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Tr_T k - CRATM COMPANY <br /> 95"V[320 PH!!: 59 <br /> August 14, 1996 <br /> Mr. Ron Rowe <br /> San Joaquin County Public Health Services Department <br /> Environmental Health Division <br /> 304 E. Weber Street <br /> Stockton, California 95201 <br /> SUBJECT: Construction Specifications, Piezometer Installation, Occidental Chemical <br /> Corporation Lathrop Groundwater Remedial Program. Reference No. 197. <br /> Dear Mr. Rowe: <br /> As you are aware of, the geologic pilot borehole drilled for EW-4 replacement well (EW- <br /> 4A) installation strati grap hic/materials classification will be converted to a piezometer. <br /> The piezometer was originally planned as a temporary data point to be utilized along with <br /> EW-4A replacement pumping tests. The piezometer was to be abandoned immediately <br /> after conclusion of the pumping tests. Mr. Alexander MacDonald of the CRWQCB <br /> agreed that the piezometer would be a valuable asset to hydrogeologically characterize <br /> the deep zone aquifer surrounding proposed EW-4A. Therefore, the piezometer will be <br /> constructed as a permanent water level monitoring well. Because of the permanent <br /> status given to this well, the piezometer will be constructed to the following nominal well <br /> specifications as required by the San Joaquin County Department of Public Health <br /> Services, Environmental Health Division (PHS - EHD): <br /> The existing 4 1/4" diameter pilot borehole, which has been drilled to a depth of <br /> 215 feet bgs and geophysically logged, will be reamed to a diameter of 6 inches. <br /> A 1 1/4" (1.67" OD) diameter, schedule 40 PVC, 0.020 slot screen will be set at a <br /> depth of 213 feet bgs, extending to 173 feet bgs followed by 1 1/4" blank PVC <br /> casing to 2 feet above the surface. A sand filter pack consisting of #3 sand will <br /> be tremmied to a depth of 2 feet (minimum) above the top of the screen followed <br /> by a tremmied bentonite seal (minimum 2 feet thick). The sanitary seal will be <br /> completed by bentonite grout tremmie to the surface and surface completed by <br /> concreting in a 6" diameter locking metal surface casing protected by 3 concrete <br /> filled guard posts. The well will be developed by surge and bailing 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 />