Wash. Rev. Code § 54.16.020
A district may construct, condemn and purchase, purchase, acquire, lease, add to, maintain, operate, develop, and regulate all lands, property, property rights, water, water rights, dams, ditches, flumes, aqueducts, pipes and pipe lines, water power, leases, easements, rights-of-way, franchises, plants, plant facilities, and systems for generating electric energy by water power, steam, or other methods; plants, plant facilities, and systems for developing, conserving, and distributing water for domestic use and irrigation; buildings, structures, poles and pole lines, and cables and conduits and any and all other facilities; and may exercise the right of eminent domain to effectuate the foregoing purposes or for the acquisition and damaging of such property and rights, or property of any kind appurtenant thereto, and for the purpose of acquiring the right to make physical connection with plants and plant facilities of all persons and municipalities. The right of eminent domain shall be exercised pursuant to resolution of the commission and conducted in the same manner and by the same procedure as is provided for the exercise of that power by cities and towns of the state in the acquisition of like property and property rights. It shall be no defense to a condemnation proceeding that a portion of the electric current generated or sold by the district will be applied to private purposes, if the principal uses intended are public: PROVIDED, That no public utility owned by a city or town shall be condemned, and none shall be purchased without submission of the question to the voters of the utility district. In a condemnation proceeding, the court shall submit to the jury the values placed upon the property by the taxing authority for taxation purposes, and in respect to property, plants, and facilities of persons using public highways for furnishing public service without franchises, shall consider in determining the value thereof the fact that the property, plants, and facilities are subject to be removed from the highways by reason of being so operated without a franchise.
RCW 54.16.020
Eminent domain: State Constitution Art. 1 s 16 (Amendment 9).
Eminent domain by cities: Chapter 8.12 RCW.