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  NWO-2015-00766-MTH
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NWO-2015-00766-MTH

Posted: 12/26/2017

Expiration date: 1/23/2018


Regal Talc Mine expansion consists of modifying and or relocating approximately 1330 linear feet of Hoffman Creek impacting 0.72 acre of wetland.

The impacted Hoffman Spring Creek channel reach of approximately 730 linear feet is located on the downstream half of the drainage immediately above its confluence with Hoffman Creek. The 730 linear feet of impacted Hoffman Spring Creek channel includes about 530 linear feet that will be removed by the expanded mine pit (including adjacent safety bench, berm, and access road), and about 200 linear feet that will be affected by construction of the uppermost part of the realigned channel, including a catchment basin and cutoff wall. The engineered realigned channel will extend from the new catchment basin constructed in the existing channel, and then to Hoffman Creek through uplands, with an elevation change of approximately 47 feet. At the confluence, the realigned channel will merge with the natural Hoffman Creek channel, and will include a groundwater cutoff wall constructed beneath and perpendicular to Hoffman Creek immediately upstream of the confluence. All of these areas are characterized by intermittent stream flow.

The impacted Hoffman Creek channel of approximately 600 linear feet will be located both upstream and downstream of its confluence with Hoffman Spring Creek. The modification will consist of channel consolidation with natural sealing minerals (bentonite) mixed to a depth of approximately 6 inches, and native soft armoring utilizing existing channel debris/stone and local riparian cuttings.