Design-Build Remediation System for Coal Ash Pit
A national energy company has a comprehensive environmental remediation strategy to address the impacts of historic coal fly ash disposal. The approach at a former coal ash placement pit was expanded to include a new groundwater extraction (GWE) system to prevent impacted groundwater from migrating to nearby residential communities.
GES designed the system, prepared the equipment specifications, obtained the necessary permits, provided oversight of the piping installation and building construction, and installed the GWE equipment, monitoring equipment, and system control panel. Following system startup, GES has continued to perform operation, maintenance, and monitoring (OM&M) activities and monitor performance.
The system, housed in a fabricated metal structure, is capable of processing up to 175 gallons per minute from up to five extraction wells, with water discharged through a 1,700-foot line to engineered passive treatment ponds and then to an on-site manmade wetland. The discharge line was installed using horizontal directional drilling (HDD), which offered significant cost, safety, and logistical advantages to standard installation via pipe trenching. Green features include solar-powered wireless transmitters that send outputs from pond transducers to the GWE building. Advanced telemetry and system controls enable remote monitoring and management of variable groundwater levels and flow rates.
The cost-effective design reduces long-term OM&M costs with built-in redundancies and adaptability to changing site conditions. System design and installation strategies significantly lowered the construction and ongoing operational costs while offering operational advantages. The use of HDD for line installation was clearly the safer, more economical, and less disruptive approach, shaving time from the system construction work plan. The installed system maintains hydraulic control of the on-site plumes, with reduced labor requirements and increased responsiveness gained from automated capabilities.