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HYDROLOGY <br /> <br />The hydrologic impacts of the ongoing mining operation by Colorado <br />ldestmoreland, Inc. at Orchard Valley Kline has been discussed in some <br />detail by Leaf (1977). The mine is located in "4lestmoreland Canyon," a <br />tributary of Stevens Gulch, which joins the North Fork of the Gunnison <br />River at Paonia, Colorado. <br />DRAINAGE PLAN <br />The proposed drainage plan would safely control storm runoff with <br />~• <br />minimuri environmental damage. Figure 1 shows the primary components of <br />this plan under full mine development. It is proposed that ultimately, <br />at least eight small check dams be constructed and maintained to adequate- <br />ly control sediment. As will be discussed later in this report, four <br />dams are proposed for locations immediately dovrnstream from the mine in <br />order to comply with recent State and Federal regulations. It is recom- <br />mended that the proposed structures be designed as shovrn in Detail B of <br />Figure 1. <br />Diversion Channel <br />A channel with sufficient capacity and freeboard to carry the Probable <br />^laxiinum Thunderstorm should have a 5-foot wide by 2-foot deep heavily <br />riprapped low-flow channel and a 25-foot r•~ide (bottom width including <br />lov+-flo~•r channel} by 5-foot deep trapezoidal high-flow channel. Side <br />slopes of the high-flow channel should be 2:1. The upslope cut should <br />also be 2:1. The attached Figure 2 sho~•rs all the key features of a <br />typical cross section. <br />I '• <br />