Phase 1 of Beaverton Underground Water Treatment Facilities Completed
The City of Beaverton foresees a revitalization of its downtown area and is taking a proactive role to provide stormwater treatment within drainage areas that could experience redevelopment activity in the near future. The City is currently investing in regional underground public stormwater facilities at two locations as part of this project.
Construction of one of the two facilities was completed in August, which included two large vaults – one to facilitate sedimentation and one to provide enhanced water quality treatment. The construction site was situated near the Beaverton Round on Watson Avenue, just south of the Watson and Hall Blvd. couplet split. This location is near the downstream end of a large tributary area (mostly untreated under pre-project conditions) that could see multiple redevelopment projects in the future. The project was constructed with the goal to provide regional treatment, thus allowing lots within the tributary area to be redeveloped without having to provide individual on-site treatment.
Ashley Cantlon, Senior Water Resources Engineer and Project Manager, has been leading the Otak team that is providing engineering design and support services from preliminary concept through to final construction. The range of services includes hydraulic and hydrologic analysis, survey, design, and visual mitigation (planning/architect), as well as construction management and construction support services. Sub-consultants included 3D Infusion for drafting services and GRI for geotechnical exploration and analysis. The contractor on the project was MEI.
Working within the existing infrastructure in and around the area presented a unique set of challenges. For example, the need to fit the water collection and treatment system into the existing roadway and pipe infrastructure required using flow splitters and as little relocation of utilities as possible. Feasibility studies were conducted at the outset to gain a more complete picture of conflicts and constraints. These studies exposed potential problems which could then be mitigated, but also revealed opportunities to complete a portion of the project in conjunction with other concurrent city-led projects, including replacement of a water line, which will increase efficiencies and cause fewer interruptions to the public.
Flow split structures and other conveyance infrastructure associated with completing the connections to the Watson vaults will be completed in conjunction with other city projects in the nearby area to minimize road closures and traffic disruptions and keep costs down.
This first phase of the water treatment facilities project (installation of the sedimentation and treatment vaults), which broke ground on June 3, 2020, was completed on August 5, within a critical 58-day construction window. Phase 2 (flow split and conveyance infrastructure) is being coordinated and integrated into the other city-led projects and is slated for construction during the summer of 2021, at which point the treatment vaults will be brought online.
Otak came to the project with experience and knowledge of the area from previous work completed under multiple contracts with the City of Beaverton. “We have developed a good working relationship with the City and really enjoy working with their team,” Ashley said. Other stakeholders involved in the project include Clean Water Services, TriMet, and private property owners.