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Former Beacon Station No474 September 22, 2005 Stockton California Work Plan.for an Additional Subsurface Investigation monitoring well MW-10 is not impacted with DCA and other gasoline constituents such as benzene and methyl-t-butyl ether (MTBE); monitoring well MW-10 is located in the predominant up gradient direction from the source area for both water table and deep aquifer intervals; and there is no immediate threat from groundwater conditions at monitoring well MW-10 to sensitive receptors northwest of the site. All fieldwork shall be conducted in accordance with Horizon Field Methods and Procedures contained in Appendix B. The fieldwork shall consist of the following tasks: Task 1 Select and schedule a C-57 licensed drilling subcontractor to provide drilling and well installation services; obtain required well permits from the SJCEHD for installation of groundwater monitoring wells; update the site-specific health and safety plan; and notify Underground Service Alert (USA) to identify and locate utilities in the site area. Task 2 Drill and install.monitoring wells MW-18 and MW-19 in the area between the northeast corner of the station building and the underground storage tank(UST) basin, and monitoring wells MW-20 and MW-21 near the southeastern and southwestern corners, respectively, of the site; record soil descriptions, field screening and sampling data and well construction details on soil boring logs during drilling and well. installation; describe soils using the Unified Soil Classification System (USCS); collect soil samples at 5-foot intervals starting at 5 feet bsg with,a split spoon sampler; field screen soil samples for presence of volatile hydrocarbons with a photo-ionization detector (PID) or equivalent device; stockpile drill cuttings on and cover with plastic sheeting. Advance monitoring well borings and set screen intervals as follows: advance MW-18 to approximately 70 feet bsg or approximately 10 feet below the first encountered groundwater and set screen at 50 to 70 feet bsg; advance MW-19 to approximately 100 feet bsg and set 5 feet of screen at approximately 95 to 1-174„1,l)-0, Project No. 1474.16 4 HORIZON ENVIRONMENTAL INC.