Laserfiche WebLink
<br />STATE OF COLORADO <br />DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8106 <br />INTERNAL MEMORANDUM <br />COLORADO <br />D IV IS I ON OF <br />RECLAMATION <br />MINING <br />SAFETY <br /> Bill Ritter, Jr. <br /> Governor <br /> <br />TO: Dan Mathews Harris D. Sherman <br /> Executive Director <br /> Ronald W. Cattany <br />FROM: Mike Boulay Division Director <br /> Natural Resource Trustee <br />DATE: June 13, 2008 <br />SUBJECT: Yoast Mine Permit No. (C-1994-082) <br />Technical Revision No. 37 (TR-37) <br />As requested I have reviewed the TR-37 application package for the Yoast Mine with regard to <br />hydrology and permanent post-mine features and facilities. I have the following gdequacy review <br />`comments. <br />The revised As-Built Report for Pond 010 contains new SEDCAD demonstrations for the 10- <br />year and 25-year, 24-hour events. The 100-year, 24-hour event is discussed in text but was not <br />revised with this submittal. The 100-year, 24-hour event demonstration would only be required <br />if the impoundment meets the size criteria of 30 CFR 77.216(a) or if it meets the Class B or C <br />criteria for dams in NRCS Technical Release No. 60. However, since the As-Built Report <br />states that the spillway geometry and peak discharge are based on the 100-year, 24-hour storm <br />event it would be appropriate to update the 100-year, 24-hour SEDCAD demonstration with <br />this revision. Please submit a revised 100-year, 24-hour demonstration for inclusion into the <br />revised As-Built Report. <br />2. Pond 011 As-Built Report Introduction page references Pond 010 instead of Pond 011. Please <br />revise this page accordingly. <br />3. The subwatershed hydrology detail including peak discharges submitted with the revised Pond <br />011 As-Built Report are not consistent with the existing postmine channel designs for YPM-9, <br />YPM-12, and YPM-13 which flow to Pond 011. According to our records YPM-9 was <br />designed in 1998, and YPM-12 and 13 were designed in 2003. The hydrology details for the <br />channel system should be consistent with the input to the model for the Pond 011 As-Built <br />report. Likewise the existing channel design for YPM-12 which contains information for <br />Pond 011 A appears to have inaccurate information regarding structure details including <br />spillway elevations for Pond 01 IA. Please submit a revised Channel System design for YPM- <br />9, 13, Pond 011A and YPM-12. Please revise the YPM-12 design accordingly so that it <br />matches the existing As-Built information for Pond 011A (Exhibit 13-5C). <br />4. The Postmining channel design SEDCAD4 results (Appendix 13-12.3) was last revised 08/07 <br />with TR-36. The table of contents for this appendix (page 13-12.3-i) does not indicate a design <br />for YPM-12 and YPM-13. Please update page 13-12.3-i. <br />Office of Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines