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��s�vTaax Once the depth to the top of the filter material has-been verified, bentonite )r fine sand may be placed in the annular space as a transition seal between the filter material a: d the grout. A sufficient quantity of bentonite or fine sand will be poured to fill the annula space to a level of about 2 feet above the top of the filter pack. If bentonite is to.be placed beiry standing water, a high-solids bentonite grout will be pumped through a tremie pipe, or pelle s 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 prohib :ed by well conditions, each lift should be hydrated using approximately 1 gallon of pots , e 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 trar� don seal, the fine sand will be mixed with potable water and placed as a slurry through the C imie pipe or poured dry through the annulus. The depth to the top of the transition seal w='l be verified by measuring, using the tremie pipe or a weighted tape. A neat cement grout, cement/sand grout, cement/bentonite grout, or high-solid; bentonite grout will be placed from the top of the transition seal to the ground surface. he grout seal will be placed by pumping through a tremie pipe lowered to within 5 feet of thL, top of the transition seal in mud rotary borings. The grout seal will be placed in hollow s ;m auger borings by free fall through the augers as they are incrementally raised or by pL aning through flexible hose or tremie pipe lowered to near the bottom of the zone to be groute_ . 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. Typic 1 specifications of grout mixtures include: (a) neat cement/bentonite grout, consis r; of a mixture of one sack (94 pounds) of Portland Type I/II cement, approximately 2 ; 5 percent by weight (of cement) powdered bentonite, and approximately 6 to 8 gallons of watr •; (b) neat cement grout, consisting of one sack of Portland cement and approximately 5 to gallons of water; and (c) cement/sand grout, consisting of no more than two parts sand to C e part cement and approximately 7 gallons of water. Only potable water will be used tc 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 MSC%PR0T0-1W.= REVISION DATE:MARCH 1996 IW-4