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confined aquifer conditions or high vadose zone contamination is encountered, the <br /> well screen is usually not set above the depth of first encountered ground water. <br /> Wells are usually not set in areas of suspected significant soil contamination. <br /> • The PVC pipe and end caps are steam-cleaned prior to installation. <br /> • The annular space between the screen and the wall of the boring is backfilled with <br /> the appropriate clean Lone Star Industries 0/30 or 2/12 Monterey sand to <br /> approximately 2 feet above the top of the perforated sections. Based on soil logs or <br /> a sieve test, modifications may be made regarding the size of sand to be used. <br /> Installation of the 0/30 sand may require that the sand be tremmied, using clean <br /> water. In this event, a sample of the tremie water is collected, unless the source is <br /> known to be clean. <br /> • A 3- to 5-foot bentonite plug is placed above the sand pack to provide a seal <br /> against surface water infiltration. <br /> • The remaining annular space is filled to the surface with tremmied <br /> cement/bentonite grout to the surface. <br /> • The wells are secured in a locking stovepipe. The well heads may be enclosed in a <br /> cement utility box set flush to the ground surface located in a traffic area. <br /> A-3.2 Monitoring Well Development and Sampling <br /> The wells are developed to reduce the effects of drilling on the formation and to increase the <br /> effective hydraulic radius of the well. <br /> Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to <br /> set. Each well is first sampled with a clear acrylic bailer to visually inspect for hydrocarbon <br /> layer or sheen. If no product layer or sheen is observed on the water, the well is developed by <br /> surging, pumping, or bailing. Surging along the screened interval of the well is performed to <br /> draw the sediment from the formation into the filter pack and the well and to set the sand <br /> pack. The sediment laden water is purged from the well at a rate of between 0.75 to 10 <br /> gallons per minute (gpm) depending on recharge rate and casing size. Development <br /> continues until the discharge runs relatively clear of fines. Approximately 5 to 10 well volumes <br /> 117226.E02/ST013R0176 Page A-4 January 31, 2013 <br /> Copyright 2013 Kleinfelder <br />