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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. In the case of fluoride, <br />the two PSCM wells (BPl and 19) that have elevated levels have <br />historically displayed high levels. All three wells are also unique in <br />displaying a sodium bicarbonate type water with relatively high pH <br />values. It is suspected that the high fluoride values are related to <br />this type of water chemistry (Hem, 1989, pg. 121). All wells exist <br />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, especially in alluvial <br />material (Hem, 1989, pgs. 86 -89). Manganese exceedances have occurred at <br />all alluvial wells, including the one Grassy Creek alluvial well <br />upstream of Seneca II (Well 71). 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 PSCM region), <br />a more appropriate standard would be 10 mg /1 (EPA, 1976). This year, <br />none of the PSCM alluvial wells displayed a value higher than 3 mg /l, <br />and no spoil wells displayed a value higher than 5 mg /1. <br />Spoil Well 27 exceeded the selenium standard, 20 ug /l, with a value of <br />39.9 ug /l. In the previous ten years, this site has exceeded the <br />selenium standard twice (out of twenty samples). The selenium value from <br />PSCM's GWPOC well in the Grassy Creek basin was less than the standard <br />(see below). <br />Finally, water quality analyses performed on the one sample obtained at <br />the PSCM shop well (STCS) for this year were compared against both human <br />health (mandatory) and secondary (i.e., recommended but not mandatory) <br />7 <br />