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ATC Associates Inc. 1117 Lone Palm Avenue, Suite 201 Modesto, California 95351 209-579-2221 MTC A S S O C T A T E S I N C . fax: 209-579-2225 STANDARD OPERATING PROCEDURE GROUNDWATER MONITOR WELL INSTALLATION AND DEVELOPMENT Prior to drilling, ATC will complete a notice of intention to drill a monitoring well and obtain groundwater monitor well construction variances from the appropriate regulatory agency. Copies of the original permits will be on site during drilling operations. Following completion of each well boring, a well will be constructed using 2-inch or 4-inch nominal diameter, Schedule 40, 0.020-inch machine slotted, polyvinylchloride (PVC) well screen from the bottom of the borehole to an appropriate distance above the static depth to groundwater to account for any season water level fluctuations. The remaining well string will be constricted of 2-inch or 4-inch nominal diameter Schedule 40 blank PVC casing. The bottom of the perforated interval will be capped with a flush-threaded PVC cap and the monitor well casing will be assembled and lowered into the open end of the drill pipe. No PVC cement of other solvents or glues will be used in construction of the monitor well. All well casing and screen material will be delivered to the site in factory containers. The ammlus of the well will be backfilled with clean #3 Monterey sand (or equivalent) filter pack to approximately 2 feet above the top of the well screen. The top of the filter pack will be direct measured with a weighted tape. A minimum 1.5400t layer of bentonite pellets will be placed on top of the filter pack and hydrated to form an annular seal . The bentonite pellets will be hydrated by adding approximately 1 gallon of water for each linear foot of bentonite. The remaining annular space to the surface will be filled with cement grout. The well will be completed at the ground surface with watertight flush-mounted, traffic rated vault. A minimum of 24 hours after well completion, the groundwater monitor well will be developed to remove sediment and to stabilize the filter pack by a combination of surging and pumping groundwater from the well. Purging will continue until movement of the fine sediment stabilizes or ceases and turbidity stabilizes. Groundwater purged from the well will be contained in 55-gallon dru ns and will remain on site pending the groundwater analytical results. I