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- Mid-Continent <br /> As indicated by the permit, the precipitation event exemption limitations were <br /> determined applicable to Outfall 016 in recognition of the commingling of surface <br /> discharges with mine water. <br /> PERMIT LIMITATIONS AND CONDITIONS <br /> Outfall 016 originally was for surface rainfall event discharges; since the amendment <br /> of 511311987, mine water from the Dutch Creek No. 1 Mine can also be diverted into <br /> the Rock Tunnel sedimentation ponds. <br /> It remains the case that discharge from the underground workings of the mine is <br /> commingled with surface runoff which flows into the pond series above Outfall 016. <br /> The sources of the runoff are an area of surface mining disturbance, the rock tu,nnel <br /> waste disposal area, Known as the waste pile, (Area C of the illustration); and an <br /> undisturbed area immediately south of the ponds (Area A of the illustration). <br /> The rock tunnel waste disposal area (Area C on the illustration), known as the waste <br /> pile, is directly uphill from the pond series. This is an area of ongoing activity, which has <br /> not yet reached capacity. For that reason, it has not been reclaimed or re-seeded. The <br /> ponds were placed to catch runoff from this area of surface disturbance, for sediment <br /> control. <br /> The outslopes of the waste pile are approximately 26 1/20, situated at an elevation of <br /> approximately 8600'. It is surrounded by steep mountain terrain which shades the area <br /> during winter. The result is heavy snowpack and heavy runoff. Runoff during rainstorms <br /> is also rapid. Drainage flows from the pile directly to the ponds, and also flows into <br /> the drainage ditch which parallels the waste pile area and carries mine discharge water <br /> to the sediment ponds. Runoff from the waste pile commingles with mine drainage in <br /> the ditch and in the ponds. <br /> South of the ponds is an undisturbed area (Area A of the illustration) of steep slopes, <br /> averaging 400. Runoff from this area goes directly into the ponds. Because of the <br /> steep slopes, the area is not well vegetated, and the natural runoff from this <br /> undisturbed area tends to be sediment lac,en. <br /> The slopes are north facing, with elevations of 8700' to 9100'. Snowpack is significant <br /> here, and this is an avalanche urea. Avalanches carry significant amounts of sediment. <br /> The avalanche paths run directly to the ponds or uphill of the pond areas, so sediment <br /> is deposited directly in or drains into the ponds. <br /> Uphill from both the waste pile and Area A (Area B of the illustration) is a natural area of <br /> steep slopes, averaging 400. An interceptor ditch prevents runoff from this area <br /> reaching the disturbed area of the waste pile and carries this water to Dutch Creek. <br /> However, this is also a north facing slope at high elevations, ranging from 8600 to <br /> 9150', which experiences snow accumulations and avalanching. <br /> 3 <br />