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• 2.05.6 <br />r1 <br />U <br /> <br />PR-OS <br />/9 IPRov~ <br />Y/z5/a3 <br />As stated in section 2.04.7, if continuous mine discharge occurs, the effluent <br />will be piped over or around the Deer Trail Ditch and the Fire Mountain Canal <br />to avoid any potential quality degradation. At a continuous mine discharge <br />rate of 175 gallons per minute, the Deer Trail Ditch would take on the <br />characteristics ofmine water. As demonstrated above the degradation to the <br />Fire Mountain Canal is not significant. <br />If continuous mine discharge occurs from either the B-Seam or D-Seam, the <br />operator will construct a pipeline from the mine portals to convey mine water <br />to D Gulch, outfall 006. The mine water will be treated in underground <br />sumps so no outside settling ponds will be required. D Gulch is a well <br />defined ephemeral channel that drains into the North Fork of the Gunnison <br />River. The predominant vegetation in the ephemeral channel is oak brush. <br />The Deer Tail Ditch is piped under D-Gulch and there is an undershot in D <br />Gulch for the Fire Mountain Canal. Therefore, no structures are required to <br />keep mine water out on the irrigation structures. Furthermore, D Gulch's well <br />defined ephemeral channel will assure the mine water has no impact on <br />water users, the alluvial valley floor or prime farmland, if any, after if leaves <br />the mine property but before it enters the North Fork of the Gunnison River. <br />The mine water will be contained in the D Gulch channel so it will not effect <br />or come in contact with irrigation water for adjacent lands. <br />Leachate from the proposed refuse and coal stockpile could also degrade <br />the water quality of the river. The proposed refuse and coal pile will <br />encompass 5.5 and 4.9 acres at full capacity respectively. Based on the <br />geochemical analysis presented in Volume III, Exhibit 6, the average <br />conductivity of the roof, interburden and floor samples is 4,263 and coal is <br />810 umhos/cm. According to Section 2.04.8 the average annual rainfall in <br />the area is 18.5 inches. If all of this rainfall percolated through the piles <br />during the year, the equivalent flow would be 10 gallons per minute. In its <br />Cumulative Hydrologic Impact Study for the North Fork of the Gunnison <br />dated September 25, 1992, the DMG assumed infiltration through a refuse <br />pile is the result of snowmelt and it was estimated 2.8 inches per year would <br />infiltrate during a 60 day period. The equivalent flow for this assumption over <br />the 10.4 acre piles is 9 gallons per minute over the 60 day period. The two <br />different leachate production estimates produce similar equivalent flow <br />values. However, based on the estimated equivalent flow figures, leachate <br />production and associated potential degradation is insignificant compared to <br />the potential degradation from mine water discharge. <br />Alluvial wells AW-1 through AW-6 were installed to monitor groundwater <br />contamination. AW-1, AW-2 and AW-3 are near the coal stockpile and AW- <br />4, AW-5 and AW-6 are near the gob pile. The water quality in the wells is <br />2.05 - 74 - 07/03 <br />