Laserfiche WebLink
B. No development on slopes over 20% - As discussed in the Reclamation Plan <br />(Appendix A), final slopes produced around the perimeter of the pit will be at a <br />maximum of 3 horizontal to lvertical (3:1) which is 33.3%. Although this exceeds <br />the 20% (which would be a 5:1 slope) no development will occur on these slopes. <br />These slopes will be planted with alfalfa and used for grazing cattle or other <br />similar agricultural purposes. The bottom of the pit will be essentially flat. <br />C. Control surface drainage, erosion and sedimentation sources - During the <br />operation, control of drainage and sedimentation that would occur from active <br />mining areas will be contained within the operation. During the mining, as has <br />occurred in the past, the operation is conducted in what amounts to a very shallow <br />closed basin. Storm water that runs off of unfinished slopes or causes sloughing of <br />vertical faces where mining is currently occurring is contained in this basin. The <br />basin, covering several tens of acres and a few feet deep, contains just about any <br />conceivable storm event before it would actually be able to discharge to Running <br />Creek. Because the pit bottom is composed of sand, the deep water that <br />sometimes accumulates in the pit after large stones, quickly sinks into the ground <br />and charges the alluvial aquifer along Running Creek. Even two or three feet of <br />water in a particular hole in the bottom of the pit can percolate into the ground <br />within a day or two and sometimes much less. The pre-mining land adjacent to <br />Running Creek has a general upward slope from the riparian corridor. Before <br />mining, water containing sediment, would flow directly into the forest and the <br />stream. With the mining pit, that water now reaches the stream primarily through <br />the ground and is much cleaner after large stones. At the end of the operation, the <br />pit bottom will be reconnected to the stream, but with a pit bottom that is basically <br />flat and will cover about 90 acres, the quality of the water reaching the stream <br />should still contain less sediment than it did prior to mining when runoff was <br />swift and sediment loads higher. Any erosion of the 3:1 backslopes around the pit <br />perimeter would be contained in the large flat area of the former pit bottom. It is <br />important to point out though, that past reclamation efforts using only alfalfa on <br />3:1 slopes has resulted in little gully erosion and only minor to moderate sheet <br />erosion. Therefore, with regard to the adequacy of the reclamation to achieve the <br />end purposes, that has already been demonstrated in the existing operation. As has <br />been demonstrated on coal strip mines, when alfalfa is planted it produces a <br />nitrogen rich pocket of soil where many grasses and forbs can invade. That <br />improves vegetation cover and species diversity using natural processes rather <br />Miller Gravel Pit -Special Use Permit Page 10 of 26 <br />