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Building Requirements in Special Flood Hazard Areas

Courtesy King CountyThurston County regulates construction in Special Flood Hazard Areas in order to protect lives, property, and the environment. These areas include locations that experience river flooding and groundwater flooding.

Some of the regulations are found within Thurston County's Building Code; others are found within the county's Critical Areas Ordinance. This page summarizes key provisions of both codes.

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What is a Special Flood Hazard Area?

A Special Flood Hazard Area is any area:

  • Subject to a base of one-hundred year flood (areas of special flood hazard are shown on a flood hazard boundary map or Flood Insurance Rate Map as Zone A, AO, A1-30, AE, A99, AH, VO, V1-30, VE, V).
  • High Ground Water Flood Hazard Areas Resource Map on file with the Resource Stewardship Department.
  • Highest known recorded flood elevation.

Click here for a description of some of the tools Thurston County uses to determine which properties are in a Special Flood Hazard Area.

Permit Requirements

Thurston County participates in the National Flood Insurance Program (external link), which means our building standards for Special Flood Hazard Areas are based upon federal floodplain regulations set by FEMA.

  • When applying for a building permit in a Special Flood Hazard Area, applicants are required to provide a pre-construction elevation certificate that confirms the vertical height requirement for flood protection.
  • The building plans must conform to the Thurston County requirements for construction in Special Flood Hazard Areas (see below). Among other things, the floor elevation of the new home must be 2 feet above the base flood elevation as established by a professional surveyor. Floor elevation will be verified during the home’s floor framing or manufactured home’s blocking inspection. Also, the foundation must contain flow through vents for the passage and draining of flood water.
  • An as-built elevation certificate must be completed by a professional surveyor. This is additional information gathered from the surveyor’s inspection of the completed home.
  • Proof of flood insurance for the home must be submitted to the Thurston County Building Development Center.
  • The owner must subscribe to the Thurston County flood warning system. This subscription is free and can be arranged by calling (360) 754-3360.

Building Requirements in Special Flood Hazard Areas

Thurston County participates in the National Flood Insurance Program, which means our building requirements (codes) for Special Flood Hazard Areas are based upon federal floodplain regulations set by FEMA.

  • In Special Flood Hazard Areas, the lowest floor (including basement) and all flood-susceptible materials must be elevated at least 2 feet above the base flood elevation as established by a professional surveyor. Floor elevation will be verified during the home’s floor framing or manufactured home’s blocking inspection. In high-groundwater areas, construction must also be set back 50 feet from the area that experiences open water.
  •  The foundation must contain flow through vents for the passage and draining of flood water.
  • To see Thurston County's building standards for Special Flood Hazard Areas, visit section 14.38.050 of Thurston County Code Title 14. These standards may reference floodplain zones designated by FEMA, such as "Zone A" or Standards may vary depending on which floodplain zone a property is in. Click here for a description.
  • FEMA provides technical bulletins to help property owners comply with local codes. Click here for a list. Also see page 35 of the NFIP Guide Book.

red arrowBuilding standards in Special Flood Hazard Areas are complicated, but you don't need to do it alone!  The Building Development Center is here to help.  Click here to contact residential plan reviewer Tim Rubert at rubert@co.thurston.wa.us or call (360) 867-2123.

How is "Base Flood Elevation" Established?

Base Flood Elevations are established using several different sources, including FEMA maps.  Click here for a description. Building applicants don't figure out this information on their own; rather, Thurston County requires applicants to submit a pre-construction Flood Elevation Certificate when applying for a permit.

Buffers

Please be advised that Thurston County's Critical Areas Ordinance and Shoreline Master Program also establish buffers along rivers, streams and marine water bodies.

Contact Us

For questions about building in a Special Flood Hazard Area, contact Tim Rubert at 867-2123 or e-mail  rubert@co.thurston.wa.us.

 

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