Estuary restoration is essential to the recovery of both the Bellingham Bay and Puget Sound, making the restoration of the Padden Creek Estuary a top priority for the City of Bellingham.
This project uses Low Impact Development (LID) and a high efficiency bioretention system, the Filterra Bioscape, to treat stormwater runoff from 90 acres of urban development prior to discharging into the Padden Creek Estuary. The project which is located on Harris Avenue in the Fairhaven District of Bellingham, was funded in part by the Washington Department of Ecology.
After evaluating a number of potential treatment solutions, a 4,200 square foot Filterra Bioscape was selected to treat the water quality volume. Filterra is similar to bioretention in its function and application, but has been optimized for high volume/flow treatment and high pollutant removal. Its small footprint allows it to be used on highly developed areas such as residential and commercial sites, parking lots, and streetscapes.
Before runoff enters the Filterra Bioscape it is pretreated using a Vortechs hydrodynamic separator. The Vortechs combines swirl concentration and flow controls into a shallow treatment unit that traps and retains trash, debris, sediment, and hydrocarbons from stormwater runoff.
Pretreating the Filterra with a Vortechs reduces downstream loading and maintenance costs, as trash and sediment are collected in one easy to maintain structure.
The Filterra Bioscape was selected for its high efficiency flow rate which allows the footprint of the treatment system to be significantly smaller than traditional bioretention. The high flow rate, pollutant removal capabilities, cost competitiveness, and simple maintenance made Filterra Bioscape the best solution for the site.
The Filterra Bioscape is scalable and customizable; offering unique flexibility when working with challenging site conditions. On this project, Contech worked with the engineer to incorporate “bubblers” into the system that disperses the incoming flow. The Filterra Bioscape systems was installed using tiered, cast-in-place boxes to match the site grade.
Vegetation is an integral part of the Filterra Bioscape system. Many of the biological processes for which biofilters are named occur underground in the root zone where the plant interacts with the soil environment, taking up captured pollutants and rejuvenating the media. Native plantings were used as they are best suited for the local climate and blend in seamlessly with the surrounding area. This translates into greater long term sustainability of the stormwater management facility, providing cost savings for the facility owner.