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• ,~~~ r 8 <br />• GEC MINERALS, IN • <br />FLORENCE. COLORADO 81226 <br />P.O. BOX 225 <br />L, i~ <br />III IIIIIIIIIIIIIIII <br />sss n~~u QED <br />D~3t;~~4261980 <br />MINED LAND RECLAMATION =CORE <br />COLO. DEPI, OF NATURAL RESOURCES <br />December 19, 1980 <br />Mr. Peter N. Evans <br />Reclamation Specialist <br />Department of Natural Resources <br />Mined Land Reclamation Division <br />423 Centennial Building <br />1313 Sherman Street <br />Denver, Colorado 80203 <br />RE: Technical Revision to State Mining Permit 1177-48 <br />Dear Peter: <br />Per our pleasant meeting yesterday regarding the requirements of <br />Sec. 1.9 of the Rules and Regulations as promulgated from 34-22-112, <br />Colorado Revised Statutes, 1973, as amended, GEC Minerals, Inc. is <br />herewithin requesting technical revision to modify the approved GEC <br />State Mining Permit 1177-48 concerning the Dam D area undisturbed <br />runoff diversion calculation as well as the revised Dam D and the <br />related ditches calculation. <br />As we discussed before, in order to separate the undisturbed runoff <br />from the disturbed runoff, the most reasonable approach to handle <br />Dam D area will be to build up a small bank at the bottom of the <br />existing un-named stream (see attached map). The size of the bank <br />will be approximately 70' long, 8' high, and 10' wide, upstream of <br />the bank shall use riprap rock to prevent possible erosion. The <br />attached Dam D undisturbed runoff diversion pipe calculation indicates <br />that a 300' long, 27" diameter round pipe will be needed to divert <br />a total of 60.6 cfs during a 10 year, 24 hour precipitation event, <br />(the pipe was specifically located on the attached map). Owing to the <br />long lead time to purchase and get the specific pipe, a temporary ditch <br />will have to be designed and put up prior to any mining action taking <br />place in Dam D; the revised Dam D calculation reveals that the new <br />dam itself will be 320' x 55' as shown on the attached map. The <br />existing Dam D was a little bit oversized, based on previous calcu- <br />lations, to serve a total of 31.76 acres of land, however, GEC would <br />rather stay on the conservative side and leave the dam as it was, if <br />it can be approved by the MLRD. <br /> <br />