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- Spoils. One well monitors the spoils above NPDES Pond 002. Well 27 <br />displays a recent stable TDS trend, with TDS values peaking in 1998. <br />Well 61 is located a half mile south of the Pecoco Pond. It displays a <br />stable TDS trend. Well 62 is located above NPDES 004 Pond. It recently <br />displays a decreasing TDS trend. <br />Comparison of Ground Water Quality to Water Use Standards. The PSCM 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 (CDPHE) ground water standards (CDPHE, Reg. 41, May 2008). <br />Table 6 provides a comparison of ground water quality data this year to <br />agricultural standards. This Paradox database generated table does not <br />include the units of concentration (mg /1 or ug /1) for each parameter. <br />The units used for each parameter are the same as those listed on the <br />standards table (Table 5) and are also the same as those used in the <br />water quality reports. The frequency column on Table 6 indicates, in <br />this order: uncensored, that is, the number of exceedances above the <br />Method Detection Limit (MDL) / the number of exceedances between the MDL <br />and the Practical Quantitation Level (PQL) / censored, that is, the <br />number of sample values below the MDL but the MDL was higher than the <br />standard / the total number of samples. Below is a summary of standards <br />that were exceeded. Given in parenthesis is the source and use of each <br />standard. <br />Parameter # of Wells / # of Excursions <br />pH (CDPHE, irrigation) 8/16 <br />Fluoride (CDPHE, irrigation) 3/7 <br />Iron (CDPHE, irrigation) 1/1 <br />Manganese (CDPHE, irrigation) 5/9 <br />Elevated levels of iron and fluoride may be attributed to natural (i.e., <br />not mining related) conditions, since elevated levels for those <br />parameters are not found in PSCM spoil wells. However, elevated values <br />of iron and fluoride were found in many wells before, as well as <br />upgradient of, mining. In the case of fluoride, the wells that have <br />6 <br />