2019-04-29_PERMIT FILE - C1981019A (6)

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RULE 2 PERMITS The generalized multi -seam dragline sequence at the Colowyo operation is as follows: The Bucyrus -Erie 1300W and Marion 8050 draglines begin the sequence removing the overburden over the "B", "C", and "D" seams in a single sidecast mode, spoiling the overburden into the previously mined -out pit. The `B" and "F" overburden is removed from the spoil side of the pit. The spoil from the benching operation will be placed to allow the draglines sufficient room and adequate reach to remove overburden while operating on the spoil side. The draglines construct temporary ramps in order to walk to the spoil side. The "B" overburden is first drilled and blasted, removed by the draglines, "B" coal is removed behind the advance of the draglines, then the drilling is initiated on the overburden of the "C" seam. This sequence is typical through the "F" seam. Upon complete removal of the overburden over the "F" seam, the draglines walk around the end of the pit to the next cut to begin removal of the overburden over "B" coal seam. Overburden Monitoring Program Historically, beginning around 1983, Colowyo initiated overburden monitoring in both the pit (truck/shovel materials) and on regraded overburden. See DRMS Permit Exhibit 6, Item 4 as described in the associated January 4, 1983 Colowyo memo to Dan Mathews, DRMS, for an overview of this initial program. Starting in 1990, Colowyo eliminated the in -pit sampling program. Sufficient data had been collected to indicate that all weathered overburden material (ie within — 50 fee of the ground surface) was suitable for replacement onto the reclaimed surface prior to topsoil replacement. Three revisions were submitted to the Division and approved on January 24, 1984, August 17, 1983, April 24, 1990, and PR -02 respectively. The following summarizes the requirements of the current regraded overburden (backfill) sampling program and supersedes all previous commitments. It is based on the following limitations of the earlier program. 1. Placing weathered overburden material onto reclamation areas prior to final regrading, and 2. Sampling regraded overburden at a density of one composite surface sample per 5 acres of regraded spoil. The regrading of overburden is an event that takes place sporadically during the year. Once backfill areas are regraded, but prior to topsoil replacement, the new locations are identified and sampled. A life -of -mine sampling grid has been established on 500 -foot centers, and each sample location on the grid corresponds to a letter/number combination as established on the sampling map. Using this grid interval, each sample location represents an areas of about 5.7 acres in size. A hand shovel is used to take small, representative surface samples of spoil across the sample area. Regraded Overburden Suspect Levels: Parameter Suspect Level H Less than 5 or greater than 9 standard units Rule 2 Permits 2.05-3 Revision Date: 5/25/18 Revision No.: RN -07