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-2- ' at the base of hills in areas where grades are estimated to be flatter than 20 percent. Based on our personal observation at the mine and a review of topographic maps provided, it does not appear that any haulage or access road embankments have been constructed in areas where grades exceed 20 percent. MRLB has requested that the applicant report maximum embankment slopes on all embankment roads to allow the division to verify compliance with 4.031 (3)(d)(ix) and 4.03.2 (3)(d)(vii) and to enable the Division to assess stability and erasion potential of the slopes (Item G, Page 2). The per- formance standards for the two mentioned sections require that embankment fills be flatter than 1 vertical to 2 horizontal. One road embankment is evident on Map IV-9. The embankment is located on an access road, outside of the permit area, in the southeast quadrant. This slope is about 2 verti- cal to 2 horizontal and about 20 feet in height on the downhill side. We have observed that there are numerous embankments for haulage and access roads which are not indicated on the topographic map. In general, these embankments are less than 10 feet in height and are steeper than the maxi- mum specified by the performance standards. We understand that most of the roads within this mine area have been present during the life of the mine (20+ years). At the time of our site visit, no areas of instability were evident. We understand that embankment and cut slopes have generally been performing satisfactorily. Based on our personal observations at the mine site, there appears to be some cut slopes and road embankment slopes which are steeper than specified by the Performance Standards. Considering that these slopes have performed satisfactorily over a number of years, we believe that the slopes are structurally stable. We believe that the slopes will remain structurally stable provided slope conditions do not change in the future. If the slopes are steepened by undercutting or erosion, it is possible that some instability could develop. We reco+rmiend that Empire Energy monitor all cut and embankment slopes periodically for signs of instability. If some movement is observed, then the slopes should be flattened. If we can be of further service in discussing the contents of this letter, the attached maps, or the mine from a geotechnical point of view, please call. Very truly yours, CTL/THOMPSON, INC. By am C. rtotrnrari rt;'Jr., Yro3¢ct tngineer Reviewed by: I8LL~/ ~Q`:~ •TH~~i,•p A~~4~%~ _..,., Qom: •6`8~S^' ~J President E • ~ Robert W. Thompson, , Y 7078 WCH:RWT:kt • .~ (3 copies sent) 'rt~~~0,";;; •~,P~ . f nF rn~~~