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GEOMATROX Once the depth to the top of the filter material has been verified, bentonite or fine sand may be placed in the annular space as a transition seal between the filter material and the grout. A sufficient quantity of bentonite or fine sand will be poured to fill the annular space to a level of about 2 feet above the top of the filter pack. If bentonite is to be placed below standing water, a high-solids bentonite grout will be pumped through a tremie pipe, or pellets may be poured through the annulus. If bentonite is to be placed above standing water, a high-solids bentonite grout should be used or pellets may be placed in 6-inch lifts. Unless prohibited by well conditions, each lift should be hydrated using approximately 1 gallon of potable water per lift of pellets. The completed bentonite transition seal will be allowed to hydrate for at least 30 minutes prior to placing the grout. If a layer of fine sand is placed as the transition seal, the fine sand will be mixed with potable water and placed as a slurry through the tremie pipe or poured dry through the annulus. The depth to the top of the transition seal will be verified by measuring, using the tremie pipe or a weighted tape. A neat cement grout, cement/sand grout, cement/bentonite grout, or high-solids bentonite grout will be placed from the top of the transition seal to the ground surface. The grout seal will be placed by pumping through a tremie pipe lowered to within 5 feet of the top of the transition seal in mud rotary borings. The grout seal will be placed in hollow stem auger borings by free fall through the augers as they are incrementally raised or by pumping through flexible hose or tremie pipe lowered to near the bottom of the zone to be grouted. The grout must be tremied if there is standing water in the augers above the transition seal. Grout/additive/water mixtures will be determined on a site-specific basis. Typical specifications of grout mixtures include: (a) neat cement/bentonite grout, consisting of a mixture of one sack (94 pounds) of Portland Type I/II cement, approximately 2 to 5 percent by weight (of cement) powdered bentonite, and approximately 6 to 8 gallons of water; (b) neat cement grout, consisting of one sack of Portland cement and approximately 5 to 6 gallons of water; and (c) cement/sand grout, consisting of no more than two parts sand to one part cement and approximately 7 gallons of water. Only potable water will be used to prepare the grout. No work will be done on the monitoring well until after the grout has set approximately 24 hours. INSTALLATION AND DESTRUCTION OF WELLS Page 4 of S MSCIPROTO4W.TYT REVISION DATE:MARCH 1996 IW-4