2013-04-05_REVISION - C1981019 (2)

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4.9 Surface Water Hydrology Surface water information is found in Sections 2.04.7 and 4.05 (Volume 1 for the East Pit, West Pit, Section 16 Pit, Facilities Area and Gossard Loadout and Volume 12 for South Taylor); Maps 11, 11A, 12, 12A, 32 and 37; and Exhibit 7 of the PAP. Surface water information for the South Taylor and Lower Wilson areas can be found in Section 2.04.7(2) Surface Water Resource Information and Section 4.05 Hydrologic Balance in Volume 12. Tables 2.04.7 -30 to 36, Volume 12, also present surface water information for the South Taylor and Lower Wilson areas as do Figures 2.04.7 -22 to 32, again found in Volume 12. Map l0A and Map 11A in Volume 14 provide monitoring and other hydrologic feature locations for the South Taylor and Lower Wilson areas. The permit area is drained by two perennial streams: Good Spring Creek on the east and Wilson Creek on the west. Taylor Creek, an intermittent stream located just inside and generally parallel to the west boundary of the permit area, and generally parallel to Wilson Creek, flows into Wilson Creek north of the rail loadout. Several ephemeral drainages occur on the permit area, including the Streeter Drainage. This drainage profile was raised as a result of excess spoil fill in the Streeter Canyon, the deepest fill (the Streeter Fill) near the confluence of Streeter Drainage and Good Spring Creek. These drainages are tributaries to Milk Creek, which flows into the Yampa River about seven miles north of the permit area. Precipitation averages 18 inches annually on the property and runoff is limited. Flows in the drainages are mainly in response to snow melt or intense thunderstorm events. Water sampled from the drainages is quite hard, dominated by calcium and magnesium cations and bicarbonate and sulfate anions. The relatively high alkalinity and pH of the system impedes the solubility and transport of heavy cations, thus minimizing potential toxicity problems associated with heavy metals or acid drainage. Springs and seeps are abundant in the area, with 59 originally identified during an inventory completed in 1985. A more recent inventory and study resulted in additional springs and seeps in the South Taylor and Lower Wilson areas. Four springs were found to be perennial, two tributary to Wilson Creek and two tributary to Good Spring Creek. The locations of all monitored springs and seeps are shown on Map 10A, Volume 14. Spring and seep information is included in Tables 2.05.6 -1 and 2 in Volume 12 for the South Taylor and Lower Wilson areas. No AVFs exist within the area to be mined. However, the alluvial deposits of Good Spring Creek, Wilson Creek, and lower Elkhorn Creek meet the geomorphic and irrigation criteria of an AVF and are discussed in the Findings portion of this document (Section B, Item XXII). The Wilson Reservoir, from which water is drawn for mining activities, is an important fishery of the area. The Wilson Reservoir was built in 1941, and is under the regulatory jurisdiction of the Colorado Division of Water Resources. Except for a pumping station, the Wilson Reservoir is not within the permit area, and is not a part of the Permit. The pumping station at the reservoir, and the pipeline from the pumping station to the main areas of the Mine, are included in the Permit. Proposed Decision and Findings of Compliance January 2012 Permit Renewal 06 Page 116