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Environmental <br /> Ms.Wendy Cohen Resources <br /> 10 March 1999 Management <br /> Page 2 <br /> remaining five wells (MW-2, MW-3, MW-4, MW-5, and MW-6) all tagged <br /> at or within three feet of their reported completion depth. <br /> ERM performed well abandonment activities on 22 December 1998. Well <br /> abandonment procedures were overseen and approved by a San Joaquin <br /> County inspector. The following is an outline of the procedures utilized <br /> to abandon wells MW-2, MW-3, MW-4, MW-5, and MW-6: <br /> • Well casings were overdrilled with ten-inch diameter hollow-stem <br /> augers to an approximate depth of three feet below ground surface <br /> (bgs). <br /> • A steel guide rod was inserted in the well casings to depth and <br /> pushed through the bottom of the wells; <br /> • The boreholes were backfilled with neat cement. The cement was <br /> placed with a tremmie pipe as the casings were removed in five-foot <br /> sections; <br /> • Once the casings had been removed, the neat cement was brought up <br /> to a depth of approximately three feet bgs; and <br /> • The remaining boreholes were backfilled with native soil. <br /> The well abandonment procedures for MW-1 were as follows: <br /> • Prior to drilling, a steel guide rod was inserted in the well to ensure <br /> that the drill stem stayed centered on the well; <br /> • Hollow-stem augers (ten-inch diameter)were used to drill out the <br /> grout seal,casing, and filter pack. The abandonment borehole was <br /> extended into native material approximately two feet further than the <br /> original borehole; <br /> • The over drilled borehole was backfilled with neat cement to within <br /> three feet bgs using a tremmie pipe as the augers were removed from <br /> the borehole; and <br /> • The remaining borehole was backfilled with native material. <br />