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margins, grading to establish level drill -pads and construct or improve roads, placement of gravel as surfacing for the
<br />tight -use road, excavation of temporary cuttings pits on the drill -pads, drilling and casing of the boreholes, and
<br />installation of protective access manholes. On completion of drilling and casing operations, the cuttings pits are
<br />allowed to dry -out, material excavated from the pits is replaced and graded, and the pad surface is graveled to control
<br />erosion and sediment and provide an all-weather operating surface. The completed thickener underflow borehole
<br />installations include light -use road access, one or more soil material stockpiles (pad and road); the drill -pad (1MN —
<br />25 x 180 feet, 6RT- 70 x 70 feet, 7RT — 100 x 75 feet, 2MN — 75 x 75 feet, 1 SWMD — 250 x 170 feet max.); the 6- to
<br />12 -inch cased boreholes, 16 to 18 -inch cemented surface casings, and covered 8 -foot diameter CMP culvert manholes
<br />with lightning protection. The Sandstone Sub Test Borehole, because it will be completed on the existing substation
<br />pad, will not require soil handling, an access road, pad construction, or surface casing or a manhole, and drainage will
<br />be contained on the pad by a constructed berm.
<br />With timing and weather constraints, portions of the pipeline may be temporarily installed on the surface, to be
<br />buried when ground conditions are more favorable. Pipeline installation will involve removal and windrowing of
<br />soil materials from the pipeline construction corridor (maximum - 40 -foot wide); trenching in most areas;
<br />placement of suitable bedding materials; placement, connection, and pressure testing of the pipelines; backfilling
<br />and compaction of suitable fill materials around and over the pipelines; backfilling and compaction of the trench;
<br />regrading; replacement of soil materials; and revegetation of all disturbed areas. Where the pipelines pass under
<br />RCR27, the Twentyin le Mine railroad spur, and Foidel Creek, the pipeline trench was expanded to provide room
<br />for horizontal boring equipment, and the pipelines were trenched or bored under these features. Because pipeline
<br />placement and/or construction of portions of the 6RT, 7RT, iMN, 2MN, and SWMD pads necessarily involved
<br />activities within the Foidel Creek buffer zone, TC is requesting a temporary variance for pipeline construction and a
<br />longer-term variance for the limited pad areas from the regulatory requirements for operations within a buffer zone.
<br />The pipelines are a double HDPE pipe system in critical areas, with a 6 to 8 -inch carrier pipe inside a larger
<br />(maximum size - 12 -inch diameter) containment pipe, buried approximately 5 -feet deep. The IMN pipeline
<br />extends approximately 1,800 feet, with the 6RT pipeline extending approximately 8,000 feet and continuing
<br />another 1,600 feet to 7RT. The 6RT/7RT pipeline is immediately adjacent to the 2MN Borehole, so only a short
<br />connecting pipe was necessary. The SWMD pipeline will extend approximately 7,700 feet from the SWMD
<br />Borehole, connecting into the 1 MN TUF pipeline. Electronic moisture sensors, along with pump controls, and shut-
<br />off valves provide for timely detection, shut-off, and isolation of the pipelines in the event of pipeline leakage.
<br />Access/inspection manholes and pipe -tees for the moisture detection system are located at key points along the
<br />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 Il 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 1I 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 11 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 Wasliplant. 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 1I. The building sets on a reinforced concrete slab floor (20 x
<br />60 x 0.75 feet thick).
<br />MR] 7-3 03 2.05-32.5 01/27/17
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