Laserfiche WebLink
L_J <br />EDNA MINE <br />MOFFAT AREA <br />SLOPE STABILITY ANALYSIS <br />INTRODUCTION <br />The purpose of this report is to analyze the stability of the <br />proposed out-of-pit spoil in the Moffat Area at the Edna Mine. <br />The stability analysis for this report was determined using the <br />SWASE and REAME computer programs. The basic parameters used in <br />this stability analysis were determined from field observation, <br />drill hole information and research completed by Water, Waste & <br />Land, Inc. (WWL) on previous stability analyses completed for this <br />area. Reference is made to WWL's studies throughout this report. <br />GENERAL CONDITIONS <br />Figure 1 shows a plan view of the Moffat Area including the <br />approximate location of the boxcut, sediment basin and proposed <br />out-of-pit spoil. The Wadge seam has been removed south of the <br />Moffat Area boxcut from the previous mining in East Ridge. The <br />previously mined area was backfilled with spoil material in the <br />mining process after the Wadge seam was removed. The area shown <br />• between the previous mining and Trout Creek is primarily <br />undisturbed by mining activities. <br /> <br />A cross section of the general stratification in the area of <br />the proposed out-of-pit spoil is shown on Figure 2. As shown on <br />this drawing, the Wadge seam intersects the creek embankment <br />slighlty above the bottom of the Trout Creek drainage channel. <br />Based on drilling information, the Lower Wadge does not appear to <br />intersect the creek embankment in this area. The Wadge coal seam <br />is typically five to six feet thick with the Lower Wadge at two to <br />three feet thick. As shown on the cross section, the Wadge and <br />Lower Wadge seams are separated by several feet of shale and <br />interbedded sandstone and shale. A thin coal seam, called the <br />Rider seam, is commonly present above the Wadge. <br />WWL reports that in many of the previous explorations, a soft <br />weathered shale was encountered underlying the coal seams. This <br />shale becomes soft in some places and is often termed "underclay." <br />The underclay has a potential to confine water and may cause the <br />build-up of excess water pressures in the coal aquifers. WWL also <br />states that the upper Wadge coal seam does not contain an aquifer <br />in this area but it appears an aquifer exists in the Lower Wadge <br />which coincides approximately with the top of the Lower Wadge coal <br />seam. WWL also indicates that perched ground water mounds can <br />form in this strata during periods of extended rainfall and <br />snowmelt. <br />1 <br />