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(YVATC SCOPE OF WORK Field Activities ATC proposes to abandon an unused facility supply well located at the DWG facility. The well is located adjacent to a staircase inside of the DWG building, the well location is shown on Figure 2. The well is located within a concrete below-grade vault below a concrete floor. The vault is rectangular and has dimensions of approximately 5-feet by 5-feet by 6-feet deep. The well head is mounted flush to the bottom of the vault. The vault is covered with a metal cover. During a previous investigation welding equipment was used to cut a hole in the immovable metal cover to allow access to the well. During a previous site investigation on May 2, 2003, video well logging was performed to evaluate the condition and construction details of the on-site facility well. The total depth of the facility well borehole was observed to be 133 feet below top of casing. The bottom 25 feet of the borehole was open. Based on observations from the bottom 25 feet of the boring, the borehole diameter was estimated to be 18 to 24 inches. The well casing was constructed of steel pipe with a diameter of approximately 1 foot and extended to a depth of 108 feet from the top of casing. The well was vertically perforated beginning at a depth of 67 feet below top of casing and extended to the bottom of the casing. The casing was in fair condition. The well will be abandoned by lowering a perforating tool into the well to the bottom of the casing and perforating the casing as the tool is extracted from within the well. Once the casing has been perforated and the perforating tool removed from the well, the well casing, filter pack, and the open space beneath the well casing will be filled with neat cementfbentonite grout. The grout will be emplaced by pumping a grout mixture into the well using a conductor pipe (tremie pipe). The conductor pipe will be extended to the bottom of the well and slowly raised toward the top of the well at a rate no faster than the grout material fills and displaces water from the well and until the well is completely filled. Based upon well construction details, an estimated volume of approximately 966 to 1,223 gallons of grout will be used to abandon the facility supply well depending on the actual borehole diameter. Grout volume calculations are attached. The vault will not be filled with concrete. Report Preparation Upon completion of the well destruction activities, a summary report will be prepared for submittal to the SJCEHD and the CRWQCB. The report will include a description of the field activities. s:\environmental\62583\rev-wellabmdonmentwp.doc 2