Wash. Rev. Code § 35.43.230
Except as herein otherwise provided all matters and proceedings relating to such local improvement district, the levying and collecting of assessments, the issuance and redemption of local improvement warrants and bonds, and the enforcement of local assessment liens hereunder shall be governed by the laws relating to local improvements; and all matters and proceedings relating to the purchase, acquisition, or construction and equipment of the improvement and the operation of the same hereunder and the issuance and redemption of utility bonds and warrants, if any, and the use of general or utility funds, if any, in connection with the purchase, acquisition, construction, equipping, or operation of the improvement shall be governed by the laws relating to municipal public utilities.
RCW 35.43.230