Wash. Rev. Code § 70.37.070
All revenues received by the authority from a participant derived from a particular project of such participant to be applied on principal and interest of bonds or for other bond requirements such as reserves and all other funds for the bond requirements of a particular project received from contributions or grants or in any other form shall be deposited by the authority in qualified public depositaries to the credit of a special trust fund to be designated as the authority special bond fund for the particular project or projects producing such revenue or to which the contribution or grant relates. Such fund shall not be or constitute funds of the state of Washington but at all times shall be kept segregated and set apart from other funds. From such funds, the authority shall make payment of principal and interest of the bonds of the particular project or projects; and the authority may set up subaccounts in the bond fund for reserve accounts for payment of principal and interest, for repairs and replacement and for other special requirements of the bonds of the project or projects as determined by the authority. In lieu of itself receiving and handling these moneys as here outlined the authority may appoint trustees, depositaries and paying agents to perform the functions outlined and to receive, hold, disburse, invest and reinvest such funds on its behalf and for the protection of the bondholders.
RCW 70.37.070