The guiding documents for Pit management require ongoing assessment and evaluation of the Horseshoe Bend Water Treatment Plant and the technology used to treat contaminated Pit water until several years prior to full-scale implementation. That implementation is required when water levels at any monitoring compliance point reach the Critical Level of 5,410 feet above sea level.
A review of treatment technologies is required 4 years before any compliance point is projected to reach the Critical Level. Current projections show that the Critical Level will be reached in 2023; therefore the technology review will start in 2017 and must be completed by 2019. AR and Montana Resources are already evaluating treatment alternatives, and this work will continue through 2017. This includes treatability studies and testing on the expected quantity and quality of contaminated water. Construction upgrades are scheduled for 2019 through 2021, with upgrades completed at least 2 years before the Critical Level is reached.