PERMFILE112893 - Laserfiche WebLink

Home Browse Search

Doc Date:12111/2001 sss ~/ SECTION 3.0 Drainageway Reconstruction, Improvement and Repairs at Trapper Mine in 1990. 3.1 Drainage reconstruction 1987-90 At Trapper Mine, all or portions of five major drainageways (Coyote, Johnson, E. Buzzard, E. No-Name and W. No-Name) and their tnbutaries were regraded and appropriately treated to reduce the erosion rate and assist in permanent channel stabi- lization in 1987, 1988, 1989, and 1990. At the conclusion of the 1990 field season, approximately 37,950 linear feet (7.2 miles) of permanent drainageway reconstruction had been completed at Trapper Mine (see attached "Drainage Reconstruction" map). 3.2 Vegetation Sampling Methods Herbaceous plant canopy cover, annual herbaceous primary production and woody stem densities were measured on twelve postmine reclaimed drainage sites and on two undis- turbed premine drainage locations in 1990. Plant canopy cover was estimated in three 100-m transects spaced 10-m apart at each site. Herbaceous plant canopy cover and percent mulch cover were estimated by species using the point-hit technique (Optical Point Bar) (Viert 1985). Herbaceous production was estimated by clipping six 1/4-m plots (20-m spacing) on each of the three line transects at each site. Woody stem density • on undisturbed drainage segments was calculated using the point-center-quarter (PCQ) method (Dix 1961). Five PCQ's were conducted on each line transect at 20-m spacing. Distances from the center of each PCQ to the nearest line stem in each quarter was recorded. Woody stem densities in reconstructed drainage segments is an approxima- tion of the actual seedlings planted at each site. 33 Erosion Control Methods A wide variety of erosion control materials, methods and sediment reducing measures were used in reconstructed drainageways, on reclaim sideslopes and on regraded spoils. The following list of measures and/or materials were applied in combination to decrease the likelihood of accelerated erosion, to reduce flow rates and to reduce the sediment loading in downstream sedimentation structures. Dozer basins (sediment basin) were constructed to trap and store sediment on newly stripped topsoil areas and on regraded spoils to reduce or abate the sediment load. Basins are used to prevent the siltation of diversions, waterways, livestock ponds, and streams; to trap sediment originating from the active mine site and to prevent undesir- able deposition on undisturbed bottomlands and reclaimed areas. The dozer basins primary use is to trap sediment, reduce on-site erosion, reduce peak flows at down- stream locations, and reduce gully erosion. Livestock watering tanks (ponds) are used to trap water on reclaimed sideslopes, in • drainageways, and to reduce peak flows at downstream locations making available reli- able water for wildlife use. The location of livestock ponds is such that a minimal amount of sediment will be deposited. This was accomplished by installation of ponds at