RCW 35.33.131

Moneys received from the sale of bonds or warrants must be used for no other purpose than that for which they were issued. If any unexpended fund balance remains from the proceeds realized from the bonds or warrants after the accomplishment of the purpose for which they were issued it must be used for the payment of principal of or interest on such indebtedness consistent with applicable provisions of federal tax law. Where a budget contains an expenditure program to be partially or wholly financed from a bond issue to be authorized thereafter, expenditures of amounts anticipated to be reimbursed from the proceeds of the issuance and sale of such bonds must be made or incurred consistent with any applicable federal tax law requirements.