Wash. Rev. Code § 4.16.030
An action to collect any special assessment for local improvements of any kind against any person, corporation or property whatsoever, or to enforce any lien for any special assessment for local improvements of any kind, whether said action be brought by a municipal corporation or by the holder of any delinquency certificate, or by any other person having the right to bring such an action, shall be commenced within ten years after such assessment shall have become delinquent, or due, or within ten years after the last installment of any such special assessment shall have become delinquent or due when said special assessment is payable in installments.
RCW 4.16.030
Actions brought by code city: RCW 35A.21.200.
Actions to foreclose special assessments in cities or towns: RCW 35.50.050.