2019-12-06_HYDROLOGY - M1977342 - Laserfiche WebLink

Home Browse Search

2019 Reclamation Cost Estimate Update—Henderson Mine& Mill Following regrading, the disturbed area will be revegetated by the drill seed method and plants and trees will be planted across approximately 110 acres. 2.6 Mill Yard and Access Road The Mill Yard and Access Road will be regraded and reclaimed. As such, and following demolition of the Mill buildings and associated infrastructure (covered under the Mill Site Demo task), the Mill Yard and (site) Access Road will be regraded (approximately 182,000 cy and 60,000 cy, respectively) to blend with the adjacent terrain and to meet natural drainage patterns. Following regrading, the disturbed area of over 120 acres will be revegetated by the drill seed method and plants and trees will be planted. 2.7 East Branch, Horseshoe and Ute Creek Reservoirs The East Branch Reservoir is currently used for reclaim water storage, but it will be reclaimed after it is no longer needed for production operations and converted to a fresh water reservoir. Final reclamation will involve excavation of up to 20,000 cy of sediment. For all 3 reservoirs, it is anticipated that a nominal amount of maintenance fertilization will be required for the access roads to the facilities, approximately 5 acres total. 2.8 Tailing Deposition Area The TDA will be reclaimed when it is no longer required for production operations using a dry cover. The entire top surface will be capped and revegetated. The borrow areas, roads, and tailing dams will be regraded. Additional fill may be required for the tailing impoundment to account for any settlement. Rock armor will be placed over the embankment/dam area, as required. A new spillway will be excavated through native ground to the north which will drain to Ranger Gulch or down the left tailing dam abutment. The dry beach area will be capped with a minimum of 24 inches of cover material over 685 acres for a total of approximately 2,210,000 cy. The wet slimes and pond footprint area will be capped with a multi- layer system likely to include a geogrid layer under a minimum of 24 inches of cover material over 542 acres for a total of approximately 1,749,000 cy. The area will be hydroseeded and trees and shrubs will be planted. Additional reclamation tasks include the construction of an inlet structure for the new spillway and removal of the barge and its associated systems. Finally, diversion channels will be constructed to convey stormwater around and off the reclaimed top surface of the TDA. The diversion channels will include nonwoven geotextile and riprap liners. The Ultimate Canal will likely remain post closure to assist with the diversion of large stormwater events around the reclaimed TDA. 2.9 Main Gravel Pit below 1-Dam The gravel pit below 1-Dam will be reclaimed in accordance with a standard regrade, cover and revegetation approach. Regrading of the quarry will result in slopes no steeper than 2HAV with some areas considerably less steep, for a total of approximately 64,000 cy. This will be followed by the haulage and placement of approximately 15,000 cy of topsoil. Revegetation by drill seeding and the planting of trees and shrubs will occur over the 40-acre footprint. 2.10 Laydown Yard at Rectifier 6 The Laydown Yard at Rectifier 6 will be reclaimed in accordance with a standard regrade and revegetation approach. Regrading of the yard will require a total quantity of approximately 27,000 cy. This will be followed with revegetation of the regraded surface by drill seeding and the planting of trees and shrubs over the 5-acre footprint. 2.11 Mill Site Demolition Structures at the Mill site not to be used post mining will no longer be required during the post- reclamation period and will be demolished. These structures include the Primary Conveyor 2 (PC2)/PC3 Transfer Building, PC3/SC1 Transfer Building, Conveyor (Loci) Maintenance Shop, Tailing and 3 Dec 2019