Wash. Rev. Code § 47.20.630
The department shall have power to sell at public or private sale any building, equipment, or fixtures acquired in the acquisition of the real estate for such price as it shall fix and to execute to the purchaser upon payment of the purchase price a bill of sale in the name of the state. Proceeds of the sale shall be placed in the motor vehicle fund of the state treasury. The department shall have power to permit occupation of buildings on real estate so acquired for such specified limited time as it deems will lapse before construction of the approach, underpass, and highway can be undertaken; and in behalf of the state it may be shown in any condemnation proceeding the period during which such occupancy will be permitted for the purpose of mitigating damages.
RCW 47.20.630