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<br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman 51., Room 215 <br />Denver, Colorado 80203 D I v 15 1 0 N O F <br />Phone: (303) 866-3567 MINERAL S <br />FAX'. {303)832-8106 be <br /> GEOLOGY <br />INTEROFFICE MEMORANDUM M EN I N GM ATF E T Y <br /> <br /> Bill Owens <br /> Governor <br /> Greg E Walchcr <br />TO• Sandra Brown <br />• Enecmwe Director <br /> Michael B Long <br /> <br />FROM: Mike Boulay ul Dwisinn Dneclor <br />DATE: August 24, 1999 <br />SUBJECT: Seneca II-W -Permit No. C-82-057, 1998 Annual Hydrology Report Review <br />I have reviewed Seneca Coal Company's (BCC's) 1998 Annual Hydrology Report (AHR) for the <br />Seneca II-W Mine. As noted in your memorandum to me dated March 23, 1999, the frequency <br />of data collection is incompliance with the approved monitoring plan contained in the Seneca II- <br />Wpermit document. SCC did a good job at collecting and reporting the required monitoring <br />data. <br />The Division had several comments on the 1997 AHR in our review letter dated October I5, <br />1998. SCC addressed these comments and incorporated the Division's recommendations into the <br />1998 AHR. The Division has [he following comments concerning the 1998 AHR. These <br />comments could be inserted directly into a review letter to the operator. <br />1. SCC has compiled a list of ground water standards for agricultural uses (Table 5) and a <br />list of surface water standards for agricultural uses (Table 9). As suggested by the Division, <br />these lists have been composed mostly of Colorado Department of Public Health and <br />Environment (CDPHE) ground water standards as of April 1996 and CDPHE surface water <br />standards as of August 1997, respectively. Please note that the standards have been recently <br />updated. The last effective update for both the ground water standards and surface water <br />standards was March, 1999. <br />2. The Division notes that the AHR record indicates apparent exceedances of the CDPHE <br />Basic Standards for Ground Water. As reported in the 1998 AHR and previous AHRs, isolated <br />exceedances of ground water standards have occurred for certain metal constituents, chloride, <br />fluoride total dissolved solids (TDB), and sulfate. TDS increases in groundwater resulting from <br />mining activities are presented in detail in the Probable Hydrologic Consequences (PHC) <br />discussion in the permit document. In addition, [rend analysis is provided for TDS at each <br />ground water well location in the AHR. Has SCC identified the potential source for the apparent <br />elevated levels of certain metals, chloride, fluoride, and for sulfate presented in Table 6 of the <br />