2019-01-09_PERMIT FILE - M2019001 (3)

Home Browse Search

Materials Handling - Backfilling It is estimated that approximately one million cubic yards (cyds) of combined topsoil and overburden will be available for backfilling. At the southern end of the site, the pit will be backfilled to existing grade, or approximately 5570 amsl (see Exhibit F, Reclamation Plan Map). From the southern end, backfilling the pit to an approximate elevation of 5570 amsl will continue north until the top of the backfill elevation matches grade with the bottom of the mined-out pit. With the north to south pre-mining ground surface grade of about 0.7-0.8 percent, and backfilling the south end of the pit to create a near flat (0.1 percent) final backfill surface grade, this will occur approximately 1,500 feet north of the southern proposed permit boundary and require less than 0.5 million cyds of backfill. The remainder of the pit floor to the north will receive only enough overburden backfill to establish a growth medium for revegetation. The pit slopes in the northern portion of the site, and any others not previously backfilled, will be backfilled to achieve final reclaimed slopes of 3H:1 V or flatter (see Exhibit F, Reclamation Plan Map). Backfilling of the pit and side slopes as described will place the material necessary to grade the site for vegetation growth and drainage. Materials Handling - Grading Blending of the pit into the natural drainage will be important to prevent pooling of water in the pit bottom. The backfilled southern portion of the pit will be graded to let stormwater flow freely through the reclaimed site. The final grading will blend the topographic contouring from the pit floor with the undisturbed topography south of the site. Where 3H:1 V pit side slopes exist, they will be graded to transition into the relatively flat pit floor gradually, avoiding a sharp slope break that could encourage erosion. Grading of the pit floor may leave a subtle rolling topography rather than a completely flat bottom depending on varying depths of the sand and gravel deposit. The variations in topography will not create water catchment areas, but shall be graded to drain freely. The gentle slope of the topography will control water flow and create a variety of microenvironments for vegetation growth. The side slopes will also not be graded smooth, but will contain a low profile ridging pattern that follows the contour. Final grading that leaves this type of ridging pattern helps to capture water for plant growth as well as reduce the velocity of runoff and slope erosion. On these slopes, erosion may present a maintenance issue for the first year or two of revegetation if there are large, drenching thunderstorms, but more normal low intensity thunderstorms should not create more than minor rilling. All backfilling and grading will be done to stabilize the material and control erosion. Final grading and seeding will be done as soon as possible after backfilling, grading, and topsoiling have been completed. There will not be known toxic or hazardous materials in the backfill material. The reclamation will not leave high walls on the property. In addition, there will be no auger holes, excavations, or shafts left on the property. Lazy Two Pit DRMS 112 Permit Application Page 11