Laserfiche WebLink
Materials Handling - Backfilling <br /> The pit floor will receive only enough backfill to create final grading for drainage and to <br /> establish a growth medium for revegetation. The pit slopes will require backfilling to achieve <br /> final reclaimed slopes of at least 31-1:1 V (see Exhibit F, Reclamation Plan Map). Because of the <br /> pit size and possible limited overburden, it may not be possible to achieve complete side slope <br /> reclamation by backfilling with available overburden material. In addition to the side slopes, <br /> overburden material may also be required to cover the pit floor for drainage grading and to <br /> establish a vegetation growth medium. The result is, depending upon the amount of overburden <br /> material recovered and available for reclamation, side slope backfilling may need to be enhanced <br /> with an initial "cut and fill" of the near vertical side slopes (see Exhibit F, Reclamation Plan <br /> Map). The degree of "cut and fill" required, if any, will be determined during mining as <br /> overburden material quantities and pit depths are verified. <br /> Materials Handling - Grading <br /> The 31-1:1 V pit side slopes will be graded to transition into the relatively flat pit floor. Grading of <br /> the pit floor may leave a subtle rolling topography rather than a completely flat bottom <br /> depending on varying depths of the sand and gravel deposit. The variations in topography will <br /> not create water catchment areas, but shall be graded to drain freely. The gentle slope of the <br /> topography will control water flow and create a variety of microenvironments for vegetation <br /> growth. <br /> The side slopes will also not be graded smooth, but will contain a low profile ridging pattern that <br /> follows the contour. Final grading that leaves this type of ridging pattern helps to capture water <br /> for plant growth as well as reduce the velocity of runoff and slope erosion. On these slopes, <br /> erosion may present a maintenance issue for the first year or two of revegetation if there are large <br /> drenching thunderstorms, but more normal low intensity thunderstorms should not create more <br /> than minor rilling. <br /> Blending of the pit into the Lone Tree Creek drainage will be important to prevent pooling of <br /> water in the pit bottom and to avoid creating a steep slope at the pit edge that encourages erosion. <br /> The final grading of this transition area will blend the topographic contouring from the pit floor <br /> with the undisturbed topography beyond the pit edge. Some of this transition area will involve <br /> lowering the high, steep embankment associated with the incised creek channel, while other <br /> areas will transition into lower terraces that separate the mine excavation from the ephemeral <br /> channel (see Exhibit F, Reclamation Plan Map). <br /> All backfilling and grading will be done to stabilize the material and control erosion. Final <br /> grading and seeding will be done as soon as possible after backfilling, grading, and topsoiling <br /> have been completed. There will not be known toxic or hazardous materials in the backfill <br /> material. The reclamation will not leave high walls on the property. In addition, there will be no <br /> auger holes, excavations, or shafts left on the property. <br /> Carr Pit East <br /> DRMS 112 Permit Application Page 12 <br />