2018-03-09_REPORT - C1982056 (3)

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(COG -850051) was subsequently approved in January 2010 by CDPHE, effective February 1, 2010, expiring June 30, 2016. The permit is currently under Administrative Extension with CDPHE. Outfall 001A did not discharge in 2017. CDPHE Discharge Permit COG -850054 The 18 Left Vent Fan Pad area drains into two sedimentation ponds which could discharge into a small unnamed tributary leading to Fish Creek. In February 2009, TC submitted an application to CDPHE to make this a permanent CDPS site (also see TR09-70). A permit (COG -850054) was subsequently approved by CDPHE, effective April 15, 2010, expiring June 30, 2016. The permit is currently under Administrative Extension with CDPHE. DRMS is copied on CDPHE DMRs for this site. The site did not discharge in 2017. 3.7 Mine Water Discharge Sites Four mine water discharge sites are currently associated with the TC operations are monitored. Site 109 (Twentymile Facility) requires quarterly monitoring for flows, field parameters, and water quality samples (when flowing). Note that this site has not discharged in about 20 years, and will not be discharging in the conceivable future. Site 115 (Fish Creek Borehole) 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. Site 7 discharged during the second and third quarters of 2017 water year. Outfall 005A requires weekly, twice monthly, monthly, and quarterly water quality sampling when flowing, under CDPS Permit CO -0027154. Note that mine water is pumped from underground to the surface (from the old WMD), and was historically (beginning in 2005) treated via an electro -coagulation process at the surface, where water enters the 3 former treatment ponds that can also be directed through discharge site 115, that can be directed to Fish Creek. This form of treatment ceased around 2014. This water was 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. 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). Site 115 discharged for a couple of hours one day in early 2015 due to a broken pipeline, which was subsequently repaired. Following approval in 2016 from CDPHE and DRMS to use a flocculant for mine water treatment, the site discharged April through early June of 2017. 15