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eh <br />ESPEY. HUSTON & ASSOCIATES, INC. <br />• <br />eligibility for placement in a durable rock fill as set forth in 30 CFR 715.15(d) and <br />814.74 when such material has actually been removed from Run of Mine coal by a <br />rotary breaker, and thus will meet the interpretive rules set forth in the Federal <br />Register, Vol. 45, No. 75, Wednesday, April 16, 1980, 715.15 (d), 816.74, and 817.74. <br />13.1.2 The Proposed Project <br />Northern Coal Company proposes to place the waste material on the <br />southern slope of the first ridge southwest of the Northern No. 1 mine. The <br />boundaries of the pile have been selected to avoid interference with surface <br />drainage, to avoid overly steep natural slopes, to stay below the ridge top and to <br />maximize available storage volume. The slopes were selected to ensure stability <br />and ease of maintenance (30 CFR 817.71). Terraces have been specified every 50 <br />feet vertically with a width of 20 feet to increase stability of the fill and to control <br />runoff from the face of the fill, (30 CFR 817.1021, (Figs. 13.1.2 and 13.1.3). These <br />• figures aze conceptual in nature and aze intended to allow evaluation of Phase I of <br />the project in light of the plans for the life of the mine. This application, however, <br />is for a permit for Phase I only and the detailed plans which aze discussed in the <br />following pages concern Phase I only, except as noted (see Figs. 13.1.4 and 13.1.5). <br />The Pbasu~ facil;ty ~as n6t loeca ~,:.scdt on. a cQ,orable rock -F+l~, <br />13.2. THE EXISTING ENVIRONMENT <br />13.2.1 Soils <br />The surficial geology of the mine plan azea is chazacterized by thinly <br />mantled bedrock overlain bq unconsolidated colluvial and alluvial materials. The <br />steep-sided valley walls within the mine plan azea are generally mantled with a thin <br />layer of residual soil and/or colluvium and slope wash. These deposits thicken on the <br />lower portions of the valley side slopes and interfinger with limited alluvial deposits <br />associated with the small northwest trending tributary to Curtis Creek which <br />traverses the disposal area. The stream channel associated with this tributary <br />u <br />13-2 <br />y/~rg7 <br />