2010-04-16_PERMIT FILE - C1996083A (10)

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• 2.05.6 Leachate from the refuse piles and coal stockpile could also degrade the water quality of the river. Refuse Pile #1, refuse piles #2 & 4, refuse pile #3, and the coal pile will encompass 1. 1, 36.4, 15.8 and 4.9 acres at full capacity respectively. Based on the Upper B -Seam geochemical analysis presented in Volume 111, Exhibit 6, the average conductivity of the roof, interburden and floor samples is 1190 and coal is 505 umhos /cm. According to Section 2.04.8 the average annual rainfall in the area is 18.5 inches. If all of this rainfall percolated through the piles during the year, the equivalent flow would be 55.6 gallons per minute. In its Cumulative Hydrologic Impact Study for the North Fork of the Gunnison dated September 25, 1992, the DRMS assumed infiltration through a refuse pile is the result of snowmelt and it was estimated 2.8 inches per year would infiltrate during a 60 day period. The equivalent flow for this assumption over the 58.2 acre piles is 51.2 gallons per minute over the 60 day period. The two different leachate production estimates produce similar equivalent flow values. Alluvial wells were installed to monitor groundwater contamination. AW -1, AW -2 and AW -3 are near the coal stockpile. AW -4, AW -5 and AW -6 are . near the gob pile No. 1. AW -15, AW -16 and AW -17 are below Gob Pile No. 2. The water quality in the wells is poor to good. Following is a summary of baseline conductivity measurements (umhos /cm) for the alluvial wells obtained from the Annual Hydrology Reports. Predicted based on conductivity measurement from an Upper B -Seam coal sample. • TR-64 2.05-74 09/09 i9 PPePavga AW -1 AW -2 AW -3 Min 8900 1075 3600 Max 9300 9700 3600 Average 9100 5344 3600 Coal Pile Leachate 505 505 505 Predicted based on conductivity measurement from an Upper B -Seam coal sample. • TR-64 2.05-74 09/09 i9 PPePavga