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Work Plan—PEA Page 6 Former Haley Flying Service GPE Project 474.2 installing sufficient bentonite to form a 1-foot thick seal. The remaining annulus will be filled with neat cement grout. A well completion diagram similar to Figure 4 will be developed after the wells are constructed. The wells will be secured with a watertight locking cap and encased within a traffic safe well box that is slightly elevated above the ground surface (approximately 2 inches) and protected with a 4-foot square, 6-inch thick concrete apron. If a well is constructed in the field north of the irrigation canal, it will be placed inside a locking, steel well monument at least 2 feet high, and protected by a concrete apron. If needed, outlying crash posts or bollards may also be installed around the well monument. The following table summarizes the construction details of these wells. Boring Depth of Depth of Filter pack Transition Annular Seal Depth Blank Screen Seal MW's 1-4 10' 8' -0' 18'—8' 18' —6' 1 6' -5' 5 -0' All numbers are depths below grade. 2.7 Well Development and Surveying The new monitoring wells will be developed after the well sealing materials have set for at least 48 hours. The wells will be developed using mechanical surging and pumping, or bailing methods until a clear stream of water is generated and the conductivity, pH, and temperature are stabilized. This will be done to assure the slots are clear and allow free fluid flow through the filter pack material. All development water will be containerized in 55- gallon DOT approved containers labeled as investigative derived waste, and stored on site in the eastern hangar until its disposal can be arranged. To allow for calculation of the direction of groundwater flow, the true vertical and lateral position of the well heads will be established by a licensed surveyor using methods and protocols established by the California Water Resource Control Board for LUST investigations. The well survey will be accomplished within 30 days of the well installation and development. 2.8 Groundwater Sampling Upon completion of the well development, the new wells will be sampled in accordance with standard well sampling procedures. The initial samples will be collected no less than 48 hours after well development. Prior to collecting the groundwater samples, three to five casing volumes of water will be purged from each well until the conductivity, pH and temperature are stabilized. Should achieving stabilization of the three parameters prove impractical, the site Geologist will use best professional judgment to determine when adequate volume water has been purged before sample collection. The purge water will be containerized as previously described. After the initial sampling event, the wells will be 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto, Ca 95356 Fax: (209) 569-0295