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Mr. Philip Isorena Proposal P93-040.31 <br /> July 12, 1993 <br /> Page 7 <br /> The sampler and CPT rods will be decontaminated by steam cleaning after each sample <br /> is collected to eliminate potential cross-contamination between borings. Steam cleaning <br /> water will be drummed for disposal. Borings will be grouted to the ground surface using <br /> either a bentonite cement grout or a bentonite grout tremied to the base of the boring. <br /> Task 7. Exploratory Borings and Monitoring Well Installation <br /> Groundwater monitoring well locations will be determined following review of CPT and <br /> field screening data. Specific completion intervals and well construction details will be <br /> based upon the results of the CPT and analytical data from the HydroPunch program. The <br /> results from the CPT and HydroPunch sampling program will be incorporated into the <br /> geologic cross sections to determine the optimum location and completion intervals for <br /> the subsequent groundwater monitoring wells. These results will be reviewed with the <br /> STTC and RWQCB to obtain concurrence on the proposed well installations. <br /> Exploratory borings will be drilled using air-rotary casing hammer equipment to minimize <br /> the potential for cross-contaminating deeper water-bearing zones. The casing hammer <br /> method utilizes a heavy wall metal casing that is driven along with the drill bit to seal off <br /> the boring from the surrounding formation. This drilling method permits continuous <br /> sampling of the soils while generating no drilling fluids, which therefore permits <br /> recognition of saturated and non-saturated intervals. This method was selected over the <br /> mud-rotary drilling method based on lower overall costs. Detailed boring logs will be <br /> prepared by an EMCON geologist based on samples and drilling return materials. Samples <br /> will be logged according to the Unified Soils Classification System and all work will be <br /> supervised by a Registered California Geologist and will conform to regulatory standards. <br /> Drilling equipment and samplers will be decontaminated by steam cleaning after each <br /> boring to eliminate potential cross-contamination. <br /> Monitoring wells will be constructed using 2-inch-diameter schedule 40 polyvinyl chloride <br /> casing, and 10-foot sections of factory-slotted casing will be used for screened intervals. <br /> Gravel pack intervals will extend 2 to 5 feet above the screened interval, and a 2-foot <br /> bentonite seal will be placed above the sand. The annular space will be grouted to the <br /> surface using cement bentonite grout. <br /> Monitoring wells will be developed by surging, bailing, pumping, or a combination of <br /> these methods. Wells will then be purged and sampled using procedures described in <br /> Appendix A. Water purged from the wells will be drummed pending chemical analysis <br /> and evaluation of disposal options. <br /> SAGPR(M93\P9304031.bc-93 Imc:S <br />