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?
KC Surface Water Design Manual 2021 (KCC 9.04 + adopted by reference in most KC cities) sets the 2,000 sqft new+replaced impervious threshold for "small project" drainage review; ≥5,000 sqft triggers full drainage review. Different thresholds in critical-area drainage basins.
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 2026-09-05
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.
Stormwater permit fee estimate in City of Seattle
Worked example for a $25,000 stormwater / drainage project (building permit). Your actual fee scales with project valuation.
| Building permit fee | $508.63 |
| Plan review | $330.61 |
| Technology surcharge | $25.43 |
| WA state surcharge | $6.5 |
| Estimated total | $871.17 |
Drainage review fee commonly tiered by project size; small project ~$300-$800, full drainage review $1,500+. Computed from the City of Seattle fee bracket schedule · source ↗. Impact/utility fees may apply separately.
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 (typical: —). Respond to reviewer comments promptly.
- 5. Pay issuance fees (Drainage review fee commonly tiered by project size; small project ~$300-$800, full drainage review $1,500+.) 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?
KC Surface Water Design Manual 2021 (KCC 9.04 + adopted by reference in most KC cities) sets the 2,000 sqft new+replaced impervious threshold for "small project" drainage review; ≥5,000 sqft triggers full drainage review. Different thresholds in critical-area drainage basins.
How much does a stormwater / drainage permit cost in City of Seattle?
For a $25,000 stormwater / drainage project, the estimated City of Seattle permit fee is about $871.17 — building fee $508.63 + plan review $330.61 + surcharges. Fees scale with project valuation per the city schedule.