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INTERIM REMEDIAL AMON PLAN <br /> 4491 West Durham Ferry Road <br /> . Tracy, CaLfnr:ua <br /> Delta Project No 40-91-732 <br /> Page 4 <br /> 3.0 RESULTS <br /> 3.1 Site Soils and Geology <br /> On August 28, 1991, two soil borings were drilled on site to depths of 25 feet below the ground surface <br /> and were completed as monitoring wells (MW-2 and MW-3, monitoring well MW-1 had previously been <br /> installed) The monitoring well locations are shown In Figure 2, and the soil boring Logs are presented <br /> in Appendix A Generally, the llthology was comprised of dark to light brown silty clay and sandy silt <br /> with medium to fine grained sand lenses The sand lenses were approximately 2 feet thick at a depth of <br /> approximately 3 feet Sampling procedures are presented in Appendix B <br /> 3.2 Monitoring Well Installation and Develo ment <br /> Two 2-mch-diameter monitoring wells (MW-2 and MW-3) were installed at the site, and their locations <br /> ' are shown in Figure 2 The wells were constructed with Schedule 40 PVC riser pipe, 0 020 slot-size <br /> screen, No 3 Monterey sand filter pack, and sealed with bentonite and cement grout Construction <br /> details are presented in Appendix C Monitoring wells MW-2 and MW-3 were screened from 10 feet <br /> below the ground surface to their completed well depths of 25 feet All wells, including monitoring well <br /> MW-1, were developed after installation by removing approximately 10 well casing volumes of water to <br /> remove any fine-grained sediment <br /> 3.3 Surve of Monitoring Well Elevations <br /> iOn August 28, 1991, Delta personnel surveyed the horizontal location and the elevations of the top of <br /> each monutoring well casing and the adjacent ground surface in reference to a temporary bench mark <br /> ' The bench mark was a utility cover located In the center of Durham Ferry Road with an assumed <br /> elevation of 100 feet <br /> 3.4 Ground Water Table Measurements <br /> ' <br /> Groundwater was encountered at approximately 10 feet below the ground surface during drilling Depths <br /> to ground water were measured and recorded for each monitoring well on September 4, October 13, and <br /> 20, 1991, and April 9, and July 10, 1992 All field measurements are presented In Table 1 The <br /> direction of ground water flow on September 4, 1991, was calculated to be toward the southeast, the <br /> RPT045 TA <br />