Wash. Rev. Code § 85.08.190
For the purpose of taking or damaging property for the purposes of this chapter, counties shall have and exercise the power of eminent domain in behalf of the proposed improvement district, and the mode of procedure therefor shall be as provided by law for the condemnation of lands by counties for public highways: PROVIDED, That the county, at its option, pursuant to resolution to that end duly passed by the board of county commissioners, may unite in a single action, proceedings for the acquisition and condemnation of different tracts of land required for rights-of-way which are held by separate owners. The court may, on motion of any party, consolidate into a single action separate suits for the condemnation of different tracts of land held by separate owners whenever from motives of economy or the expediting of business it appears advisable to do so. In such cases the jury shall render separate verdicts for the different tracts of land.
RCW 85.08.190