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Section 7.0. Sediment Control System for Operation <br />The permit area is basically divided into 2 areas, the eastern area that contains significant pre -law <br />disturbance and the western area, which has only begun to be excavated. The eastern area primarily <br />drains to the Plant Settling Pond and the Plant Infiltration Pond. There are other numerous piles and <br />valleys which trap runoff and infiltrate it into the ground. Due to the extremely porous nature of the <br />gravel, the numerous depressions and the 2 main ponds present in this area, there has never been a <br />problem with disturbed area runoff leaving the site. For this reason, no new sediment control facili- <br />ties are planned for this area. <br />For the western portion of the permit, a system of two collection ditches and one mine sediment <br />pond will be installed to trap runoff and provide 24 hour detention time. As shown on Map C -2, Col- <br />lection Ditch #1 will be along the northwest perimeter of the disturbance and will parallel Sacra- <br />mento Creek and then turn east to the Sediment Pond. Collection Ditch #2 will deliver disturbed area <br />runoff from the north portion of the permit area. The ditches will be constructed of the existing site <br />gravel, which is very porous and it is likely that runoff water will never even reach the pond, since it <br />will infiltrate into the ground rapidly, as it does in other areas of the permit. <br />The pond will be constructed to contain the 100 year event from the disturbed drainage area, thus <br />eliminating the need for a discharge permit. The pond will also be entirely incised and its bottom will <br />be the same porous gravel that allows significant infiltration. Map C -2 shows a maximum drainage <br />area that will enter the pond of 33.40 acres. <br />A CN of 60 is assigned to the gravel since it is nearly void of fines and almost all runoff penetrates <br />into the ground very rapidly. Once the mining pit moves into the area, all runoff will enter the pit, but <br />the sediment system of the pond and the two ditches will be left in place until the site is reclaimed. <br />The calculations to demonstrate that this pond is adequate to contain the 100 year 24 hour event are <br />shown below: <br />Gloria Z Mine 2013 Amendment 18 <br />