Olympia, WA Environmental Rules: Flood Zones (2026)

OMC chapter 16.70 applies to all areas of special flood hazard within the City of Olympia. Section 16.70.030.B adopts by reference the Flood Insurance Study for Thurston County, Washington and Incorporated Areas dated May 15, 2018 and the accompanying Flood Insurance Rate Map dated May 15, 2018, with any revisions. Both are on file at the City of Olympia Permit Assistance Center at 601 - 4th Avenue E. Where this chapter and another ordinance, easement, covenant or deed restriction conflict or overlap, whichever imposes the more stringent restriction prevails.

The development permit under § 16.70.040.A is required for all structures, including manufactured homes, and for all development, including fill. The application is made on City forms and includes plans in PDF drawn to scale showing the nature, location, dimensions and elevations of the area, existing or proposed structures, fill, storage of materials and drainage facilities. It must also show the lowest floor elevation on a current FEMA elevation certificate, the elevation to which any structure is floodproofed, and an engineer or architect certification of floodproofing for nonresidential structures. A structure proposed in a V, V1-30 or VE zone needs a V-zone design certificate, and development in a floodway needs an engineering analysis indicating no rise of the Base Flood Elevation.

The Building Official, appointed as Floodplain Administrator, determines whether the site is reasonably safe from flooding, checks whether the project is in the floodway, confirms that other federal, state and local approvals are in hand, and notifies FEMA when annexations occur in the Special Flood Hazard Area. Before any watercourse is altered or relocated, the City must notify adjacent communities and the Department of Ecology. A person contesting a mapped boundary is given a reasonable opportunity to appeal the Building Official's interpretation.

Section 16.70.050 adds the construction rules. In an AE zone with base flood elevations but no designated floodway, no new construction, substantial improvement or other development, including fill, is permitted unless the cumulative effect will not increase the water surface elevation of the base flood more than one foot at any point. In coastal V and VE zones, buildings must be landward of the reach of the mean high tide, and new manufactured home placement is prohibited except in an existing manufactured home park or subdivision. Recreational vehicles must be on the site fewer than 180 consecutive days, or be fully licensed and ready for highway use. Subdivision proposals of at least 50 lots or 5 acres, whichever is less, must generate base flood elevation data where none exists.