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Project Number 1804BK01 September 17.200 and creating a void between the point and the point holder for the collection of a soil gas sample. The aboveground end of the sample tubing will be connected to a vacuum pump capable of pulling 27 inches of mercury. The pump will be operated to purge at least 1.5 times the volume of the tubing and point holder. A soil gas sample will then be collected in a TedlaC� bag. After sampling, the vacuum pump will be disconnected and the sampler pulled from the boring. The polyethylene tubing will be discarded after each use. The Tedlar' sample bag will be stored in a box for protection from the sunlight. The samples will be transported via overnight carrier to Columbia Analytical Services in Simi Valley, California, a State of California-certified analytical laboratory, for chemical analysis. Shallow Groundwater Monitoring Well Installations After completing each shallow groundwater monitoring well borehole at a total depth of approximately 61 feet bgs, approximately 10 feet into groundwater, each monitoring well borehole will be converted into a groundwater monitoring well. Each well will be constructed with 2-inch-diameter Schedule 40 PVC casing with 15 feet of screen at the bottom (10 feet below the water table and 5 feet above) followed by blank casing to the surface. Filter pack sand (No. 3 is anticipated) will be emplaced by gravity feed in the annular space from the bottom to a point at least two feet above the screened interval followed by three-feet of hydrated bentonite chips to seal the filter pack. Neat cement-bentonite (5 percent bentonite powder) slurry will be used to fill the annular space to the surface. The wellhead will be equipped with a locking cap and a traffic-rated steel box set in cement slightly above grade to complete the installation. A typical shallow groundwater monitoring well schematic diagram is provided in Figure 5. Deep Groundwater Monitoring Well Installations The borehole for each deep groundwater monitoring well will be advanced to approximately 95 feet bgs using the air-percussion hammer drill rig. Each well will be constructed with 2- inch-diameter Schedule 40 PVC casing with 5 feet of screen at the bottom followed by blank casing to the surface. Filter pack sand (No. 3 is anticipated) will be emplaced by gravity feed in the annular space from the bottom to a point at least two feet above the screened interval followed by three-feet of hydrated bentonite chips to seal the filter pack. Neat cement-bentonite (5 percent bentonite powder) slurry will be used to fill the annular space to the surface. The wellhead will be equipped with a locking cap and a traffic-rated steel box set in cement slightly above grade to complete the installation. A typical deep groundwater monitoring well schematic diagram is provided in Figure 6. Aquifer Test Well Installation The boring for well EX-1 BB will be drilled using the air percussion hammer drill rig to accommodate installation of 6-inch-diameter Schedule 40 PVC well casing. The well will be constructed with 10 feet of screen casing (0.020 inch slot is anticipated) at the bottom followed by blank casing to the surface. Assuming a depth to groundwater of 50 feet bgs and approximately fifteen feet of saturated sediments, the extraction well will be advanced to approximately 65 feet bgs and the well will be screened over the bottom 10 feet to allow for drawdown during aquifer testing. An appropriately sized sand filter pack for the aquifer will be placed around the screen up to approximately 2 feet above the top of the screen. The well will be designed based on a grain size analysis done while installing the deep groundwater monitoring well on East Oak Street. A bentonite seal approximately 3-feet thick will be placed on top of the sand pack, and cement-bentonite grout will seal the E,C Pemediation 4