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gill <br /> .... ............... <br /> Page 2 <br /> Between sampling attempts, the sampler eras dissassembled <br /> and washed in a trisodium phosphate (TSP) solution, rinsed <br /> twice with purified water, and reassembled w'i.th new brass <br /> ring liners to mi. imize the potential of cress contamination. <br /> Auger cuttings from the drilling operation were placed in <br /> approved steel drums on--site. Those auger cuttings which did <br /> not exhibit the obvious presence of contamination by field <br /> screening with a portable photoionization detector were <br /> segregated into "clean" drums. Results of chemical analysis <br /> conducted on those samples obtained from exploratory soil <br /> borings will dictate the proper disposition of those <br /> contaminated soils. Exploratory soil borings not completed <br /> as monitoring wells were backfilled to the surface with <br /> cement ground upon termination. <br /> Groundwater Monitorin Well Installation <br /> The ten groundwater monitoring wells were constructed <br /> using 2-inch and 4-inch flush-thread pvc schedule 40 well <br /> _ pipe, and completed to a depth of 50 feet. A 20 foot section <br /> of 0.020 inch slotted well screen was installed in each of <br /> I�w the monitoring wells, with approximately two-thirds of the <br /> screen interval set below the encountered water table. The <br /> filter pack around the screened interval, was placed by <br /> I backfilling through the hollow-stem augers to ensure an even <br /> distribution in the annular space. The filter pack, which <br /> consisted of a washed #3 sand, was completed to approximately <br /> one foot above the top of the screened interval. A seal <br /> Fw composed of bentonite pellets was placed to a thickness of <br /> approximately two and one-half feet atop the filter pack, and <br /> ' ! was hydrated. The remaining annulus was backfilled with a 3% <br /> bentonite cement grout from the bentonite seal to the surface <br /> vault. A locking well cap was installed, and water-tight <br /> surface vault was placed at grade for well security. The <br /> design of the groundwater monitoring wells is in general <br /> compliance with the State of California Department of Water <br /> Resources Bulletin 74-90 Monitoring Well Standards (DWR <br /> ! 163907) . Please refer tc the Logs of Borings in Appendix C <br /> �- which illustrate a schematic of each monitoring well <br /> construction. <br />