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~~I ~I~II~~I~~I~~ I~I • 999 DIVISION OF MINERALS AND GEOLOGY Departmem of Natural Resources 1313 Sherman 51., Roum 215 Dem~er, Colorado 80?OJ Phone: 13031 866-35b7 FAX 13031 A72-8106 August 13, 1999 Bil I Owens Governor Michael G Altavilla . ereg E. walcner Seneca Coal Company EnecW rve Director P.O. Box 670 Michael B Long Dwis~on D~reuor Hayden, CO 81639 Re: Seneca II ivline (Permit No. C-80-005) 1998 Annual Hydrology Report Review Dear Mr. Altavilla: The Division has reviewed Seneca Coal Company's (BCC's) 1998 Annual Hydrology Report (AHR) for the Seneca II Mine. The frequency of data collection is in compliance with the approved monitoring plan contained in the permit document. SCC did a good job at collecting and reporting the required monitoring data. The report is well written and the data are presented in a concise manner. The Division has the following comments concerning the 1998 AHR. 1. SCC has compiled a list of ground water standards for agricultural uses (Table 5) and a list of surface water standards for agricultural uses (Table 9). As suggested by the Division, these lists have been composed mostly of Colorado Department of Public Health and Environment (CDPHE) ground water standazds as of April 1996 and CDPHE surface water standazds as of August 1997, respectively. Please note that the standards have been recently updated. The last effective update for both the ground water standards and surface water standards was March, 1999. 2. The Division notes that the AHR record indicates apparent exceedances of the CDPHE Basic Standards for Ground Water. As reported in [he 1998 AHR and previous AHRs, isolated exceedances of ground water standards have occurred for certain metal constituents, TDS, flouride, and sulfate. TDS increases in groundwater resulting from spoil dischazge is discussed in the Probable Hydrologic Consequences discussion in the pernlit document (PHC). In addition, trend analysis is provided for TDS at each ground water well location in the AHR. Has SCC identified the potential source for the apparent elevated levels of certain metals, tlouride, and sulfate presented in Table 6 of the 1998 AHR? Are concentrations for these constituents significantly higher than corresponding baseline levels, and does the overall trend indicate increasing or decreasing concentrations for these constituents? STATE OF COLORADO DIVISION OF MINERALS GEOLOGY RECLAMATION MIN ING•SAFETY