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March 29, 2006 <br />RECEIVED <br />Attn: Allen Sorenson /qpR 0 ~ 2006 <br />State of Colorado J/ Oirisisrt ~f h}in~ret$ Ash Oeob~y <br />Division of Minerals and Geology <br />Office of Mined Land Reclamation <br />1313 Sherman Street, Rm. 215 <br />Denver, Colorado 80203 <br />RE: Rock Dog #1 Pit, File # M-20U5-045, Proposed Detention Pond <br />Dear Mr. Sorenson: <br />The following with attachments is in response to your latest request for additional <br />information concerning the proposed detention pond and stormwater analysis for the <br />proposed Rock Dog #] Pit. <br />The responses to follow are in the numerical order to your memorandum of March 27, <br />2006: <br />Diversion Ditches <br />Based on the Run-on flow analysis shown on attached pages 4 and 5, the <br />diversion ditches to the north and east of Phase A have the same cross- <br />sectional dimensions as those described for the ditches within Phase A. <br />2. Run-on Diversion <br />It has been decided to forego the use of overburden berms to divert up- <br />gradient stormwater for reasons addressed in your memorandum. The <br />diversion of the potential Run-on flows will be accomplished with ditches as <br />described herein. <br /> <br />a) Even though diversion ditches are now proposed for the <br />perimeter of Phase A, topsoil berms have been relocated inside of <br />the overburden berms for further protection from erosion (see <br />attached Figure 1). <br />b-d) It is not now necessary to utilize overburden material for <br />constructing perimeter berms for stormwater diversion. <br />An up-gradient (Run-on) hydrology report is attached as page 4. The areas <br />considered in this report are shown on Figure I. <br />