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<br /> <br />Requirement <br />Requirement <br />citation Require- <br />ment <br />complied <br />with ? <br />es/no <br /> <br />Comment <br /> There is no known impairment of water use caused by the mine outside the permit area. <br /> North Fork Gunnison River. The West Elk Mine discharges surface water into the North Fork at <br /> two mine water discharge points (outfalls 017A and 018A) and at five sediment control ponds <br /> MB-3, MB-1, MB-2R, RPE,and SG-1 ). The West Elk Mine appeared to not degrade water in the <br /> North Fork in 2006 based on a comparison of samples taken from the North Fork immediately <br /> upstream from the mine (page C-1 of 2006 AHR) and the North Fork immediately downstream <br /> from the mine (page C-2 of 2006 AHR). TDS in North Fork water showed a decrease where the <br /> stream passes the mine. TDS concentration immediately downstream from the mine was 110 mg/1, <br /> which is well below a 700 mg/1 threshold that may be considered a level of concern for irrigation <br /> water use. Amass-balance analysis attached to DRMS's review summary of the 2004 annual <br /> hydrology report indicated that in an extreme worst-case scenario, TDS in the North Fork would <br /> remain well below the 700 mg/1 threshold. <br /> Natural springs -Monitoring showed reduced spring flows compared to previous years. Spring <br /> hydrographs indicate seasonal precipitation fluctuations are a more likely cause of the reduced <br />U. Prevention of flows than mining. <br />material <br />damage to the CDRMS <br />regulation <br />yes <br />Bedrock ground water - Data from the down-gradient bedrock monitoring wells (03-11-1 and O1- <br />hydrologic <br />4.05.1(1) 11-1) indicate there have been no significant impacts to bedrock ground water outside the permit <br />balance outside area. High TDS in one monitoring well appears anomalous and warrants further discussion. TDS <br />the permit area in B seam monitoring well SOM-129H increased from 2970 mg/1 to 8400 mg/I in 2002, and since <br /> then has remained around 8400 mg/1. This increase appears to indicate water has flowed from the <br /> Rollins Sandstone into the well, based on the chemistry of water in the well that is similar to the <br /> Rollins (a sodium chloride/bicarbonate water type and the relatively high concentration). The <br /> Rollins likely is in hydraulic communication with the B seam where the intervening sequence is <br /> relatively thin. The change in water quality in the SOM-129H well does not threaten the water <br /> quality in bedrock units due to the low permeability of those units. (Discharge of this high TDS <br /> water to the alluvium or surface water of the North Fork through the B seam subcrop in the <br /> alluvium does not threaten alluvial water quality because such a discharge is not an increase above <br /> what would naturally discharge from the subcrop of the Rollins in the North Fork alluvium.) <br /> Alluvial ground water - Amass-balance analysis attached to DRMS's review summary of the <br /> 2004 annual hydrology report indicates that in an extreme worst-case scenario TDS in the North <br /> Fork alluvium would not increase to a level that impairs the use of the water. <br /> Page 6 <br />