WORK PLANS_PART 1 FILE 1 - Laserfiche WebLink

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A transition zone consisting of four feet of clean fine grained sand shall be placed above the filter pack or as directed by WESTON. A bentonite seal shall be placed immediately above the transition zone. 2 . 2 . 11 Bentonite Seal A bentonite seal consisting of one-quarter (1/4) inch diameter bentonite pellets such as Volclay (or equivalent) will be emplaced on top of the filter pack material within the well annulus. This seal will be at least five (5) feet thick and will be put in place by pouring the pellets slowly into the well annulus from the surface. The volume of pellets required to form the seal will be calculated prior to constructing the seal. The actual seal thickness will be determined by probing with a weighted sounding device during the sealing procedure. Precautions will be taken to insure that the bentonite seal is free of voids and that the bentonite pellets do not bridge above the specified seal interval. 2 . 2 . 12 Grout Seal Following placement of the bentonite seal, the annulus must be grouted from the top of the bentonite seal to ground surface. The grout must be pumped using tremie techniques to displace drilling fluids from the drill casing, withdrawing the casing as the grout level rises. It is left to the discretion of the supervising geologist to determine if tremie methods through the drill casing are required for the entire well for proper completion. Grout will consist of a 20: 1 mixture of Portland I neat cement to bentonite powder and must be thoroughly mixed before placement in the borehole. A maximum of eight gallons of water per 94-pound bag of cement will be used. The grout mixture can be produced on-site by the contractor or trucked in from an outside source. 2 .2 . 13 Development by Swabbing Following a minimum 24-hour waiting period to allow for grout set- up, the wells will be developed by bailing, swabbing and air- lifting techniques. Well development shall be initiated by bailing with a suitable sized bailer to remove any formational or filter pack materials from the bottom of the well bore. Swabbing will take place beginning at the bottom of the screen and progressing vertically until there is no sand, silt, and mud in the development water. 2 . 2 . 14 Development by Pumping The Contractor shall furnish, install, operate, and remove a deep- well turbine pump for developing the well. It is estimated that the pump will require a maximum capacity in excess of 350 gpm. The total heads for maximum capacities are expected to be on the order of 20 to 40 feet. 2 - 6