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r~ III III III III IIII III STATE OF CGLVt~liv MINED LAND RECLAMATION DIVISION Department of Natural Resources 1313 Srterman SI.. Room 215 Denver, CO 80203 303 866-3567 FAX~303 832-8106 pF ~0~~ ti"/, ee = ~;~..i~ r-. ~ /e ~/b ~ Rov Fiume: Governo Fetl R. bama. Drvaion D:rerior DATE: March 8, 1990 T0: Tony Waldron FROM: Jim Pendleton RE: Eagle No,/~- (Rerm.it _~.~- ~nce Monitoring C-B1-044) Cyprus Empire Corporation (CEC) is about to commence longw311 production mining from the "E" Seam in its Eagle No. 6 mine. They have requested our direction concerning subsidence monitoring above the Eagle No. 6. I forward the following comments for your consideration. The life-of-mine plan for the Eagle No. 6 mine projects mining beneath a number of critical structures and renewable resource lands: State Highway No. 13, the alluvial valley floors of the Yampa and Williams Fork rivers, the Colowyo and Empire DRGBW railroad spur, and an AMOCO oil transportation pipeline. The Division presented concerns regarding the potential subsidence of these structures and renewable resource lands in its earlier adequacy comments, prior to the last permit renewal. CEC responded by observing that only the oil pipeline could potentially be affected during the current 5-year permit life. Further, they committed to mining no closer than 100 feet horizontally from the pipeline. These conditions are chronicled within the findings document. In response to our adequacy comments, CEC also committed to employing a combination of new and existing subsidence monitoring monuments, as well as visual inspection of the surface, to continue subsidence monitoring above the Eagle No. 5 and Eagle No. 6 mines. To its credit, CEC has conducted an exemplary subsidence monitoring program above both the roan 8 pillar and the longwall workings of its Eagle No. 5 Mine. In August of 1988, the Division approved cessation of subsidence monitoring above the Eagle No. 5 Mine workings. CEC had demonstrated that its subsidence monitor°ing program had documented the character, distribution, and magnitude of subsidence above the Eagle No. 5 workings. Further, it demonstrated that its predicted angle of draw and vertical subsidence magnitude projections both exF:eeded the actual observed subsidence occurrence. As stated by the Division in adequacy comments and the findings document concerning the proposed life-of-mine extraction within the "E" Seam, it will be necessary for CEC to verify their projections of subsidE~nce due to the superposition of the "E" Seam subsidence upon the existing "F" Seam subsidence. The character, magnitude, distribution, and time of occurrence of subsidence of these superimposed workings will be required as a portion of any demonstration submitted by CEC to obtain approval to mine beneath any of the