French Drains & Drainage Systems in Marysville, WA

Drainage & French drains in Marysville: what to know

The outlet decides the design. A drain needs a discharge point lower than the trench, so the yard is surveyed for the lowest workable spot before any layout. Where the Marysville series is mapped, its weathered siltstone begins at 20 to 40 inches, so the trench depth is read from the cut and the outlet is set to it.

The stormwater rules attach to the outlet. MMC 14.15 adopts Ecology’s 2019 Stormwater Management Manual for Western Washington with local changes, and its review turns on threshold conditions such as added impervious surface. Downspouts run through solid pipe to a separate outlet, and the trench bottom falls toward the outlet. Any run that reaches the right-of-way is confirmed with city staff first.

Permits and rules in Marysville

Drains are checked against three questions before pricing: whether the stormwater review applies to the outlet under MMC 14.15, whether the trench volume reaches the city’s 50-yard grading line, and whether the route touches the public right-of-way. We check the stormwater pollution prevention plan the city requires before nonexempt construction starts, and we record each answer on the drawing before the quote goes out.

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

How we approach it

Survey for the lowest accessible outlet before any layout
Slope the trench bottom steadily toward the outlet
Run downspouts through solid pipe to a separate outlet
Confirm any right-of-way review before the trench opens

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

Questions from Marysville homeowners

What does Marysville’s stormwater chapter ask of a drain outlet?

MMC 14.15 leaves its threshold conditions to Ecology’s 2019 manual with local changes, so the city confirms the outlet for each job. In practice we plan an outlet onto ground that can take the flow, or into a storm line the city has approved, and keep the road and neighboring lots clear.

Does a Marysville yard drain trench over 50 yards need a grading permit?

The city’s permit table calls for a grading permit at land disturbance of 50 yards or more, with the unit confirmed with city staff. Trench depth, the outlet, and any tie to the public right-of-way are also confirmed with city staff before excavation.

Does the Marysville siltstone layer limit a French drain?

It can. Where the Marysville series is mapped, its description puts a weathered siltstone at 20 to 40 inches in the typical profile, so a trench deeper than that can reach it. We survey the grade and the layers first, then propose a drain where the water has a workable exit.