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<br />-Q- <br />4. On page 4.05-LO the applicant requested a valiance f[om <br />stream buffer zones to accomodate the main entries of the <br />mine. The Division will issue it's decision on the request <br />after a finding on the impacts of subsidence have been made, <br />the effects of mining on the surface and ground water systems <br />have been determined and findings on alluvial valley floors ale <br />made. At this point, it does not appear this will be a major <br />trouble spot. <br />5. Sevecal concerns we[e noted with the revised design <br />calculations contained in Exhibit 6, Table A. In using the SCS <br />TR-55 watershed model, the applicant failed to adyust peak <br />[unoff rates for varying slope and basin shapes. The applicant <br />should [efe[ to Appendix E of SCS TR-55, PeaK Flows in <br />Colo[ado. 1977 and make the appropriate ad]ustments. <br />6. Problems were identified with Table B, Exhibit 6 with <br />regards to culvert sizing. The Manning open channel equation <br />ie only applicable to a depth of flow of 94! of capacity, afte[ <br />which closed conduit hydraulics apply. Culvert designs should <br />be rechecked using an appropriate closed conduit design <br />procedure. <br />7. Page 4.05-19 of Volume 1 and page 3, Exhibit 6 of Volume <br />2 state that the Division approved a sediment storage c[1te[on <br />of 0.02 ac-ft/ac of disturbance on January 29, 19fl2 for the <br />CYCC mines. This statement is incorrect and should be deleted <br />from the application. When this e[iteria was proposed in the <br />winter of 1981-82, the Division responded with a letter of <br />concerns that needed to be addressed prior to our approval of <br />the criteria. Thai lette[ was dated December 10, 1981 from <br />Sandy Emrich of MLRD to Kent Watson of CYCC. Instead of taking <br />the time to respond to this lettec CYCC instead chose to pursue <br />a quick solution to the issue by developing a sediment yield <br />criteria fo[ a specific subwatershed. The response was <br />contained in a letter dated Decembe[ 11. 1981 f[om Michael <br />McCarthy to Sandy Emrich (hand delivered). The Division <br />reviewed this criteria and found it to be acceptable for the <br />pa[ticula[ watershed. Howeve[, approval was never granted to <br />allow its use over the enti[e basin. Topog[aphlc (GS) facto[s <br />vary too much to allow such a site specific criteria over a <br />wise region. <br />It should be noted that the Division [eviewed the sediment <br />ponds considering the old sediment storage criteria (O.1 <br /> <br />