Gilt Edge Mine Superfund Site, Lawrence County, South Dakota

Overview

HGL, with wholly owned subsidiary Spectrum, is implementing an interim remedial action, including long-term remedial action, and conducting remedial construction at the Gilt Edge Mine Superfund Site, a 360-acre former open pit and cyanide heap-leach gold mine. Mining operations produced acid rock drainage with high metals content, which is treated by a high-density sludge water treatment plant. HGL and Spectrum operate the plant, manage waste sludge, monitor and maintain the facility and grounds, maintain the water balance in multiple capture systems to prevent releases, and conduct remedial construction to support remedy implementation efforts for area surface water and groundwater.

Project Highlights
Implemented an interim remedial action for the operation and maintenance of acid rock drainage treatment system and management of capture ponds and pump backs.
Provided engineering support for and constructed automation upgrades, including a 40-foot communication tower, to allow through a SCADA (supervisory control and data acquisition) system real-time monitoring and on-demand pumping of remote capture systems to prevent releases.
Treated and discharged 180 million gallons of groundwater while operating at 99% on-stream efficiency.
Completed system automation upgrades that eliminated the need for a night shift, reducing labor costs.