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STATE OF COLOIZ~DO DIVISION OF MINERALS AND GEOLOGY Department of Natural Resources 1313 Sherman St., Room 215 Denver, Colorado 80203 Phone: (303) 8663567 FAX: (303) 832-8106 March 26, 2004 Dennis Jones Seneca Coal Company P.O. BOX 670 Hayden, CO 81639 Re: Yoast Mine (Permit No. C-94-082) 2003 Annual Hydrology Report Review Deaz Mr. Jones: COLORADO DIVISION O F MIN aRALS GEOLOGY REC LANATION•NIN ING SAFETY•SCIEN CE Bill Owens Governor Russell George Eaecu[ive Director Ronald W. Cattany Division Director Natural Resource Trustee The Division has reviewed Seneca Coal Company's (BCC's) 2003 Annual Hydrology Report (AHR) for the Yoast Mine. The AHR was received on January 20, 2004 and contains water quality and quantity data for the 2003 Water Yeaz. The 2003 AHR is well written and the data are presented in a concise manner. The frequency of data collection is in compliance with the approved monitoring plan contained in the permit document. The Division notes that a few samples could not be obtained due to wells being dry or no flow conditions at certain surface water sample locations. Only one of the required triannual water level measurements could be obtained at Well YWU16 due to the well being dry in July and October. Well YOV29 located in the Wadge Overburden was dry during all three attempts to obtain water level measurements or samples for water quality analyses. Surface water site YSSF3 was dry during the baseflow period and the third triannual water quality sample could not be obtained. Semiannual water quality samples for laboratory analysis were not obtained for springs YSPG6 and YSPG10 due to no flow. Samples for field parameters were collected at both spring locations, from the clear well at YSPG6 and from standing water at YSPG10. The PHC predicts TDS increases in all down gradient bedrock units and alluvium. This prediction is consistent for all of the alluvial wells sampled to date. All seven alluvial wells display an increasing trend in TDS concentrations. Average TDS values from samples from three alluvial wells in 2003 exceed the corresponding PHC predicted TDS value. These wells are located in the Armand Draw, Grassy Creek and Sage Creek alluvium, respectively. Only two out often bedrock unit monitoring wells (Wolf Creek Coal and Wolf Creek Underburden) sampled in 2003 display an increasing trend in TDS concentration. The TDS increase is considered slight in these wells. None of the bedrock unit monitoring wells sampled in 2003 showed average TDS values in excess of PHC predicted TDS values. Office of Mined Land Reclamation Office of Active and Inactive Mines Colorado Gmlo¢i[al Survev