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Parameter <br />pH (CDPHE, irrigation) <br />Fluoride (CDPHE, irrigation) <br />Iron (CDPHE, irrigation) <br />Manganese (CDPHE, irrigation) <br /># of Wells / # of Excursions <br />7/12 <br />3/6 <br />1/1 <br />7/12 <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 />elevated levels this year have historically displayed high levels. All <br />three wells are also unique in displaying a sodium bicarbonate type <br />water with relatively high pH values. It is suspected that the high <br />fluoride values are related to this type of water chemistry (Hem, 1989, <br />pg. 121). All wells exist within the PSCM permit boundary. <br />The high levels of iron displayed in Alluvial Well 71 may be the result <br />of organic matter and plant debris present in the alluvium (Hem, 1989, <br />pg. 77). This well has historically exhibited high iron values (seven <br />out of forty- seven) and exists within the PSCM permit boundary. <br />High manganese values may, in part, be due to recharge from the spoil <br />aquifer, although high values are often common due to naturally <br />occurring geochemical conditions, especially in alluvial material (Hem, <br />1989, pgs. 86 -89). Manganese exceedances have occurred at all alluvial <br />wells, including the one Grassy Creek alluvial well upstream of Seneca <br />II (Well 71)and one wadge coal well located just West of NPDES Pond <br />002(Well 17). This standard is used to protect crops grown in soils with <br />a pH value lower than 6.0. In January 2008, CDPHE revised their ground <br />water agricultural standard to reflect this pH qualifier. In soils with <br />a higher pH (as are found in the PSCM region), a more appropriate <br />standard would be 10 mg /l (EPA, 1976). This year, none of the PSCM <br />alluvial wells displayed a value higher than 4 mg /1, and no spoil wells <br />displayed a value higher than 8 mg /1, and the wadge coal well did not <br />display a value higher than 0.5 mg /1. <br />7 <br />