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Surface Water Resources <br /> All aspects of the proposed operation are purposefully located away from surface water resources,and there <br /> are no streams that will receive drainage directly from operations. The proposed portal is approximately <br /> 540 feet to the west and 200 feet in elevation above CR20A and the banks of Corkscrew Gulch. <br /> Corkscrew Gulch drains a relatively small watershed comprising roughly 940 acres. It is a perennial stream <br /> that releases consistently low flows into Red Mountain Creek approximately 5,300 feet downstream from <br /> the intersection of CR20A and RMT's private road. Roughly 7.5 miles further downstream,Red Mountain <br /> Creek joins other tributaries to form the Uncompahgre River inside the town limits of Ouray. <br /> As part of broader investigations of the Red Mountain Creek watershed USGS,CDPHE,the Idarado Mining <br /> Company (IMC) and the Uncompahgre Watershed Partnership (UWP) have been gathering water quality <br /> data from Corkscrew Gulch since at least 1999. Red Mountain Creek and its tributaries have been the focus <br /> of intense study due to poor water quality caused by natural geologic conditions and impacts from historic <br /> mining. <br /> Readily available information about water quality of Corkscrew Gulch was first summarized by CDPHE <br /> Hazardous Materials and Waste Management Division in September 1999(O'Grady, 1999). Water quality <br /> and sediment samples collected in Corkscrew Gulch exhibited elevated concentrations of metals (e.g. <br /> dissolved zinc concentrations ranged from 0.253 mg/L to 15.6 mg/L) and demonstrated that the stream is <br /> acidic with pH values between 2.90 to 4.0. However, since Corkscrew Gulch has relatively low flow rates, <br /> it was measured to only contribute 2 pounds per day of zinc to Red Mountain Creek(O'Grady,2000; IMC, <br /> 2012; UWP, 2018). <br /> EPA's STORET database has published baseline water quality data gathered by CDPHE from 2004 to 2005 <br /> from three locations along Corkscrew Gulch that bracket the proposed project: 1) Corkscrew Gulch <br /> downstream of the Midnight Mine (immediately upstream of the project); 2) Corkscrew Gulch 0.6 miles <br /> downstream from the Midnight Mine(downstream of the project);and 3)at the mouth of Corkscrew Gulch <br /> before entering Red Mountain Creek. The sampling locations are depicted on Attachment Al Location <br /> Map. The list of analytes and results by location are shown in Table B-2. <br /> Bi-annual data from 2007-2012, gathered by IMC as part of its evaluation of zinc loading in Red Mountain <br /> Creek consistently shows that Corkscrew Gulch accounts for 0.95 to 2.0 pounds of zinc per day to Red <br /> Mountain Creek at baseline flows—or roughly 2% of the zinc load of Red Mountain Creek. <br /> Page 5 of 7 <br />