2010-12-17_REVISION - C1981019 (108)

Home Browse Search

RULE 2 PE RMITS Probable Hydrologic Consequences section. There are no registered beneficial -use wells other than monitoring wells in the Colorado Division of Water Resources well database within at least one mile downgradient of the mining area (Map 11B). 2.05.6 (3)(b)(i & ii) Hydrologic Controls Surface water and groundwater drainage from the mining area will be controlled as described in Section 2.05.3(4) and Section 4.05 of this application and in the Stormwater Management Plan and stormwater discharge permit. Surface water flow will be diverted around the mining operations. Stormwater that enters the mining operations and water that occurs on the mining operations will be allowed to evaporate or infiltrate. 2.05.6 (3)(b)(iii) Probable Hydrologic Consequences Rule 2.05.6(3)(b)(iii) requires determination of probable hydrologic consequences for the proposed mining operations. This rule indicates that these consequences must be defined for both the permit area and adjacent areas, for quantity and quality of surface and ground waters. Baseline conditions must be established, and possible impacts from the proposed activities must be anticipated. Summary of the Probable Hydrologic Consequences The anticipated probable hydrologic consequences of mining coal as proposed in this application are: • Springs near the Little Collom X and Collom Lite pits might experience increased and/or decreased flow. • The Little Collom X and Collom Lite pits, facilities pad, and spoil pile will eliminate several seeps and springs. • Dewatering of the Little Collom X pit is not anticipated, but dewatering of the Collom Lite pit is probable. • Hydraulic conductivity within the backfilled pit will be higher than in the adjacent unmined areas. • Springtime peak flow in the West Fork of Jubb Creek may be reduced by up to 42 percent during and after mining. This estimate is highly uncertain and likely very conservative due to limited monitoring data, low flow rates, uncertain recharge basin boundaries for the affected springs causing the decrease, and tendency of spring/seep flows from the upper watershed to reinfiltrate into the valley fill. The West Fork of Jubb Creek does not produce baseflow. Actual effects are likely to be less significant than the percentage change reported here. • No other statistically significant changes to surface water quality or quantity are anticipated. These consequences are discussed in the following subsections. Potential Impacts to Springs and Seeps Springs in the Colowyo Mine area result from three general sources: 1) typified by a relatively deep soil accumulation immediately upslope and shallow bedrock downslope of the point of discharge, 2) discharge within valley bottom deposits, and 3) from sheer bedrock faces on hillsides (CDM 1985b). The first two of these sources may mask or contribute to bedrock sources of the springs. The seeps and low volume springs flow generally in response to snowpack accumulation and subsequent melting resulting in seasonal flows. • Collom — Rule 2, Page 126 Revision Date: 1/23/09 Revision No.: PR -03