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Drainage & Wastewater
Property owners and developers must properly convey the following to an approved discharge location:
In the City of Seattle, all proposed development needs a review if it will disturb more than 750-square feet of land or hard surface (such as pavement). This review determines the impact on existing drainage and wastewater infrastructure.
- On private property, the Seattle Department of Construction and Inspections (SDCI) reviews master use and construction permits.
- In the public right-of-way, the Seattle Department of Transportation (SDOT) issues a street use permit or utility major permit. This is often in conjunction with an SPU review.
You may need to make infrastructure improvements when existing infrastructure is unavailable or inappropriate.
Drainage is stormwater and groundwater. It must be managed to avoid damage to people, property, or the environment.
The Stormwater Code and Manual has requirements for onsite stormwater management when certain development thresholds are exceeded.
Wastewater is sewage. Examples include water from toilets, bathtubs, commercial applications, or other sources of contaminated water.
Not all contaminated water can be disposed of as wastewater in Seattle’s or King County’s sewer systems. As outlined in SDCI’s Side Sewer Code site, water must be pre-treated by a specialized facility or managed in another way if it’s contaminated with:
- Petroleum products
- Certain chemicals
- Bio-hazardous materials