Northridge Detention Retrofit: A Partnership for Water Quality

Joy Monjure has been with the city of Bellingham Public Works Department since 1986 developing and implementing environmental and public works- related outreach and education.

The city of Bellingham has been working for several years to improve the effectiveness of stormwater facilities, with a priority on those in the Lake Whatcom watershed. The emphasis on stormwater management has come about because of the need to reduce pollution carried into our waterways by stormwater runoff.

Cities must now comply with a National Pollutant Discharge Elimination System (NPDES) permit. This means that Bellingham is responsible for the water quality in the waterways within the city limits. That’s a tall order because stormwater comes into waterways from many sources. Two approaches that help are: 1) to make the system work better and 2) ask citizens to pick up pet waste and refrain from washing cars on roads or driveways (which stops pollution at the source).

Northridge Detention Retrofit is one example of how citizens and city staff can work together to find creative solutions to stormwater pollution, resulting in a win/win for everyone, including the drinking water reservoir.

The Brentwood subdivision is located in the hills above Basin One of Lake Whatcom, in the Silver Beach neighborhood. There are 70 homes in this development and they are bound by covenants with oversight by the Northshore Hills Community Association (NSHCA).

“Our neighborhood board has worked diligently with the city over the last year to make this project a reality,” said association president Rob Westford. “We realized that by changing the boundaries of our park, we could assist the city in improving the quality of water in our watershed. This is a true win/win for everyone involved. We are fortunate to have John Matzinger, civil engineer, on our neighborhood board to help with project development and execution.”

The original Northridge detention pond handled stormwater from approximately 38 acres of developed residential land, a portion of which is in the Silver Beach neighborhood. Water from the pond drained into Lake Whatcom and when tested this water showed high levels of metals, suspended solids and phosphorus. (The retrofit hopes to solve this problem.) The city owns the land where the pond is located, along with a nearby lot. Northshore Hills Community Association owns a parcel immediately adjacent to the pond and uses it as a neighborhood park.

Stormwater staff determined that an expansion and upgrade of the existing facility could greatly increase the pond’s performance without the need for new piping. When deciding on the best approach, staff found that certain aspects of the city-owned lot were not well suited for stormwater infiltration, and the logistics of creating a second facility away from the original pond was problematic. At this point city staff approached the neighborhood association with a proposal to swap properties.

Bellingham’s engineering and stormwater staff worked with NSHCA and the planning department to remove some of the covenants that would have blocked the project and to revise the platted lot lines such that equal properties were exchanged. The proposal included improvements that would recreate the existing park on the new parcel.

The neighborhood reviewed the proposal and revised the layout to keep the existing park access while allowing of construction of the new stormwater facility. City staff worked on a design that would expand the existing pond, add specific treatment for phosphorus and retain the park aesthetics for the neighborhood association.

NSHCA approved the initial plan at a special meeting, and board members and city staff worked extensively over the winter to produce a final layout that was acceptable to the neighborhood (and within the city’s project budget). With a final land exchange agreed to by all parties, the swap was completed, deeds recorded and the project began construction the third week in August.

The city is grateful for the cooperation of the Northshore Hills Community Association, and, as they continue working to improve other stormwater facilities throughout Bellingham, will be looking for other opportunities to work with neighborhoods to find creative solutions that benefit all parties. Association members and directors are pleased to be able to work with city staff and contribute to the enhancement of Lake Whatcom water quality.

For more information about the Northridge Detention Retrofit project, contact project engineer Freeman Anthony at fanthony@cob.org or 778-7900. §