Contractors with the Environmental Protection Agency will being work this summer on a repository north of Silverton to permanently store waste removed from mines within the Bonita Peak Mining District Superfund site.
The site, located near the Mayflower on County Road 2, will provide a final resting place for sludge removed from the drainage of the Gold King Mine as well as solid waste from the other 47 mines in the district. It will have a capacity of 375,000 cubic yards within its three stages, with an estimated life span of 60-80 years.
The repository will address one major challenge facing cleanup operations. While water from acid mine drainage can be treated, solid waste can be more difficult to deal with. It must be contained so that it isn’t moved into waterways and covered so that precipitation does not percolate through it. The repository will address both those issues.
Currently, the Gladstone Interim Water Treatment Plant, which was built immediately after the 2015 Gold King Mine Spill, is treating that mine’s drainage and producing 4,600 to 6,000 cubic yards per year of sludge that contains heavy metals. And space is running out.
In accordance with a 2021 Interim Record of Decision, the EPA now has a plan to construct the permanent storage facility.
In accordance with the public’s wishes, the agency selected a site that has already been contaminated by mine waste. It considered four tailings impoundments near the Mayflower Mill and selected Impoundment 4 because of its size and distance from the historic mill.
Phase 1 of the project will include a 40,000-cubic-yard impoundment for sludge and a pond to catch water that has leached through the sludge.
Phases 2 and 3 will add an additional 335,000 of repository space for dry waste, which may be stacked above the edge of the cell’s berm, depending on pending testing. The system will also include multiple liners, a leak detection system and groundwater monitoring.
The estimated life span of the repository may change depending on if and how waste drying systems improve and how much waste from sites other than the Gladstone Interim Water Treatment Plant is added to the cells.
Construction on Phase 1 is expected to begin this summer and will continue through the fall.
rschafir@durangoherald.com
