January 20, 2026
Chehalis Regional Water Reclamation Facility: How Grit King® Saves Plant from Near Disaster
The City of Chehalis, Washington, located midway between Portland and Seattle, faced growing challenges with its aging wastewater treatment plant.
Originally built in 1948 and upgraded several times, the plant could no longer meet projected flow rates or stringent Department of Ecology permit requirements.
To address this, the city launched a design-bid-build project for a new Chehalis Regional Water Reclamation Facility, designed to treat an average flow of 1.3 million gallons per day and peak flows exceeding 10 million gallons per day several times per year. The new facility also included a reclaimed water program to irrigate a 250-acre poplar tree plantation, requiring advanced treatment processes. While grit removal was not initially a top priority, the city needed a system that was simple, reliable, and required minimal moving parts.
Challenge
Shortly after start-up, a pump malfunction caused high-grade silica sand from the effluent filters to bypass the intended recirculation path and enter the plant drain system, sending large volumes of sand back to the headworks. This unexpected event posed a serious risk of overwhelming downstream processes, including Sequencing Batch Reactors (SBRs), and could have led to costly shutdowns and equipment damage.
Solution: Grit King®
The facility installed two 11-foot diameter free-standing Grit King® units and a grit classifier as part of its headworks design. Oldcastle Infrastructure’s Grit King system, engineered by Hydro International, uses advanced hydrodynamic separation to remove 95% of grit 150 microns and larger at peak flows of 13 million gallons per day. When the sand filter malfunction occurred, the Grit King® units captured the excess sand, preventing it from reaching critical downstream processes.
Operators increased grit discharge frequency to manage the additional load, and the plant continued operating without interruption. The system’s all-hydraulic design, minimal moving parts, and ease of installation proved invaluable.
As the Wastewater Superintendent noted, “Construction of the new system was easy. It was delivered to the site, and the contractor bolted it in place within days.”
Sustainability Impact
The Chehalis facility incorporates sustainable practices, including reclaimed water reuse of up to 3.5 million gallons per day for irrigation, production of Class A biosolids sold to local farmers, and reduced maintenance and energy use thanks to the Grit King’s pump-free design.
By preventing grit accumulation in SBR tanks, the system reduces cleaning frequency and associated resource use. Annual cleaning of one SBR now reveals only a wheelbarrow of grit compared to what could have been significant buildup without effective grit removal.
Overall Impact
The impact of the Grit King® system has been substantial. The plant avoided costly downtime during a major equipment malfunction, reduced maintenance costs, and improved operational reliability. The grit removal system has been virtually trouble-free since installation, producing cleaner grit with fewer odors and requiring minimal intervention.
As the superintendent summarized, “The Grit King system has worked great without any problems. It has been virtually trouble free.”
Conclusion
The Chehalis Regional Water Reclamation Facility demonstrates how investing in a robust grit removal system can safeguard operations, even when grit removal isn’t initially considered critical. The Grit King system not only met design requirements for simplicity and reliability but also proved its value during an unexpected event, ensuring uninterrupted service and long-term sustainability.