2009-02-10_PERMIT FILE - C1981022 (5)

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Salim - 2.04.5 varying due to upstream control of discharge from Paonia Reservoir, seasonal climatic factors, and • extensive downstream agricultural withdrawals of water for irrigation. The watershed of the North Fork is generally characterized by relatively steep mountainslopes and high mountain parks that are intersected by numerous steep, narrow, drainage valleys, as shown by the Regional Geology/Hydrology Map, (Map 2.04-M2). Smaller area drainages typically demonstrate an ephemeral flow pattern, flowing only in response to spring snowmelt or major thunderstorms. Larger drainages may drain significant sub-watershed areas and carry intermittent or perennial flows. The valley associated with the North Fork is generally narrow and v-shaped with a broad, deeply incised flow channel and limited floodplain. Relatively thick deposits of coarse alluvial/colluvial material occur along the margins of the narrow floodplain, as remnant terraces or pediments associated with previous river levels as the river cut its way downward. Surface water quality is generally fair to good with a calcium-carbonate chemistry and relatively low dissolved solids. Natural suspended solids levels can be high, particularly during snowmelt runoff and major thunderstorm events, due to the steep terrain and relatively high runoff and flow velocities. Dissolved metals concentrations are characteristically low, but total metals concentrations can be significantly higher and are generally associated with the elevated suspended solids. Regional Ground Water Hydrology The regional ground water basin, which includes the mine permit and adjacent areas, generally corresponds to surface watershed area for the North Fork of the Gunnison River. Due primarily to the rugged terrain, with deeply incised drainages and some faulting, ground water is generally not available near the ground surface except as isolated occurrences of perched ground water and in the alluvium associated with the North Fork The North Fork alluvium is considered an important aquifer in the area with direct recharge from and discharge to the river depending on river levels. • Downstream alluvial wells have reported yields of several hundred gallons per minute (gpo. Perched ground water occurrences are limited in both volume and flow and, since they are dependent on surface recharge and direct infiltration, may dry?up during any prolonged periods of drought. Ground water flows are commonly associated with some of the coal seams and associated clastic interburden sequences due to the increased secondary permeability of these units resulting from natural fracture and cleat patterns. The Rollins Sandstone, which is the lowermost unit of the Mesa Verde Formation, is also know to contain some water in fractured zones, but is not considered an aquifer and is not utilized as a ground water source due to its depth, low permeability, low porosity, and high TDS values. Ground water quality can be highly variable dependent on its source. Generally, perched ground water discharges and alluvial waters associated with the North Fork drainage have similar chemistry and quality to surface waters. Ground waters associated with both the coal seams and Rollins Sandstone are commonly of poorer quality with increased levels of dissolved solids and slightly higher PH 2.04.6 - Geology Description This section of the permit application describes site-specific geologic conditions in the mine permit and adjacent areas as a basis for characterization of mining conditions, evaluation of potential mining- related impacts, and development of any appropriate plans for conservation of resources and control or mitigation of impacts related to site geology. The information presented in this section is based on research of available published reports and documents; contacts with Federal, State, and local agencies; and the results of several exploration programs over the period from 1954 through 1998. • The various exploration drilling programs involved drilling and logging of a total of over 90 exploration drillholes and sampling and analysis of selected core samples from these drillholes. PR04 2.04-8 Revised August 2000