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Tiredf2,k- CRATM COMPANY <br /> PH J'„7 <br /> H 2: I S <br /> August 19, 1996 <br /> Mr. Ron Rowe <br /> San Joaquin County Public Health Services Department <br /> Environmental Health Division (PHS-EHD) <br /> 304 E. Weber Street <br /> Stockton, California 95201 <br /> SUBJECT: Construction Specifications, New Piezometer (2-inch) Installation, <br /> Occidental Chemical Corporation Lathrop Groundwater Remedial Program. <br /> Reference No. 197. <br /> Dear Mr. Rowe: <br /> As was discussed with you on August 16, 1996, the 1 1/4 inch diameter observation <br /> piezometer which was to be installed as part of the EW-4A extraction well installation <br /> program was not successfully completed due to PVC casing/screen failure. The <br /> piezometer was subsequently abandoned by pressure grouting. In light of this situation <br /> we would like to propose the installation of a new, 2-inch diameter piezometer near the <br /> location of the failed piezometer. The new piezometer will be installed immediately <br /> following the well EW-4A installation and will be constructed to the following nominal <br /> specifications: <br /> A 7-inch diameter borehole will be drilled to a depth of 215 bgs. A 2-inch (2.375" <br /> OD) diameter, schedule 40 PVC, 0.020 screen will be set at a depth of 213 feet <br /> bgs extending to 173 feet bgs, followed by 2-inch blank PVC casing to 2 feet <br /> above the surface. A sand filter pack consisting of #3 sand will be tremmied to <br /> a depth of 2 feet (minimum) above the top of the screen interval followed by a <br /> tremmied bentonite seal (minimum 2 feet thick). The sanitary seal for the well will <br /> be completed by bentonite grout tremmie to the surface and surface completed <br /> by concreting in a 6-inch diameter locking metal surface casing protected by 3 <br /> concrete filled guard posts. The well will be developed by surge and bailing <br /> and/or submersible pumping technique. <br /> Environmental Technology & Remediation Systems <br /> 2055 Niagara Falls Blvd. 2441 Crowne Point Drive 2701 East Hammer Lane <br /> Suite Three Cincinnati, OH 45241 Suite 103 <br /> Niagara Falls, NY 14304 513/326-7600 Stockton, CA 95210 <br /> 716/297-2160 FAX 513/326-7601 209/472-2020 <br /> FAX 716/297-2265 FAX 209/472-2027 <br />