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9 <br />The bentonite may consist of 1/4- or 1/2 -inch pellets, or may be in the form of a slurry. <br />If pellets are used, they will be hydrated prior to grouting the well, by adding at least one <br />gallon of water for every bucket of pellets. The thickness of the bentonite seal will depend <br />upon local regulatory requirements. <br />The remainder of the well annulus will be sealed with a 6 -sack sand -cement, or cement <br />grout slurry containing 3 to 5 percent bentonite. For wells more than 15 feet deep, the seal <br />will be emplaced through the hollow augers, which will extend to within 15 feet of the <br />bentonite seal. If required by the local regulatory agency, the seal will be emplaced by <br />pumping through a tremie pipe which extends to within 15 feet of the bottom of the boring. <br />The tremie pipe or augers are withdrawn from the boring in 5 -foot increments as the boring <br />fills with grout. A watertight well cap will be placed on top of each groundwater monitoring <br />well, and a 3 -foot steel standpipe with locking cover or a traffic -rated box will be installed <br />around the wellhead. Monitoring wells will be locked to restrict access to unauthorized <br />personnel. <br />Monitoring well construction details will be recorded on the field well construction form. <br />Construction information will be transferred to Monitoring Well construction schematics for <br />presentation in final reports. <br />A-4 Groundwater Monitoring Well Development: When possible, <br />initial well development will be performed during installation of the sand pack. A minimum <br />of 48 hours following installation, groundwater monitoring wells will be developed in order <br />to remove sediment that may accumulate in the well during installation, and to settle the <br />filter pack. Groundwater monitoring well development will be performed using a <br />combination of bailing, pumping, and surging. <br />The development of each groundwater monitoring well will continue until a minimum of five <br />well casing volumes of water have been removed, and the displaced water is relatively clear, <br />free of sediment, and the values of pH, temperature, and specific electrical conductance <br />(EC) have stabilized. Well development data will be recorded on the Sampling/Well <br />Development Log (Attachment A). <br />Purged water will be containerized in Department of Transportation -approved drums, and <br />stored on site in an area inaccessible to the general public. The purged water is typically <br />characterized either by sampling it, or on the basis of the groundwater sample analytical <br />results. Twining can recommend an appropriate method for disposition of the purged water. <br />Disposal will be the responsibility of the client. <br />