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MITTELHAUSER <br /> corporation <br /> 7901 Stoneridge Drive,Suite 123 <br /> Pleasanton,California 94566 <br /> Bus: (510)416-2900 <br /> Fax: (510)416-0957 <br /> January 19, 1993 <br /> RpTiiklyX <br /> Mr. Michael Infurna <br /> San Joaquin County Public Health Services JAN 2 21993 <br /> Environmental Health Division <br /> 445 N. San Joaquin Street ENVIRONMENTAL HEALTH <br /> Stockton, California 95202 PERMIT/SERVICES <br /> Subject: Workplan for Well Abandonment <br /> Diamond Property Site <br /> Corner of Tracy Blvd. and 11th Street <br /> Tracy, California <br /> Dear Mr. Infurna: <br /> At your request, Mittelhauser Corporation (Mittelhauser) <br /> has prepared this workplan for the abandonment of six wells located <br /> on the Unocal/Diamond Property site (see Site Location Map, Figure <br /> 1) . This well abandonment will be performed in preparation for <br /> site closure as per San Joaquin County guidelines. <br /> BACKGROUND <br /> The six wells include five groundwater monitoring wells <br /> and one vapor extraction well, as shown in the Well Location Map, <br /> Figure 2 . Four quarters of non-detect findings for the <br /> constituents of concern resulted in County approval for site <br /> closure. The following workplan outlines the well destruction <br /> procedure. <br /> WELL ABANDONMENT <br /> Abandonment of the groundwater monitoring wells will <br /> involve a two phase procedure. The monitoring wells will be tremie <br /> grouted with neat cement to remove the groundwater and then <br /> pressurized to complete the well destruction. The grout will be <br /> mixed at a proportion of one bag of cement to 5 to 10 gallons of <br /> water with a maximum of 3 to 5 percent bentonite. <br /> The vapor extraction well will be abandoned by emplacing <br /> a thick cement mixture on the bottom of the vertical riser to plug <br /> this section of the piping system. Destruction of the groundwater <br /> monitoring wells would then be performed in order to allow time for <br /> the cement plug to set. If groundwater is encountered above the <br /> ® CHICAGO, It_ BAKERSFIELD, CA INDIANAPOLIS, IN LAGUNA HILLS, CA <br />