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Ge4gical Tecknics I=. Well Abandonment W,P. Page 3 Project No.989,2 LA February 25,2005 and Appendix B Checklist Report discussing the work approved in the work plan and 'r requesting site closure. In a letter dated January 28, 2005, Margaret Lagorio, SJCEHD, stated that the site investigation and remedial action of contamination resulting from an unauthorized release from the underground storage tank(s) formerly and/or currently located at the VWDC site has been completed. A Case Closure Summary was included with the letter. The attached work plan addresses the abandonment of monitoring wells associated with the VWDC facility. V 2.0 WELL ABANDONMENT There are nine (9) water table monitoring wells and one (1) deep monitoring well associated with the VWDC site. GTI proposes properly decommissioning these wells in an effort to meet requirements leading to a "No Further Action Letter". All monitoring wells associated with the site have been monitored regularly and are in good condition. No obstacles have been observed in any well. A summary of well construction is included as Table 1 and well locations are denoted in Figure 2. A competent C-57 well driller (selected through bidding process after work plan approval) will be employed to decommission the monitoring wells. Permits will be secured as necessary and the local regulatory agency will be notified 48 hours prior to commencing work. La The wells will be divided into two categories: o Category 1 — Wells with contaminants detected more than one quarter during the *` previous eight quarters including: MW-1, MW-4, MW-5, MW-6, MW-8 and MW-9. o Category 2 — Wells that have been non-detect for at least seven of the last eight quarters including: MW-2, MW-3, MW-7 and MW-101. Category 1 wells will be over drilled using 8-inch hollow stem augers guided down the center of the well casing via a guide rod attachment on the drill bit. Grout, a cement-bentonite mixture, will be used to seal the borehole. To prevent bridging and ensure a good seal, the grout will be kept under pressure by the use of a tremie pipe to feed grout into the borehole through the augers. The tremie pipe will be submerged several feet below the level of grout at all times. The borehole will be grouted to within three feet of the surface and the uppermost few feet will be backfilled with clean material. The surface will be capped with 4 the appropriate material (i.e. concrete or asphalt) to match the surrounding surface conditions. Category 2 wells will be filled with grout via a tremie pipe followed by pressurizing the grout filled well. Approximately 35 psi of pressure will be applied to the well for up to five minutes. The pressure cap will be removed and the process will be repeated if there is more