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EUGENE M. SHEARER <br />5720 SOUTH JASMINE STREET <br />ENOLEW OO D, COLORADO BOI10 <br />303.771.2371 <br />• 18 December 91 <br />Mr. Bryan Archer <br />Sun Coal Company <br />10200 West 44th Avenue, Suite 120 <br />Wheat Ridge, Colorado 80033 <br />Dear Bryan: <br />Thank you for forwarding Mr. Carl Mount's letter of <br />5November9l to my attention. Mr. Mount requests: 1) an <br />emergency spillway outfall design to augment the emergency <br />spillway design report and drawing submitted 300ctober9l, <br />and 2) all supporting spillway calculations, documents and <br />drawings used to establish the requirements of Rule <br />4.05.6(3) above shall be included in the permit <br />application." The following comments are in response to said <br />requests. <br />1. Regarding positioning of the emergency spillway, my <br />300ctober9l letter states that 'the emergency spillway be <br />located on the north sedimentation pond embankment, in a <br />position that optomises flow from the spillway, northward <br />towards the Yampa River." This suggestion allows for con- <br />struction costs consideraticn. The least expensive loca- <br />• tion will be positioned at the point of minimum embankment <br />width coupled with a iow, 2: or less, grade for the out- <br />fall. Inasmuch as an adequate, small contour interval. <br />large scale map is not available covering the area frcm <br />the north sedimentation port embankment to the Yampa <br />River, the outflow grade, decending on spillway location, <br />may vary from less than one percent to an estimated 15 <br />feet vertically to forty feet horizontally or 38 per- <br />cent. In the absence of a detailed profile from the out- <br />fall terminus of the emergency spillway to the Yampa <br />River, it is recommended that, assuming the outflow can- <br />not be directed into a natrual drainage or onto the <br />nearly horizontal alluvial valley floor ,a v-shaped channel <br />be riprapped with 0.5 foot angular rock in a matrix of0.05 <br />foot gravel where the grade is 2 to 4 percent. If the <br />grade exceeds 4 percent the 0.5 foot riPrap should be set <br />in concrete. The outfall riprapped channel should have the <br />same cross-section dimensions as the riprapped portion of <br />the emergency spillway as set forth on the 30ctober9l, <br />Emergency Spillway Design drawing. <br />2. A review of the origina: computations for the Yampa <br />• <br />f ~~ ~' <br />