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West Elk Mine 2008 Annual Hydrology Report 19 <br />3.1.5.1 North Fork of the Gunnison Temperature Data Loggers <br />3.1.5.1.1 NFG-1 Temperature Data Logger <br />The NFG-1 temperature data logger monitoring site is located in the North Fork of the Gunnison <br />River, upstream of the confluence with Sylvester Gulch, near the USGS stream gage (#09132500) <br />(Figure 8 and Photo 1). The rebar supporting the logger was driven in the thalwag, eight feet from <br />the south stream bank and about 40 feet upstream of the control dam used by the USGS. The <br />thalwag is the deepest continuous line along a watercourse. On the July 18, 2008 site visit, <br />HydroGeo's technicians observed the logger was broken off at the spot where the plastic logger <br />housing connects to the rebar. A replacement logger was deployed on July 18, 2008 and affixed to <br />a permanent four-inch diameter steel cable in the streambed. <br />3.1.5.1.2 NFG-2 Temperature Data Logger <br />The NFG-2 temperature data logger monitoring site is located in the North Fork of the Gunnison <br />River, approximately 750 feet downstream of its confluence with Sylvester Gulch (Figure 8 and <br />Photo 2). The rebar supporting the temperature logger was placed approximately 25 feet from the <br />south stream bank near a large triangular shaped boulder (3'x3'x3') that is visible above the water <br />level. On the July 18, 2008 site visit, HydroGeo's technicians observed the temperature logger and <br />the rebar had washed away as a result of flood level flows, breaking the cable that was attached to <br />the shore. A replacement temperature data logger was deployed on July 18, 2008 in the eddy <br />immediately downstream of the large boulder, and attached to the boulder itself using 1/16 inch <br />aircraft grade galvanized steel cable. <br />3.1.5.1.3 NFG-3 Temperature Data Logger <br />The NFG-3 temperature data logger monitoring site is located in the North Fork of the Gunnison <br />River downstream of all West Elk Mine activities, approximately 0.9 miles west of the West Elk <br />Mine main entrance (Figure 8 and Photo 3). The logger was placed 25 feet from the north stream <br />bank. On the August 23, 2008 site visit HydroGeo's technicians noted that the rebar stake had <br />uprooted and the logger was found on the stream bank, attached to the shore cable. The data logger <br />was securely reaffixed to a buried and submerged section of railroad track near the north bank, in <br />order to prevent it from being washed away or floating to the shore in the future. <br />• <br />June 2009 HydroGeo, Inc.