2016-10-24_REPORT - C1994082 - Laserfiche WebLink

Home Browse Search

which was higher than the CDPHE standard of 100 ug/l. 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, 1985, 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 2.57 mg/l. 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, 1985, pg. 121). Several wells at SCC's Seneca II Mine with high fluoride values also exhibit this type water. Ground Water Points of Compliance Two GWPOCs have been established for the Yoast Mine. Attachment 15-1 of the Yoast Mine PAP provides the details. The ground water standards for Grassy Creek Alluvial Well SGAL70 are provided in this AHR on Table 7. Data from Well SGAL70 may be found in the Peabody Sage Creek Mine AHR, Appendix C. No exceedances of those standards were observed the sample collected from this well this year. The ground water standards for Sage Creek Alluvial Well YSAL3 are provided in this AHR on Table 8. Data from Well YSAL3 may be found in 6