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MMRR quarry DMG Adequacy Review Response Page <br />3/15/2005 <br />F). They are sized to convey the flows resulting from a 100-year recurrence interval storm. The <br />ditches will be generally excavated in non-erosive rock; in cases where they are excavated in <br />earth a riprap lining will be placed to prevent erosion. <br />Sediment Ponds <br />The sediment ponds were sized to contain the volume of runoff resulting from a storm having a <br />10- year recurrence interval. Pond A will capture flows from the Access Road and Staging Area. <br />Natural mnoff from the area north and east of the Access Road will be allowed to run over the <br />edge of the upper benches and will provide water to the vegetation on the benches. Water that is <br />not retained in the reclamation soils or consumed by evapotranspiration will discharge to the road <br />drainage system and Sediment Pond A. <br />Pond B will capture flows from the Waste Rock Pile and adjacent areas. Pond C will capture <br />flows from the processing area and pit floor. <br />Post Mining Drainage <br />Under reclaimed' conditions (Exhibit F), the sediment ponds will be backfilled and vegetated <br />following the establishment of vegetation on the benches, waste rock pile and other azeas to be <br />vegetated. Diversion ditches A and B will remain to convey runoff azound the waste rock pile <br />and across the pit floor, respectively. An additional ditch will be excavated in the easterly potion <br />of the pit to create a meandering channel for runoff from the area above the pit and the pit floor. <br />These channels will also be ephemeral. Post mining runoff volume and peak flows will be <br />similaz to pre mining conditions. <br />Slope Configuration and Drainage (Alan Sorensen Memo to Tom Schreiner, January 25 <br />2005). <br />Review Comments: <br />2. Cut Slopes in Access Road Corridor and Processing Area - <br />Exhibits C-2A, C-2B, C-2C and C-2D have been revised to reflect the inclusion of <br />benching in the cut slopes. The slopes and bench dimensions are based on the <br />recommendations in Exhibit 6.5, MMRR Quarry Rock Mechanics, May 12; 2004 by Dr. <br />John F. Abel, Jr. <br />4. Waste Rock Storase - <br />a) A note has been placed on Exhibits C-2A, C-2B and C-2C stating that the <br />Waste Rock Pile footprint will be stripped of soil, vegetation and snow or <br />ice down to stable bedrock prior to placing waste rock. The useable soil <br />will be stockpiled for use in revegetation. A geotechnical investigation <br />will be completed before waste rock placement to determine slope stability. <br />Benching of the subgrade will be completed if required for waste rock pile <br />stability. <br />b) An underdrain constructed of poorly graded rock will be placed in the <br />thalweg of the ephemeral drainage following clearing and prior to <br />placement of waste rock. The rock will consist of shot rock having a <br />