Wash. Rev. Code § 43.180.180
All revenues received by the commission including funds received from contributions or grants or in any other form to pay principal of and interest on bonds or for other bond requirements such as reserves shall be deposited by the commission in any trust company, savings bank, savings and loan association, or bank having the powers of a trust company within or without the state, to the credit of a special trust fund or funds. The commission may establish a bond fund or funds, and a reserve, sinking fund and other accounts therein, for payment of principal and interest and for other special requirements of the bonds as determined by the commission. In lieu of the commission receiving and handling these moneys as outlined in this section, the commission may appoint trustees, depositaries, paying agents, and other financial institutions 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. Such revenues and funds, whether received and held by the commission or by others on its behalf, shall not be or constitute public funds of the state of Washington but at all times shall be kept segregated and apart from all other funds.
RCW 43.180.180