Wash. Rev. Code § 89.30.523
Such bonds shall not constitute an obligation of the reclamation district and shall so specify on their face, but said bonds shall constitute a general obligation of the general improvement or divisional district for the benefit of which the same are issued and all the lands included in such general improvement or divisional district shall be and remain liable to be assessed for their payment until the principal and interest of said bonds are fully paid: PROVIDED, That in case the plan of improvement contemplates the construction of units progressively, the levy and collection of assessments against lands in any undeveloped unit, may at the option of the district board be deferred until such lands are sufficiently developed to equitably bear such exactions.
RCW 89.30.523