RCW 39.40.010: Forty percent poll of voters required.

No general obligation bonds of any county, port district, or metropolitan park district upon which a vote of the people is required under existing laws shall be issued, nor shall they become a lien upon the taxable property within such county or district unless, in addition to all other requirements provided by law in the matter of the issuance of general obligation bonds by such county or district, the total vote cast upon such proposition shall exceed forty percent of the total number of voters voting in such county or district at the general county or state election next preceding such bond election.