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Section - 2.05.3
<br />Subsequently, approximately 25,000 cubic yards of material from the refuse pile were placed in the
<br />stockpile pad, opening up approximately five years of available disposal capacity in the Eas[ Yard area
<br />at then-current disposal rates.
<br />After evaluating several potential disposal sites, the West Valley Coal Refuse Facility site was selected
<br />for future disposal of coal refuse materials. The new disposal site is located in the first ephemeral
<br />drainage to the west of the existing Elk Creek surface facilities. This area was selected because existing
<br />slopes are flatter than several of the other prospective disposal azeas, upslope drainage could be readily
<br />diverted, the area is readily accessible from the existing mine facilities, and it provided sufficient
<br />disposal capacity for anticipated future mining operations. Initial development for the West Valley
<br />Coal Refuse Facility was completed in conjunction with the mine expansion activities initiated in ]995,
<br />and construction of the refuse pile and waste placement occurred progressively over the life of this
<br />disposal facility.
<br />With development of the Elk Creek Mine, the quantities of mine development waste exceeded
<br />OMLLC's original projections, with the result chat the West Valley Coal Refuse Facility reached its
<br />design capacity much sooner than anticipated. Siting of a replacement facility for active coal refuse
<br />disposal was based on essentially the same criteria used in siting the West Valley Facility. The
<br />replacement coal refuse disposal facility, designated as the II West Coal Refuse Facility, is located in
<br />the second significant ephemeral drainage to the west of the existing West Valley Coal Refuse Facility.
<br />The II West Coal Refuse Fauliry was designed, and will be operated, and reclaimed in essentially the
<br />same mannez as the West Valley Coal Refuse Facility. The following sections describe coal refuse
<br />characteristics; general coal mine waste pile design, construction, operation, and reclamation
<br />considerations; and specific design information for the two existing refuse disposal areas.
<br />Coal Refuse Characteristics -Generation of coal mine refuse from the Somerset and Sanborn Creek
<br />• Mines has been limited to mine development refuse, minor amounts of rock resulting from roof falls,
<br />and coal refuse separated from the coal by the grizzly in the dump station. Current and future mining
<br />operations in both the Sanborn Creek and Elk Creek Mines will generate the same types of refuse
<br />materials. The quantities of roof fall materials may, however, be reduced by the change to longwall
<br />operations and quantities of coal refuse may be increased by the introduction of screening operations.
<br />Mine roof and floor sample analyses, which aze representative of all coal mine refuse materials, are
<br />summarized in Section 2.04.6 Geology Description. Sample analyses for existing coal mine refuse
<br />piles showing similaz values, aze summarized in the same section for the Elk Creek, Hubbard Creek,
<br />and Bear Mine coal mine refuse materials. Based on available analysis results, none of the refuse
<br />materials have been identified as potentially acid- or alkali-forming or toxic-producing.
<br />Coal Refuse Pile Design, Construction, Operation, and Maintenance -Consistent with
<br />applicable regulatory requirements under Rules 2.05.3(8), 4.09, and 4.70, coal refuse facilities have
<br />been designed taking into consideration site topography; geologic conditions; the occurrence of seeps,
<br />springs, or surface instability; surface drainage; and the physical and chemical properties of the refuse
<br />materials. Specifically, refuse facilities are designed to assure their long-term stability (minimum static .
<br />safety factor of 1.5), prevent combustion, and avoid potential adverse impacts to public health and
<br />safety, water quality, and the environment.
<br />Required diversion and collection ditches are designed to safely pass the peak flows from the 100-
<br />year, 24-hour design storm event and include appropriate channel protection, where required, to
<br />assure long-term stability and prevent excessive erosion. Surface drainage designs for the coal refuse
<br />facilities are included in Exhibit 2.05-E3, Drainage and Sediment Control Plan. Designs for required
<br />rock underdrains address potential seepage from direct precipitation on the refuse pile surface. The
<br />• designed underdrains follow the alignment of the natural drainage under each coal refuse facility,
<br />extend from just beyond the toe to the head of the designed fill, and, because the subject drainages are
<br />fairly narrow, provide adequate lateral coverage to effectively collect any seepage or drainage from the
<br />pile.
<br />TR-43 2.05-45 Revised August 2003
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