Stormwater permits in City of Mercer Island: fees, timeline & requirements (2026)
Everything you need to know about pulling a stormwater / drainage permit in City of Mercer Island, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Apply via MyBuildingPermit.com..
Free lookup, no account needed — your lot polygon, zoning, setbacks and overlays, cited to City of Mercer Island's source.
When does a stormwater / drainage need a permit in City of Mercer Island?
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 Mercer Island's own code
“A. There is hereby created and established, by the adoption of this chapter and the provisions therein, a city storm water management program, hereinafter referred to as "the program." The program shall set forth the primary authority and responsibility for carrying out the Action Agenda for Puget Sound including, but not limited to, responsibilities for planning; establishment of requirements for new development and redevelopment; public education efforts to educate citizens; design, construction, maintenance, administration, operation and improvement of the city's storm and surface water…”Source ↗verified 2026-05-02
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 Mercer Island?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout City of Mercer Island and King County. Kolmo prepares the drawings and submittals, files the stormwater / drainage permit with Apply via MyBuildingPermit.com., carries the project through review and inspections, and performs the construction. Call (206) 410-5100 for a City of Mercer Island 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 Mercer Island 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: Apply via MyBuildingPermit.com. ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (Drainage review fees are commonly tiered by project size in the city's 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 Mercer Island every month. We prepare the drawings and submittals, file with Apply via MyBuildingPermit.com., handle reviewer comments, and build the project.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Stormwater permits in City of Mercer Island — FAQ
When does a stormwater / drainage need a permit in City of Mercer Island?
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 Mercer Island?
Current fee per the City of Mercer Island fee schedule: Drainage review fees are commonly tiered by project size in the city's fee schedule.. Plus ancillary plan-review/tech-surcharge fees per city schedule.