2010-06-30_REPORT - C1980007 (5)

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• West Elk Mine 2009 Annual Hydrology Report 12 3.1.1 Upper North Fork Drainage Basin Surface Water Monitoring Stations 3.1.1.1 Deep Creek (Upper, Lower) Deep Creek is a perennial stream drainage that drains the Box Canyon B-seam mine panel area, and the east side of the South of Divide (SOD) and West Flatiron mine plan areas. The Upper Deep Creek monitoring station does not have a flume or data logger and is located up-gradient of the Box Canyon mine panel area (B-seam panels 14 -1 7 and 22 - 24) and the West Flatiron area. The Lower Deep Creek monitoring station does not have a flume or data logger and is located down-gradient of the SOD area and is directly east of the Box Canyon panels (Map 2). In 2006, the flow monitoring at the Deep Creek monitoring sites was changed from continuous flow recording to instantaneous recording three times a year. This change was made for two reasons: mining in this area was nearly complete and the Deep Creek stream channel is highly variable, resulting in continuous flow data that were unreliable and that did not represent actual conditions. 3.1.1.2 Raven Gulch [Upper, Lower) Raven Gulch is a perennial stream that drains the east side of the West Flatiron mine plan area. The Upper Raven Gulch monitoring station was established in 2005 and is located upstream from the confluence with the West Flatiron drainage. The Lower Raven Gulch monitoring station was established as a new site in 2005 and is located at the mouth of Raven Gulch, near its • confluence with the North Fork of the Gunnison River. Neither of the Raven Gulch monitoring stations have a flume or data logger. The locations of these monitoring sites are depicted on Map 2. Monitoring of the Upper and Lower Raven Gulch monitoring stations began in May 2005. 3.1.1.3 Box Canyon Box Canyon is an ephemeral (intermittent) stream drainage. The upper reach of the drainage is typically dry and the lower reach of the drainage only flows during storm events and during the spring months in above average precipitation years. The Box Canyon monitoring station is located at the mouth of the drainage and was established to monitor the area down-gradient of the Box Canyon B-seam panel area (Map 2). There is no flume or data logger in Box Canyon and data have been collected at this site since 1999. 3.1.1.4 North Fork Upper The North Fork of the Gunnison River is a major perennial stream that drains the northern mine area. The North Fork Upper monitoring station is at the site of the USGS gaging station (North Fork Gunnison River near Somerset, CO, USGS 09132500) located up-gradient of the mine facilities area and up-gradient of the mine discharge points. The underground mine water discharge flows into Sylvester Gulch then into the North Fork of the Gunnison River. The mine . surface water runoff is treated and routed to holding ponds and is then discharged to the North Fork, if necessary. All of the mine water discharge occurs between the North Fork Upper and June 2010 HydroGeo, Inc.