French Drains & Drainage Systems in Olympia, WA

Drainage & French drains in Olympia: what to know

Olympia’s June 2023 guidesheet sorts projects by area. Work below the 2,000 square foot line for new or replaced hard surface, and below 7,000 square feet of ground disturbance, needs no stormwater plan, though erosion controls still apply. Paving past the 2,000 square foot line calls for an abbreviated plan, and past 5,000 square feet a full plan with a scoping meeting. Disturbance over 7,000 square feet also brings a full plan.

The storm connection follows OMC 13.16.020, which requires the owner to apply for an engineering permit before stormwater is discharged into the storm drainage system. The stormwater chapter’s definition of development covers clearing, grading, or filling with no minimum area, so even a small trench gets a check. An outlet aimed at a slope that meets the landslide hazard line also gets a critical-area check under OMC 18.32.610 before the trench is laid out.

Permits and rules in Olympia

Screening comes before layout. Paving that is new or replaced is compared with the 2,000 and 5,000 square foot lines, the ground the crew disturbs is compared with the 7,000 square foot line, and we settle whether the outlet reaches the storm system, which needs an engineering permit under OMC 13.16.020. We look up any slope that meets the landslide line within the drain route, and we confirm the buffer answer with the city in writing when one applies.

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

How we approach it

Total new and replaced hard surface and disturbed ground before sizing
Keep any storm connection on hold until the engineering permit issues
Check the drain route for slopes that meet the landslide hazard line
Write the outlet on the plan with its review path beside it

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

Questions from Olympia homeowners

Where can an Olympia yard drain discharge?

Any discharge into the city’s storm drainage system needs an engineering permit under OMC 13.16.020 before it goes in. We compare the outlet choices against the lot, the review path, and any slope on the route, then write the chosen point on the plan.

Does an Olympia French drain need a stormwater plan?

It depends on its size and the ground it disturbs. Work that adds less than the 2,000 square foot line and disturbs less than 7,000 square feet calls for no plan under the June 2023 guidesheet. Larger work needs an abbreviated or full plan, and we confirm which applies in writing.

Does a yard drain near an Olympia slope need extra review?

It can. The landslide hazard rule in OMC 18.32.610 covers slopes of 40 percent or steeper with a vertical rise of ten feet or more, and slopes of 15 percent or steeper where water-resistant layers and seepage are present. When a drain route meets that line, we ask the city about the buffer in writing before the trench is laid out.