French Drains & Drainage Systems in Steilacoom, WA

Drainage & French drains in Steilacoom: what to know

A French drain or curtain drain is designed around its outlet. SMC 13.50 covers outfalls, infiltration, treatment, and flow control at SMC 13.50.730, and its discharge prohibitions sit in SMC 13.50.670 and 13.50.720. The stormwater manual the town adopts in SMC 16.04.160 is Ecology’s 2012 Stormwater Management Manual for Western Washington, with later versions, so the outlet is read against that manual as well.

Trench work is checked against the earth-moving rules. A cut over 50 cubic yards calls for a site development permit under chapter 13.70, cut and fill slopes stay no steeper than 2 to 1 unless the town approves, and exposed soil is covered within the day limit in SMC 13.70.050(B)(1). A drain that reaches the street or a curb falls under the street work permit in SMC 12.20.

Permits and rules in Steilacoom

Before a drain is quoted, we confirm three answers with town staff: whether the outlet needs a storm connection permit under SMC 13.12.020, whether the trench volume passes the 50-cubic-yard line in chapter 13.70, and whether the route crosses the street or a curb under chapter 12.20. A cut of 100 cubic yards or less is exempt from SEPA review under SMC 16.04.080, but SEPA review and the site development permit are separate questions, so we check each one. Each answer is logged on the drawing, and the quote lists any item still waiting on the town.

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

How we approach it

Fix the outlet location before any trench grade is set
Place curtain drains uphill of the saturated ground
Carry roof water through solid pipe to its own outlet
Resolve any town frontage review before excavation

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

Questions from Steilacoom homeowners

Can a Steilacoom French drain tie into the sanitary sewer under SMC 13.28?

No. SMC 13.28.020(a) bars stormwater from the sanitary sewer, so a drain cannot be run into the sewer line. The outlets we plan for are ground on the parcel that can absorb the water, or a storm connection the town approves.

Which Steilacoom drain work needs the SMC 13.12.020 storm connection permit?

A drain that ties to a storm line needs the permit and connection charge in SMC 13.12.020. A trench that moves more than 50 cubic yards needs a site development permit under chapter 13.70, which is a separate question from the connection.

How steep can a Steilacoom hillside drain trench bank be cut?

The town’s ceiling for a cut bank is 2 to 1 under SMC 13.70.050(A)(3), and a steeper bank needs town approval first. A steep bank above a drain can also raise the slope questions in SMC 16.16.710, so we measure the slope before the trench is laid out.