Laserfiche WebLink
COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />May 11, 2015 <br />To: Brock Bowles <br />From: Jason Musick <br />RE: New Horizon Mine, C- 1981 -008 <br />TR -68, Adequacy Review Memo <br />Per your request, I have reviewed the proposed stream buffer zone variance for the Calamity Draw pump <br />station associated with the above referenced revision. In order to address the Division's adequacy <br />question concerning a request for sediment control measures associated with the temporary pump <br />station, Tri -State provided a SEDCAD demonstration to show that the undisturbed vegetation surrounding <br />the Calamity Draw pump station provides adequate sedimentation control such that the drainage from the <br />pump station disturbed area are in accordance with Rule 4.05.2(3)(a). The Division reviewed the <br />proposed demonstration to determine if the if the demonstration meets the criteria for an exemption <br />from the requirements of Rules 4.05.2 and 4.05.18. <br />Based on the information presented in both the SEDCAD demonstration and Map 4.05.18 -2, the Division <br />has determined that the utilization of a grass filter for the sub - watershed, which includes the calamity <br />draw temporary pump station, is based on conservative inputs. The variables used in the demonstration <br />concluded that the grass filter has a trap efficiency of 89.7 %. The Division believes that the inputs used <br />and the demonstration presented provides justification for an exemption of Rule 4.05.18 under Rule <br />4.05.18(1) and 4.05.2 under 4.05.2(3)(a). <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us <br />John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />OF'c <br />\876. <br />