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0 <br /> 0 <br /> A. The Contractor shall calculate volumes of sand pack, bentonite pellets, and grout <br /> required,based on borehole and well casing dimensions. <br /> B. The Contractor shall inspect the casing, screen, and any other well construction <br /> materials prior to installation to assure that no damage has occurred. The well <br /> screens, bentonite seals and neat cement seals shall be installed in accordance <br /> with the following sequence: <br /> 1. The 10-foot long screen shall be set below where the water level is <br /> encountered. <br /> 2. The annular space for the-screened interval shall be filled with a sand pack to <br /> 5 feet above the screen' <br /> 3. A 5-foot bentonite seal above the sand, and a neat cement seal to the ground <br /> surface. <br /> C. The Contractor shall connect and carefully lower the well casing assembly to the <br /> depth directed by the on-site geologist. A casing centralized shall be attached at <br /> the top of each screened interval to assure that the well is centered in the borehole. <br /> The well casing assembly should be suspended by the installation rig and should <br /> not rest on the bottom of the borehole. The top of the well casing shall extend <br /> approximately 2 to 3 feet above the ground surface. <br /> D. In the event the well casing assembly was dropped, lowered abruptly, or for any <br /> other reason suspected of being damaged during placement, the well casing <br /> assembly shall be removed from the borehole and inspected. If the well casing <br /> assembly rises after being placed in the borehole due to heaving formation <br /> material, the Contractor shall not place any drilling equipment (drill pipe, <br /> hammers, etc.) to prevent the casing from rising. The Contractor shall notify the <br /> on-site geologist of the amount of rise. <br /> E. The Contractor shall place the sand pack into the annular space around the <br /> screened interval. Clean water and a tremie pipe may be used to assist with the <br /> sand pack tremie operation. If the well assembly is installed through the hollow <br /> stem augers, the augers shall be pulled slowly during sand pack installation. <br /> F. The Contractor shall monitor the sand pack settlement by measuring the sand <br /> level with a weighted tape. The Contractor shall also monitor the top of the well <br /> casing to detect any movement due to settlement or from drive casing removal. If <br /> the top of the well casing moves upwards at any time during the well installation <br /> process, the Contractor shall not set drilling equipment (drill pipe, hammers, etc.) <br /> on the top of the casing to prevent further movement. The Contractor shall notify <br /> the on-site geologist of the amount of rise. <br /> Corral Hollow EMP WP.DOC Page 5 of 8 February 28,2007 <br />