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Mr Edward Ralston July 11, 1995 <br /> Page 2 <br /> WELL ABANDONMENT <br /> FIELD PREPARATION <br /> Prior to beginning field work at the site, Mittelhauser obtained workplan approval and a <br /> well abandonment permit from SJCPHSIEHD A copy of the workplan is attached as <br />' Attachment 1 and a copy of the permit for well abandonment is attached as Attachment <br /> 2 Mittelhauser prepared a Site Safety Plan to address safety hazards associated with <br /> drilling equipment and pressure grouting The Site Safety Plan was reviewed during the <br />' "tailgate safety meeting" <br />' WELL ABANDONMENT PROCEDURES <br /> Soil Exploration Services (C57 License No 582696) performed the following well <br /> abandonment procedure under the observation of Mittelhauser field personnel <br /> • First, the monitoring wells were tremae grouted with neat cement to remove the <br /> groundwater The grout was mixed at a proportion of one bag of neat cement to <br /> 5 to 10 gallons of water with a maximum of 3 to 5 percent bentonite <br /> • The well casings were then pressurized to complete the well destruction The well <br /> casings were pressurized at approximately 20 pounds per square inch (psi) for 15 <br /> minutes, except for MW-4 which was pressurized for approximately five minutes <br /> • Afterroutin and pressurizing the well casings, the upper 2 feet of the wells were <br /> 9 9 <br /> drilled out to provide approximately 2 feet of vertical distance from the ground <br /> surface to accommodate future grading The resulting cavity was then backfilled <br /> with bentonite slurry overlain by the surrounding gravelly sand soils <br /> GROUT VOLUME OBSERVATIONS <br />' The volume of grout estimated for well abandonment was approximately 35 to 40 <br /> gallons Former monitoring wells on the east side of the property (MW-3A and MW-1 ) <br /> took a maximum of approximately 40 gallons of grout under pressure for 15 minutes <br />' On the west side of the site, however, former wells MW-2 and MW-4 took approximately <br /> 105 and 60 gallons of grout, respectively Mittelhauser field personnel verified the <br /> absence of fresh grout in the nearest storm drain inlet During the County's grout <br /> inspection, Mr Harlin Knoll(SJCPHS/EHD) attributed the excessive grout absorption to the <br /> presence of permeable sand lenses <br />