2010-02-03_REVISION - C1982056 - Laserfiche WebLink

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cloth) at the pump inlet location to create a pump suction pool, and limit flows to the construction disturbance area ¦ Initiate pumping to temporarily route any stream flows around the construction disturbance area ¦ After a brief interval to allow the area to dry out or freeze, utilize a track-hoe setting on the bank to strip soil material from the construction disturbance area and temporarily place it on the bank ¦ Similarly, use a track-hoe to excavate a trench for pipe placement across the stream channel, placing the excavated material on the stream-bank. If stream underflow results in any significant amount of water inflow to the trench excavation, a second portable pump will be used to transfer this water to the suction pool upstream from the crossing disturbance area ¦ Place and properly bed the pipe in the trench (note that pipe will be pre-welded in a section long enough to completely span the channel crossing, and drug into place) ¦ Backfill and compact the previously excavated material over the pipeline ¦ Grade bank areas at the pipeline crossing to blend with the upstream and downstream channel banks ¦ Replace the previously excavated soil material ¦ Place rock armoring material over the backfilled excavation, to minimize the potential for down-cutting ¦ Remove the upstream straw bale flow barrier and discontinue pumping (the downstream straw bales and silt fence will be left in place for approximately two weeks to catch residual sediment) ¦ Check for and clean-out any significant sediment accumulations above the downstream straw bales ¦ Remove the downstream straw bales and silt fence • Reseed bank disturbance areas in the Spring It is anticipated that the actual pipeline excavation, pipe placement, and backfilling in the crossing area will take 3-4 days, and in no event longer than a week. With the float-operated diversion pump, the suction pool behind the temporary flow barrier is not expected to exceed 180 cubic feet of water (6' wide x 3' deep triangular channel, backed-up 20' behind temporary flow barrier). As noted in the construction summary, a secondary pump will be maintained in the crossing construction area to address any leakage through the flow barrier, underflow, and to serve as a back-up in the event the primary transfer pump were to fail. Please feel free to contact me with any questions, or to discuss the planned activities. Best regards, Twentymile Coal Jerry . N ton Environ a al Manager cc: Mike Berdine/TCC Jesse Burkett/TCC Janet Binns/CDRMS