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R■ KLEINFELDER File No.20-3978-01.W 13 January 22, 1997 • A 3- to 5-foot bentonite plug is placed above the sand pack to provide a seal against surface water infiltration and to reduce the potential for cement grout to infiltrate into the water. • The remaining annular space is filled to the surface with cement/bentonite grout. • The wells are secured in an aboveground or underground locking stovepipe. The well heads may be enclosed in a water tight cement utility box set flush to the ground surface when located in a traffic area. B-3.2 Monitoring Well Development The wells are developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the wells. Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to set. Each well is first sampled with a clear disposable bailer to visually inspect for a hydrocarbon layer or sheen. If no product layer or sheen is observed on the water, the well is developed by surging, pumping or bailing. Surging along the screened interval of the well is performed to draw the sediment from the formation into the filter pack and the well, and to set the sand pack. Development continues until the discharge runs relatively clear of fines. Approximately 5 to 10 well volumes are generally removed from each monitoring well. Discharge water is stored in 55-gallon drums and left on site for later discharge or disposal by the client, depending on laboratory results. The drums are labeled with the date, well number, and a contact person and phone number. B-3.3 Equipment Decontamination To reduce the potential for cross-containination between wells, developing equipment is washed in a trisodium phosphate or non-phosphate detergent solution and rinsed in distilled water or steam cleaned prior to use in the next monitoring well. B-3.4 Well Survey The locations of soil borings and monitoring wells, and the elevation of the top of the PVC casings are usually surveyed and tied into permanent markers, if readily available. Survey accuracy is 0.1 foot for the "x" and "y" coordinates and .01 foot for the 'Y' coordinate. The depth to static groundwater is measured from a set location at the top of the PVC casing (usually the north rim). The depth of water is then subtracted from the elevation of the top of the well casing to provide a groundwater elevation for each monitoring well location. 20-3978-OI.Wl3/207PE030 Page B-5 0/997, Kleinfelder, Inc.