Wash. Rev. Code § 54.16.060
A district may build and maintain intertie lines connecting its power plant and distribution system with the power plant and distribution system owned by any other public utility district, or municipal corporation, or connect with the power plants and distribution systems owned by any municipal corporation in the district, and from any such intertie line, sell electric energy to any person, public utility district, city, town or other corporation, public or private, and, by means of transmission or pole lines, conduct electric energy from the place of production to the point of distribution, and construct and lay aqueducts, pipe or pole lines, and transmission lines along and upon public highways, roads, and streets, and condemn and purchase, purchase or acquire, lands, franchises, and rights-of-way necessary therefor.
RCW 54.16.060