Laserfiche WebLink
3.5 Natural Spring Monitoring <br />Two natural springs, SWl and SW2, located over previously mined areas in the Southwest Mining District <br />required semiannual monitoring during 2007. Prior to mining, SW-2 typically flowed throughout the year, while <br />SW1 flows were sporadic. In recent years flows at SW-2 have been minor, and in the case of SW-1, non- <br />existent. Minor flow was observed in SW-2, in May of 2007, and no flow in September 2007. Analytical values <br />were within historic limits. No flow was observed in SW-1 in 2007. <br />In May 2007, a spring and seep survey was also conducted in the northern mining district to identify potential <br />discharges to Fish Creek. No new or significant springs were identified in 2007. The northern mining district is <br />located within the Twentymile Park Syncline. The predominant lithologic unit nearest the surface and occupying <br />most of the basin is the Lewis Shale, which can be upwards of 700 feet thick. The lack of significant bedding <br />planes, faulting, or fracture zones in this area may account for the lack of springs in the central portion of this <br />basin. The few seeps observed in the basin may be the result from surface weathering of the Lewis Shale, which <br />may allow some accumulation of water beneath overburden. This may result in a short period of seepage <br />immediately following spring runoff. <br />3.6 Mine Water Discharge Sites <br />• Two mine water discharge sites associated with the TCC operations are monitored. Site 109 requires quarterly <br />monitoring for flows, field parameters, and water quality samples (when flowing), and site 115 is monitored as a <br />CDPS discharge point in accordance with the requirements set forth under CDPS Permit No. CO-0042161. <br />There was no flow from site 109 to Foidel Creek for several years, and none in 2007. Site 115 has not discharged <br />to Fish Creek since early 2005. Piping leading to the discharge channel to Fish Creek was closed off in 2006, <br />Currently, water is pumped from underground to the surface (from the former Western Mining District), and is <br />treated via an electro-coagulation process at the surface, where water enters the 3 former treatment ponds for site <br />115, and is eventually pumped back into the mine for underground dust suppression. Additional overflow piping <br />was added, so the treatments ponds cannot overflow. Overflow water would be directed back into the mine via a <br />former pump well. <br />Historically, when pumping mine water from the Fish Creek Borehole (mine discharge site 115) the flow <br />becomes a contributor to sulfate levels in Fish Creek. When pumping mine water from the EMD Dewaering <br />Well (mine discharge site 109) the flow becomes a contributor to sulfate levels in Foidel Creek. Fish Creek and <br />Foidel Creek, in turn, contribute to the sulfate levels in Trout Creek. Trout Creek currently has a secondary <br />drinking water standard limiting sulfate concentrations above 250 mg/1. The 2007 Water Year data for mine <br />water discharge site 115 is presented on Table 53. Table 53a provides historical water quality data. Figures 110 <br />and 111 present graphical data for this site. <br />• <br />12 <br />