Wash. Rev. Code § 35.56.050
If an ordinance is passed as in this chapter provided, and it appears that in making of the improvements so authorized, private property will be taken or damaged thereby within or without the city, the city shall file a petition in the superior court of the county in which such city is situated, in the name of the city, praying that just compensation be made for the property to be taken or damaged for the improvement specified in the ordinance and conduct proceedings in eminent domain in accordance with the statutes relating to cities for the ascertainment of the compensation to be made for the taking and damaging of property, except insofar as the same may be inconsistent with this chapter.
The filling of unimproved and uncultivated lowlands of the character mentioned in RCW 35.56.010 shall not be considered as a damaging or taking of such lands. The damage, if any, done to cultivated lands or growing crops thereon, or to buildings and other improvements situated within the district proposed to be filled shall be ascertained and determined in the manner above provided; but no damage shall be awarded to any property owner for buildings or improvements placed upon lands included within said district after the publication of the ordinance defining the boundaries of the proposed improvement district: PROVIDED, That the city shall, after the passage of such ordinance, proceed with said improvement with due diligence.
If the improvement is to be made at the expense of the property benefited, no account shall be taken of benefits by the jury or court in assessing the amount of compensation to be made to the owner of any property within such district, but such compensation shall be assessed without regard to benefits to the end that said property for which damages may be so awarded, may be assessed the same as other property within the district for its just share and proportion of the expense of making said improvement, and the fact that compensation has been awarded for the damaging or taking of any parcel of land shall not preclude the assessment of such parcel of land for its just proportion of said improvement.
RCW 35.56.050
Eminent domain, cities: Chapter 8.12 RCW.