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URS Ms. Margaret Lagorio Page 2 San Joaquin County Environmental Health Department June 1, 2004 through V-6, and groundwater extraction well E-1 by over-drilling with 10-inch outside-diameter (OD) hollow-stem augers (HSA) to total depth and filling the boreholes with a Portland cement grout containing<5%bentonite powder to near surface. Monitoring wells W-lA, W-2, and W-213, and vapor wells V-7 and V-8 could not be over-drilled with the available drill rig due to the proximity of the rig tower to three overhead high-voltage power lines when the rig was in position over the wells, therefore the remaining monitoring wells and vapor wells were pressure grouted at 30 pounds per square inch (psi). The top three feet of wells W-1A and W-2B were over-drilled with 10-inch-OD HSA and well W-2 was over-drilled with 18-inch-OD HSA.Exposed well casing was then cut and a grout cap put in place. Vapor wells V-7 and V8 were hand cleared to 6- inches below the bottom of the well vault and a grout cap was put in place. In an effort to keep the top of the borehole plugs from being destroyed during future regrading of the site, surface completion consisted of a concrete cap placed on top of the grout cap such that the entire plug remained a minimum of 2 feet below ground surface. The remaining two feet of open borehole was filled with loose soil flush with the ground surface. During excavation of the USTs, the concrete vault containing vapor well V-6 and associated remediation piping was removed and the top of the well was broken off. When the UST pit was closed, V-6 was neither properly destroyed nor was its location marked. Based on historic piping diagrams, relocation and excavation of the original well site uncovered the broken well. The well was then over- drilled to total depth using 10-inch-OD HSA and filled with a Portland cement grout containing <5% bentonite powder to near surface. After properly destroying all on site wells, eight concrete well vaults, which housed extraction well E-1 and vapor wells V-1 through V-5 and V-7 and V-8 and associated remediation piping were removed. A backhoe was used to excavate and pull out the vaults. Concrete and piping refuse created during vault excavation was placed in an open-top refuse bin and stored on site. Soil cuttings generated during the well destruction activities were placed in a closed-top soil bin and stored on site as well. Composite soil samples were collected from the soil cuttings and submitted to Sequoia Analytical Laboratory in Petaluma, California, for analysis of gasoline range organics (GRO) by EPA Method 8015B (preparation EPA Method 5030), benzene, ethylbenzene, toluene, xylene, (BTEX) by EPA Method 8260B (preparation EPA Method 5030), and lead by EPA Method 6000/7000 series. Analytical results from these samples are included in Table 1. The laboratory analytical report is included in Attachment B. On April 26, 2004 and May 4, 2004, Dillard Trucking, Inc. removed vault refuse and soil cuttings from the site. Soil cuttings and vault refuse were transported to Republic Landfill in Livermore, California where it was disposed of a non—hazardous waste. Soil cutting and vault refuse disposal documentation is included as Attachment C. K:\Wprocess\J5 BP ARCO\00434\Site Closure\434 Well Destruction Report V2.doc