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Recommended Actions: <br /> (1) During active mining: <br /> (1) Establish and maintain a setback from permit/property boundaries and ALL <br /> stockpiles of any type to the top of highwalls during mining: <br /> (a) 20 feet from north and east boundaries, including from two power poles on <br /> north side. <br /> (b) 5 feet from south boundary. <br /> (c) 10 feet from stockpiles (earth, materials, construction rubble, tires, metal, etc.) if <br /> highwall is 20 feet or higher. <br /> (2) Clearly mark limits with stakes and lathe and maintain those markers at all times <br /> until reclamation is complete. <br /> (3) Limit highwalls to vertical heights of 40 feet with minimum bench widths of 20 feet. <br /> (4) Mine by lot (block), to allow reclamation including final slopes to be achieved <br /> during active mining operations on as much of the affected area as possible. <br /> (5) Establish drainage swale between top of highwalls and permit/property boundary <br /> to prevent runon of storm water down highwalls and reclaimed slopes. <br /> (6) Integrate inspection of top of highwalls and slopes as part of storm water <br /> inspections, including: <br /> (a) Inspection of buttressed slope for minimum of 12 months, including standard <br /> MSHA techniques for evaluating highwalls, weekly and following precipitation <br /> events, and quarterly and annual inspection by professional engineer. <br /> (b) Repair slope as necessary, including use of geomembrane reinforcement and <br /> replacement of soil, reseeding. <br /> (c) Documentation of inspection and repairs (photography and written reports). <br /> (2) During reclamation: <br /> (1) Reclaim final slopes to 1:1 maximum unless engineered retaining walls or other <br /> features are used (in selected areas) to permit steeper grades. (NOTE: DRMS may <br /> require review of engineer's design of retaining walls or other features in advance.) <br /> (2) Bring lower benches to final grade as much as possible first (before upper benches), <br /> and at minimum, provide initial buttressing (to 0.5H:IV) for lower bench before <br /> backfilling upper bench. <br /> (3) Buttress toe of highwalls on floor and bench with larger boulders, concrete rubble, <br /> and other clean fill materials to protect toe during backfilling and compaction. <br /> (4) Backfill lower bench (to height 40 feet above final floor elevation) with selected <br /> engineered fill (excavated and recompacted Lewis shale with other imported <br /> materials including concrete and asphalt rubble). <br /> (5) Compact backfill to 90% standard Proctor density at optimal moisture content <br /> (OMC), at a 1:1 to 0.5:1 slope, before placement of soil, recommended 12-inch lifts <br /> compacted to 6-inch in-place final thickness. 1 compaction test per 10,000 CY of <br /> backfill (not counting large boulders/rubble). <br /> (6) Backfill of upper bench (to height 80 feet above final floor elevation), after backfill <br /> of lower bench. <br /> (7) Revegetate with selected seed mix to 90% potential ground cover, including <br /> seeding with hydromulch, and reseeding as required, including selected transplant <br /> of mature specimens of local native shrubs. <br /> (8) Use selected soil amendments and other soil stabilization techniques during initial <br /> Technical Revision to M1985-001 J&J Pit, LaPlata County, dated 24 AUG 2016 Page 28 <br />