Wash. Rev. Code § 53.34.080
The resolution, resolutions, or trust agreement providing for the issuance of revenue bonds or notes pursuant to the provisions of this chapter shall create and establish a special fund of the district into which the district shall be obligated to deposit as collected all income, revenues, receipts, and profits derived by the district through the ownership and operation of any project or projects acquired or constructed from the proceeds of the sale of such revenue bonds or notes: PROVIDED, That additional separate special funds or accounts may be created by such resolution or trust agreement into which the district may obligate itself to deposit the proceeds of the sale of such revenue bonds and notes, the proceeds of the sale or other disposition in whole or in part of any project or projects, the proceeds of any policies of insurance on such projects, and any other additional moneys received by the district and applicable to such projects. All such moneys shall be held by the district, the depositories and trustees of such funds and accounts, in trust for the equal and ratable benefit and security of the holders from time to time of the revenue bonds and notes issued pursuant to the resolution, resolutions, or trust agreement establishing such special funds or accounts, and shall be collected, held, deposited, and disbursed solely for the acquisition, construction, operation, maintenance, renewal, replacement, improvement, extension, and betterment of such project or projects and the payment of the principal of and interest and premium, if any, on the revenue bonds and notes issued pursuant to such resolution, resolutions, or trust agreements, and the creation and maintenance of reasonable reserves for all such purposes: PROVIDED, HOWEVER, That the district may in its discretion and subject to any agreements with the holders of such revenue bonds and notes expend amounts of such moneys as are not required for the purposes aforesaid for other corporate purposes of the district.
The district may pledge such moneys or revenues of the district subject to prior pledges thereof, if any, for the payment of such notes and may in addition secure the notes in the same manner as herein provided for revenue bonds.
RCW 53.34.080