2011-03-14_REPORT - C1982056 (3)

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• 3.7 Mine Water Discharge Sites Four mine water discharge sites associated with the TCC operations are monitored. Site 109 requires quarterly monitoring for flows, field parameters, and water quality samples (when flowing), and site 115 is monitored as a CDPS discharge point in accordance with the requirements set forth under CDPS Permit No. CO-0042161. Two other mine water discharge sites are discussed in greater detail under a subsection to Section 3.6 above. To dewater the old WMD and EMD, pumps and piping were installed to direct mine water from the Fish Creek Vent Shaft (FCVS) and TORT #1, to the Area # 1 Pit. Overflow from the Pit passes through site 7 to Pond D, and subsequently through CDPS Outfall 005A to Foidel Creek. Site 7 requires quarterly analyses when flowing per DRMS Permit No. C-82-056. Outfall 005A requires weekly, twice monthly, monthly, and quarterly water quality sampling when flowing, under CDPS Permit CO-0027154. There has been no flow from site 109 to Foidel Creek for several years, and none in 2010. Site 115 had not discharged to Fish Creek since early 2005, but was reactivated in 2008 and 2009, both for a limited times (i.e. approx. one to three months) with low flows (25 - 500 gpm). In 2010, site 115 did not discharge. Note that mine water is pumped from underground to the surface (from the former Western Mining District), and is treated via an electro-coagulation process at the surface, where water enters the 3 former treatment ponds that can be directed through site 115. However, the majority of this treated water is pumped directly back into the mine for underground dust suppression. Additional overflow piping was added, so the treatments ponds cannot overflow. Overflow water is directed back into the mine via a former pump well. Historically, when pumping mine water from the Fish Creek Borehole (mine discharge site 115) the flow becomes a contributor to sulfate levels in Fish Creek. Fish Creek in turn contributes to the sulfate levels in Trout Creek. Trout Creek currently had a secondary drinking water standard limiting sulfate concentrations above 250 mg/l. Section 3.7, under the Emergency Discharge Permit section, discusses the sulfate issues dealt with in 2010. The 2010 Water Year data for mine water discharge site 115 is presented on Table 53. Table 53a provides historical water quality data. Figures 110 and 111 present graphical data for this site. 3.8 2010 Inflow Survey During the fall of 2010, an inflow study was conducted underground. Flow rates and field parameters were recorded for measurable inflows from the accessible areas of the underground mine. Results of the 2010 survey are presented on Figure 117, 2010 Inflow Study Mined Area (in map pouch at back of report). Note that this map also includes historic data for older underground areas, most of which have dried up. The WMD was closed in 1996. At that time inflows were 52 gpm. Note that water elevations for the WMD were monitored periodically at the Fish Creek Borehole. Our best estimate is that inflows for the WMD are still on the order of 50 to 60 gpm. 16