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• - 1 rr.. • <br />degree. The Qtl terrace is, thw:cforc, of primanF introrest, due to the Limited <br />occurrence of the pt2 terrace within the study area. This is documented by the terrace <br />mapping shown on Map 2.5-21. <br />The applicant has estimated that the mean annual water yield for Oak Creek is approxi- <br />mately 10,800 acre-feet/year, again indicating that ample water would be available to <br />support irrigation practices on the alluvium. At t,hi.s time, however, irrigated agri- <br />culture is not a current practice on the Oak Creek AV!' within the study area. <br />According to Exhibit 2.9-1 of the permit application, current land use of the OaF: <br />Creek~AVF within the study area is shrub an rl brush rangeland. In the vicinity of the <br />Edna mine, the Oak Creek valley is constructed. There is only a limited amount of <br />flood irrigable alluvial terrace lands available for agricultural use. <br />Vegetative species indicative of subirrigated conditions also e.rist along Oak Creek. <br />These are shown on Map 2.4-1 of the permit nnp.iicntz:on. Thr_ presence of the indicator <br />species, and ground water depth of less than 10 feet, support the contention that the <br />Oak Creek AVF maintains a suhirriyation potcr.t.ial. <br />TOPSOIL <br />The proposed permit area is occupied Dy te.•o sell nrde rs, ~~follisols and An:disols. Tize se <br />soils are typical of soils found in steep semi-arid re ti.ons of Northwestern Colorado. <br />A soil complex which contains soils of the Cntisol order is encountered in small <br />intermittent areas, located acijacant to streams and illuvial Valley Floors. Part of <br />the area has been pre vinusly disturbed. As o conser7uence of this, no topsoil remains. <br />An analysis of overburrler. m,rterials demonstrates no problem with toxicity. <br />[/ith the exception of some small .z re as found in association ~.aith rocF: outcrops, the <br />majority of the soils in the permit area are r?cep and well-drained. There are three <br />main factors that limit topsoil ,alvayiny operations: coarse fragments, heavy clay <br />accumulations, and slope steepness. <br />The Edna mine's topsoil salvn~]c operation entails the removal of vegetation followed <br />by topsoil stripping. nctmll stripping of the snit material will ire done with scrapers <br />capable of taking material to ~.;zthin ore znch of trr~ desired stripping depth. <br />Once the actual salvaging operations have taken place, the material will be placed in <br />either an active or inactive stockpile. Topsoil will Lr line-handled whenever possible, <br />a practice which is advoc.rted by this office. <br />Stockpiled topsoil will be protected from wind and mater erosion by the establishment <br />of a quick growing vegetative cncer. If erosion problems are encountered, other <br />control measures will be uCili zu.9. <br />Information giving greater cL~tai1 of the soil on vironm,nt and topsoil salvage operation <br />can be found in Volume 2, section 2.3, and !volume 10, Section 4.3 of the permit appli- <br />cation. <br />VE'GETAT TON <br />The vegetative communities of the area are not as typical of those found in this area of <br />Northwest Colorado. In general, the Pioffat area consists of expanses of sagebrush and <br />mountain shrub communities, with into rs persi ens of aspen and oak clumps. Corrun uniti es <br />along the drainages of Oak CreeF: and Trout Creek arc characterized by riparian vege- <br />