2018-02-06_REVISION - M1982090 - Laserfiche WebLink

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B. PHASE 1: PREVENT EROSION OF HISTORIC TAILINGS Phase 1 Task 1: Obtain restoration materials. Description: Estimate the type, quantity and source of restoration materials required by the project. These materials include but may not be limited to:topsoil, hydro mulch, rip-rap,cover material and road improvement media (if necessary). Some rip-rap may be obtained from the United States Mountain rock slide area along County Road 361. If the United States Mountain source is to be used, improve the approximately 0.5-mile- long, 4-wheel drive road between the tailings cells (^'9,800 ft. elev.) and the rock slide (^'10,500 ft. elev.) and use the road to transport a limited amount of rip-rap from the rock slide down to the removal area using off road haul trucks. Maintain traffic control and public safety on the road during construction and use. Public traffic may be diverted to the nearby logging road during the road improvement and use. County Road 361 will not be improved nor used if suitable alternative source(s)of rip rap and cover material are identified. Access: Portions of County Road 361 pass through United States Forest Service (USFS) lands. Input and/or access from both Ouray County and USFS will be required prior to initiating road improvements. Timeline: The road improvements, if necessary, may be initiated during spring and early summer of 2018 ideally before the road to Imogene Pass is re-opened. Use of the road for transport of rip-rap materials, if necessary, would continue into the 2018 construction season. Deliverables Due Dates DRAFT estimation of type, quantity and source of restoration materials. 15 days after ratification FINAL estimation of type, quantity and source of restoration materials. May 1, 2018 DRAFT map of proposed road improvements (if necessary). May 1, 2018 DRAFT Traffic Control and Safety Plan (if necessary). May 1, 2018 FINAL map of proposed road improvements (if necessary). June 1, 2018 FINAL Traffic Control and Safety Plan (if necessary). June 1, 2018 Phase 1 Task 2: Stabilize the downstream historic tailings cell. Description: The downstream tailings cell is located on the southeast side of Canyon Creek, is uncapped and is bisected by a north-south trending side channel ("bisecting channel") that flows into Canyon Creek. Construct a new drainage channel along the southern perimeter of the tailings cell to capture and divert runoff and sheet flow above the tailings cell. Excavate the upper portion (approximately one-fourth) of the tailings east of the bisecting channel, and place into the void of the bisecting channel. Continue the constructed channel down gradient onto the newly exposed native slope, and around the newly formed southeast slope of the tailings cell. Direct flows of the constructed channel into the natural perennial drainage east of the tailings cell. Regrade oversteepened portions of the remaining slopes and fill any remaining void of the bisecting channel with waste materials generated from the Site. Armor the constructed channel, and design and construct erosion control features across the entire disturbed and uncapped areas. Cover the entire disturbed and uncovered areas on either side of side channel with hydro mulch,topsoil and/or compost. Establish vegetation as needed to stabilize all exposed areas. Timeline:The excavation,grading, erosion control, capping and revegetation is anticipated to begin in 2017 and to be completed during the 2018 construction season. Notes: A portion of this area is on USFS property. Input and/or access from USFS will be required prior to initiating task. Deliverables Due Dates DRAFT design of excavation, grading, erosion control and restoration features. _ 15 days after ratification FINAL design of excavation, grading, erosion control and restoration features. 30 days after ratification Construction completion. October 1, 2018 Page 3 of 5