Turning coal combustion residual liabilities into renewable assets

Repurposing environmental liabilities for clean energy

Power plants face challenges with coal combustion residuals (CCR) due to strict environmental regulations, contamination risks, costly closure and remediation requirements, and limited options for safe reuse. Many properly capped CCR sites remain dormant, offering little return on investment. Following the closure and capping of a dry CCR stack and ash pond at the Shawnee Fossil Plant in Paducah, Kentucky, TVA faced a critical challenge: how to transform a large, previously unusable footprint into a productive asset without compromising environmental integrity. TVA sought a solution that would not only meet regulatory requirements but also align with its long-term sustainability goals. Renewable energy developers have also kept sustainability in focus, seeking creative expansion on property that cannot be otherwise developed.

We collaborated with Watershed Geo to deliver an innovative approach — installing an energy-dense solar PV system directly on the closure cap. This concept eliminates the need for land acquisition and demonstrates how legacy sites can be repurposed for renewable energy generation. Our team utilized innovative solutions to design this new solar PV facility while leaving the closure undisturbed and intact. All cabling was collected, routed and conveyed via aboveground cable tray systems; replacing the need for underground duct banks. Access roads for maintenance and operations, as well as equipment pads, were constructed utilizing built-up aggregate sized to accommodate allowable bearing pressure at the top of the closure cap. By leveraging advanced geosynthetic and solar technologies, the project sets a precedent for sustainable land reuse, turning environmental liabilities into clean energy assets and creating a replicable model for utilities nationwide.

Engineering innovation for environmental compliance

We provided comprehensive engineering design and construction support for the integration of Watershed Geosynthetics’ ClosureTurf® and PowerCap™ systems. ClosureTurf® serves as the closure cap system, offering superior erosion control and environmental protection compared to traditional soil covers. PowerCap™ enables solar modules to be mounted securely without penetrating or compromising the integrity of the cap — a critical requirement for maintaining compliance with CCR closure regulations. The design accounted for site-specific challenges, including slope stability and wind uplift resistance. Module support racks were engineered to withstand sliding forces on slopes up to four horizontal units to one vertical unit (4H:1V) and resist wind pressures based on local conditions. This level of precision ensures long-term durability and safety, even under extreme weather events. By combining geotechnical expertise with renewable energy engineering, we delivered a solution that meets stringent environmental standards while maximizing energy output.

Delivering scale and impact

The project spans approximately 300 acres across the closed landfill and Ash Pond 2 areas, making it one of the most ambitious solar installations on a CCR site. The solar PV system includes high-efficiency modules, PowerCap™ support racks, inverters, cabling, weather monitoring stations and a SCADA system for real-time performance tracking. With a nameplate capacity of almost 100 megawatts, the installation is designed to generate significant renewable energy, offsetting carbon emissions and reducing reliance on fossil fuels. Beyond its technical achievements, the project demonstrates the economic viability of integrating renewable energy into closure strategies. By utilizing existing land, TVA avoids the costs and environmental impacts associated with new site development. This approach also accelerates progress toward corporate sustainability targets and positions TVA as a leader in innovative energy solutions.

Setting the standard for sustainable energy solutions

By combining our deep CCR closure expertise and solar engineering capabilities, the project delivers a cost-effective, environmentally responsible solution that meets multiple objectives: regulatory compliance, renewable energy generation and long-term site stability. For TVA, this initiative provides a tangible demonstration of its commitment to sustainability and innovation. The implications extend far beyond Shawnee. Utilities across the country face similar challenges with legacy CCR sites. This project offers a proven model for transforming these liabilities into assets, creating opportunities for clean energy development while reducing environmental risk. As the energy sector continues to prioritize decarbonization, projects like this will play a critical role in shaping a resilient, sustainable future.