French Drains & Drainage Systems in Bainbridge Island, WA

Drainage & French drains in Bainbridge Island: what to know

Start on the bluff side, where slope water enters the yard. The city applies BIMC 15.20 together with the 2019 Western Washington manual, and the city’s notice on the update says the manual favors low impact development and adds source control best management practices. We look at low impact options first where the site allows, then size the interception line uphill of the wet ground.

Roof water runs in solid pipe with its own exit, kept apart from the perforated run so the gravel bed stays open. Earthwork of 50 cubic yards or more needs a building permit application under the grading checklist, and a trench that reaches the right-of-way needs a permit under BIMC 15.12. We confirm the discharge point with the city before the trench opens.

Permits and rules in Bainbridge Island

A drain can raise right-of-way, grading, and shoreline questions, and we check each one before quoting. We check whether the trench reaches the right-of-way, whether earthwork reaches the 50 cubic yard line, and whether the work lies within 200 feet of the ordinary high water line. The city’s LID guidance page says the site assessment review covers all projects and gives no size cutoff, so we confirm how that review applies before work is scheduled.

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

How we approach it

Map where slope water enters the yard
Place the interception line uphill of the wet ground
Run roof water in solid pipe with its own exit
Confirm right-of-way, grading, and shoreline reviews first

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

Questions from Bainbridge Island homeowners

What outlets can a Bainbridge Island French drain use?

We confirm the outlet with the city before the trench opens. The city’s rockery handout requires drain tile behind a wall to run to an approved discharge, and we apply the same check to a French drain on your parcel.

Does a drain here need a permit?

It depends on the earthwork quantity, whether the trench reaches the right-of-way, and whether the work lies within 200 feet of the ordinary high water line. We confirm each of those before work begins.

Will a drain fix the wet yard below my Bainbridge Island bluff?

It may help when water comes off the bluff, but the slope may need evaluation first. We survey the grade and soils before proposing a design, and a drain is recommended only where it addresses the actual source of the water.