Askam Borehole AMD Treatment System
During the course of operations, the Blue Coal Corporation mined much of the land within the 8.2 mi² Nanticoke Creek. When the company filed for bankruptcy, the mine workings were abandoned. Above ground, stripping pits and culm banks defaced the landscape. Below, underground shafts and tunnels became flooded. These conditions led not only to flooding of homes and businesses, but also to ongoing damage of the environment.
As discussed in the AMD overview, boreholes are one method of handling underground mine waters. The Askam Borehole, named after a nearby village in Hanover Township, was drilled by the Pennsylvania Department of Environmental Resources to relieve water pressure from a mine pool that was forcing groundwater to backup into homes. Although the flooding stopped, once the mine waters were discharged into the Nanticoke Creek, AMD resulted. These flowed downstream, polluting the stream and surrounding watershed.
In 1999, Earth Conservancy built a wetlands system across the road from the Askam Borehole to help mitigate the AMD pollution, and for nearly a decade it successfully mitigated the discharge. However, in 2008 the borehole collapsed. Localized flooding returned. In response, the U.S. Department of the Interior’s Office of Surface Mining drilled two new boreholes, both of which again released their effluent into the Nanticoke Creek.
With the Dundee Road Wetlands offline, EC sought a new solution to treat the AMD discharge. Previously, in its Section 206 – Ecosystem Restoration Report (2005) for the Nanticoke Creek watershed, completed with the Pennsylvania DEP, DEP’s Bureau of Abandoned Mine Reclamation, and the United States Army Corps of Engineers, EC had explored using an oxidizer for AMD mitigation. An oxidizer is a semi-passive treatment system, able to treat higher volumes of effluent more quickly and in a smaller space than a traditional wetlands. Contaminated water flows into a large, chambered unit in which it is injected with massive amounts of air. Strong turbulence results, so powerful that dissolved metals precipitate from the water. The water then exits into a settling pond divided by screening baffles, which continue to filter the iron, prior to the water’s release into a polishing cell and then back into the primary waterway. In light of the sitution, constructing an oxidizer below the boreholes seemed ideal. Construction of the new treatment system began in 2013, featuring a Maelstrom® oxidizer, and was completed in 2014. The project was supported by grants from the Pennsylvania DEP, the U.S. Department of the Interior’s Office of Surface Mining, and the Pennsylvania Association of Conservation Districts, and through EC’s own reserves. Approximately $950,000 was spent on the Askam project.
In 2015, EC received a grant from the PA Department of Community and Economic Development to add enhancements to the system, as well as support operations and maintenance costs. These included adding boulders below the boreholes to increase natural aeration of the water; increasing the height of the outlet to retain water longer; and adding a valve to allow draining of the pond to remove sludge buildup.
