Strategic Approaches to Address the Unique Challenges of Groundwater Remediation at Coal Ash Facilities

摘要

The need to evaluate groundwater remediation options in conjunction with closure of coal ash impoundments is becoming more important as Coal Combustion Residuals (CCR) Rule corrective action deadlines approach. While traditional technologies, including barrier walls, grout curtains, pump and treat, and permeable reactive barriers are being considered, the nature of coal ash impoundments requires modification of typical approaches for these technologies to be technically feasible and cost effective. Specifically, coal ash impoundments often have large surface areas and long perimeters. They are typically located adjacent to space-constraining surface water bodies, where discharge of groundwater may also need to be addressed. Also, groundwater impacts may include a mix of inorganic constituents that require different treatment approaches. Here, characterization and design concepts adapted to address these technical and logistical challenges are explored. The scale of groundwater impacts might render typical designs for pump and treat and permeable reactive barrier approaches infeasible or cost prohibitive. Strategies to improve efficiency and feasibility of these approaches include mass flux-based characterization and design, segregation of clean and impacted water, and passive water collection and treatment techniques. Case studies from other industries are used to demonstrate how a focus on mass flux was used to improve efficiency and how approaches for segregating, managing and treating water via techniques such as groundwater diversions, drainage swales, covers, and permeable reactive barriers were used to address sites with COCs such as arsenic. Finally, the use of an innovative passive monitoring device (Min-Trap~(TM)) to quantify the potential for natural and enhanced in situ mineral precipitation and/or transformation will be discussed.