Wash. Rev. Code § 43.180.170
Proceeds from the sale of all bonds issued under this chapter received by the commission shall be deposited forthwith 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, in a special fund or funds established for the particular purposes for which the bonds were issued and sold, which money shall not be funds of the state of Washington. Such fund or funds shall at all times be segregated and set apart from all other funds and held in trust for the purposes for which such bonds were issued as determined by the commission. Money other than bond sale proceeds received by the commission for these same purposes, such as private contributions or grants from the federal government, may be deposited in such fund or funds. Proceeds received from the sale of the bonds may also be used to defray the expenses of the commission in connection with and incidental to the issuance and sale of bonds, as well as expenses for studies, surveys, estimates, plans, inspections, and examinations of or incidental to the purposes for which the bonds were issued, and other costs advanced therefor by third parties or by the commission. In lieu of the commission receiving and handling these moneys in the manner outlined in this section, the commission may appoint trustees, depositaries, paying agents, and other financial institutions within or without the state 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 43.180.170