2006-05-01_REVISION - C1980007 - Laserfiche WebLink

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United States Forest Paonia USDA Department of Service Ranger District Agriculture PHONE NO. 970-527-4131 P.O. Box 1030 N Rio Grande Ave. Paonia, CO 81428 FAX 970-5274151 File Code: 2820-4 Date: April 27, 2006 Tom Kaldenbach Environmental Protection Specialist Colorado Department of Minerals and Geology 1313 Sherman St., Room 215 Denver, CO 80203 Dear Tom, RE C, 7-,NED tim 012006 Division of Minerals and Geology The Grand Mesa-Uncompahgre-Gunnison National Forests', Paonia Ranger District, has completed its review of the March 2006 version of Mountain Coal Company's (MCC) Permit Revision 10 (PR-10). Specific comments on this revision are found below. In addition, per our recent correspondence with CDMG and MCC, I've listed MCC's responses to our January 28, 2005 letter to CDMG (which was subsequently omitted from the previous round of comments/response). Comments specific to the March 2006 version of PR-10: • Page 2.05-149, last sentence, under bullet 2), as well as pg 2.05-150 under bullet 3) and 4)-although it is stated, "...other appropriate agencies will be notified immediately..." we request that the USFS be listed specifically as the dam and associated reservoir is a permitted use on USFS lands. • Page 2.05-151, 2nd paragraph - USFS would also like to receive copies of the quarterly monitoring reports. • 2.05-169 - with respect to a breach of Monument Dam, we request that MCC includes a copy of Minnesota Ditch and Reservoir Company's Emergency Preparedness Plan (see State of Colorado, Rules and Regulations for Dam Safety and Dam Construction, Rule' #16). This could be included as an Exhibit, or at the minimum included by reference. • Exhibit No. 72 - The USFS has reviewed the GEI seismic evaluation for Monument Dam. Within the report, assumptions were made for the dam and the landslide on the downstream left side of the abutment in order to perform the analyses. A steady- seepage analysis for the dam yields a less than 1 factor of safety (or not stable), and a lower water surface analysis yields only slightly above 1 (not sufficiently stable). The landslide pre-failure static analysis has an assumed factor of safety of 1 (pg. 21), although movement is known to occur, this is puzzling. Post-failure stability analysis yields a factor of 1.03. The outcome indicates barely stable to less than stable conditions currently exist. With respect to the dam itself, a stability analysis, assuming specific preventive measures are taken, yields a factor of safety of 1.6 for the dam and the landslide, and 1.5 is the minimum acceptable FOS. However, since it is well known that the dam is built on unstable foundation conditions, and details about these conditions are currently only assumed, it is the USFS' position that a Factor of Safety would be more acceptable in the range of 1.8 to 2.0. Caring for the Land and Serving People Printed on Recyded Paper do