2016-12-01_PERMIT FILE - C1980007 (6)

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2016 Recommended Modifications to the West Elk Mine Hydrologic Monitoring Network EXECUTIVE SUMMARY HydroGeo, Inc. (HydroGeo) has conducted the hydrology monitoring program for Mountain Coal Company, LLC (MCC) since November 2001. MCC recently retained HydroGeo to review the data collected from the existing hydrologic monitoring network and make recommendations to update and streamline the monitoring system. This includes potentially reducing the number of monitoring sites in areas that have not been actively mined for more than ten years and where no future mining is planned. This Technical Memo contains recommendations for reducing the number of spring/seep/ surface water hydrologic monitoring sites at the West Elk Mine (WEM); specifically, the Gribble Gulch, Box Canyon, and Raven Gulch areas. Hydrologic monitoring in Gribble Gulch began in 1977 and continues to the present. Hydrologic monitoring in Raven Gulch began in 2002 and continues to the present. Box Canyon monitoring began in 1998 and continues to the present. The spring/seep and/or surface water hydrologic monitoring sites selected as candidates for proposed elimination from the WEM hydrologic monitoring network have shown no adverse trends in water quantity (flow) and/or water quality since active mining operations in the area stopped. HydroGeo recommends that all 13 of the currently monitored Gribble Gulch and Raven Gulch springs: G-25, G -26a, G -28a, G-30, G-31, G-35, G-49, CR -12, 24-3, E-13-1, E-13-2, E-13-3, E- 13-4, and the Lower Gribble Gulch, Lower Raven Gulch, and Upper Raven Gulch surface water monitoring stations be removed from the WEM's hydrologic monitoring network. The WEM operations in the Gribble Gulch area were completed over 15 years ago, no mining operations are planned in the West Flatiron area under Raven Gulch (MCC, 2016), and spring and surface flows and water quality data do not show any adverse historical trends. HydroGeo also recommends that Seep E-14-1, located in Upper Box Canyon, be removed from the monitoring network, because this seep had no flow throughout the period of record, and the site was covered by a mine ventilation borehole (MVB) pad in August 2006. The site was reclaimed in 2012 and the seep (a muddy area) again developed (MCC, 2016). As noted in multiple Annual Hydrology Reports (HydroGeo, 2002 through 2015) submitted annually to the Colorado Division of Reclamation, Mining and Safety (CDRMS), numerous groundwater monitoring wells have been damaged and/or compromised over the years.. As a result, HydroGeo also recommends that 14 compromised and/or damaged dysfunctional wells be eliminated from the current monitoring network. The compromised and/or damaged wells recommended for removal from the hydrologic monitoring network include the following: SOM-21-1, SOM-16-H, 96-27-1, SO.W-1, SOM-45- H2, SOM-3E, SOM 13, SOM 129-H, SOM-23-H-1, SOM-23-H-2, SOM-23-H-3, SOM-313, 96- 2-2, and SOM-23-H-4. These revisions are recommended because the wells are irreparable and water level and water quality data can no longer be collected. August 2016 HydroGeo, Inc.