An essential service for Portland
Every Portland resident, business, and visitor relies on the Columbia Boulevard Wastewater Treatment Plant. Located in North Portland, the plant serves more than 650,000 customers every hour of every day. The treatment plant manages an average of 70 million gallons of wastewater daily, but on rainy days, the plant can treat up to 450 million gallons.
The improvements underway will enhance the plant’s reliability and efficiency to meet both current and future demands.
Key improvements
New secondary clarifiers
Two new 150-foot diameter clarifiers were constructed to increase the plant's biological treatment capacity and operational resiliency. These clarifiers are deeper and wider than the existing clarifiers and are seismically reinforced to improve structural resilience during earthquakes.
The new clarifiers became operational in December 2024, meeting regulatory requirements set by the Oregon Department of Environmental Quality (DEQ).
Upgraded biosolids processing facility
A new biosolids handling and processing facility is being built to replace the original facility that dates back to the 1970s. The new solids facility will have more advanced technologies, enhance the efficiency of solids treatment, and increase its capacity to keep up with population growth.
Biosolids are the treated solids separated from wastewater—a valuable resource recovered during the treatment process.
Aeration basins restoration
Upstream of the secondary clarifier are the plant's eight aeration basins, which use microorganisms to break down organic material in wastewater. These basins were also built in the 1970s and are undergoing concrete surface restoration to extend their useful life. This work is being phased over four summers to ensure uninterrupted plant operation.
New multi-use building
A new multi-use building is under construction to house staff, shops, and increase storage space. This facility will provide healthier, effective, energy-efficient workspaces and is being built to LEED Gold standards for environmental and energy efficiency.
Timeline and budget
Early construction work began in June 2019 and successfully met its regulatory milestone of December 2024 with the completion of the clarifiers. The overall project is projected to finish under its $515 million budget by early 2027, an impressive accomplishment amid rising construction and inflation costs.
Community benefits and workforce expansion
STEP is implementing a Community Benefits Agreement (CBA) to address historic inequities in the construction workforce and contracting. The project is investing millions of dollars in subcontracting work with minority-owned, women-owned, and disadvantaged businesses, while offering workforce training and development opportunities to women and people of color.
As of March 2025:
- 309,691 hours (36% of the total project hours) were completed by minority workforce
- 78,725 hours (9% of the total project hours) were completed by women
- 157,438 hours were completed by apprentice workforce; the next generation of workers:
- 75,516 hours (48% of total apprentice hours) were completed by minority apprentices
- 34,000 hours (22% of total apprentice hours) were completed by female apprentices