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• <br />and downstream station on the Williams Fork River indicate that there is no detectable effect of mining on <br />river water quality. Dissolved solids decrease with increasing flow rate in the rivers, due to runoff dilution. <br />3.2.2 Springs <br />There is one active spring on the mine site area, known as the No. 1 Strip Pit Discharge, or 1SP. There are a <br />few other springs and local permanent "damp spots" that flow sporadically in the spring; however, their <br />combined flow is normally less than 10 gpm and is therefore not significant. 1SP Discharge is a CDPS <br />monitoring point (Outfall 022). There is no sediment pond associated with this spring. Spring water runs <br />down a narrow path through a vegetative filter and discharges directly to the Williams Fork River. The POR <br />discharges for the 1SP are presented in Figure 23 and the 2010 discharge measurements are presented on <br />Figure 24, respectively. The discharge from 1SP increased significantly back in 1989. This may have been <br />due to seepage from the ditch that conveys the 7 North Angle discharge (measured at site 9P3, a.k.a. CDPS <br />Outfall 024)). Site 9P3 discharge began in January of 1989, and has been sporadic. Site 9P3 Discharge rates <br />from 1990 through 2003 are significantly lower. 9P3 has not discharged since 2003. Nevertheless, snowmelt <br />and ditch seepage both appear to have some influence on 1SP discharge, as the discharge typically drops to <br />just a few gpm from January through May with a small peak typically in March coinciding with spring runoff. <br />1SP is typically dry from July through September, may flow briefly in October through December, and stops <br />flowing.again in January and February due to freezing. <br />Summaries of the water quality data for this spring are presented in Tables 31 and 32. A plot of POR total <br />dissolved solids for 1SP is presented in Figure 25 and POR iron concentrations are presented on Figure 26. <br />Figure 25 indicates TDS concentrations that are consistent with historic concentrations, with the exception of <br />an elevated value in late July. This may be related to an earlier clearance of cat tails and other vegetation <br />from in front of the site's weir. The site ceased flowing shortly thereafter. Figure 26 illustrates the variable <br />nature of total recoverable iron concentrations in 1SP discharge. Since 2002, there has been a gentle upward <br />trend in iron concentrations, however these levels are still within historic ranges seen for this site, with the <br />exception of an elevated value in late July 2010. This may also be related to the vegetation clearance <br />discussed above. Note that this site did experience a two periods of total recoverable iron NPDES <br />exceedances in July and December of 2010. This occurred during very low flow periods shortly before the <br />spring stopped flowing altogether. BTU EC will continue to monitor this trend, and anticipate a modification <br />of the vegetative filter in the spring or summer of 2011 to minimize elevated iron concentrations during low <br />flow periods. <br />3.2.3 Ponds <br />With the exception of Outfall 003 (discussed under section 3.1.2), there was no recorded discharge from the <br />• other on-site sediment ponds in 2010. <br />Page 7 <br />GAEnvironmentahEMPIRE\AHR\2010\Empire2010AHR. doc