The Ballard Natural Drainage System (BNDS) project made progress last week with Seattle Public Utilities issuing a Determination of Non-Significance (DNS) for environmental impact.

Seattle Public Utilities, the lead agency for this proposal, has determined that the project does not have a probable significant adverse impact on the environment.

The DNS is a step needed for the BNDS proposal to move forward. The proposed project is for construction of raingardens along 22 city blocks in Ballard. The project has been in the design phase (second phase) since last year. Last September the Ballard News-Tribune wrote an update on the project www.tinyurl.com/p99a36c, which revealed that the first phase of the project tested stormwater mitigation with raingardens. SPU found that the raingardens reduced peak flow rates by over 80 percent and reduced the amount of overflow into Salmon Bay. Then later in 2013 preferred blocks were identified after public outreach and initial investigations that analyzed infrastructure and soil composition.

SPU’s end goal 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.

With the addition of a future storage tank closer to the Salmon Bay, raingardens and storage will provide almost six million gallons of storage capacity in the Ballard Basin.

What are raingardens?

Rain gardens are areas with infiltrating soil that absorb influxes of stormwater. They are designed to act as natural landscapes, lush with plants and natural materials that soak up rain like a sponge and filter water. The more beds, the more filtered storm water and less pressure on Ballard’s combined overflow system.

The proposal has two types of raingardens: planting strip beds and curb bulb-out beds. The planting strips are beds running along right-of-ways. Curb bulb-out beds would be used to mitigate traffic and make pedestrian and bicycle sightlines more visible, while also making cross walk distances shorter. One example of this is would occur at Northwest 80th Street and Northwest 77th Street. The intersection is a problem intersection identified by SDOT’s Safe Routes to School program. Furthermore, the project would construct pedestrian and safety improvements such as curb ramps at up to 15 intersections adjacent to the raingardens.

In addition, inlet curb cuts would be installed to route stormwater from the roadways to the raingardens. During high flow events, outlet cuts will be constructed to guide water to the nearest down stream combined overflow inlets.

Location of Proposed 22 blocks:

• 17th Avenue Northwest: 7700, 7800, 7900, 8000, 8100, and 8200 blocks

• 19th Avenue Northwest: 7500 and 7600 blocks
• 25th Avenue Northwest: 8000, 8100, and 8200 blocks
• 26th Avenue Northwest: 7700, 7800, 7900, 8000, 8100, and 8200 blocks

• Northwest 75th Street: 1700, 1800, 2000, 2100, 2200, and 2300 blocks

• Northwest 77th Street: 1700, 1800, and 2500 blocks

Potential intersection improvements (such as curb ramps):

• Northwest 75th Street and 17th, 18th, 19th, 20th, 21st, 22nd, 23rd, and Jones Avenue Northwest

• Northwest 77th Street and 17th, 18th, 25th, and 26th Avenues Northwest

• Northwest 80th Street and 17th, 25th, and 26th Avenues Northwest

Comments must be submitted by December 4, 2014 and sent to Betty Meyer, SEPA Responsible Official at betty.meyer@seattle.gov or visit the project site at www.seattle.gov/cso/ballard 

Deadline for appeals is Dec. 11.