ARCHIVED REPORTS_REMEDIAL ACTION DOCUMENT

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REMEDIATION COMPLETION REPORT-LATHROP DEHYDRATOR STATION 3.0 FIELDACTIVITIES feet outside and east of the property boundary fence.Because permission for access to MW-10 had not been granted by the property owner at the time,the well was abandoned by staging well abandonment equipment within the station fence and using a boom arm over the fence to remove the well casing. A telescoping boom was used to place grout in the well void. Before grouting of the well could be conducted,the sand filter pack of the well sloughed to about 10 feet bgs. As discussed with the San Joaquin County Inspector at the time,the grout mixture was thinned to facilitate grouting the sand below the 10-foot level. The borehole was grouted from 10 feet bgs to 4 feet bgs. On February 13,2004,monitoring well MW-10 was overdrilled to comply with San Joaquin County's request. MW-10 was abandoned by overdrilling the well location to 23 feet bgs with a 10-inch hollow-stem auger. The borehole was then grouted to the surface with a cement and bentonite mix. A copy of the approved well abandonment permit is included in Appendix A. 3.3 Site Preparation and Demolition Activities Site preparation activities included clearing the Site,constructing the project and installing temporary fencing to enclose the work area for security. Project facilities included a wash area for personnel decontamination (emergency eyewash,boot wash and hand wash basin), and a pressure-washing area for equipment leaving the Site. Exclusion zones(soil handling) and support zones (vehicle parking and equipment staging) were clearly identified and delineated. The demolition and excavation areas were staked and marked and USA was notified. Structures demolished at the Site include the reboiler slab, two equipment pads along the northwest boundary of the Site, the production fluids tank pad and containment berm,a burner pad,and a small building. An excavator,backhoe,and concrete breaker were used for demolition of concrete pads and containment,while hand excavation was employed around gas lines,valves,and risers. In addition to the demolition of concrete pads, the contactor tower and production fluids tank were rinsed and flushed out, disconnected (by PG&E) and removed.Per PG&E direction,the contactor tower concrete pad was not demolished. Figure 3 shows the demolished features including abandoned concrete slabs and pads,a light pole,former sump and lines,and the production fluids tank and contactor tower removed from the Site. At the completion of demolition activities and prior to excavation activities,field work was suspended due to inclement weather forecasted for the following two weeks.All equipment was demobilized and the Site was secured by February 20,2004. A second mobilization of equipment and site set-up for excavation activities commenced on April 12,2004. Equipment mobilized to the Site included an excavator,dozer,scraper,and compactor.The proposed excavation area was staked and painted and USA notified prior to �• commencing work.Copies of the USA call-in sheets are included in Appendix A. The excavation activities conducted during the second mobilization included soil excavation, verification sampling,backfilling,and site restoration,as described in Sections 3.5,3.6,3.7, 1� and 3.8 of this report,respectively. SFOILATHROPCOMPLETIONREPORT 12-1-04.DOC 5