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1995 Reclamation Bids July 7, 1995 Page b <br /> Ditch 8 has a component which has a steep gradient (19.2 percent <br /> according to TR25). Use of a coconut fiber liner in the steep stretches of <br /> this ditch is warranted. Mr. Lewicki's recommendation, based on <br /> experience at another mine site, is to use a more resistant liner in the steep <br /> reaches of Ditch 8 such as Mirafi Miramat. This synthetic mat resists <br /> erosion and decomposition better than the coconut fiber liner (C 125) and <br /> would provide a more favorable substrate for revegetation at this location. <br /> In general, the configuration of the Sutey Stream Diversion is consistent <br /> with that approved in TR25. One significant exception is at the reach <br /> between station 0+90 to 1 +30. In this reach a curve in the Sutey Stream <br /> Diversion occurs, which requires measures to minimize erosion on the <br /> outside bank of the diversion. CDMG proposes to elevate the outside bank <br /> or cut the outside channel deeper in this location. Either is acceptable, <br /> provided deeper excavation of the outside channel does not alter the <br /> prevailing ditch grade. The concern arises where CDMG appears to be <br /> proposing 4.8 feet of riprap in the bottom of the ditch in this reach. If this <br /> is the design, that volume of riprap will promote erosion of the channel. <br /> TR25 addressed erosion on the outside bank in this location by placing the <br /> large riprap on the outside bank slope, in effect armoring the outside bank. <br /> I believe CDMG has embraced the thinking behind TR25, but misstated the <br /> design in the bid document. As with the other ditches described <br /> previously, CDMG has proposed that the entire length of the Sutey Stream <br /> Diversion be lined with a coconut fiber liner. My previous comments on <br /> the necessity and wisdom of using the fiber mat in this application apply <br /> here also. <br /> One comment was made by Mr. Lewicki regarding the Spring Conveyance <br /> Ditch. He urged the Division to construct this ditch prior to any <br /> construction or reconstruction at the Sutey Stream Diversion, in order to <br /> assure flow and suitable grade of this ditch as it ties in with the Sutey <br /> Stream Diversion. <br /> My greatest concern with the Surface Drainage task is the apparent <br /> overdesign of the surface drainage at this location. The reconstruction of <br /> in-place ditches and overly zealous use of expensive and unnecessary liners <br />