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downgradient of each disturbance area. Auger drilling is a dry drilling operation, so no mud pits were required, and
<br />no discharge of drilling fluids occurred. Because the auger -holes and test pits were in reclaimed mine spoils on a
<br />hillslope, the potential for intercepting any significant quantities of ground water was negligible. Air was not used
<br />a circulation medium, so dust generation was not a concern.
<br />Immediately following completion of sampling, each auger -hole and test pit was backfilled with excavated material
<br />and leveled, with seeding of all sample sites following, either prior to snowfall, or in early spring when ground
<br />conditions permitted. It should be noted that all minor surface disturbance associated with the site geotechnical
<br />investigations falls within both previously disturbed areas, and the footprint of the proposed Refuse Pile Expansion,
<br />and will be re- disturbed by Refuse Pile Expansion foundation preparation activities.
<br />Design of the CRDA Expansion is based on design of, and operating experience gained from, the existing CRDA;
<br />historic designs for a similarly -sized refuse disposal facility in the same location (CTL /Thompson, Inc., 08/14/92);
<br />and site - specific topographic and foundation testing information. Design work for the CRDA Expansion has
<br />included design of required foundation, perimeter, and surface drains by Hydro - Environmental Solutions, Inc.;
<br />design of the required Coal Refuse Haulroad and refuse fills by Civil Design Consultants, Inc. and completion of
<br />design stability analyses, and overall project management and coordination by NWCC. The designed CRDA
<br />Expansion will contain a maximum of approximately 20.0 MM cy of refuse material, will be approximately 200-
<br />250 feet high (relative to the existing terrain), and will be constructed with 3H: IV slopes with 20 foot intermediate
<br />benches at 50 foot vertical intervals, resulting in overall slope angles of approximately 3.5H:1V. The CRDA
<br />Expansion and associated facilities will re- disturb a total of approximately 140 acres of the existing refuse pile and
<br />areas of reclaimed spoils. The upper surface of the CRDA Expansion will slope back to the southeast to prevent
<br />drainage over the outslope, and a toe drain and designed perimeter drains will provide for drainage off of and under
<br />the refuse fills.
<br />Stability analyses of the proposed CRDA Expansion resulted in an overall Factor of Safety of 2.0, given
<br />consideration of reasonable input design parameters. One of the key input parameters was the assumption that the
<br />pile will be self - draining (based on experience with the existing RDA). In order to validate this assumption, TCC
<br />will install three piezometers at the locations shown on the design drawings. Piezometers will be installed on
<br />completed fill benches by drilling through the coal refuse materials and 5 feet into the foundation materials, casing
<br />the holes with slotted 2.0 -inch Schedule 40 PVC pipe, with a sand pack and grout seal. The piezometer casing will
<br />be protected by a PVC riser and a steel casing with lockable cap. Piezometers will be monitored monthly, and the
<br />results will be included in the quarterly refuse pile reports. While stability analyses indicated that the overall
<br />CRDA expansion would be stable, as designed, there is some potential for localized shallow surficial slope failures.
<br />If shallow failures occur, they would be expected to be associated with moist fine materials, and would be
<br />addressed by removing these materials and replacing them with compacted coarse materials. If such failures occur
<br />with any frequency, the slope configuration may be modified or other measures implemented to minimize the
<br />potential for future failures. Design documentation for the road and refuse pile design and stability analyses is
<br />presented in Exhibit 26C, Coal Refuse Disposal Area Expansion. Designs for drainage structures associated with
<br />the CRDA are presented in Exhibit 8EE — Coal Refuse Disposal Area Expansion — Drainage Designs.
<br />Construction of the CRDA Expansion will be progressive, both from north to south, and with the pile increasing in
<br />elevation, as dictated by refuse placement requirements. Construction will begin with implementation of temporary
<br />erosion and sediment control measures, including placement of silt -fence and /or straw wattles downslope from
<br />initial construction areas. Available soil materials will then be removed from the initial road corridor, drainage
<br />channels, and refuse toe bench area (includes east - facing slope of existing RDA Area 1). It is anticipated that soil
<br />material recovery will be extended, both to provide for approximately two years of scheduled refuse placement, and
<br />to provide a reasonable buffer between the active construction and refuse placement activities and undisturbed
<br />(reclaimed and revegetated) areas. Soil materials from the initial CRDA construction areas will be placed in
<br />designated temporary stockpiles for future use in reclaiming completed CRDA benches or areas. Stockpile areas
<br />will be accessed by temporary scraper tracks within the CRDA footprint. As CRDA construction progresses, the
<br />option will exist to live - handle the soil materials, with recovery from new placement areas and direct placement on
<br />completed CRDA areas, or placement in /recovery from stockpile. To the extent operationally practical, TCC will
<br />attempt to use live - handling practices in order to obtain the best reclamation results. Soil material volumes and
<br />recovery and stockpiling operations are summarized by Table 49A, Soil Stockpile Summary.
<br />TR13 -83 2.05 -97.3 05/14/14
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