Seattle Public Utilities has released an update on the Ballard Natural Drainage System project.

SPU reported that they have received construction bids and plan to go with a construction contract by the end of the month.

The Ballard Natural Drainage System is a project undertaken by the City with a goal of preventing 1 million gallons of untreated sewage and stormwater from entering Salmon Bay by building rain beds in a northern quadrant of Ballard.

SPU plans to build raingardens along 22 city blocks in Ballard. SPU found that the raingardens reduced peak flow rates by over 80 percent and reduced the amount of overflow into Salmon Bay.

Back in 2013 preferred blocks were identified after public outreach and initial investigations that analyzed infrastructure and soil composition.

The end goal of the project is to prevent no more than one overflow per year. The overflows happen when storm water runoff overwhelm Ballard’s combined overflow sewage system. Millions of gallons of runoff enter Salmon Bay via overflow sites. 10 percent of that water is raw sewage.

In 2013, Ballard accounted for over one-third of the entire City’s overflows. That year Ballard overflowed 58 times, totaling 14.9 million gallons washing into the bay.

To prepare for the future construction, minor pre-construction utility work and tree transplantation may happen later this year. SPU would like the beds to be operational before the rainy winter season, and so primary construction will begin in Spring 2016. Neighbors of project areas will be notified before the work begins.

There are two other major projects happening in Ballard that coincide with the BNSD project: Expansion of Loyal Heights Loyal Heights Elementary School and the 17th Avenue Greenway.

SPU is coordinating with Seattle Public Schools so that the projects have very little disruption and rework costs.

To do this SPU plans to finish rain construction adjacent to areas near the school by Fall 2016. These areas include NW 80th St and 26th Ave NW and to the south end of the school along NW 77th. By building the garden earlier it allows at least a year of growth for the plants in the beds.

In addition, SPU has been collaborating with Seattle Department of Transportation in planning the construction of the new raingardens on the 17th Ave NW between NW 77th St and NW 83rd St. Greenway construction started earlier this month and should be finished by the end of January 2016.

For more information visit http://www.seattle.gov/util/environmentconservation/projects/ballardnat…