Presenting a Large-Scale Approach to Water Quality at APWA WA 2025
October, 2025
Showcasing the details behind one of the largest water treatment facilities in Washington State, a presentation at the American Public Works Association (APWA) WA 2025 Fall Conference on the Monroe Avenue Infiltration Facility included insights from two Otak engineers responsible for its design. Led by representatives from the City of Renton (project client), the presentation gave an in-depth look at the project’s background, the alternatives considered, and how it ultimately will enhance water quality and flood mitigation for the surrounding community.
Project leaders Russ Gaston and Joe Brascher were on-hand for a Q&A that followed to give firsthand accounts of what went into the design and environmental science that made the project possible. This session was open to the sold-out gathering of attendees for the annual APWA WA event. The group forms a large, dynamic, and engaged community of professionals dedicated to advancing improvement goals at the local level. In addition to opportunities like this to share innovative infrastructure examples with peers, the occasion also aims to foster professional growth and facilitate meaningful connections that promote excellence in the industry. Learn more about this example of green stormwater infrastructure that was presented below.
About the Monroe Avenue Infiltration Facility
Over the previous few decades, the community of Renton, Washington experienced multiple historic flooding events, causing damage to property and infrastructure. These consequences also extended to the Cedar River and broader water quality in the area. Temporary solutions with drainage easements and overflow pipes were implemented over the years but a new approach was needed for managing stormwater runoff for the 260-acre subbasin. As a result, the city made plans for additional stormwater infrastructure to address the issue that would become the Monroe Avenue Infiltration Facility.
With an emphasis on water quality targets, long-term performance, as well as construction and maintenance cost, several alternatives were considered leading up to this project. Using hydrologic and hydraulic modeling, estimated peak flows were incorporated across all the designs to account for everything up to a 100-year storm event.
The selected alternative delivered a final design that balances cost efficiency and low maintenance with maximum water quality and a smaller facility footprint. The 14-acre site where the facility exists was originally a permitted sand and gravel pit from 1962 to 1982 and had since been used as a reclamation site. After extensive work with land rights, funding, and material availability, a storm tech chamber infiltration facility and water quality treatment vault would be the main components of what now exists at the location.
With a connection to existing stormwater infrastructure, the Monroe Avenue Infiltration facility includes a flow splitter along with primary and secondary isolator rows to address normal and high flow situations. A pretreatment removes debris and a bioscape unit within the treatment vault enhances water quality and lowers water temperature as it makes its way back into the water system. Designed with longevity and maintenance in mind, easy access to features for upkeep include a hammerhead access road to allow vactor truck turnarounds. Altogether the final product was constructed four months ahead of schedule.
