2010-06-30_REPORT - C1980007 (5)

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West Elk Mine 2009 Annual Hydrology Report 19 3.1.5.1 North Fork of the Gunnison Temperature Data Log ers 3.1.5.1.1 NFG-1 Temperature Data Logger The NFG-1 temperature data logger monitoring site is located in the North Fork of the Gunnison River, upstream of the confluence with Sylvester Gulch, near the USGS stream gage (#09132500) (Figure 8 and Photo 1). The rebar supporting the logger was driven in the thalwag, eight feet from the south stream bank and about 40 feet upstream of the control dam used by the USGS. The thalwag is the deepest continuous line along a watercourse. The logger and rebar are affixed to a permanent four-inch diameter steel cable in the streambed. 3.1.5.1.2 NFG-2 Temperature Data Logger The NFG-2 temperature data logger monitoring site is located in the North Fork of the Gunnison River, approximately 750 feet downstream of its confluence with Sylvester Gulch (Figure 8). The rebar supporting the temperature logger was placed approximately 25 feet from the south stream bank near a large triangular shaped boulder (3'x3'x3') that is visible above the water level. At some point during peak flows in 2009, the data logger was washed away. On August 4, 2009 a replacement logger was deployed near the northern shore of the river in slower moving water and affixed to a boulder on the shore using 1/16 inch aircraft grade galvanized steel cable. 3.1.5.1.3 NFG-3 Temperature Data Logger The NFG-3 temperature data logger monitoring site is located in the North Fork of the Gunnison River downstream of all West Elk Mine activities, approximately 0.9 miles west of the West Elk Mine main entrance (Figure 8). The data logger is securely affixed to a buried and submerged section of railroad track near the north bank of the river. On March 20, 2009, the logger's internal memory became full and the logger stopped recording. The logger was downloaded and redeployed on July 30, 2009, and programmed to record temperature once an hour, in order to prevent the memory from filling during extended periods of inaccessibility in the winter and spring months. 3.1.5.2 Sylvester Gulch Temperature Data Loggers 3.1.5.2.1 MCSG-1 Temperature Data Logger The MCSG-1 temperature data logger monitoring site is located in the unnamed tributary to Sylvester Gulch, approximately 130 feet downstream of the MWPF mine water discharge point (Figure 8). 3.1.5.2.2 MCSG-2 Temperature Data Logger The MCSG-2 temperature data logger monitoring site is located in the same unnamed tributary as MCSG-1 and is 18 feet upstream from the confluence with the main stem of Sylvester Gulch (Figure 8). June 2010 HydroGeo, Inc.