Stormwater permits in City of Seattle: fees, timeline & requirements (2026)
Everything you need to know about pulling a stormwater / drainage permit in City of Seattle, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Seattle Department of Construction & Inspections (SDCI).
Free lookup, no account needed — your lot polygon, zoning, setbacks and overlays, cited to City of Seattle's source.
When does a stormwater / drainage need a permit in City of Seattle?
Ecology's Stormwater Management Manual for Western Washington (SWMMWW, 2024 edition) is the state floor. A municipal stormwater permittee may instead adopt a REGIONAL manual Ecology has determined equivalent, and most do — some counties publish their own, some cities publish their own, and others adopt Ecology's directly. WHICH MANUAL APPLIES IS A PER-JURISDICTION FACT and it changes the numbers: review thresholds for new plus replaced impervious surface and for land-disturbing activity differ between manuals, so read this jurisdiction's own adopting chapter before quoting one. Critical-area and closed-basin parcels get stricter review under every manual.
From City of Seattle's own code
“A. Thresholds for drainage control review. Drainage control review and approval as described in subsection 22.807.020.B is required for any of the following: 1. Preliminary drainage review and approval is required for applications for the following approvals:”Source ↗verified 2026-09-07
What City of Seattle says in its own permit handout
From Construction Permit Checklist - Single-Family Add Alt, published by City of Seattle. This is the jurisdiction's own guidance on its permit process, not the ordinance text — where the two differ, the code governs.
“1. Drainage Plans (DWC and CSC/SOIL Plans) are not required for projects with less than 750 sf of new plus replaced hard surface and/or 5,000 sf of land disturbing activity unless the project is in an environmentally critical area (ECA) or buffer. Preparation by a licensed civil engineer is required if there is 5,000 sf of more of new plus replaced hard surface.”Checklist ↗read 2026-09-05
Required submittals
- drainage report (full or simplified)
- site plan with impervious calc
- BMP / facility detail
- geotech if infiltration claimed
Inspection sequence
- pre-construction (BMPs in place)
- facility installation
- final stabilization
Contractor specialties needed
general
Who can do this work in City of Seattle?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout City of Seattle and King County. Kolmo prepares the drawings and submittals, files the stormwater / drainage permit with Seattle Department of Construction & Inspections (SDCI), carries the project through review and inspections, and performs the construction. Call (206) 410-5100 for a City of Seattle stormwater / drainage quote.
Notes & caveats
Issuing body is city public works / county DPER, often parallel to the building permit. On-site infiltration / detention required where infeasible to discharge to municipal storm. Critical-area parcels (steep slope, salmon-bearing watercourse) get more conservative review.
How to apply yourself
- 1. Confirm your parcel's zoning & overlays. Run an address lookup for your City of Seattle stormwater / drainage — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline/ECA/historic overlays.
- 2. Assemble submittals (4).
- 3. Submit through the city portal: Seattle Department of Construction & Inspections (SDCI) ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (Drainage review fees are commonly tiered by project size in the local fee schedule.) and pick up the permit. Inspection card travels with the job.
Or have Kolmo do it
We pull stormwater / drainage permits in City of Seattle every month. We prepare the drawings and submittals, file with Seattle Department of Construction & Inspections (SDCI), handle reviewer comments, and build the project.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Stormwater permits in City of Seattle — FAQ
When does a stormwater / drainage need a permit in City of Seattle?
Ecology's Stormwater Management Manual for Western Washington (SWMMWW, 2024 edition) is the state floor. A municipal stormwater permittee may instead adopt a REGIONAL manual Ecology has determined equivalent, and most do — some counties publish their own, some cities publish their own, and others adopt Ecology's directly. WHICH MANUAL APPLIES IS A PER-JURISDICTION FACT and it changes the numbers: review thresholds for new plus replaced impervious surface and for land-disturbing activity differ between manuals, so read this jurisdiction's own adopting chapter before quoting one. Critical-area and closed-basin parcels get stricter review under every manual.
How much does a stormwater / drainage permit cost in City of Seattle?
Current fee per the City of Seattle fee schedule: Drainage review fees are commonly tiered by project size in the local fee schedule. Plus ancillary plan-review/tech-surcharge fees per city schedule.