In 2015 the EPA mandated the regulation and management of Coal Combustion Residuals (CCR) from electric utilities. This rule led to impoundment closures at coal-fired power plants all over the country.
These impoundment closure projects consist of three basic components; design, dewatering, and construction. These components are challenging in that there are unknown variables that can lead to change orders and cost overruns. Engineering these components correctly throughout the closure process can reduce the Owner's risk. To complete closure designs, good background data collection for the impoundments is required. The proper approach and institutional knowledge of the site lead to the success of the dewatering component.
Impoundment closures are water management projects until dewatering is completed, at which point they become heavy construction projects. The dewatering aspect of the project can be a time consuming but an important part of the project from an efficiency and safety perspective. Once dewatering is completed and construction begins there are many moving parts; grading CCR materials and soils, water management, geomembrane capping materials, vegetation growth, etc., that can create logistical challenges.
This talk will discuss these challenges from the perspective of the owner and the engineer, the process to successfully complete the closure, the lessons learned during the process, as well as provide insight to the valuable experience the project team gained while working through these challenges. We will discuss the contractor selection and construction process used for two projects, that combined, are approximately 300 acres of impoundment closure. As with all projects, getting started and working together can be a challenge and these projects are no different.
The talk will discuss the engineering for construction support as site conditions changed when dewatering began, and the adjustments made. In addition, different material properties were discovered during excavation causing additional adjustments to the process.
- Geosyntec Authors: Nathan Higgerson
- All Authors: Nathan Higgerson, Geosyntec Consultants; Matt Balance, Vistra Energy
- Title: The Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 3
- Event or Publication: Event
- Practice Areas: Water and Natural Resources
- Citation: Nathan Higgerson (St. Louis) will present on "Closure of CCR Impoundments: A Discussion of Construction Issues and Strategies from the Owner and Engineering Perspective" at the Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 3 on July 27, 2020.
- Date: July 27, 2020
- Location: Virtual
- Publication Type: Platform Presentation