2008-03-21_PERMIT FILE - C1980007 (5)

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Affected Environment and Environmental Consequences Chapter 3 indicate corresponding low averages over the per.iod of record for annual precipitation and annual snow water equivalent for the North Fork watershed. Chemical analyses from the West Elk monitoring program have shown that deep groundwater resources in the vicinity of the mine are part of a deep inactive system that is not in direct contact with near-surface water, thereby limiting any potential effects to surface water flow. 3.3.4 Environmental Consequences changes in the gradient of the channel. The overall gradient of the creek would remain similar to pre- mining; however pooling may occur in the areas of differential subsidence and would be more pronounced if the B Seam was also mined. Minor channel adjustments may also occur as the land surface moves. It is believed that because Deep Creek is a high-energy and dynamic stream system, that potential gradient changes, pooling, and channel adjustments due to subsidence would not be readily discernible from the natural conditions of the drainage. CJ 3.3.4.1 Direct and Indirect Effects Alternative A Under the No Action alternative, there would be no mining-induced effects on water resources in the Dry Fork LBA area. Natural variation in spring and stream flow would occur based on climatic variations. Alternative B Subsidence may alter surface water and groundwater hydrology by altering groundwater flow regimes, surface water drainages, seeps, and ponds. Subsidence under surface water drainages could result in changes in channel morphology and gradient, thereby affecting water quality by inducing minor cutting, pooling, soil erosion, and sedimentation. Surface-tension cracks have the potential to develop within the surrounding surface drainages, resulting in an initial period of erosion and sedimentation after initial periods of runoff after subsidence occurs. However, the potential fir surface fractures to develop in drainages where unconsolidated materials occur will be partially mitigated by the ductile nature of the unconsolidated alluvium/colluvium (Agapito 2005, see Appendix B). Under the RFMP, Deep Creek would be undermined by four E Seam longwall panels. Portions of Deep Creek may also be undermined by two additional B Seam panels. The creek would pass over four areas where the land surface would be in a tensional state after mining is complete (i.e., over gateroads). Differential subsidence amounts between the gateroads and longwall panel centers (up to four feet vs. up to seven feet) as it relates to the configuration of the creek may cause local Surface cracking could occur in the Deep Creek channel, especially over the gateroads. It is believed that cracks, should they form, would not persist in the alluvial materials in the stream bottom. Cracking could also occur in the bedrock strata under the drainage. The cracking could cause some interception of flow in the creek. Flow could change along small segments of the creek, although it is not anticipated that flows would be permanently diverted from the drainage. Cracks that may form are expected to attenuate in a few days to weeks depending on flow conditions and availability of sediment. The two inferred faults in the tract cross Deep Creek almost at right angles. If these faults exist, and if they affect the normal subsidence process, there could be translated affects to the drainage causing water loss, however these cannot be quantified or verified with the available data. Additional monitoring on Deep Creek over these zones would assist in identifying if impacts occur. • As discussed in the RFMP, the longwall panels would be oriented roughly perpendicular to Deep Creek drainage and parallel with Dry Fork drainage. This orientation will likely induce gradient changes within the Deep Creep channel as subsidence develops into regular-repeatable troughs perpendicular to the orientation of Deep Creek. Gradient changes can also be expected in the Dry Fork of Minnesota Creek channel as the intermittent stream meaders back and forth across long wall panel subsidence troughs. Wright Water Engineers (WWE) performed a stream channel survey on Deep Creek in which they estimated that subsidence may alter the slope of Deep Creek by 1.5 percent in areas of preferential subsidence over the proposed 3-20 Dry Fork Lease-By-Application FEIS