Ord 1990-014 - Laserfiche WebLink

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tension while the annular materials (sand and bentonite pellets) are gravity fed from the surface. For wells in which the pilot hole is unstable, the well and annular materials will be installed inside the auger string. As the annular materials are gravity fed into the auger string, the augers will be gradually withdrawn from the hole, allowing the materials to fill in around the well. The remaining annulus will be filled with a cement/bentonite grout. The casing string, the design of which will be determined by the field hydrogeologist based on the geologic log, will consist of two-inch ID Schedule 40 PVC flush-joint threaded blank and slotted casing (factory decontaminated and plastic wrapped). The slots will be O.OlO-inch machine-slotted and spaced 1/8-inch apart. Viton o-rings will be used in the joint connections. Filter sand (such as Texas Mining Co. 16-30 frac sand) will be emplaced to a level of no more than feet above the top of the slotted portion of the casing. The sand level will be verified with a weighted tape marked in hundreds of a foot. A bentonite pellet seal several feet thick will be placed above the filter sand. Distilled water will be poured on the pellets to initiate swelling if water is not present at the top of the pellet seal. The position of the bentonite pellets will be verified with a weighted tape. The cement/bentonite grout will be comprised of a slurry mixture of Portland Type I cement and two percent powdered bentonite. A lockable steel protector casing will be installed from approximately two feet below ground level to slightly above the top of the PVC casing. A 6-foot by 6-foot concrete pad, six inches thick and reinforced with steel, will be constructed around the surface casing. Prior to commencement of drilling operations and between wells, the drilling equipment that will corne in contact with the borehole or casing materials will be thoroughly steam cleaned. The monitoring wells will be developed by bailing and/or hand pumping. Detailed well development and sampling records will be prepared. Upon arriving at each well and immediately after opening the well, the air in the well will be sampled for volatile organic compounds by inserting the probe of an organic vapor meter several inches into the well and recording the measurement in parts per million by volume (ppmv). Prior to geveloping the wells, water levels and total well depths will be measured with an Olympic water level probe (to the nearest 0.01 feet), and the volume of water in each well will be calculated. Next, sampling will be performed to check for the presence of immiscible layers. The possible presence of immiscible layers 3