2013-04-25_REPORT - C1994082 (2)

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- Wadge Underburden. Well YWU30 recently displays a decreasing TDS trend (SF 0.5) with the peak values occurring in December 1990 and August 2007. - Wolf Creek Coal and Underburden. As of September 2002, Well YWC33 monitors the Wolf Creek coal water quality in the Sage Creek basin. This well displays a decreasing TDS trend, with the peak value occurring in 2005. Mining of this seam began in November 2002. Well YWCU33 now monitors the Wolf Creek underburden water quality in the Sage Creek basin. It displays a decreasing TDS trend with the peak value occurring in August 2003. Comparison of Ground Water Quality to Water Use Standards. SCC has compiled a list of ground water standards for agricultural uses (Table 5) . This list is composed of Colorado Department of Health ground water standards (CDPHE, Reg. 41, May 2008). Table 6 provides a comparison of ground water quality to agricultural standards. This Paradox database generated table does not include the units of concentration (mg /l or ug /1) for each parameter. The units used for each parameter are the same as those listed on the standards table (Table 5) and are also the same as those used in the water quality reports. The frequency column on Table 6 indicates, in this order: uncensored, that is, the number of exceedances above the Method Detection .Limit (MDL) / the number of exceedances between the MDL and the Practical Quantitation Level (PQL) / censored, that is, the number of sample values below the MDL but the MDL was higher than the standard / the total number of samples. Below is a summary of standards that were exceeded. Given in parenthesis is the source and use of each standard. Parameter # of Wells / # of excursions Manganese (CDPHE, irrigation) 1/1 High manganese values may, in part, be due to recharge from the spoil aquifer, although high values are often common, especially in alluvial material (Hem, 1969, pgs. 86 -89) . The well displaying high manganese 4