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Comparison of Ground Water Quality to Water Use Standards. SCC has <br />compiled a list of ground water standards for agricultural uses (Table <br />5). This list is composed of Colorado Department of Health ground water <br />standards (CDPHE, Reg. 41, May 2008). <br />U <br /> <br />Table 6 provides a comparison of ground water quality to agricultural <br />standards. This Paradox database generated table does not include the <br />units of concentration (mg/l or ug/1) for each parameter. The units used <br />for each parameter are the same as those listed on the standards table <br />(Table 5) and are also the same as those used in the water quality <br />reports. The frequency column on Table 6 indicates, in this order: <br />uncensored, that is, the number of exceedances above the Method <br />Detection Limit (MDL) / the number of exceedances between the MDL and <br />the Practical Quantitation Level (PQL) / censored, that is, the number <br />of sample values below the MDL but the MDL was higher than the standard <br />/ the total number of samples. Below is a summary of standards that were <br />exceeded. Given in parenthesis is the source and use of each standard. <br />Parameter <br />Manganese (CDPHE, irrigation) <br />pH (CDPHE, irrigation) <br /># of Wells / # of excursions <br />2/2 <br />1/1 <br />High manganese values may, in part, be due to recharge from the spoil <br />aquifer, although high values are often common, especially in alluvial <br />material (Hem, 1989, pgs. 86-89). The wells displaying high manganese <br />values this year also did so prior to mining. This standard is used to <br />protect crops grown in soils with a pH value lower than 6.0. In January <br />2008, CDPHE revised their ground water agricultural standard to reflect <br />this pH qualifier. In soils with a higher pH (as are found in the Yoast <br />region), a more appropriate standard would be 10 mg/l (EPA, 1976). This <br />year, no well displayed a value higher than 0.499 mg/l. <br />Ground Water Points of Compliance <br />Two GWPOC's have been established for the Yoast Mine. Attachment 15-1 of <br />the Yoast Mine PAP provides the details. The ground water standards for <br />5