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• <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 data this year to <br />agricultural standards. This Paradox database generated table does not <br />include the units of concentration (mg/l 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 />Manganese (CDPHE, irrigation) <br /># of Wells / # of Excursions <br />2/4 <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). Manganese exceedances have previously <br />occurred at all alluvial wells. This standard is used to protect crops <br />grown in soils with a pH value lower than 6.0. In January 2008, CDPHE <br />revised their ground water agricultural standard to reflect this pH <br />qualifier. In soils with a higher pH (as are found in the Seneca II <br />region), a more appropriate standard would be 10 mg/1 (EPA, 1976). This <br />year, none of the Seneca II alluvial wells displayed a value higher than <br />3.515 mg/1. <br />One sample had a lead value that was less than an elevated detection <br />limit (200 ug/1 vs. a normal detection limit of 40 ug/1), which was <br />E <br />• <br />5