2009-02-26_REPORT - C1982057 (10)

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are decreasing. All wells with high iron values exist within the Seneca II-W permit boundary. 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). 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 Seneca II-W region), a more appropriate standard would be 10 mg/l (EPA, 1976). This year, none of the Seneca II-W wells displayed a value higher than 2.98 mg/1. One well, WW14, exhibited a boron value of 1090 ug/l, which exceeded the CDPHE standard of 750 ug/1. According to the CDPHE, the 750 ug/l standard is set for sensitive crops (CDPHE, Reg. 41, May 2008), and that the limit otherwise is 5000 ug/1. None of these sensitive plant species are grown commercially in this area. Well WOV17 exhibited a selenium value of 208 ug/1, which exceeds the agricultural standard of 20 ug/l. The previous maximum value was only 9 ug/l. More data will be needed to determine if this year's value was an anomaly. At the Seneca II-W shop well, Well 201TC, CDPHE drinking water standards were used to determine its suitability. No human health standards were exceeded. The secondary standard for iron (0.3 mg/1) was exceeded with a value of 5.2 mg/l. The secondary standard for manganese (0.05 mg/1) was exceeded with a value of 0.079 mg/1. However, bottled water is consumed at Seneca II-W. Also, since the aquifer for the shop well (Trout Creek Sandstone) starts at 280 feet below the Wadge Coal and is separated by confining shale layers, water from this well should not be affected by mining and, therefore, reflects the natural characteristics of the aquifer. 10