2010-06-04_PERMIT FILE - C1982056A (9)

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• Continuous readings from an ash analyzer on the main underground production coal conveyor determine • whether the production flow on the slope conveyor is routed to the Run -of -Mine (ROM) Coal Stockpile or the Low — Quality Coal Stockpile by the flop -gate at the discharge of the slope conveyor. Since the new Washplant is designed to process a significant portion of the ROM coal flow, the ash cut -off threshold for designation as low- quality coal was increased. This change results in an increase in the percentage of coal routed to the ROM Stockpile and a reduction in percentage to the Low - Quality Coal Stockpile. • The coal - handling system for the low- quality coal was simplified to eliminate the flex -tooth crusher, one intermediate conveyor, and the two associated transfer points • The tailpiece for the existing Overland Conveyor was moved to the west and the belt shortened by approximately 700 feet to accommodate the elevated belt from the ROM Stockpile reclaim system to the top of the new Screening/Crushing Building. Belt speed was increased to accommodate a feed rate of 2,200 tph (12.OMM tpy) • The thickener overflow sump for Washplant I was eliminated and replaced with piping to carry thickener overflow to the larger overflow sump constructed for Washplant II • The primary and secondary crushers, and stoker coal and coal sampling systems in the BOB area were removed and the associated chute -work modified to allow direct pass - through of the product coal stream, since screening, crushing, and sampling will now occur in the Washplant II area. The associated Primary Crusher, Secondary Crusher, and Sampling buildings were retained, along with utilities and dust - control equipment to address potential air emissions from coal - handling and transfer points. The following sections describe the construction and operation of the various components of the new Washplant II complex. Facility locations, configuration, and operating relationships are shown by the Freshwater Systems and Surface facilities Map, Map 24 (Sheet 1/3), and the design drawings and process flow diagrams included in Exhibit 49K, Washplant II Design Drawings. The entire Washplant II area was disturbed by soil pre -strip activities associated with the previous surface mining activities, therefore, no soil material remained in this area. Drainage from and through this area is controlled by the existing Sedimentation Ponds D and E. Due to changes in site topography resulting from construction grading activities, the following drainage modifications were necessary: • Ditch D -2 was relocated to the south, paralleling the Refuse Haulroad, two culverts were added under the Washplant H yard -area access, and the eastern inlet to Sedimentation Pond D was shifted to the south and west. Contributing watershed areas and conditions did not change significantly, ditch and culverts sizes were maintained, and ditch condition and configuration were improved, therefore, revised drainage calculations were not necessary. • Washplant construction would encroach on the existing Pond D emergency spillway, so the spillway was relocated to the center of the Pond D embankment, near the principal spillway. This location also improves pond function by increasing the distance between the pond inlets and emergency spillway and improving routing. As part of the design process, four soil borings were completed for design of the foundation structures for the major Washplant facilities (refer to Washplant H Foundation Design Report in Exhibit 25). Site backfill and grading work for Washplant II involved removal of potentially unsuitable soil materials, ripping and scarification of the entire washplant pad area, cut and fill grading, and controlled placement and compaction. Cut volumes were approximately 24,000 cy, and approximately 12,000 cy of suitable fill and 10,000 cy of graded rock material were placed and compacted, consistent with the foundation design recommendations. Backfilled and compacted pad areas were then graded to direct surface runoff flows to the designed drainage and sediment control structures, and (except for building foundation areas) graveled to control erosion, dust, and surface drainage. Graveled areas will be utilized as yard -area driveways for equipment and operations /maintenance access to the Crushing/Sceening • Building, Washplant, thickener, and Refuse Bin. Based on the foundation design recommendations, reinforced concrete caissons were poured to support building foundations and conveyor supports. Reinforced concrete floor slabs and grade walls were then formed and poured to connect to the concrete caisson support system. TR08 -65 2.05 -32.2 07/08/08