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Mr. Richard A. Mills - 2 - March 21, 1986 Table 1: Disparities in Monitoring Surface Discharge Outfalls Between the 1985 AHR and the NPDES Permit Parameter Frequency AHR NPDES EC Weekly Not Listed Temperature Weekly Not Listed TSS Not Listed Monthly Total Iron Not Listed Monthly TDS Not Listed Quarterly Please change the AHR to correspond to the requirements of the current NPDES permit(s). Data Interpretation Annual Hydrologic Reports have two major functions: the reporting of hydrologic data collected throughout the year and an analysis of that data. The data analysis should include a discussion of anomalies in the data and exceedences from applicable water quality standards, an evaluation of trends on a seasonal basis, an annual basis and with respect to baseline data, and lastly an appraisal of how and why the data varies from the PHC predicted by the permit. This should be done in a narrative format supported by graphical projections of the data. An interpretation similar to that found in Empire's AHR is acceptable, but should address the concerns listed above. Quality Control The Division is interested in verifying and upgrading the quality of hydrologic monitoring data produced by Colorado Yampa Coal Company (CYCC). Two separate issues were raised in the evaluation of your data; mass balance discrepancies and the failure to achieve detection levels five times lower than applicable receiving stream standards. The Division performed random checks of mass balance by comparing cation and anion equivalents and by comparing the summation of the ions reported with TDS values of an analysis. Values ranged from twenty-two percent below to fourteen percent above cation values, although they usually ran below cation values. Ion summations were generally higher than the TDS values, but ranged from fifteen percent lower to forty-seven percent higher than the TDS values. It is suspected that cations are being over-reported. The data is marginally acceptable as reported and could use improvement. The Division proposes that the lab scrutinize their procedures more carefully and calculate and report mass balance whenever adequate data on a sample is analyzed (Lists A, B, C, D). CYCC is failing to obtain adequate analyses for the heavy metals cadmium (Cd), mercury (Hg), Molybdenum (Mo) and Copper (Cu) (Table 2) as detection limits exceed applicable standards between two hundred to two thousand percent. The Division is aware of the difficulties involved with analyzing brine-like solutions, and subsequently we recommend that CYCC examine the analytical