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1 <br /> Lang ston's.,Varket <br /> 15615 Seventh Street, Lathrop, California October f, 1995 <br /> 46 Interim Secontlary Source Removal& 1t-Aon toring Hell ltcpla ryrrnjent Page: 6 <br /> bentonite to the top of the clay and the well screcn set at that depth EW-1 and <br /> MW-2 are four-inch wells that can be used for groundwater extraction, if needed <br /> MW-3 & 4 are two-inch wells (Appendix C) <br /> ' Permits were obtained as necessary for all wells (including borings) before drilling <br /> began The sodjxmLigs were accomplished using a mobile mounted drilling ng <br /> ' employing the use of a hollow Stem flight auger no less than 3 1/4" i d and 8 7/8" <br /> o d 1� °" <br /> ' All drilling equipment was thoroughly steam-cleaned before drilling began, to <br /> prevent the introduction of contamination from off site and betwecn borings to <br /> prevent cross contamination <br /> The borings were logged under the direct superrasion of a reg-stered pto fessional <br /> using the Unified Soil Classification System (Appendix E) 11ie color, texture, <br /> moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil <br /> or bedrock characteristics and any evidence of contamination wei e noted All <br /> water bearing zones and the depths at which they were encountered were noted on <br /> these logs <br /> ' All borings were drilled in such a manner as to prevent Grass coni aniination <br /> between sti ata Exploratory soil borings within the ui =-jrated trine were <br /> backfilled with nest cement <br /> Upon termination, the boring into the saturates' zo;Ic was completed as a , <br /> monitoring well and backfilled with concrete grout, after a Bentonite seal had been <br /> placed The boring for the monitoring Aell was of a diameter at least 3 inches J <br /> greater than the diameter of the well casing used <br /> The cuttings fiom the drilling opeiaoon were containerized cin-site during drilling <br /> for proper disposition `rhe pnuper method of disposal will be dependent ul+on <br /> results of'laboratory analysis <br /> ' <br /> 34 Well Construction <br /> ' All materials used in well (onstruction was thoroughly cleaned prior to <br /> introduction into the boring A Bentonite or cement and Bentonite grout was <br /> placed at the bottom of the boring as necessary After the seal had been allowed to <br /> set long enough to support the weight of the casing, a 2 or 4- inch diameter PVC <br /> well casing with end cap and factory perforations for placement in the saturated <br /> zone (taking into account seasonal variation) was placed in the boring The screen <br /> and filter pack sizes are as noted in the Boring/Well Completion Logs (Appendix <br />