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i I8 �i I :I Borehole Drilling. BC will supervise the drilling of one borehole and the installation of a groundwater extraction well in that borehole. The location is shown on Figure 2. The borehole will be drilled using air rotary drilling. To prevent caving of the Borehole wall, a casing will be driven into the borehole as the drilling advances. Borehole diameter is expected to be 10 inches. Borehole depth is not expected to be deeper than 90 feet, the approximate depth of the deepest monitoring well W-2B. Borehole cuttings will be temporarily placed on and covered by plastic sheeting. The disposal of these cuttings is the responsibility of ARCO. ! Soil Sampling. A composite soil sample will be collected in a 2- by 6-inch brass tube from the drilling cuttings for soil disposal purp ses. Brass tubes containing composite soil samples will be covered with aluminum foil and plastic caps and sealed with! plastic tape. Each sample will be labeled on site to show the date, project number, and! sample location. The sealed samples will be stored on ice in closed chests and protected from meltwater. The composite soil sample will be analyzed for TPH by EPA Method 8015, modified. The sample will be delivered to Eureka Laboratories, Inc., in Sacramento Groundwater Extraction Well Installation. The, groundwater extraction well 1 will be completed with 6-inch-diameter mild steel casing and will be screened with 6-inch-diameter mild-steel, wire-wrapped screen, mesh size 0.040 inch. The screen will extend from approximately 55 to 85 feet below the ground surface. Blank casing will extend from the top of the perforated section to ground surface. The actual depth of the borehole and screened interval of the well will depend on conditions encountered during drilling. The well casing will be inserted inside the 10-inch-diameter borehole casing and suspended under tension. Well casing joints will be welded aind centralizers will be welded onto the well casing every 20 feet. The 10-inch-diameter borehole casing will be removed as the annular space is filled. The annular space will be packed with No. 3 and from the bottom of the screen to approximately 2 feet above the top of the screen_ A 2-foot-thick seal of bentonite pellets will be placed on the top of the sand pack. The well will be grouted with bentonite- cement slurry or neat cement from the top of the b ntonite seal to the surface. The well will be completed at grade, fitted with top and bott m mild-steel caps, and have a!locking cover installed. Typical well construction is illustrated on Figure 9. Well Development. The well will be developed by surging and bailing and then pumping until clean, sediment-free water is prod ced from the well. The length of development time will vary depending upon field conditions. Water produced during development will be contained on site. ARCO % ill be responsible for the disposal of water and product collected. Prior to and followin development, the depth to water and thickness of free product, if any, will be measured ith an oil/water interface probe' Well Surveying. Top of well casing (TOC) kvill be surveyed by BC personnel using City Bench Mark 786, located on the northeast corner of the Kettleman Lane and Hutchins Street intersection as a base el6vation. The elevation of the City Bench Mark is 43.11 li !3 :1