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■ Geotechnical Inc <br /> a� <br /> c� <br /> VIBRATING WIRE SENSOR INSTALLATION <br /> WORK DESCRIPTION <br /> Rindge Tract and Roberts Island <br /> San Joaquin County <br /> Consultant: Raney Geotechnical Inc. <br /> Drilling Contractor: Cal-Nev Geoexploration <br /> Purpose: To install vibrating wire pressure sensors. The sensors will be used in monitoring pressures <br /> developed when a gas pipeline is constructed beneath the San Joaquin River. Construction of the <br /> pipeline is scheduled to begin November 3, 2005. There is no known contamination in the area; <br /> sampling of soils or groundwater is not included in this work. <br /> Description: The sensors will be installed at four locations; two on the north side of the San Joaquin River and <br /> two on the south side. Each sensor consists of a vibrating wire transducer in a 3/4" diameter steel <br /> housing six inches long, and is attached to a polyethylene encased four-wire cable. The sensor is <br /> embedded in a sand packed zone about four feet thick at a depth of about 95 feet below the <br /> ground surface. The borehole above the sensor is sealed with bentonite chips and the remainder <br /> of the borehole will be filled with cement grout. The cable extends to the surface to allow <br /> monitoring during the construction period. Following construction, the cable will be cut off at <br /> the top of the grout backfill. See attached Installation Schematic. <br /> Method: Each sensor will be installed in a borehole varying from three to six inches diameter. The upper <br /> 40 to 45 feet of the borehole will be drilled using six-inch diameter hollow stem augers. The <br /> lower portion will be drilled using three-inch diameter rotary wash methods. The borehole below <br /> the augers will be held open with biodegradeable drilling mud. After insertion of the sensor, <br /> sand pack, and bentonite seal, the borehole will be filled with cement grout, either pumped or <br /> tremied in place, to displace the drilling fluid.. <br /> Grouting of the drill hole at the time of installation is considered to effectively accomplish <br /> destruction of the well. The sensor and below-ground portion of the cable will be left in place. <br /> For further information, please contact me. <br /> RANEY GEOTECHNICAL INC. <br /> William C. Boli <br /> Registered Geotechnical Engineer No. 2004 <br /> Office Phone: 916-371-0434 <br /> Cell Phone: 916-416-2101 <br /> 3140 BEACON BLVD.•WEST SACRAMENTO, CA 95691 •TELEPHONE 916/371-0434•FAX 916/371-1809 <br />