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?"ENEC?1 <br />Coal company <br />Seneca Coal Company <br />January 21, 2011 <br />Ms. Susan Burgmaier <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203-2273 <br />`Jt-® <br />G <br />RE: Seneca II Mine 2009 Annual Hydrology Report Review Comments <br />Dear Ms. Burgmaier, <br />We have reviewed your January 13 letter to Roy Karo in regards to the <br />2009 Seneca II AHR. You asked for a reply in regards to three of the <br />items. Here is our response. <br />Item 11. You asked about our use of a hardness value of 400 mg/l for <br />the determination of certain water quality standards. Attached to this <br />letter are water quality statitistic reports for NPDES outfalls and <br />steam sites. They are hand numbered in red on the upper right hand <br />side (these will be referred to as our pages' in this letter). Our <br />pages 1 and 2 are the hardness statistics for the month of September <br />from 2000 to 2010. Sites SSG1 and SSG2 are Grassy Creek sites. We <br />chose September as it is representative of `low flow' as specified in <br />CDPHE Reg. 31. As you can see, all mean values are well above 400 <br />mg/1. For the Fish Creek sites found on our page 3, very little <br />September data existed, so we chose July as the `low flow' month, and <br />expanded the date range to include all historic data. Again, those <br />mean values are all above 400 mg/1. <br />The CDPHE chose an entirely different approach (than the one presented <br />above) when calculating NPDES permit limits, but the results were the <br />same (i.e., the use of 400 mg/l hardness tier of standards are <br />appropriate). Attached on our pages 4 to 6 is the CDPHE's most recent <br />(August 2006) Water Quality Assessment performed for Seneca. They <br />concluded that the use of 400 mg/l standards are appropriate, and <br />present the applicable standards in Table A-6 (our page 6). <br />Item 12. You asked about Method Detection Limits (MDL's) for sulfide <br />and mercury. In regards to sulfide, we asked our laboratory (ACZ Labs <br />in Steamboat Springs) about this today. They replied that the method <br />Seneca Coal Company a P.O. Box 670 • Hayden, Colorado 81639 <br />Telephone (970) 276-5217 a FAX (970) 276-5222