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~'~ <br />DEPARTMENT OF NATURAL RESOURCES <br />D Monte Pascoe. Eneculive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON Director <br />F is hard D. Lamm <br />Governor <br />T0: <br />FROM: <br />RE: <br />tdarch 17, 1982 <br />Rich Domingue \\ <br />Jim Pendleton \ )`%,,,~(~ /L~~ <br />Portal Bench tabi y Problems at the Blue Ribbon Mine <br />Pursuant to your request, I have reviewed the supplemental submittals made <br />by Western Associates, Inc., concerning the portal bench stability problems <br />at the Blue Ribbon mine. I fozward the following comments for your consideration. <br />The proposed construction of a french d__*ain system (interceptor tile) is a <br />standard dewatering technique. Installation of the interceptor ti le at the <br />proposed 5 to 6 foot depth assumes that water inflow is occurring above that <br />elevation. The test data collected by Rocky l9ountain Geotechnical's test <br />boring program and monitoring well installations has not, to date, verified <br />that the water source is necessarily above that depth. If the situation is <br />resulting from inflow below the depth of 6 feet, the drain will serve little <br />ourpose in remedying the existing problem. <br />I recommend that we proceed as follaas: <br />(1) The operator should be required to provide sufficient data (mapping <br />of the landslide and affected areas) and a discussion of the potential health <br />and safety and environmental hazards. The purpose of this submission should <br />be to demonstrate that the existing failure situation does not constitute an <br />imminent threat to health, safety or the environment. This submittal should <br />consider such problems as potential sediment generation off-site, the health <br />and safety of mine personnel and the public, and coal stockpile integrity, <br />at a minimum. If no imminent threat is demonstrated to exist, the bench could <br />then be safely maintained until the remaining design questions are resolved. <br />The operator should be capable of submitting the appropriate map and discussion <br />within several weeks. <br />(2) The operator should be required to provide us with the water level <br />monitoring results from those piezometers now installed at the portal bench. <br />The operator should submit data collected to date immlediately, and update us <br />as data is collected in the future. <br />(3) I will review the data submitted and the map and discussion before I <br />visit the North Fork of the Gunnison the week of April 12. It is my intention <br />to visit the site at that time, in the company of Marvin Adams of Western <br />Associates Coal, and to judge the accuracy and appropriateness of their pro- <br />posed solution. <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />• ~II II~~I~~I~~~~~ ~I~ <br />