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• <br /> depths of the new wells will be determined at the time of drilling. Generally, the depth of the <br /> shallow well will not exceed 55 foot and the depth of the deep well will not exceed 140 foot. <br /> 3.3.1 Drilling Method <br /> The drilling method shall be with hollow stem augers to prevent the collapse of formation material <br /> against the well screen and casing during installation of the well. The inside diameter of the <br /> hollow stem augers shall be sufficient to allow accurate placement of the screen, riser, filter pack, <br /> seal and grout. The use of drilling aids such as bentonite, other clay-based agents, or any other <br /> foreign matter capable of affecting the characteristics of the ground water is prohibited. Any <br /> drilling fluid additive used shall be inorganic in nature. Grease or oil on drill rods, casing, or <br /> auger joints are not permitted; however,Teflon tape, vegetable oil (in solid phase form), or any <br /> other EPA approved lubricants are acceptable. The drill rig shall be free from leaks of fuel, <br /> hydraulic fluid, and oil which may contaminate the borehole, ground surface or drill tools. During <br /> construction of the wells,precautions shall be used to prevent tampering with the well or entrance <br /> of foreign material. Runoff shall be prevented from entering the well during construction. If there <br /> is an interruption in work, such as overnight shutdown, the well opening shall be closed with a <br /> watertight uncontaminated cover. The cover shall be secured in place or weighted down so that it <br /> cannot be removed except with the aid of the drilling equipment or through the use of drill tools. <br /> 3.3.2 Sampling <br /> Sampling will be conducted at three (3)intervals on each of the two new borings. Sampling will <br /> be conducted using Standard Penetrometer Tests (SPT's) in accordance with ASTM Method D- <br /> 1586-84. A 140-pound hammer with 30 inches of free fall is required to drive the sampler 18" or <br /> to refusal for conducting the SPTs. However, Standard Penetration Tests will be conducted <br /> using a California Modified Sampler or equivalent (3-inch-O.D. by 2-1/2-inch-I.D. by <br /> 18-inch-length). Three (3) stainless steel liners (2 r/2-inch OD by 6-inch length) will be used for <br /> each sample. Select liners from each sample location will be sealed at both ends using Teflon <br /> paper and plastic end caps. The Contractor shall provide all stainless steel liners,Teflon <br /> paper, and end caps for this procedure. Cost for stainless steel liners, Teflon paper, and <br /> end caps are considered incidental and included in this project. <br /> 3.3.3 Borehole Diameter and Depth <br /> The borings for monitoring well installation shall be a minimum of 8 inches in diameter, in order <br /> to permit at least 2 inches of annular space between the boring wall and all sides of the centered <br /> riser pipe and screen. Depths of individual borings shall be determined by soil conditions during <br /> drilling operations. The actual depth of the monitoring well shall be adequate to allow for the <br /> collection of representative ground water samples for chemical analysis. <br /> 02671-006 <br />