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Case Study: Passive treatment at Elizabeth Mine in Strafford, Vermont
Citation:
Butler, B. AND L. Dunnington. Case Study: Passive treatment at Elizabeth Mine in Strafford, Vermont. MINEXCHANGE 2025 SME Annual Conference & Expo, Denver, CO, February 23 - 26, 2025.
Impact/Purpose:
The Elizabeth Mine's passive treatment system treats iron in leachate from a remediated tailings facility. Field iron measurements at each component part of the treatment system have been monitored over time, along with flows and other water chemistry data. Since 2022, complete data has been collected monthly. Previous to other actions at the Superfund site there was environmental impacts to the local waterbodies. Combined with prior actions and treatment of the leachate (formerly by an active system), a stream on the impaired list has been removed. The system consistently meets the water quality criterion for iron at the compliance point. Consistent and longer-term monitoring of passive treatment systems is rare. Seasonal trends have been observed in the performances of each of the components in the system and monitoring is allowing assessment of longevity prior to when it will need maintenance (all passive systems eventually require maintenance). Understanding different passive treatment units is of interest to all remediation practitioners who use or want to consider using these systems, including RPMs, states, local governments, NGOs, academic researchers and site operators.
Description:
This is an abstract for the Feb 2025 SME conference. The passive system at Elizabeth Mine has been in operation since 2019 and treats iron from a tailings facility. The system comprises an anoxic limestone drain, settling pond, vertical flow pond, and two wetlands. To understand each components’ contribution to removal of iron, sampling has been conducted at the effluent of each component. A program through the Office of Land and Emergency Management has enabled consistent monthly sampling since May 2022. Sampling includes field iron, flows, water quality parameters, and laboratory metals analyses. Seasonal data trends and lessons learned to date will be presented.