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510299f3872 P .03 Apr-04-00 12: 26P ARCO - sftol Project 805678 Ron Rowe February 28, 2000 Page 3 Task 2 Groundwater Monitoring Well Installation Three on-site groundwater monitoring resented on Figuresi2 Ex M W-2, and MW-3) are proposed to be installed at the locations pwell locations will be based upon access and utility locations. The exploratory borings for will be advanced to a total depth of approximately 60 feet bgs (depending on subsurface drilling conditions) using 10-inch-diameter hollow stem auger drilling equipment. Anticipated depth to water is approximately 45 feet bgs. Soil samples will be collected at five-foot intervals using a 4-inch diameter modified California split spoon sampler. Sampling equipment will be washed in an alconox solution and rinsed to reduce potential cross contamination. The field geologist will prepare exploratory boring logs from soil samples consistent with the Unified Soil Classification System. Soil samples will be field-screened by conducting headspace analysis using a portable photoionization detector (PID). Soil samples will be preserved by sealing the sample liners with Teflon tape and plastic end caps. Samples will be labeled with respect to site,boring designation, and depth, and placed in a cooler with ice pending selection for laboratory analysis. The borings will be converted to 4-inch-diameter groundwater monitoring wells constructed with Schedule 40 polyvinyl chloride (PVC) casing. The screen intervals will consist of approximately 30 feet of 0.02-inch slotted casing placed at approximately 30 to 60 feet bgs. Number 3 sand will be, used for the filter pack and placed to approximately 2 feet above the well screen. A transitional bentonite seal approximately 3 feet thick will be placed above the filter pack. The remaining annulus will be sealed to within 1 foot of ground surface with cement grout placed through tremie pipe. A traffic rated vault box will be installed flush with surface grade for well head protection. A licensed surveyor will be contracted to survey the location of the wells with respect to mean sea level. Exploratory boring and well installation procedures are presented in Appendix A. Soil cuttings generated during drilling will be stockpiled on-site on plastic sheeting and sampled for disposal profiling. Following disposal profiling, the stockpile will be hauled off-site by a qualified contractor and disposed of at the proper facility. After well installation is completed, IT will develop the wells and collect groundwater samples. Development methods will include a combination of surging, bailing, and pumping to remove sediments from the well. Sac1N:ICamPk\Data\Amhive\Arco1W91Reporfs154b9p103.doc-95Vsg:I rr Corporation 02/28/OD