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• i5E C 0R (C-Zane) and seven wells will be installed to further assess the high permeability sand layer located from approximately 124 to 129 feet bgs (D-Zone). First, soil borings will be drilled using a sonic drilling rig, equipped with 8-inch diameter heavy-walled downhole casing. The casing will be advanced following the core barrel in order to seal the upper groundwater bearing zone from the lower groundwater bearing zone to prevent cross-contamination. Soil core will be collected near continuously for lithologic logging and for screening of hydrocarbons using a photo-ionization detector (PID). Based on PID readings and field observation, a minimum of three soil samples per well boring will be collected from the core barrel in 2"-diameter by 6"-long brass or stainless steel sleeves, capped at each end with Teflon® sheets and plastic end caps, and placed on ice in an insulated cooler until relinquished under chain-of-custody to a certified analytical laboratory. Samples will be submitted under chain-of-custody protocol to Kiff Analytical, a state certified laboratory located in Davis, California and will be analyzed for the following: • TPHd and TPHo by Environmental Protection Agency (EPA) Method 8015M • TPHg; benzene, toluene, ethylbenzene, and total xylenes (BTEX compounds); fuel oxygenates (MtBE, di-isopropyl ether [DIPE], ethyl tertiary butyl ether [EtBE], TBA, tertiary amyl methyl ether [TAME], methanol, and ethanol); and volatile organic compounds (VOCs) by EPA Method 82608 Upon completion of drilling to total depth, a 2-inch diameter groundwater monitoring well will be installed in each boring. The wells will be constructed with 2-inch diameter, flush-threaded, Schedule 80 PVC casing with five feet of 0.010-inch factory-slotted PVC screen. Number 2112 sand will be placed in the annular space across the entire screened interval, and will extend approximately two feet above the top of the screen interval. A bentonite pellet seal will be placed to two to four feet above the sand pack, and hydrated in place. The monitoring wells will be completed with neat cement from the top of the bentonite between the casing and the well rut will be tremmied through one-inch diameter PVC pip as the casing is retrieved, preventing cross contamination and ensuring a proper seal between the upper and lower groundwater bearing zones. The well casings will be topped with a locking expanbe ained in a ertight, traffic rated sion cap. The well heads monument well box, where lappropr appropriate. Field and laboratory l labo ae tory pro dures are x or above gradeincluded in Appendix B. 2,2.4 Well Development After at least 48 hours following well construction, SECOR will return to the site to develop the newly constructed wells. Development will be accomplished by alternately surging each well with a vented surge block followed by bailing to remove accumulated sediment. Final purging will be performed with either a submersible pump or bailer, and pH, temperature, and conductivity will be measured at regular intervals during purging. Development will be considered complete when either: 1) 8 well volumes have been removed and physical-chemical parameters trends have stabilized over three consecutive measurements (<0.05 pH, 3% conductivity, and 10% temperature); 2) 10 well volumes have been removed; or 3) the formation in which the well is screened inhibits either of the above from being accomplished and the well has been purged dry (i.e. the well does not sustain flow or is slow to recover). Additional Deep Zone Assessment Work Plan.linal.doc Tidewater Stockton March 14,2008 5