Many areas in Seattle have combined sewers where rainwater from roof and street runoff (which often carries pollutants), and raw sewage from our homes combine in the sewer pipes. During and after heavy rains the sewage flow can exceed the capacity of the waste treatment pipes and the untreated sewage overflow is discharged through Combined Sewer Overflows (CSOs) directly into waterways.
The zone immediately North of Lake Union from The Locks to Lake Washington produces a significant proportion of the raw sewage dumping into the freshwater areas of Seattle. Wallingford, Ballard, Fremont, and the U-District dumped more than 130 million gallons of raw sewage into Lake Union, Salmon Bay, and the Ship Canal during 2014 (the most recent data available) alone. King County and Seattle City CSOs discharged a total of 1.14 billion gallons over 388 events during 2014 (this includes only untreated overflows).
There is a plan in place to address the problem, but according to The Long Term Control Plan (see page 302) the NW Seattle CSO basin projects will not be fully completed until 2030. If the HALA proposals to upscale zoning are successful, the increased housing density will exacerbate the existing raw sewage problem. Every new toilet added to the system means more fecal matter in our freshwater!
We urge you to share your opinion of this situation with your elected officials in city government.
Please comment by email to the City Council:
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And please submit your comments to Mayor Murray:
Feel free to send your version of this suggested comment:
I oppose HALA up-zoning in the areas that have significant raw sewage outflows. These environmentally sensitive areas should be specifically excluded from HALA and growth initiatives until the planned sewage retrofits are completed. Both King County and City of Seattle Combined Sewer Overflows (CSOs) should be improved in the affected areas before new population growth should be considered.
It is irresponsible for you as our elected city leaders to consider exacerbating the current environmental problems in these sensitive areas with more population and more raw sewage. As government officials, it is your responsibility to ensure that we are in compliance with the State Growth Management Act, which requires concurrent growth of infrastructure with density, and the Federal Clean Water Act. The environmental impact of HALA is a significant concern for myself and my family.
For additional information:
- Seattle Public Utilities (SPU): Sewage Overflow Prevention:
- CSO Program 2014 Annual Report:
- SPU: Protecting Seattle’s Waterways. Long Term Control Plan:
See page 157 for a CSO map. Page 302 shows a final completion date of 2030 for NW CSO projects.
- Seattle Ship Canal Water Quality Project:
- Growth Management rules with regards to wastewater treatment:
- Rainwise – infomation on managing runoff, including rebates if you live in an overflow area: