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, <br /> C , C <br /> ,NZAMAR <br /> Working January 29, 1993 g To Restore Nature <br /> ARCO Service Station No 0548, Stockton, California <br /> SCOPE OF WORK <br /> 1 Work will be conducted according to our Work Plan and Site Safety Plan dated August 8, <br /> 1991, which describes the site history, local geology, and methods for drilling soil borings <br /> and sampling soil, monitoring well construction, well development, and groundwater <br /> sampling This addendum to the work plan was prepared using the Central Valley Regional <br /> Board Staff Recommendations for Initial Evaluation and Investigation of Underground <br /> Tanks (Tri-Regional Recommendations), Appendix A of the Tri-Regional <br /> Recommendations, and the Leaking Underground Fuel Tank Manual as references <br /> RESNA will conduct the following tasks <br /> TASK 1: ADDITIONAL ASSESSMENT OF SOIL AND GROUND-WATER <br /> o Obtain a well permit and update the site safety plan, discussing the <br /> precautions and protective equipment required for work at the site <br /> i <br /> o Observe drilling of four 8-inch-diameter soil borings to approximately 48 feet <br /> below surface grade, or until first detected ground water Two soil borings <br /> will be located in the vicinity of the waste-oil tank, one soli boring will be <br /> + drilled west of the northern dispenser island and one boring will be located <br /> east of the southern dispenser island Plate 2 presents the proposed locations <br /> of the soil borings These borings will be grouted to surface <br /> o Observe drilling of one 10-inch-diameter soil boring to approximately 73 feet <br /> below surface grade, or 15 feet below ground water A 4-inch-diameter <br /> monitoring well will be installed in the boring Drilling and well installation <br /> will be performed by a licensed well driller We propose installing the well <br /> downgradient of the tank cavity and monitoring well MW-1 near the property <br /> boundary (shown on Plate 2) The Schematic Monitoring Well Design is <br /> presented on Plate 3 <br /> o Collect relatively undisturbed soli samples at 5-foot intervals from the borings, <br /> identify the samples using manual and visual methods, and classify the <br /> samples according to the Unified Soil Classification System <br /> o Develop, purge, and sample the ground-water monitoring well Purge water <br /> will be temporarily stored on-site in 55-gallon drums (17-H drums) until Balch <br /> Petroleum removes water from the site <br /> i <br /> i <br /> � 30004-9w 2 <br /> �ll <br />