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

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2016 Recommended Modifications to the West Elk Mine Hydrologic Monitoring Network 47 4.1 Collapsed and Obstructed Wells The casings in numerous monitoring wells have collapsed in the past several years, as a result of mining -induced subsidence or they have been blocked or damaged from other causes. As a result, hydrologic data from these damaged wells are not available for the water years subsequent to the date noted in parenthesis in the following list, and future sampling is not possible. The damaged wells include: • SOM-2-H (July 1999; mine -induced collapsed casing) • SOM- 16-H (September 2000; mine -induced collapsed casing) • 96-27-1 (April 2002, mine -induced collapsed casing) • SO.W-I (June 2002, mine -induced collapsed casing) • SOM-45-H-2 (September 2002; mine -induced, collapsed casing) • SOM-23-H-1 (August 2006, faulty construction, broken and collapsed casing) • SOM 13 (April 2007, poor construction, obstructed casing), • SOM 129-H (May 2008, casing damaged at surface; unreliable water quality and water level due to frequent dirt and runoff water infiltration) • SOM-23-H-2 (June 2008, poor construction, obstructed casing) • SOM-313 (August 2008, obstructed casing from grease and mud buildup) • SOM-3E (May 2011, obstructed casing, bailer stuck at about 302 ft) • 96-2-2 (April 2007 and August 2011, well casing collapsed at 720 ft in WY 2007, additional collapse at 433 ft in April 2012) • SOM-23-H-3 (August 2011, lined with grease) • SOM-23-H-4 (May 2013, poor construction, obstructed casing) It should be noted that the aforementioned damaged wells are generally completed up -gradient of existing mine workings (Map 1), and had very low groundwater yields when they were functional. The 14 compromised and/or damaged wells listed above are no longer functional and it is recommended that they be eliminated from the current monitoring network. August 2016 HydroGeo, Inc.