It is lawful for the department to contract without advertising or bid, or performance bond, with any public utility, whether publicly or privately operated, or with any municipal corporation or political subdivision of the state, for the performance of any work or the furnishing of any service of a type ordinarily performed or furnished by such utility, or by such municipal corporation or political subdivision, whenever, in the opinion of the department, the interest of the public will be best served.
RCW 47.01.210