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SEDIMENT CONTROL RESPONSES <br />• 1) The access road drainage system which will be built next to the proposed access <br />road is shown on the Pase IV and V diagram (LWP-022 through LWP-006). The <br />drainage system will be 2 feet deep with 3:1 side slopes. The ditch was designed <br />to handle the 100 year design flow. Flows will either be routed to Sylvester <br />Gulch Road or to a new culvert installed at the west end of the new access road. <br />This culvert is sized to be 24 inches in diameter. The design velocities and <br />depths for the access road ditch is shown on the revised Table 6.5 which is <br />included with our response. The ditch will not have a slope steeper than 10% <br />along its entire length of the new access road. The access road also will be <br />cross loped at a 1% grade so that water collecting on the road will drain into <br />the ditch as shown on the access road cross-sections (Figure LWP-018). <br />2) Sylvester Gulch Road will be cross-sloped along its length towards the sediment <br />control ditch system as shown on the Sylvester Road cross-sections (Figures <br />LWP-002 through LWP-006). <br />3) The location of all drainage systems along State Highway 133 in the area of the <br />refuse pile have been shown on the five phase diagrams (Figures LWP-002 <br />through LWP-006). <br />4) The proposed Sylvester Gulch Road will be retained until the end of the life of <br />the mine. The Mt. Gunnison No. 1 Mine main mine fan is located in Sylvester <br />Gulch and access to this facility is necessary to the operation. The terrace and <br />top of the pile will be blocked from vehicular traffic upon completion of <br />reclamation operations by placing a berm or rock barrier eccross access points. <br />The collection ditch at the toe of the pile will be maintained until reclamation <br />bond release. We feel that having the Sylvester Gulch Road adjacent to the <br />collection ditch will facilitate the maintenance of the ditch during the life of the <br />mine. Placing a rock barrier or berm between the ditch and road will make it <br />virtually impossible to clean the collection ditch. It has been our experience at <br />the Mt. Gunnison Mine site that almost all ditches, including shortcrete lined <br />ditches, require cleaning from time to time. At the end of the life of the mine, <br />a berm will be placed between the road and the ditch. <br />5) The sediment control and clear water ditches around the topsoil and subsoil <br />stockpile areas are shown on the Phases I through V diagrams. Tables 6.1 and 6.5 <br />have been updated to include the flows from the topsoil and subsoil stockpile <br />areas. These tables show the ditch design for all five phases. Table 6.6 shows <br />the effects of the topsoil and subsoil stockpiles on the sedimentation basin for all <br />five phases. The table states the elevation at which the sedimentation basin <br />needs to be cleaned out and maximum water levels permissible. Table 6.4 has <br />been updated to include the 25-year flows from the subsoil and topsoil stockpiles. <br />The new 25-year maximum discharge is approximately 16 cfs. The current outlet <br />structure for this pond at an elevation of 1.5 feet below the top elevation of the <br />dam can dischaRGe approximately 16.5 efs. Therefore, the outlet work meets <br />all required sandards. <br />• <br />