French Drains & Drainage Systems in Silverdale, WA

Drainage & French drains in Silverdale: what to know

A curtain run set above a slope catches sheet flow before it spreads over the lawn. Its trench drops at an even grade and holds washed stone, and a collector at the low end carries what remains to the outlet. Roof water is taken off in solid pipe so the stone does not clog with roof grit.

KCC 12.20.010 sets two stormwater triggers: 2,000 square feet of hard surface, counting new and replaced together, and 7,000 square feet of ground disturbed. Either one brings in the first five stormwater requirements. The grading threshold is 150 cubic yards under KCC 12.10.030(3), and we check each drain against all three figures before the layout is final.

Permits and rules in Silverdale

Before quoting, we check each outlet against the county right-of-way boundary, the public storm connection rule, and the stormwater triggers. A pipe that would cross county right-of-way is held for a separate permit, because the right-of-way brochure requires one to construct a utility or roadway feature there. An outlet the county has not answered in writing stays open on the scope, and the tie-in waits until the county’s written reply is in the file.

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

How we approach it

Trace where sheet flow first crosses the property line
Keep a steady fall from the trench all the way to the exit
Keep roof water in a separate pipe, away from the gravel
Screen any county right-of-way crossing before excavation

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

Questions from Silverdale homeowners

Where can a Silverdale drain line send its water?

Soil that can take up the flow, a public storm connection that county staff have approved in a written reply, or a level area away from neighboring lots. A connection to a public storm drainage system needs a permit under KCC 12.10.030(2), and a pipe crossing county right-of-way is held for a separate permit. Every outlet is surveyed and written into the scope.

At what point does a Silverdale drain job reach a county permit line?

The answer turns on new and replaced hard surface, the ground disturbed, and the earth moved. KCC 12.20.010 counts new and replaced hard surface toward 2,000 square feet and land disturbance toward 7,000 square feet, and the grading brochure sets the earth-moving line at 150 cubic yards. We total all three before the layout is final.

Will a drain help a Silverdale lawn that stays soaked?

Yes, when water from higher ground keeps the grass soggy. We follow the water to where it enters the lot, then pick an exit the survey supports. A drain with no surveyed exit is not proposed.