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File No. 20-1147-44 XLE1NFELDER September 28, 1993 • The wells will be generally screened from 3 feet above to 10 feet below first ground water. The screen length may be changed if an aquitard with a minimum thickness of 5 feet is encountered. If an apparent aquitard is encountered, the well will usually be terminated 1 to 2 feet into the aquitard. We recently measured groundwater at approximately 5 to 7 feet. At the time of our original geotechnical study in 1990; however, groundwater was encountered at the 12 to 15 foot depth. Discussions with personnel at Environmental Health and readings taken recently by PRC Environmental indicate that groundwater levels are dropping. • The annular space between the screen and the wall of the boring will be backfilled with the appropriate clean Lone Star Industries 0/30 or 2/12 Monterey sand to approximately 2 feet above the top of the perforated sections. Based on soil logs or a sieve test, modifications may be made regarding the size of sand to be used. Installation of the 0/30 sand may require that the sand be tremmied, using clean water. In this event, a sample of the tremie water would be collected, unless the source is thought to be clean. • A 3- to 5-foot bentonite plug will be 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 will be filled to the surface with tremmied cement/bentonite grout to the surface. • The wells will be secured in an above-ground locking stovepipe. The wells will be developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the well. Well development will occur approximately 48 hours after the installation to allow the grout to set. Each well will be first sampled with a clear acrylic bailer to visually inspect for hydrocarbon layer or sheen. If no product layer or sheen is observed on the water, the well will be developed by surging, pumping or bailing. Surging along the screened interval of the well will be performed to draw the sediment from the formation into the filter pack and the well and to set the sand pack. The sediment-laden water will be purged from the well at a rate of between 0.75 to 10 gallons per minute (gpm) depending on recharge rate and casing size. Development will continue until the discharge runs relatively clear of fines. Approximately 5 to 10 well volumes are usually removed from each monitoring well. The locations of the monitoring wells will be measured from permanent features, such as corner posts or power poles. The elevation of the top of the PVC casings will be surveyed and tied into an assumed datum. The depth to static ground water will be measured from a set location at the top of the PVC casing. The depth of water is then subtracted from the elevation of the top of the well casing to provide a ground water elevation for each monitoring well location. Copyright 1993 KLeinfeLder, Inc. Page 2 of 4