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be left at the bottom of the pit underwater. This is more than any other pit has committed to in <br />order to avoid any problem with selenium. <br />2. Groundwater <br />The site mines an alluvial sand and gravel deposit from the Cretaceous age formed on a bend of <br />the Uncompahgre River. The alluvium is relatively shallow (less than 60 feet thick) and is <br />underlain by Mancos Shale. <br />Since the pit is on the second terrace of the Uncompahgre River, groundwater levels are not <br />close to the surface. Mining experience has shown that water levels aze approximately 2 feet <br />below the current mining surface, or an average of 30 feet below the original surface. <br />The mining below the water table for the 2006 Amendment will take place with no numning. <br />The mining will be done with equipment such as a track hoe placed on the current surface and <br />excavating the gravel that it can reach, which is estimated to be approximately 26 feet lower. By <br />doing this, United will leave some gravel (more than 5 feet) that is out of the reach of the <br />equipment. The gravel reserve will be diminished but this method will ensure that there is no <br />drop in the groundwater level due to pumping, which will ensure the protection of the wetlands, <br />ponds, riparian areas which exist to the east of the permit area on the lower river terrace and also <br />the well which exists to the north of the northeast corner of the permit azea on the Kuijvenhoven <br />property. <br />There are no wells which aze within 600 feet of the excavations below the water surface, <br />although there is a well (Kuijvenhoven) within 600 feet of the permit boundary. This well can be <br />seen on all maps to the north of the northeast corner of the permit azea. As stated above, the fact <br />that no pumping will take place will result in no water drawdown. If no water drawdown occurs, <br />there is no threat to drawdown of this well. <br />Colona Pit November 06 G-3 <br />