REP46795 - Laserfiche WebLink

Home Browse Search

of the mine discharge points. Under TC, Williams Fork surface sampling (site WF-1) is measured for water level and field parameters on an annual basis (between July 20th and August 30th), and requires water quality analysis (See Table 3). WF-2 is also monitored concurrent with WF-1. The flow data for WF-2 was historically provided by [he USGS, however, 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. Summaries of WF-1 and WF-2 water quality data are presented in Tables 13 through 16. A plot of upstream and downstream dissolved solids measurements for the river is presented in Figure 8. The data indicates that the surface water quality 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 One spring on the mine site area is being monitored under TC, the No. 1 Strip Pi[ Dischazge. The No. 1 Strip Pit Dischazge is a CDPS monitoring point (Outfall 022, a.k.a, site 1SP}. There are a few other springs and local permanent "damp spots" in [he area; however, their combined flow is normally less than 10 gpm and is • therefore not significant. The POR discharges for [he No. 1 Strip Pit are presented in Figure 9 and the 2004 discharge measurements are presented on Figure 1Q, respectively. The discharge from the No. 1 Strip Pit increased significantly back in 1989. This may have been due to seepage from the ditch that conveys the 7 North Angle discharge. The 7 North Angle dischazge began in January of 1989. However, dischazge rates from 1990 through 2004 appear lower. Nevertheless, snowmelt and ditch seepage both appear to have some influence on [he No, 1 Strip Pit discharge, as the discharge typically drops [o just a few gpm from January through May with a small peak typically in Match coinciding with spring tunoff. The summary of the water quality data for the spring is presented in Tables 17 and 18. A plot of POR total dissolved solids for the No. 1 Strip Pit is presented in Figure 11 and POR iron concentrations are presented on Figure 12. Figure 11 indicates that the total dissolved solids (TDS) concentrations increased from an average of around 900 mg/l in the eazly 1980's, to about 1500 mg/I in 1984 through 1986, stabilized to about 1,100 mg/1 between 1987 and 2003. In 2004 TDS concentrations averaged 1200 mg/l. Figure I2 illustrates the variable nature of total recoverable iron concentrations in the No. 1 Strip Pit discharge. During 2004, these levels remained within typical ranges seen for this site. 3.2.3 Ponds There was no discharge from the sediment ponds in 2004. I:\Env\Em pireW H R~2004\TeM\Empire2004AH R.doc 5