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French Drains & Drainage Systems in Snohomish, WA

Yards in Snohomish can stay wet where water runs down from a slope or sits on a slow-draining layer. We fix each French drain’s outlet after the water’s route and an allowed discharge point are both confirmed.

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French drain cross-sectionA trench wrapped in filter fabric and filled with clean drain rock around a perforated pipe, collecting water from the surrounding soil. 12345
French drain section: fabric, clean rock, perforated pipe
  1. Filter fabric keeps silt out of the rock
  2. Clean drain rock gives water an easy path
  3. Perforated pipe carries the water away
  4. Soil cover over the trench
  5. Groundwater and runoff move toward the drain

Drainage & French drains in Snohomish: what to know

The city’s stormwater review follows a two-part trigger. SMC 15.16.030 requires review only when a project meets or exceeds the threshold conditions in the Stormwater Manual and is subject to a city development permit. That manual is the 2012 Department of Ecology Stormwater Management Manual for Western Washington, as amended by the Phase II municipal permit appendix.

Its Chapter 2 introduction names 2,000 square feet or more of added or replaced hard surface, or 7,000 square feet or more of land disturbed, as the sites that must submit a stormwater plan. The outlet is also checked against SMC 15.16.090, which sets the discharges the city accepts. Roof water is handled separately, because the illicit-connection definition excludes roof drains.

Permits and rules in Snohomish

We check the drain’s added hard surface and land disturbance against those manual figures before the quote, and we confirm with the city whether the project also needs a development permit, since both conditions must be met for the SMC 15.16.030 review. A line that reaches public frontage or the right-of-way is a separate question for Public Works. We look at the outlet, the thresholds, and the frontage in one pass so the drawing matches the review.

Rules change and vary by parcel, so we confirm the current requirements with the city before we start.

How we approach it

  • Find where slope water enters the yard before digging
  • Check added hard surface against the 2,000 square foot figure
  • Keep roof water in solid pipe apart from the perforated line
  • Confirm the discharge point and any frontage review first

For the full process, see our Drainage Systems & French Drains page.

Questions from Snohomish homeowners

What outlet does SMC 15.16.090 allow for a Snohomish drain?

The city’s allowable list names foundation drains, footing drains, and uncontaminated pumped water, and its discharge bans target non-stormwater material. We confirm which rule fits the drain’s source before the trench is cut, and we confirm the outlet with Public Works.

Does a Snohomish drain that adds hard surface reach SMC 15.16.030 review?

Only if it meets or exceeds the Stormwater Manual thresholds and the project also needs a city development permit. We check the added hard surface and the land disturbed against the manual’s figures, then check the permit question, since SMC 15.16.030 requires both conditions.

Can a drain stop the damp patch below a Snohomish slope?

A drain can help when the water comes from higher ground. We survey the grade and the soil layers first, and we propose a drain only after it is matched to the water’s source.

Other work in Snohomish

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Talk to us about your project

Call or email us. We’ll talk through the work and set up a time to see the site.

Call 206-483-5334
Get a quote
Call 206-483-5334Get a quote