Wash. Rev. Code § 53.12.175
A ballot proposition to reduce the terms of office of port commissioners from six years to four years shall be submitted to the voters of any port district that otherwise would have commissioners with six-year terms of office upon either resolution of the port commissioners or petition of voters of the port district proposing the reduction in terms of office, which petition has been signed by voters of the port district equal in number to at least ten percent of the number of voters in the port district voting at the last general election. The petition shall be submitted to the county auditor. If the petition was signed by sufficient valid signatures, the ballot proposition shall be submitted at the next general election that occurs sixty or more days after the adoption of the resolution or submission of the petition.
If the ballot proposition reducing the terms of office of port commissioners is approved by a simple majority vote of the voters voting on the proposition, the commissioner or commissioners who are elected at that election shall be elected to four-year terms of office. The terms of office of the other commissioners shall not be reduced, but each successor shall be elected to a four-year term of office.
RCW 53.12.175