Wash. Rev. Code § 90.28.020
It shall be the duty of the department of transportation, if the road to be affected shall be a state highway, or of the county legislative authority of the county in which such road is located, if the road to be affected shall be a county road, or permanent highway, or of the council of any town in which the road is located, if the road to be affected shall be a street or alley, within thirty days after entry of said order or decree of public use and the filing of the bond mentioned in RCW 90.28.010, to enter an appropriate order or resolution directing the relocation and reestablishment and completion forthwith of such highway, road, street or alley in place of that so to be overflowed or inundated, and promptly thereafter to acquire all property and rights-of-way necessary therefor, instituting and diligently prosecuting such condemnation suits as may be necessary in order to secure such property and rights-of-way. The decision of the committee, board or council as to relocation and reestablishment set forth in such order or resolution shall be final and conclusive as to all matters and things set forth therein, including the question of public use and necessity in any and all condemnation suits to be brought under RCW 90.28.010 and 90.28.020. After the reestablishment and relocation of any such highway, road, street or alley and the construction and opening thereof in its entirety to public travel and the signing of the grant authorized in RCW 90.28.010, the state highway, county road or permanent highway, street or alley or such part thereof described in said grant shall be deemed to be abandoned and thereafter cease to be a highway, road, street or alley.
RCW 90.28.020
Eminent domain by corporations: Chapter 8.20 RCW.
Private ways of necessity: Chapter 8.24 RCW.