Dawn Hemminger, Shannon Dunn, Zack Thomas
John Phillips – Water Quality Planner/Project Manager/CSO control & Sediment Mgmt Programs
Tiffany McClaskey – Engineer II/Project Planning & Delivery
Shaun O’Neil – Senior GIS Analyst/Wastewater Treatment
The purpose of this meeting was to learn about how the sewer and storm lines run along 14th Ave NW from 65th to the waterfront. In particular, we wanted to find out if any of the lines were combined sewer/storm. If there are combined lines then it could be possible to leverage funding, similar to the Rainwise program, to reduce stormwater flow into the combined system, hence, reducing activation of combined sewer overflows (CSOs) which send both sewage and stormwater into waterways when the water treatment center is not able to handle high flows.
After speaking with John, Tiffany and Shaun, all of 14th Ave NW between 65th and the waterfront are separated storm and sewer. This is thanks to the efforts of Forward Thrust ballot initiative back in the late sixties which resulted in separating much of the combined sewer/storm lines east of 15th below NW 65th in Ballard. John recommended looking for photos in the archives.
Commercial lots along 14th are, however, still combined, e.g. St Alphonsus church/school and the Ballard Market. Both could benefit from parking lot bioswales.
If we were to install bioswales along 14th, what would be beneficial to do before installation?
- Do infiltration tests of the soil
- Figure out the volume going out of the sewer line on 14th that feeds into Salmon Bay. There are no known stormwater laterals for that area, however, they can be calculated knowing that rainstorm average in Seattle is 1.9″ (Zack seemed to understand how to do this calculation than I can explain in the notes)
- Ask Avalon Bay and the Ballard High school for their most recent geotech reports. We may be able to access them through UW’s Geomap Northwest site online, but without additional funding, their site’s going down at the end of March, http://geomapnw.ess.washington.edu/
- Call the utility to locate sewer lines and PSE for gas lines
- Look at Portland’s specs for bioswales built over sewer lines (just in case we’ll need to do this)
Since the 14th Ave NW Park Boulevard project wouldn’t be able to tap into RainWise program funds due to the lines already being separated, what are some other possible sources of funding?