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']'his issue; is not new to Oxbow. In 1995. Oxbow's adjacent Sanborn Creek mine experienced <br />similar toxicity to Ceriodaphnia sp. The toxicity was determined to be total dissolved solids <br />(TDS) or specifically, alkalinity. In 1995, on behalf of Oxbow, the Colorado School of Mines <br />conducted an "Aquatic Impairment Study" of the Sanborn Creek mine water discharge at Outfall <br />011 and the effects of the mine discharge on aquatic macro - invertebrate fauna living in the North <br />Fork River. (See the attached copy of the Aquatic Impairment Study). Importantly, the study <br />concluded '`that the discharge from the Sanborn Creek Mine has minimal effect on stream <br />macro- invertebrates in general, that the discharge has little. if any, effect on the overall food base <br />for fish, and that the use of the river tier fishing has not been impaired" <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 that the waiver of WET Testing with Ceriodaphnia sp also be <br />extended to Outfall 015 -B. Oxbow proposes that future WET Testing for Outfall 015 -B consist <br />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. We anticipate that pumping will likely continue until the end of July. Re- <br />entry into the mine, mine ventilation reestablishment and long -wall recovery will likely occur in <br />early August. If successful, the pumps can be permanently shut down starting in early August as <br />well. <br />If you have any questions or comments, please contact me at (970) 929 -5806. <br />Sincerely, <br />James A. Kiger <br />Environmental Manager <br />Attachments <br />Xc: Brock Bowles, CDRMS <br />Mike Ludlow, OMLLC <br />Files <br />• Page 2 <br />