2012-02-16_REVISION - M2002020 (9)

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pit bottom along the toe of the pit side slope, plus 0.0015 ft /day (5 x 10 -7 cm/sec) multiplied by the area of the bottom of the liner system or natural bedrock bounded by the perimeter wall. The performance standard shall be three times the design standard and shall be applied to an initial test of competency of the liner, as well as to the ongoing operation of the reservoir. The initial test will include a water balance analysis to demonstrate that the balance of the inflows and outflows equals the change in storage volume over a minimum of a 90 -day period. Reclamation Measures /Materials Handling Reservoir slopes left by the mining operation will be reclaimed to at least 3H:1V final grade. Major backfilling will not be required since the mine cell side slopes will be excavated at approximately 3H:1 V during mining. Final reclamation by covering slopes above the expected reservoir water level with topsoil and revegetating will follow excavation operations closely to minimize the amount of disturbance at any one time. Since backfilling for the NE and SE pond reclamation will be concurrent with mining, non- marketable material, overburden, and topsoil excavated during mining will be used almost immediately. Scrapers or haul trucks will be used to transport non - marketable and other backfill material to the NE Pond and SE Pond shorelines. Temporary stockpiles will be created along the shorelines and when sufficient material is available in the stockpile, the material will be backfilled into the previously mined areas. Once the slurry wall is constructed, additional grading of the reservoir slopes and top of bank may be performed. Prior to grading, topsoil shall be removed and stockpiled for later use. During final grading of the reservoir, trees and shrubs near the slurry wall will be removed to protect the integrity of the barrier. During reclamation activities, inlet and outlet works for the new reservoir may be installed. If constructed prior to final release of the 25 Avenue Site MLRB permit, the design specifications and plans for the facilities will be provided to the Division prior to construction. 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 slurry wall construction, backfilling, grading, and topsoiling have been completed. There will not be known toxic or hazardous materials in the slurry wall or 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. Topsoil and Revegetation Re- vegetation will only include grass seeding of disturbed areas. No tree or shrub planting is planned. Where required, topsoil will be replaced to a depth of two inches or greater. Due to the site geology and previous mining activities, topsoil at the site is very scarce. Topsoil will be placed after slurry wall construction, backfilling, and final grading of the site is completed. As the area is reclaimed, runoff or excess water from adjacent areas will not be allowed to flow over slopes being graded and seeded. If needed, berms or channels will be constructed to divert excess water and dispose of it in a safe and non - erosive manner. Greeley 25' Avenue Site DRMS 112 Permit Amendment Application Page 12