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KLEINFELDER 4.2 Monitoring Wells MW-1 and MW-2 Abandonment In order to accommodate the future development of the site Kleinfelder proposes to abandon monitoring wells MW-1 and MW-2 and install new monitoring wells (MW-Ir and MW-2r) in "like hydrogeological conditions." The locations are shown on Plate 2. The methodology for the installation of these replacement wells is as follows. During the course of abandonment, MW-1 and MW-2 will be mechanically removed by overdrilling with hollow-stem augers and grouted with bentonite/neat cement or sand-cement slurry (mortar). The grout will be tremmied into the former well boring to ensure filling to within three feet of the surface. The upper three feet will then be backfilled with on-site soil and tire-rolled with the backhoe. 4.3 Monitorine Wells MW-lr and MW-2r Installation and Sample Collection A total of two (2) monitoring wells will be installed at the project site at the locations shown on Plate 2. For purposes of the attached cost estimate, the wells will be installed to a total maximum depth of approximately 30 to 35 feet below ground surface (bgs). Approximate first groundwater is currently estimated at a depth ranging from 16 to 20 feet bgs. The monitoring wells will be installed using a truck-mounted drill rig equipped with 10-inch hollow stem augers. During the advancement of the borings, soil samples will be obtained at five-foot intervals starting from the surface for lithologic classification, but will not be chemically analyzed. A four-inch diameter well will be constructed in each boring. The wells will use a 20-foot screened section (with approximately 5 feet of screen above and 15 feet below the current groundwater level). The borings will be drilled, logged, and sampled following the Typical Kleinfelder Field Protocol described in Appendix A. Soil cuttings generated during the drilling will be placed on the ground surface. Water generated during steam cleaning of auger and/or equipment, and development/sampling of the wells will not be contained. 4.4 Well Development and Surveving Twenty-four to 48 hours after installation, the monitoring wells will be developed to remove sediment-laden water and to increase the effective radius of the wells. Development will be performed as described in Appendix A, Sections A-3.2 through A-3.3. Once the wells are installed, the top of each well will be surveyed by MCR of Manteca, California (contracted independently by Atherton Kirk Development Company) so that depth-to- groundwater measurements in the wells can be converted to groundwater elevations used to assess groundwater gradients. The wells will be surveyed relative to a local benchmark. The wells will be surveyed as described in Appendix A, Section A-3.4. 20-YPO-273/2000P331/200OW034 Page 7 of 1 I Copyright 2000,Kleinfelder,Inc. September 4,2000