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FMXX/,m/' <br />October 14, 2015 <br />COLORADO <br />Division of Recla:raroa:bion, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman S'tree't, Room 215 <br />Denver, CO 80203 <br />Chris Gilbreath <br />Colowyo Coal Company L.P. <br />1100 West 116th Avenue <br />Westminster, CO 80234 <br />RE: Colowyo Mine, Permit C-1981-019 <br />Review of 2013 and 2014 Annual Hydrology Reports (AHRs) <br />Dear Mr. Gilbreath: <br />The Division has reviewed Colowyo's 2013 and 2014 AHRs, and we have the following comments <br />regarding the text and data in the reports. <br />1) On page 2-3 of the 2013 report and page 2-4 of the 2014 report, the word "probably" should be <br />"probable." Please edit this text in future AHRs. <br />2) Please explain why there was no flow at LTC for almost 10 years. This omission in your AHRs was <br />discussed with our review of the 2012 AHR. <br />3) The 2013 data, 2014 data, and data from previous years reveal some possible long term impacts to <br />surface water quality. <br />a) At the LTC site, data in recent years appears to be significantly higher than older data for TDS, <br />sulfate, and sodium. For TDS, data in the 1980s includes concentrations in the neighborhood of <br />1,000 mg/l, while data from recent years is approximately 1,900 mg/l. For sulfate, data in the <br />1980s includes concentrations in the neighborhood of 350 mg/l, while data from recent years is <br />approximately 1,000 mg/l. For sodium, data in the 1980s includes concentrations in the <br />neighborhood of 70 mg/l, while data from recent years is approximately 300 mg/l. <br />b) At the LGSC site, data in recent years appears to be significantly higher than older data for <br />several parameters, including sodium: for sodium, data in the 1980s includes concentrations in <br />the neighborhood of 70 mg/l, while data from recent years is approximately 150 mg/l. This trend <br />is not observed in NUGSC, above mining impacts. <br />4) The Division has the following observations regarding groundwater data. <br />a) At the Gossard Well, there is an apparent upward trend for TDS, which has been increasing over <br />the entire period of record, although it has leveled since 2006. Recent values have been <br />approximately 1,700 mg/l, whereas earlier data was approximately 1,200 mg/l. A similar <br />increase can be seen for conductivity. <br />b) Sulfate concentrations have been significantly higher at the downgradient wells; for example, the <br />mean at A-6 is 140 mg/l, and the mean at NGSW Well is 770 mg/l. <br />r`u <br />n 0 <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us " <br />John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director' ` ri <br />