Remediating Acidic Mine Water
A Case Study Evaluating Green vs. Gray Infrastructure
Our site team was challenged with developing a sustainable, practical, natural infrastructure solution and creating a natural asset that does not require long-term operations and maintenance.
Senior Remediation Leader, Dow
As part of its 2025 Sustainability Goals, Dow is actively working to value ecosystem services and incorporate them in business decisions. This is an example of how making a business decision to incorporate green infrastructure – a limestone channel – created an opportunity for innovation that was good for business and better for ecosystems.
Acidic water with high levels of zinc was seeping from an abandoned mining site in Arkansas. Since the 1970s, the water in the creek has been diverted to a neutralization plant, where the water was treated before flowing into a lake. However, the goal was to restore water quality to the creek so it no longer had to be treated and diverted to the lake.
Dow constructed a sinuous channel lined with limestone, which added alkalinity to the seep water. The alkalinity raised pH and created an environment for lowering metals concentrations via biological processes within the channel. The result is a natural streambed with no operations and maintenance costs, and the mine seep water is treated before it enters the downstream creek.
The Dow team worked with the U.S. Army Corps of Engineers, the Arkansas Department of Environmental Quality and the County Soil Conservation District to re-establish and enhance a former water channel, which would ensure the least impact ecologically. Before lining the channel with the limestone riprap, several factors had to be weighed, including water chemistry, flow rates and contact time. The channel continues to be monitored and assessed.
Business and Environmental Value
This innovative solution has eliminated the need to construct a new and costly large-scale treatment system, or to operate the aging neutralization plant. Because the passive treatment doesn’t require power to operate, it also is less expensive to operate than the active treatment systems and emits fewer greenhouse gas emissions. In addition to improving water quality, the channel and wetland also supports wildlife.