SITE INFORMATION AND CORRESPONDENCE

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Working to Restore Nature The vapor-extraction wells will be drilled using a truck-mounted drill rig with 8- to 10-inch- diameter augers. A 4-inch-diameter polyvinyl chloride casing will be installed in the boring. For safety and security reasons, the top of the casing will be fitted with a locking cap and an aluminum cover with specially designed fasteners. The aluminum cover will be set approximately 2 feet above surrounding grade and painted a bright color for visibility. Each boring will take approximately 3 hours to drill, and each vapor-extraction well will take approximately 4 hours to install. We anticipate the work will be completed in approximately 2 days. Two subcontractor personnel will operate the drill rig, and a geologist from RESNA will be present during drilling. Every effort will be made to keep the work area clean and to restore the area to the original condition when the work is completed. We will contact you to coordinate drilling operations to determine which day of the week is most convenient. Our tentative schedule for the construction of the vapor-extraction wells is May or June 1993. Upon receipt of your authorization, we will schedule a date for our work and we will inform you of that date. Depending on the findings of this phase of the investigation, we may have to connect the wells to a remediation system. The vapor-extraction wells would be used to remove hydrocarbons from soil by placing a vacuum on the well and drawing the hydrocarbon vapors through a pipeline to a remediation unit to be located on the ARCO site. To connect the wells to a remediation unit at the ARCO station will require RESNA and its contractors to lay horizontal pipeline from the wells to the station. A schematic of the piping design is shown on Plate 3. This work would take approximately 1 week to complete. If the wells are connected to a remediation unit, a technician from RESNA would periodically need to gain access to the wells for data acquisition and maintenance for approximately 1 year, or as required until remediation is completed. After the soil is remediated and the wells are no longer needed, the wells will be properly destroyed by drilling them out with a 10-to 12-inch-diameter auger and backfilling the borehole with neat cement. The ground surface will then be restored to resemble the surrounding ground material. A boring will be drilled adjacent to each well to collect soil samples to confirm that hydrocarbons have been removed from the soil; the borings will be backfilled with neat cement. O110rvie\30041-05 2