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7-Eleven Store#14117 Corrective Action Plan October 12, 2007 Page 5 Oxygen Injection Well Installation The proposed oxygen injection wells will be installed at the locations depicted on Figure 2 using a truck-mounted drilling rig equipped with 8-inch-diameter hollow-stem augers. The injection wells will be installed to approximately 35 feet bgs (Table 1). Soil samples will be collected as outlined in Table 4 using a split-spoon sampler lined with 2-inch diameter brass sample tubes. Downhole drilling equipment will be thoroughly cleaned before drilling each borehole, and sampling equipment will be cleaned between each sampling interval. Each soil sample will be screened for hydrocarbon vapors using a portable photoionization detector (PID). Soils encountered during drilling will be logged by a SECOR field geologist using the Unified Soil Classification System, working under the supervision of a California registered geologist. Soil samples retained for analysis will be sealed with Teflon sheets and plastic caps, then labeled and placed on ice in an insulated container for delivery to Kiff Analytical located in Davis, California. Selected soil samples will be analyzed for TPHg, benzene, toluene, ethylbenzene and xylenes (BTEX), MtBE, TBA, ethyl-tert-butyl ether (EtBE), diisopropyl ether (DIPE), and tert-amyl-methyl ether (TAME) using U.S. Environmental Protection Agency (EPA) method 8260B. Proposed injection wells 1-2 through 1-5 will be constructed using 2-inch diameter Schedule 40 polyvinyl chloride (PVC) blank casing and 0.020-inch slotted screen. The proposed injection wells will be constructed with 15 feet of screen set at approximately 20 to 35 feet bgs. The screen depth may be adjusted based on the lithology encountered in order to ensure that the top 3 feet of screen is set into the target sand unit at approximately 20-25 feet bgs and the remaining screen into the large clay and silt unit below (see Attachment C). The larger screen interval will accommodate alternative oxidant injection technologies (i.e. iSOCO systems) in the future should modifications to the remedial approach be necessary. A sand filter pack will be placed within the annulus of the wells from the bottom of the borings to approximately 2 feet above the top of the well screens. The annulus of each well will be sealed with 2 feet of bentonite on top of the sand, and a portland cement/bentonite grout to the surface. An 8-inch-diameter, traffic-rated, watertight street box will be installed to protect the well from surface traffic. Waste Disposal Soil cuttings, debris and rinsate water generated during drilling operations will be temporarily stored onsite in properly labeled Department of Transportation (DOT) approved 55-gallon drums pending characterization, transport and disposal by SECOR's disposal contractor to an appropriate disposal or treatment facility. IMPLEMENTATION OF REMEDIAL APPROACH The proposed oxygen injection wells will be plumbed via a common trench to a single subsurface well vault located on the western boundary of the site (Figures 2 & 7). 14117 CAP 10-12-07.doc SECOR International, Inc.