Drainage Design · Snohomish County
Drainage design that clears Snohomish County review.
Snohomish County ties drainage review to the LDA — the Land Disturbing Activity permit — and to residential building permits on parcels that move water. The county's reviewers are thorough, the standards are specific, and a drainage plan written for some other jurisdiction's checklist will bounce.
AXE designs Snohomish County drainage from the Arlington office: single-family RBP support in Lake Stevens, plat drainage in Marysville and Stanwood, commercial systems on county land. The 2024 acquisition of MAC Engineering folded years of county-specific review history into this bench.
Who this page is for
- Owners whose RBP (residential building permit) requires an engineered drainage plan
- Builders triggering LDA review on county parcels
- Developers platting in Marysville, Lake Stevens, Stanwood, or the unincorporated county
- Anyone whose drainage submittal has stalled in Snohomish County review
What AXE handles
- Drainage plans scoped to county LDA and RBP requirements
- Targeted and full drainage plans under the county's adopted manual
- Detention, water-quality, and conveyance design with calculations
- Drainage reports and small SWPPPs for permit packages
- Plat-level drainage for short plats and subdivisions
- Review-comment responses on stalled county submittals
The local picture
The county's drainage manual sets review scope by new and replaced hard surface and by where the project discharges. Critical-areas overlays — streams, wetlands, steep slopes — are common on county parcels and shape the drainage path as much as the soils do.
City projects inside Marysville, Lake Stevens, or Snohomish run their own counters with their own checklists. The engineering rhymes, but the packaging differs — we format submittals per jurisdiction so the first review is the real review.
Commonly served ZIP codes in this area: 98223 · 98258 · 98270 · 98290 · 98292
How it works, start to stamp.
01 · Permit-path confirmation
LDA, RBP, city review, or a combination — we confirm exactly which drainage requirements attach to your project.
02 · Design to the county manual
Flow control, treatment, conveyance — engineered to the standards your reviewer will actually apply.
03 · Stamped package
PE-stamped plan and report assembled to the county or city checklist.
04 · Carry through review
We answer the comment letters until the permit issues — that's part of the job, not an add-on.
PE-licensed. Founded 2017. One engineer of record from feasibility through approval.
Questions we hear about drainage design in Snohomish County.
My building permit application came back asking for a drainage plan. Is that normal?
Very. Snohomish County frequently conditions RBPs on engineered drainage once a project adds enough hard surface or sits on a parcel that sheds water toward neighbors or critical areas. It's a solvable step — typically a targeted plan for single-family work.
Does every LDA permit need a full drainage plan?
No — scope follows the project size and discharge conditions. Part of our first pass is confirming whether you qualify for the lighter targeted scope before anyone engineers more than the county requires.
Can you take over a drainage design another firm started?
Yes. We review what exists, identify why it stalled, and either complete it under our stamp or redesign the parts that won't pass. The goal is the permit, not redoing work for its own sake.
County drainage requirement on your project?
Send the parcel and the county's letter if you have one. We'll map the path to approval and get you a written proposal within one business day.
Start the conversation