occupied by monitoring well MW-15. This completion method will prevent the abandoned well from interfering with subsequent road construction by the City of Stockton. Waste Containment, Profiling, and Disposal Decontamination and rinsate water and any groundwater displaced by grouting procedures will be contained in UN approved 55-gallon drums, labeled as non-hazardous waste, and temporarily stored on Site pending transport and disposal. Tracking documentation for disposal will be maintained and included in the subsequent well abandonment report that is more fully described under Task Three below. The surface well box and well debris generated by the air knifing of the upper 5-feet of the well will be disposed of as demolition refuse. All investigative derived waste will be characterized prior to proper disposal. Historical analytical data from groundwater monitoring of well MW-15 is included in Table 2 and will be provided at the Site for the purpose of waste characterization of water generated during well decommissioning. The analytical data for well MW-15 has shown non-detect results for TPHg, BTEX,fuel oxygenates, and methyl tertiary butyl ether(MTBE)for the past three quarters, and only intermittent hits at low concentrations during previous monitoring events since September 1994. These results demonstrate that transportation and disposal of the water as non-hazardous material is appropriate. ENSR AECOM