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graded, and the pad surface was graveled to control erosion and sediment and provide an all- weather operating <br />surface. The completed thickener underflow borehole installations include the light -use road (6RT only), a soil <br />material stockpile (pad and road); the drill -pad (lMN — 25 x 180 feet, 6RT- 70 x 70 feet); the 6 -inch cased <br />boreholes, 14 -inch cemented surface casings, and covered 8 -foot diameter CMP culvert manholes with lightening <br />protection. <br />Pipeline installation involved removal and windrowing of soil materials from the pipeline construction corridor <br />(maximum - 40 -foot wide); trenching in most areas; placement of suitable bedding materials; placement, <br />connection, and pressure testing of the pipelines; backfilling and compaction of suitable fill materials around and <br />over the pipelines; backfilling and compaction of the trench; regrading; replacement of soil materials; and <br />revegetation of all disturbed areas. Where the pipelines pass under RCR27, the Twentymile Mine railroad spur, <br />and Foidel Creek, the pipeline trench was expanded to provide room for horizontal boring equipment, and the <br />pipelines were trenched or bored under these features. Because pipeline placement necessarily'involved activities <br />within the Foidel Creek buffer zone, TCC requested and received a temporary variance from the regulatory <br />requirements for operations within a buffer zone. The pipelines are a double HDPE pipe system in critical areas, <br />with a 6 to 8 -inch carrier pipe inside a larger (maximum size - 10 -inch diameter) containment pipe, buried <br />approximately 5 -feet deep. The 1MN pipeline extends approximately 1,800 feet, with the 6RT pipeline extending <br />approximately 8,000 feet. Electronic moisture sensors, along with pump controls, and shut -off valves provide for <br />timely detection, shut -off, and isolation of the pipeline in the event of pipeline leakage. Access /inspection manholes <br />and pipe -tees for the moisture detection system are located at key points along the pipeline routes. <br />When the new Washplant and Thickener were installed, a new Thickener Overflow Sump was constructed to <br />contain minor amounts of washdown water and to serve as a temporary catch basin for the contents of the <br />Thickener, if required for maintenance or under upset conditions. The Thickener Overflow Sump is located <br />between the Refuse Conveyor and Sedimentation Pond D. The Thickener Sump is partially incised, incorporates a . <br />compacted clay liner to minimize seepage, and is sized to fully contain the contents of the Washplant II Thickener <br />(150,000 gallons) plus minor amounts of washdown water and incident precipitation for the design event. <br />•Impoundment design, operation, and maintenance information for the Thickener is provided in Exhibit 8X. Given <br />that the potential for both the Washplant I and Washplant II Thickeners to experience an upset or require <br />maintenance at the same time is negligible, with completion of the Washplant H Thickener Overflow Sump, the <br />Washplant I Thickener Overflow Sump was decommissioned, filled -in and replaced by a discharge pipe from the <br />Washplant I Thickener to the new Washplant II Thickener Overflow Sump. As an incised and closed basin (ie: no <br />outlet) the only potential inputs to the Sump are thickener overflow, washdown water, or minor incident <br />precipitation, which are subsequently pumped back into the system by a portable floating pump installation. The 4- <br />inch thickener overflow line has been extended to the new Thickener Overflow Sump (4,800 feet), allowing <br />overflow from either thickener to be controlled by valves and routed to the Sump. Water level in the Sump is <br />monitored and managed as part of the ongoing Washplant operations. <br />Given the power and system control requirements for the Washplant, an associated Motor Control Center <br />(MCC) /Office Building was constructed immediately adjacent to the Washplant. The MCC /Office Building houses <br />electrical, control, and monitoring equipment for the Washplant and includes office space. The building consists of <br />three connected modular steel containers (2 - 8 x 40 x 10 feet high, and 1 -8 x 20 x 10 feet high), located on the <br />north side of the Overland Conveyor and Washplant II. The building sets on a reinforced concrete slab floor (20 x <br />60 x 0.75 feet thick). <br />A new Coal Sampling Station, located on the Overland Conveyor, to the west of Washplant II and Sedimentation <br />Pond D, was installed to provide sampling capabilities prior to discharge to the BOB stockpile. The coal sampling <br />system consists of an automated sweep sampler, which cuts samples from the coal stream on the Overland <br />Conveyor at regular intervals, a small sample crusher, a sample splitter to reduce sample volume, and associated <br />chute -work and control and dust collection systems. The coal sampling system is housed in a steel frame building <br />with steel siding and roof (20 x 20 x 25 feet high), located on the south side of the Overland Conveyor. The <br />isbuilding sets on a reinforced concrete slab floor (22 x 22 x 0.75 feet thick). <br />A new 69 KV distribution line was extended approximately 300 feet from the existing 69KV line to a new <br />substation location adjacent to the Overland Conveyer. Powerline construction involved the limited disturbance <br />required to place 4 powerpoles, with pole placement avoiding the Foidel Creek buffer zone. Installation of the new <br />TR 11 -77 2.05-32.4 07/20/11 <br />