ARCHIVED REPORTS XR0010965 - Laserfiche WebLink

Home Browse Search

Geological neclmks lKc. Page 3 Well Abandonment Report Project No.750.2 January 12,2006 the Work Plan — Well Abandonment. Ms Duncan approved the work plan with notation on well abandonment procedure in a letter dated August 31, 2005. The following report discusses the destruction/abandonment of all wells associated with the COE site. 2.0 WELL ABANDONMENT There were five (5) water table, one (1) deep monitoring and four (4) vapor extraction wells associated with the COE site. GTI properly decommissioned these wells in an effort to meet requirements leading to a "No Further Action Letter". All monitoring wells associated with the site were monitored regularly and were in good condition. No obstacles were observed in any well. A summary of well construction is included as Table 1 in Appendix A and well locations are denoted in Figure 2. Woodward Drilling Company of Rio Vista, California (C-57 Lie #710079) was employed to decommission the wells associated with the COE site. Permits were secured as necessary and the local regulatory agency was notified 48 hours prior to commencing work. There was a large vault constructed on-site that housed the manifold for the vapor extraction system. Del-Tech Geotechnical Support Services using a backhoe removed the vault. The manifold was removed from the wellheads and associated piping. Wells: MW-1 MW-2 MW-4 MW-5 MW-101 VEW-3 and VEW-4 These wells, located on-site, were of typical vertical well construction. These wells were abandoned using the following procedure: • The well box and supporting concrete apron were removed by backhoe. • A vacuum truck and "wet" knife were used to excavate a hole approximately 1-foot larger in diameter than the original borehole around the annular to a depth of approximately 3 feet below grade. • The soil was stored, on-site, in DOT approved steel drums until disposal was arranged. • Grout was pumped into each well casing using 3/ inch diameter tremie pipe while displaced water was pumped into a DOT approved steel drum until disposal was arranged. It was noted that very little displaced water was present. • Pressure of approximately 35 psi was applied to each well casing for approximately 5 minutes. • The well casing was then cut off approximately 6-inches above the base of the excavated hole. • Grout was pumped into the "cut" well casing and allowed to mushroom over the casing and fill the bottom 12 to 18 inches of the excavated hole. ..r • The excavated hole was backfilled to grade with clean overburden. Wells: VEW-1 and VEW-2 These wells were located approximately 20 feet east of the site beneath Escalon Avenue. The ..� vertical extraction wells were connected to the manifold, located in the vault discussed above,by