2014-06-06_REPORT - C1981044 (7)

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Williams Fork River flow data (former site 09249750). The Williams Fork River gaging station (WF -2) is near the confluence with the Yampa River, downstream of the Eagle No. 5 Mine discharge. The staff gage (WF -1) is located upstream of the mine discharge points. WF -2 is also monitored concurrent with WF -1. The flow data for WF -2 was historically provided by the USGS, however, their monitoring of the Williams Fork stations was discontinued in 2001. Historically, comparisons between up gradient site WF -1, and down gradient site WF -2, have not show any stream depletion impacts from mine dewatering. In 2010 the State Division of Water Resources (Office of State Engineer) reactivated the site. Data for the former USGS site can be found on their website under station No. WMFKMHCO. A preliminary copy of their data is provided at the back of this AHR under Support Data. Summaries of WF -1 and WF -2 water quality data are presented in Tables 27 through 30. A plot of upstream and downstream dissolved solids measurements for the river is presented in Figure 22. Water quality data does not show any significant variation from expected values. The comparisons of data from the upstream and downstream station on the Williams Fork River indicate that there is no detectable effect of mining on river water quality. As expected, dissolved solids decrease with increasing flow rate in the rivers, due to dilution from runoff. 3.2.2 Springs There is one active spring on the mine site area, known as the No. 1 Strip Pit Discharge, or 1 SP. There are a few other springs and local permanent "damp spots" in the area; however, their combined flow is normally less than 10 gpm and is therefore not significant. 1 SP Discharge is a CDPS monitoring point ( Outfall 022). There is no sediment pond associated with this spring. Spring water runs down a narrow path through a vegetative filter and discharges directly to the Williams Fork River. The POR discharges for the 1 SP are presented in Figure 23 and the 2013 discharge measurements are presented on Figure 24, respectively. The discharge from 1 SP increased significantly back in 1989. This may have been due to seepage from the ditch that conveys the 7 North Angle discharge (measured at site 9P3, a.k.a. CDPS Outfall 024)). Site 9133 discharge began in January of 1989, and has been sporadic. Site 9P3 Discharge rates from 1990 through 2003 are lower. 9P3 has not discharge since 2003. Nevertheless, snowmelt and ditch seepage both appear to have some influence on 1 SP discharge, as the discharge typically drops to just a few gpm from January through March with a small peak typically in April/May coinciding with spring runoff. 1 SP is typically dry from July through November, and freezes over from December into March. DMRs of the water quality data for this spring are presented as an attachment to this report. A plot of POR total dissolved solids for 1 SP is presented in Figure 25 and POR iron concentrations are presented on Figure Page 7 l: \Env \Empire\AH R\2013 \Test \Empire2013 AHR.doc