Wash. Rev. Code § 35.50.230
In foreclosing local improvement assessment liens, it is not necessary to bring a separate suit for each of the lots, tracts, or parcels of land or other property or for each separate local improvement district or utility local improvement district. All or any of the lots, tracts, or parcels of land or other property upon which local improvement assessments are delinquent under any and all local improvement assessment rolls in the city or town may be proceeded against in the same action. For all lots, tracts, or parcels which contain a residential structure with an assessed value of at least two thousand dollars, all persons owning or claiming to own the property shall be made defendants thereto. For all other lots, tracts, or parcels, the persons whose names appear on the assessment roll and property tax rolls as owners of the property charged with the assessments or taxes shall be made defendants thereto.
RCW 35.50.230
Severability-1982 c 91: See note following RCW 35.50.030.
Construction-Severability-1967 c 52: See notes following RCW 35.43.042.