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v Mr. Steve Sasson Village West Workplan Addendum 11 June 14, 1995 Monitoring Well Completion The two monitoring wells will be constructed of two-inch diameter, 0.020-inch-slotted, Schedule 40, PVC well casing extending from approximately 10 feet bsg to the planned total drilled depth of approximately 35 feet bsg. Actual drilled depth will be based upon field observations of water table depth (averaging 13.75 feet bsg on January 10, 1995) and the total depths of the three monitoring wells which were previously completed at the site. The remaining pipe string from 10 feet bsg to the surface will consist of two-inch diameter, blank, Schedule 40 PVC casing. The annulus of each well will be backfilled with ##3 Monterey sand from total depth to two feet above the slotted casing interval. A minimum three-foot-thick bentonite seal will be placed immediately above the sand filter pack. After placing the sand and prior to placing the bentonite, each well will be surge-blocked to allow the filter pack to settle. The annular space above the bentonite will be sealed to the surface with a concrete/bentonite grout slurry to protect from surface infiltration. Each wellhead will be finished with a well box and locking well cap. The well casing-top elevations will be established by a California-licensed land surveyor, "tying" each well to the nearest existing benchmark of known elevation. The survey will allow for the calculation of the local ground-water flow direction and gradient underlying the property. Well Development, Sounding, and Sampling Barring unforeseen problems, new monitoring wells are usually developed a minimum of 48 hours after completion. Prior to purging, the piezometric water level in the well will be sounded utilizing a Keck® interface meter and converted to the corresponding elevation relative to Mean Sea Level. The well will be purged by pumping or bailing until the ground-water parameters of pH, conductivity, and temperature have stabilized and at least three well-volumes of water have been evacuated. When the well has recovered to 90% of its initial water level, ground- water samples will be collected. Ground-water samples will be recovered in disposable Teflon"bailers, transferred to laboratory- prepared, 40-m1 capacity VOA vials, labeled, and placed on ice or refrigerated for transport to Sherwood Labs. The samples will be analyzed for TPH-g (and TRPH-d, if required) analytes by EPA Method 5030/8015-modified and for BTEX analytes by EPA Method 602. The appropriate chain-of-custody procedures will be strictly followed from the site to delivery at the laboratory. V V 1 4