2015-03-23_REPORT - C1994082 - Laserfiche WebLink

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Cadmium (CDPHE, irrigation) Manganese (CDPHE, irrigation) PH Fluoride (CDPHE, irrigation) Lead (CDPHE, irrigation) # of Wells / # of excursions 1/1 2/4 1/1 2/4 1/1 One sample at one site YW30 had a cadmium value that was less than an elevated detection limit (30 ug /l vs. a normal detection limit of 3 ug /1), which was higher than the CDPHE standard of 10 ug /1. Likewise, the same sample had a lead value that was less than an elevated detection limit (200 ug /1 vs. a normal detection limit of 20 ug /1), which was higher than the CDPHE standard of 100 ug /1. The cause of these elevated detection limits was a decision by the laboratory to dilute the samples prior to analyses in order to reduce the effects of interferences (primarily, high salinity). High manganese values may, in part, be due to recharge from the spoil aquifer, although high values are often common, especially in alluvial material (Hem, 1989, pgs. 86 -89) . The wells displaying high manganese values this year also did so prior to mining. This standard is used to protect crops grown in soils with a pH value lower than 6.0. In January 2008, CDPHE revised their ground water agricultural standard to reflect this pH qualifier. In soils with a higher pH (as are found in the Yoast region) , a more appropriate standard would be 10 mg /l (EPA, 1976) . This year, no well displayed a value higher than 1.66 mg /1. In the case of fluoride, the two wells (YWCU33 and YWC33) that have elevated levels have historically displayed high levels. Those wells are also unique in displaying natural condition associated with a sodium bicarbonate type water; with almost no calcium, magnesium, or sulfates; and with relatively high pH values. it is suspected that the high fluoride values are related to this type of water chemistry (Hem, 1989, pg. 121) . Several wells at SCC's Seneca II Mine with high fluoride values also exhibit this type water. 5