2009-02-26_REPORT - C1994082 (11)

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displayed in the one alluvial well (YGAL15) may be the result of organic matter and plant debris present in the alluvium (Hem, 1989, pg. 77) This well displayed high levels of iron prior to mining. 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/1 (EPA, 1976). This year, no well displayed a value higher than 1.98 mg/l. Ground Water Summary TDS trends are decreasing at one well, stable at eight wells, and increasing at seven wells. One water quality well, YOV29, was dry. CDPHE agricultural ground water standards for fluoride, iron and manganese were exceeded at certain monitoring wells. In the area surrounding Yoast, ground water is not being pumped for irrigation or livestock watering purposes, nor has the CDPHE classified any aquifer in this region for any use. The above discussion is provided only to serve as a comparative basis to judge ground water quality. In the Probable Hydrological Consequences (PHC, Tab 17, Attachment 17-5) section of the Yoast Mine PAP, predictions were made as to the expected TDS increases to be observed at various monitoring wells. The following table outlines these predictions along with this year's observed average values (annual average for bedrock wells, May-September average for alluvial wells). Well Predicted TDS values (mg/1) This years average TDS (mg/1) YOV28 2587 840 YOV29 3201 Dry YOV30 3201 2000 6