Tuesday, September 10, 2024
3:45 PM - 4:15 PM
Far from "Boring" Pump Station

At a large former mining remediation site in East Tennessee, acidic, metal laden water seeps were noted at the base of a former mine tailings dam. The water from the seeps was found to contain high concentrations of iron and copper. As part of the initial remedial actions, a water collection system was installed to collect the water from the seeps at the toe of the tailings dam. Collected seep water was then transported via a pipeline into a 93-foot-deep borehole extending downgradient to a pump station several hundred feet away. During routine inspection of the seepage collection system in October 2020, water was observed backing up into the borehole, indicating the presence of an underground blockage that hindered the rate of the water flowing into the mine. To remedy this, a down-hole well pump was installed to convey water through an above grade HDPE pipeline to a water treatment facility. This was considered a temporary solution until a long term, permanent solution was identified. In December 2021, Barge prepared a feasibility study for the remedial alternatives for a permanent solution including installation of a new submersible pump station, additional bore holes and well pumps, installation of an angle boring within the mining system to allow flow by gravity to the existing pump station, and capping of the tailings area. The alternatives analysis considered factors such as feasibility, redundancy, constructability, storage and pumping capacity, reliability, and capital and O&M costs. Following the evaluation, it was decided to install a new submersible pump station upstream of the existing mine works to capture and convey the mine water directly to treatment. The project includes several interesting design features such as 8 hours of emergency storage capacity and dual force mains installed with cleanouts so that the pipes can be pressure blasted to remove scale build up, and expansion of new fiber optic SCADA communications. This presentation will review the history of the remedial actions taken place at the tailings site, review the alternatives analysis and reasonings for decision making, discuss the design features of the selected alternatives, discuss construction challenges, and view construction and final project photos.