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r <br /> PHASE I HYDROGEOLOGE-TNVFSITGATION WORK PIATt <br /> 4491 West Durham Ferry Road,Tracy,California <br /> Dela Project No.40.9I.732 <br /> Page 4 <br /> s located northeast of the former gasoline underground storage tanks. Monitoring well locations are shown <br /> i <br /> in Figure 2. <br /> Installation of these monitoring wells will be performed by a state-licensed drilling contractor and supervised <br /> by a qualified geologist under the supervision of a registered geologist. Proposed monitoring well <br /> construction details are shown in Figure 3. <br /> t <br /> Installation of the monitoring wells will iwvolve drilling an 8-Inch-diameter borehole to a depth of <br /> appraidmately 30 feet below ground surface,or a minimum of 10 feet below the ground water surface,and <br /> installing 15 feet of 2-inch-diameter,No.20 slot,polyvinyl chloride(PVC)well screen,and 15 feet of Bush., <br /> threaded blank PVC casing. The annular space surrounding the screened interval will be backfilled with <br /> No.3 Monterey sand to a point approximately 2 feat above the top of the screened interval;a 2-foot-thick <br /> 4 <br /> bentonite seal will be placed above the sand. The annular space above th,bentonite seal will be filled with <br /> jj a neat cement,and a flush:mounted well vault will be Installed to provide a secure well head. <br /> k <br /> 3A Decontominatlon <br /> All drilling and samp!ing equipment will be cleaned before each soil boring is drilled using a high-pressure <br /> steam cleaner. The California split-spoon sampler will be cleaned with phosphate-free soap and rim with <br /> water:allowing each sample collection. <br /> 3.S Solt Cuttings <br /> Drill cuttings from the soil borings will be placed an visquine and stored on site. Upon receipt of the <br /> chemical results of the soil samples collected froz the soil borings,final disposal of the soil cuttings will be <br /> r determined. <br /> i <br /> 33.6 Monitorine Well Revelonment <br /> After Installation,each monitoring well will be developed using a suction-lift pump until the water extracted <br /> is sediment-free. No water or chemicals will be introduced into the monitoring wells during well <br /> L development. Ali development water will be contained and placed in drums,and will be stored on site. The <br /> disposition of the development water will be determined based on chemical results of the ground water <br /> _ <br />