2006-07-07_REVISION - M1980189 - Laserfiche WebLink

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STATE OF COLO~O DIVISION Of MINERALS AND GEOLOGY Department of Natural Resources 1313 Sherman St., Room 215 C O L D RA D O Denver, Colorado 80203 Phone: (3D3) 066-3567 DIVISION O F M I N E RA L S FAX: (303) 832.8106 G E O L O G Y RECEANATION•NININO SAFETY•SCIENCE July 7, 2006 Bill Owens Mr. Ernie Shonts ~ Gwemor El Paso County RoRSeu cenrge 3460 N Mazksheffel Road Executive Director Ronald W. Cattany Colorado Springs, CO 80922 Division Director Natural Resource Trustee RE: DMG Permit # M-1980-189; Yoder Pit; Technical Revision # 1 Adequacy Comments Deaz Mr. Shonts: The office received your technical revision application on May 19, 2006 and it was called complete on June 19, 2006. The decision date for this revision is July 19, 2006. Following aze several adequacy comments related to the establishment of the permanent drainage across the backfilled slopes including a request for additional information. This revision was submitted in response to a financial warranty release request and inspection. The inspection revealed that the site was not ready for final release due to poor revegetation and a significant erosion feature in the northwest backfilled and re- graded slope. The material used to backfill the slope is very sandy and therefore highly erosive. This erosion is occumng due to the fact that a relatively flat but significant watershed concentrates in an azea just above the backfilled slope and creates down cutting where this water drops onto and across the slope. There was an attempt to divert the water azound these slopes using a berm at the top, however, this berm has failed to hold up over time and will likely continue to fail unless a permanent engineered berm is constructed. As a result of these observations, it was agreed that the best course of action would be to identify the area where this water will flow naturally and re-establish a permanent drainage in this azea. Since this is a 3H:1 V slope constructed with highly erosive material it was suggested that some level of design to incorporate armoring or channel lining would be necessary. The revision states that reclamation matting will be placed in the channel with the intent of slowing erosion and establishing vegetation. Please provide additional detail on how this matting will be installed to prevent head cutting at the critical transition point where water enters onto the slope from the upland watershed. It seems that some level of hazd armoring (rip-rap, concrete apron, etc) may be necessary at this point to prevent head cutting and anchor the matting in place. In addition, how will flow velocities be controlled to safely pass these overland flows down Office of Office of Colorado Mined Land Reclamation Active and Inactive Mines Geological Survey