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III III I IIIIIIIII III Doc Date:12/11/2001 <br />sss <br />• `'~lC 3ECrION 3.0 Drainages Reconstruction, Improvement and <br />Repairs at TYapper Mine in 1992. <br />3.1 Draiaagereconstruclion 1987-92 <br />At Trapper Mine, an or portions of five major drainageways (Coyote, Johnson, E. Buzzard, E. No-Name <br />and W. No-Name) and their tnbutaries were regraded and appropriately treated to reduce the erosion rate <br />and assist in permanent channel stabilization in 1987,1988, 1989,1990,1991, and 1992. At the conclusion of <br />the 1992 field season, approximately 47,450 linear fee[ (8.99 miles) of permanent drainages reconswction <br />had been completed at Trapper Mine (see attached "Drainage Reconstruction" map). <br />3.2 Vegetation Sampling Methods <br />Herbaceous plant canopy cover and annual herbaceous primary production were measured on twelve post- <br />mine reclaimed drainage sites and on two undismrbed premise drainage locations in 1992. Plant canopy <br />cover was estimated in three 100-m transacts spaced 10-m apart at each site. Herbaceous plant canopy <br />cover and percent mulch cover were estimated by species using the paint-hit technique (Optical Point Bar) <br />(Viert 1985). Herbaceous production was estimated by clipping sa 1/4-m plots (20-m spacing) on each of <br />the three line transacts at each site. <br />• 3.3 Erosion Control Methods <br />A wide variety of erosion control materials, methods and sediment reducing measures have been used from <br />1987 through 1992 in reconstructed drainageways, on reclaim sideslopes and on regraded spoils. The fol- <br />lowing list of measures and/or materials have been applied in combination to decrease the likelihood of <br />accelerated erosion, to reduce Oow rates and to reduce the sediment loading in downstream sedimentation <br />structures. <br />Dozer basins (sediment basin) were constructed to vap and store sediment on newly stripped topsoil areas <br />and on regraded spoils to reduce or abate the sediment load. Basins are used to prevent the siltation of <br />diversions, waterways, livestock ponds, and streams; to trap sediment originating from the active mine site <br />and to prevent undesirable deposition on undisturbed bottomlands and reclaimed areas. The dozer basins <br />primary use is to trap sediment, reduce on~ite erosion, reduce peak flows at downstream locations, and <br />reduce gully erosion. <br />Livestock watering tanks (ponds) are used to trap water on reclaimed sideslopes, in drainageways, and to <br />reduce peak flows at downstream locations making available reliable water for wildlife use. The location of <br />livestock ponds is such that a minimal amount of sediment will be deposited. This was accomplished by <br />installation of ponds at headwater locations or on relatively gentle grades often witltin water harvesting <br />diversions on reclaim sideslopes. <br />Water harvesting diversions are channels constructed across slopes with a supporting ridge on the lower side <br />that is used to transport excess water from areas that need protection to sites where water can be used or <br />• disposed of safely. A diversion's effectiveness as a sediment reducing measure is in diverting the runoff <br />which would otherwise flow aeons erosion suscepu'ble areas, thus detaching and transporting soil particles. <br />