South Park Flooding

November through February, Seattle Public Utilities is prepared for the wet weather season. We monitor storms, tides, and atmospheric pressure. When a lot of rainfall is predicted , SPU prepares city-wide by completing inspections of critical parts drainage system included selected culverts, ponds, inlets and more, and increasing the number of staff on stand-by. 
 
In South Park, SPU prepares for and responds to flooding from high tides. We are prepared to activate additional teams and resources based on the forecast. High tides on their own can cause minor impacts, but other weather factors like wind, low pressure, and high river levels can make things worse. Our South Park Emergency Response Plan includes three primary activities that respond to predicted flooding: 

1. Ensure sandbags availability for businesses and residents. Sandbags are a way property owners can protect their property from flood waters. Get and use sandbags.
2. Build and/or close gaps in flood control wall: In early winter, Seattle Public Utilities builds a flood control wall primarily on public property in close proximity to the Duwamish River. If there is high tide inundation, the wall will reduce impacts. Throughout the winter, it will have openings to allow for normal neighborhood activities. These opening will be closed when extreme tides are predicted.
3. Large pumps: During extreme tide events, rainwater collects in some low-lying areas and may be unable to drain. SPU will operate pumps at several of these low-lying locations to move water from inundated public roadways over the sandbag wall. 

On December 27, 2022, the Duwamish River flooded a South Park neighborhood, damaging local homes and businesses. The flooding was caused by a combination of factors including higher-than-average tides, rain runoff, and melting snow. This area has faced prior flooding, as well as environmental and health challenges due to historical inequities and industrial contamination.

The City Responded:

• The City partnered with local community groups and disaster relief organizations to provide assistance to impacted residents.
• The immediate response with partners was to provide food assistance, hotel vouchers, pumps, clean-up equipment, and other supplies.
• Once immediate needs were addressed, the City and partners began to assist with clean-up efforts, safety inspections of impacted properties, and finding long-term housing support for families who need it.
• Community partners included Duwamish River Community Coalition, Just Health Action, Khmer Community of Seattle King County, Villa Communitaria, Cultivate South Park, and SeaMar Community Health.
• Disaster relief partners included the Red Cross, Team Rubicon, King County Office of Emergency Management, and Public Health – Seattle & King County.
• City agencies involved Seattle Public Utilities, Human Services Department, Office of Emergency Management, and Department of Construction & Inspections, with support from the Mayor’s Office, Office of Sustainability and Environment, Facilities and Administrative Services, and others.

Seattle Public Utilities has invested in flooding mitigation projects and initiatives, and flood response activities including:

1. Grinder Pumps: This SPU and King County project has installed 22 grinder pumps in homes most at risk for sewer backups.
2. South Park Pump Station: This facility is now operational, and will help reduce flooding in northeast South Park by enabling drainage pipes to flow into the Duwamish River during high tide. It will reduce right-of-way flooding during many (but not all) high tide events in locations where we have drainage infrastructure.
3. South Park Roadway and Drainage Project, Phase 1: This SPU and SDOT project installed ten blocks of new roadway and drainage pipes within the industrial area, connecting those areas to the pump station. Sidewalk and landscape improvements were also included on some blocks. This project was largely funded by the King County Flood Control District.

SPU is leading and/or participating in multiple near-term infrastructure investments in South Park including:

1. South Park Roadway and Drainage Project, Phase 2. This project will install pipes to expand the footprint and the number of blocks served by the pump station.  Included blocks and improvements have not yet been finalized. It is in the planning phase and working to secure additional external funding.
2. South Park Stormwater Quality Facility.  This project will treat stormwater before it flows to the Duwamish River. It is in the planning phase and is working to acquire land that may meet community river access priorities and would require contaminated site cleanup. Anticipated to be constructed by the end of 2030 but that the schedule for completion may change given that the project is in the planning phase.
3. King County Wastewater Treatment Division’s (WTD) Sewer Capacity Long-term Planning. SPU is participating is this work which is evaluating long-term approaches to prevent wastewater backups throughout South Park.

SPU is also working with several City departments on climate adaptation and long-term resilience in the Duwamish Valley. To protect South Park from flooding, there needs to be both drainage/sewer improvements and climate adaptation improvements.