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confining layers of shale separated this aquifer from mined seams. All <br />values have been at or below 700 mg /1. <br />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 Public Health and <br />Environment ground water standards (CDPHE, Reg. 41, May 2008). <br />Table 6 provides a comparison of ground water quality collected this <br />year to agricultural standards. This Paradox database generated table <br />does not include the units of concentration (mg /l or ug /1) for each <br />parameter. The units used for each parameter are the same as those <br />listed on the standards table (Table 5) and are also the same as those <br />used in the water quality reports. The frequency column on Table 6 <br />indicates, in this order: uncensored, that is, the number of exceedances <br />above the Method Detection Limit (MDL) / the number of exceedances <br />between the MDL and the Practical Quantitation Level (PQL) / censored, <br />that is, the number of sample values below the MDL but the MDL was <br />higher than the standard / the total number of samples. Below is a <br />summary of standards that were exceeded. Given in parenthesis is the <br />source and use of each standard. <br />Parameter <br />pH (CDPHE, irrigation) <br />Iron (CDPHE, irrigation) <br />Manganese (CDPHE, irrigation) <br /># of Wells / # of Excursions <br />1/1 <br />3/3 <br />4/4 <br />Elevated levels of iron (i.e., greater than 5 mg /1) may be attributed to <br />natural (i.e., not mining related) conditions, since the highest level <br />of iron found in spoil springs at this mine this year was 0.34 mg /1. The <br />one bedrock well (WW14) that often exhibit high levels may have higher <br />than usual concentrations of iron pyrite in the rock. The high levels of <br />iron displayed in the two alluvial wells this year may be the result of <br />organic matter and plant debris present in the alluvium (Hem, 1989, pg. <br />77) . <br />6 <br />