Wash. Rev. Code § 35.84.030
Every city or town owning its own electric power and light plant may exercise the power of eminent domain as provided by law for the condemnation of private property for any of the corporate uses or purposes of the city or town: PROVIDED, That no city or town shall acquire, by purchase or condemnation, any publicly or privately owned electric power and light plant or electric system located in any other city or town except with the approval of a majority of the qualified electors of the city or town in which the property to be acquired is situated; nor shall any city or town acquire by condemnation the electric power and light plant or electric system, or any part thereof, belonging to or owned or operated by any municipal corporation, mutual, nonprofit, or cooperative association or organization, or by a public utility district.
RCW 35.84.030
Eminent domain by cities: Chapter 8.12 RCW.