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iiiiuiiiiiiiiuiii <br />999 <br />oc cow <br />~~, <br />o <br />~`~ b~ <br />ire 16 ~• <br />DIVISION OF MINERALS AND GEOLOGY <br />Department o(Natural Resources <br />131 3 Sherman Sr., Raom 215 <br />Denver,CO 80203 <br />Phone: (3031 866-3567 <br />FAX: (303) 832-8106 <br />DATE: October 28, 1993 <br />TO: Christine Johnston <br />FROM: Jim Pendleton <br />RE: Mt. <br />Roy Romer <br />Governor <br />Michael B Long <br />Div icion Director <br />STATE OF COLORADO <br />Technical Revision No. 66 <br />No: C-80-00'n <br />I reviewed the TR-27 application submitted by Mountain Coal Company <br />(MCC) for the repair of a small soil slump and the extension of the <br />lower refuse pile over the effected area. The conceptual design <br />should function properly to stabilize the slump by dewatering and <br />confinement. The constructed underdrain should intercept, conduct <br />and discharge the groundwater seepage into the adjoining drainage <br />ditch. The stability analyses included within the application as <br />exhibits appear to have been appropriately and conservatively <br />prepared. <br />I think it appropriate, however, to monitor the performance of the <br />underdrain and the resulting stability of the refuse embankment. <br />In order to accomplish these two tasks, I recommend that you <br />require the installation of appropriate monitoring facilities. The <br />effectiveness of the underdrain can <br />installation of a piezometer in down gr. <br />drainage blanket. MCC will need to <br />gravel packed piezometer pipe approxima <br />the neck down in the drainage blanket. <br />properly the water level should not be <br />blanket elevation. Further, in order <br />the refuse embankment a line of si <br />installed and monitored down the fac <br />embankment vertically above the drain. <br />stability monuments should be monitor <br />several years. If no movement or water <br />the monitoring frequency could then be <br />cc: Dave Berry <br />Doc: M:\COAL\JAP\MTISLUMP.MEM <br />be monitored through the <br />Ldient from the 30 foot wide <br />Luger a hole and install a <br />tely 10 feet down slope from <br />If the drain is functioning <br />elevated above the drainage <br />~o monitor the stability of <br />lrvey monuments should be <br />e of the completed refuse <br />Both the piezometer and the <br />'d quarterly for the first <br />table elevation is detected <br />relaxed. <br />JP/jP <br />