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PRELIMINARY HYDROGEOLOGIST AssESsmFyr izFPORT <br /> 34800 West Frontage Road <br /> .. Manteca,California <br /> Delta Project No.40-88.474 <br /> Page 13 <br /> 6.2 Soil Classification <br /> Al soil samples were examined in the field by a geologist and described for color, grain size, moisture <br /> i., <br /> content,mineral content,and odor,and were classified in accordance with the Unified Soil Classification <br /> System. <br /> 4.3 Monitorin2 Well Installation <br /> t <br /> Monitoring wells MW-3 and MW4 were installed using 2-inch-diameter flush-threaded Schedule 40 PVC <br /> - blank casing and 0.010 inch slot screened interval. Construction details for these monitoring wefts are <br /> presented in Appendix C. Following the placement of the well :.sing and screen, a sand filter pack, <br /> extending from the bottom of the screen to about 2 feet above the top of the screen,was placed in the <br /> annitlar space between the well screen and the borehole;. A 2-foot-thick bentonite seal was placed above <br /> the filter pack using bentonite pellets. The annular space above the bentonite was filled with a cement- <br /> . t:r3 <br /> bentonite grout which extended to the ground surface. Each well was fitted with a lockable water-tight <br /> cap and a protective-steel well cover. <br /> F-a 6.4 Well Develotsment <br /> l "e. In order to remove natural aquifer fines and drill cuttings from the vicinity of the well screen; each <br /> monitoring well was developed with a dedicated hand pump. A piece of PVC tubing the length of the <br /> well was inserted in each well with a check valve on the bottom. The tubing was quickly moved up and <br /> down forcing sediment and water to the surface and out the top of the tubing. Development water was <br /> stored on site in labeled 55-gallon drums pending disposal, as required. <br /> Approximately 25 gallons of water was c-lacuated from each well. Electrical conductivity was monitored <br /> and recorded for each well. When the turbidity of discharge waters and the conductivity stabilized, <br /> development was temiinated. <br /> 6.5 Ground Water Sam lin <br /> Ground water samples were collected from all monitoring wells, All wells were sampled using the <br /> dedicated pump described above. Because the pump never leaves the well, it reduces the risk of sample <br /> contamination. Each well was purged by pumping three to five wetted casing volumes of ground water <br /> before actual sample collection. <br />