2018-05-30_REVISION - M1983035 (3)

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Reclamation Unit: East cut faces. North of the currently eroded southeast corner is the former working face of the pit. Although the existing slope here is not bad(at 2.5:1), even if it was 3:1 it would not be acceptable due to the extensive erosion present on this face. Most of this erosion is produced by rain simply falling on the slope. Very little water flows over the top of the slopes. Therefore,the erosion certainly illustrates just how incredibly erodible the material mined actually is. This erosion is a problem in its own right, but the greatest problem is that the sediment and the flow collects in a broad area at the base of the slope and that prevents much vegetation from developing. This water then flows southward to the south basin in the southeast corner of the pit where it joins other runoff from the southeast corner. In fact, water and sediment from the east cut slopes has created a"river channel"that sometimes exhibits, at a small scale, the kind of flow patterns seen in much larger streams and rivers. Using a cut and fill approach on the cut face,the slope will be reduced to at least a 3:1 grade from the top of the slope to near the edge of the adjacent somewhat vegetated area. Thus,the crest of the current slope can be expanded a short ways further east to push that material over the cut slope. In any event, a low ridge of material will be left at the top of the slope to prevent water from flowing over the crest of the slope which could induce new erosion on the cut faces. This new slope will then be topsoiled with a minimum of 6 inches of soil taken from the eastern end of the North Berm. More depth can be used,but less than 6 inches will not provide sufficient water holding capacity in the soil to support good revegetation. Care should be exercised in creating the final graded slope prior to topsoiling that equipment such as a dozer run lengthwise along the slope rather than up and down the slope. This will produce a ridged surface parallel to the contours that the soil will bind to more readily. The slope, either before or after topsoiling will not be smoothed,but will remain rough so water falling on the slope doesn't immediately run down the slope but catches in small pockets and on the upside of ridges where it has time to soak into the soil rather than immediately running off. The degree of roughness should be around an inch or so of relief. Less than that is not very effective and more than that creates a bit too much ponding that can break through and start rill erosion. New rill erosion is likely to develop to some extent,but that can be limited by leaving a rough surface. This roughness will actually aid in the establishment of the grasses whereas a smooth slope will not keep enough water on the slope to percolate into the soil and be available for plant growth. The trick is to not encourage rill development by creating patterns where the water can get some velocity flowing down hill or develop large puddles that can breach and flow downhill. This grading and topsoiling will extend from near the north end of the east cut faces all the way to where it converges with the southeastern corner erosion correction area. In effect, the entire eastern Vollmer Pit Technical Revision June 2018 Updated Reclamation Plan Page 12 of 26