2012-01-06_PERMIT FILE - C1982057 (18)

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sandstone is 130 feet. Above the Twentymile sandstone is the upper unit of the Williams Fork Formation. This unit, exposed to the west of the permit area, consists of sandstones, shales, and thin coals. The Quaternary age deposits within the permit area consist of thin alluvial (Exhibit 6-1 and 6- 1 B) and colluvial deposits. During the course of mining and facility construction there have been areas of surfical instability encountered on the steeper or saturated slopes usually associated with final pits prior to backfilling or haulroad construction. Stabilization of these areas is generally accomplished by avoidance, pit backfilling, or slope reduction. Site specific remediation/stabilization measures are implemented on as needed situations. The areas of instability are shown on Exhibit 6-1B and in Attachments 13-3A, 3B, 4A, 4B and 4D. There are not any outcrops of Miocene extrusive igneous rock nor any evidence of intrusive rocks at the mine site. Overburden Assessment The original overburden samples obtained from the Seneca II-W Mine study area were analyzed to identify any acid-forming, toxic-forming, alkalinity producing, or other inhibitory materials associated with the Wadge seam mining area. Physical properties of the overburden were determined to define compaction, stability, permeability, erodibility, and water holding characteristics. Chemical and physical analyses also reveal the most desirable overburden strata to be placed at the spoil surface and in the pit base. This baseline information is required prior to mining to effectively prepare a mine plan that restores landscape productivity and which also minimizes environmental degradation. Now that SCC has decided to mine select areas of the Sage Creek and Wolf Creek seams, a generalized overburden assessment was conducted. SCC has no overburden suitability analyses from the specific area proposed for mining. However, in August 2001 Seneca drilled a monitoring well (WWCU-24) approximately 1,600 feet down dip (west) of the proposed mining area to monitor ground water from the Wolf Creek underburden. During drilling, overburden chip samples were collected to further assess the overburden characteristics in the Sage Creek/Wolf Creek mining area. The sample intervals collected represented the Sage Creek overburden, the Wolf Creek overburden and the Wolf Creek underburden. Although the overburden samples were collected from only one locale outside the proposed mining area and therefore may not represent the actual overburden characteristics of the entire proposed mining area, these analysis results were used in conjunction with the overburden assessment at the Yoast Mine to estimate reclamation suitability of the Sage Creek/Wolf Creek overburden material. The Yoast Mine Permit, Tab 21, Minesoil Reconstruction, indicated that..... PR04 8 Revised 04/02