Wash. Rev. Code § 35.97.100
For the purpose of providing funds for defraying all or a portion of the costs of planning, purchase, leasing, condemnation, or other acquisition, construction, reconstruction, development, improvement, extension, repair, maintenance, or operation of a heating system, and the implementation of the powers in RCW 35.97.030 and 35.97.040, a municipality may authorize, by ordinance or resolution, the creation of a special fund or funds into which the municipality shall be obligated to set aside and pay all or any designated proportion or amount of any or all revenues derived from the heating system, including any utility local improvement district assessments, any grants received to pay the cost of the heating system, and any municipal license fees specified in the ordinance or resolution creating such special fund.
RCW 35.97.100