2018-02-05_REVISION - C1992081 (29)

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The majority of the runoff from the rail loop, as well as the runoff from the three small area exemptions in the Loadout area, is not treated; however, runoff from these sources passes through a vegetative filter and does not appear to affect water quality. No adverse impacts from mining operations were projected in the HGT PAP and none have been observed to date. Runoff from the Loadout area that is not diverted around the area of disturbance is retained in sedimentation ponds for a maximum of 36 hours. Water retained in the two sedimentation ponds experiences some losses through evaporation and seepage. The Dry Creek diversion downstream could potentially be impacted by losses of water due to storage in the sediment ponds. The acreage served by the two sediment ponds accounts for less than one - thousandth of the acreage drained by Dry Creek. Since the area to be affected is a fraction of the total watershed, the watershed will not be significantly affected and runoff from the permit area will continue to reach Dry Creek. All waters utilized for dust suppression, showers, and other operations at the Loadout were piped in from a well in the Yampa River alluvium (H -G Shallow Well No. 1), located two miles north of the Loadout. H -G Shallow Well No. 1 was sealed in 2011. HGT owns an additional 90 acre-feet of water rights in the downstream Walker Ditch, which are not currently being utilized. Facilities were dismantled in 2011, and the remaining office trailers were removed from the site in 2013. Plumbing to the trailer was dismantled during the removal of the office trailers. These water rights can be utilized to compensate any downstream users for loss of water due to consumption at the Loadout. In addition, HGT has an agreement with the United States Fish and Wildlife Service (USFWS) to mitigate against losses of water to the Yampa River as a result of water consumption at the Loadout. Please refer to Volume 3, Tab 21 of the permit application and Item XII of this document. 2. Ground Water Impacts The Lewis shale has low conductivity values and is generally considered to be an aquitard that retards transmission of surface water to the Twentymile Sandstone, the underlying regional aquifer. This low conductivity unit results in low well yields that preclude the use of waters from the Lewis shale for other than stock watering (See Seneca II -W Permit, C-1982-057, Tab 7). Water samples from the two existing alluvial wells at the Loadout, which are completed in part in the underlying Lewis shale, often exceed water quality standards for stock watering. Operations at the Loadout should not impact this ground water. 23