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As Oxbow has previously noted in the July 16, 2013 DMR report submitted last month, this issue <br />is not new to Oxbow. In 1995, Oxbow's adjacent Sanborn Creek mine experienced similar <br />toxicity to Ceriodaphnia sp. The toxicity was determined to be total dissolved solids (TDS) or <br />specifically, alkalinity. In 1995, on behalf of Oxbow, the Colorado School of Mines conducted <br />an "Aquatic Impairment Study" of the Sanborn Creek mine water discharge at Outfall 011 and <br />the effects of the mine discharge on aquatic macro - invertebrate fauna living in the North Fork <br />River. Importantly, the study concluded "that the discharge from the Sanborn Creek Mine has <br />minimal effect on stream macro - invertebrates in general, that the discharge has little, if any, <br />effect on the overall food base for fish, and that the use of the river for fishing has not been <br />impaired" Please find a copy of that report included with our July 16, 2013 DMR. <br />Permit Rationale - Page 7, Permit No. CO- 0000132 (see attached) provides further discussion <br />regarding the potential TDS toxicity issue. First, regarding the 1995 Impairment Study, the <br />Division and EPA reviewed the study and came to similar conclusions that there was no <br />"discernible impact" from the discharge to the North Fork River. It was determined that future <br />testing using Ceriodaphnia sp. would be of little value. Second, when mine water Outfall 015 <br />was subsequently permitted for the Elk Creek Mine, it was determined that the toxicity of this <br />outfall would be similar to that of Outfall 011. On this basis, the WET testing using <br />Ceriodaphnia sp. was waived for Outfall 015. <br />Therefore, it is clearly appropriate and consistent that the waiver of WET testing with <br />Ceriodaphnia sp also be extended to Outfall 015 -B. Oxbow proposes that future WET testing for <br />Outfall 015 -B consist only of the Fathead Minnow P. promelas. <br />Pumping Update <br />The Division is aware that the pumping of the mine workings from the alternate Outfall 015 -B <br />location was made necessary to recover the mine after an unforeseen event where the mine had <br />to be sealed due to elevated carbon monoxide levels indicating spontaneous combustion in a <br />mined out section of the mine. Oxbow has been pumping water from the Mine at Outfall 015 -B <br />since June 3, 2013. As of August 6, 2013, Oxbow had successfully drawn the mine water level <br />down such that the mine entry procedures can be conducted. With assistance from MSHA, mine <br />recovery operations are to start tomorrow August 9. The mine water pump is currently throttled <br />down to match the suspected 150 - 200 gpm of mine inflow. We anticipate that pumping will <br />likely continue until we at least reenter the mine, reestablish mine ventilation and long -wall <br />recovery. <br />If you have any questions or comments, please contact me at (970) 929 -5806. <br />Sincerely, <br />I� <br />es A. Kiger <br />nvironmental Manager <br />Attachments <br />Xc: Brock Bowles, CDRMS <br />Mike Ludlow, OMLLC <br />Files <br />• Page 2 <br />