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L. Perino Page 2 March 2, 1994 <br /> system specified for the 1250 Reynolds Adit Bulkhead at the <br /> Summitville Mine. <br /> 2) and 3) The original bypass pipe design for the American <br /> Tunnel specified nominal 12-inch Schedule 80 (Extra Strong) steel <br /> pipe. Standard weight Schedule 40 steel pipe with a 0. 375-inch <br /> pipe wall thickness would have been sufficient to provide the <br /> maximum 2500 gpm water flow requirement. However, the 0. 500-inch <br /> pipe wall thickness Schedule 80 steel pipe was specified to provide <br /> additional steel to accommodate corrosion during construction and <br /> until the valve is eventually closed. <br /> Forty-six 1/2-inch diameter by 2-inch long shear studs welded <br /> to the bypass pipe were specified to resist the maximum thrust of <br /> approximately 72600 lb that may develop after closure of the bypass <br /> valve (Abel, 1993 , p22) . A thrust ring is an alternative to the <br /> shear studs. Quality control for a factory welded single thrust <br /> ring should exceed that possible for field welded shear studs. The <br /> shear studs can be welded to the bypass pipe in the Sunnyside Mine <br /> shop before being taken into the mine, but some stud breakage and <br /> bending should be anticipated during transport and installation. A <br /> thrust ring should be a more reliable design. <br /> A alternative design for the American Tunnel bypass pipe has <br /> been suggested. This involves a 10-foot long, 316L Stainless Steel <br /> Schedule 40 (Standard Weight) pipe at the downstream bulkhead face <br /> with High Density Polyethylene (HDPE) pipe utilized for the <br /> remaining bypass pipe. The stainless steel pipe would include a <br /> thrust ring 6. 5 feet inside the downstream bulkhead face, as <br /> presented in the February 26, 1994 memo "American Tunnel, Bypass <br /> Pipe Calculations" enclosed. The increased corrosion resistance of <br /> 316L Stainless Steel will increase the life of the bypass pipe <br /> under full flow conditions. <br /> The February 26, 1994 memo verifies that a nominal 12-inch <br /> Schedule 40, 316L Stainless Steel pipe provides sufficient capacity <br /> for the 2500 gpm maximum flow. In fact, the lower friction factor <br /> of stainless steel represents overdesign. Friction factors for <br /> 12-inch HDPE pipe are not available, but Hazen and Williams Formula <br /> "C" pipe coefficient values for HDPE (155) , old steel (125) and new <br /> steel (140) demonstrate that the friction factor for HDPE pipe must <br /> be lower than for steel pipe. The friction factor for stainless <br /> steel pipe is less than for steel pipe, see attached memos. The <br /> larger than necessary pipe size assures that sufficient capacity <br /> would be provided by this alternative design. Additionally the <br /> HDPE pipe is chemically inert to acidic mine drainage water flowing <br /> through it. <br />