In 2019, the state of Colorado passed a law requiring certain power producers to submit “clean energy plans” for reducing emissions of greenhouse gases (GHGs) associated with generating electricity sold to consumers.
The Colorado Public Utilities Commission approved the first such plan, prepared by Xcel Energy, in 2022. One element of the plan was converting Xcel’s Pawnee generating station, in the state’s northeastern region, to burn natural gas instead of coal while maintaining its 505-megawatt capacity.
Barr is contributing to the repowering project by designing a wastewater treatment system that will provide the water-reuse opportunities and water-volume reduction needed to preserve the facility’s zero-liquid-discharge operation.
The new treatment system had to overcome a complex challenge: achieving compliance with environmental regulations while (1) removing significant amounts of dissolved solids and scale-forming compounds from the water so it could be reused for plant operations, and (2) reducing the volume of wastewater reject to prevent off-site overflow, which would eliminate the need to construct additional evaporation ponds.
Barr engineers evaluated several treatment technologies and chose the one that maximized water recovery. We helped Xcel procure water and wastewater equipment and developed detailed designs for the remaining components.
Our overall work as the owner’s engineering consultant includes:
- Developing conceptual and preliminary designs for water and wastewater treatment systems and equipment
- Creating bid packages for equipment procurement and construction services
- Supporting technical-bid evaluations and contracting processes
- Integrating treatment technology (filter presses) into the plant’s existing water-treatment infrastructure
- Performing balance-of-plant civil, structural, mechanical, and electrical engineering for the new wastewater-treatment system, including installing a pre-engineered metal building to house the treatment equipment, all building systems, and the tie-in to Xcel’s existing infrastructure
- Providing construction administration and commissioning support
The conversion project will be completed by the end of 2025.