Wash. Rev. Code § 87.22.230
No tract of land shall be assessed by the district during the life of the proposed bonds when issued for the purpose of paying the principal of or interest on said bonds in an aggregate amount in excess of double the amount determined in the decree fixing maximum benefits under subdivision (1) of RCW 87.22.040, together with the interest on the principal computed at the rates specified in the bond, and any assessment in excess thereof shall be void. In addition to its regular normal assessment for the principal or interest of said bonds, no tract of land shall be assessed in any one year to make up past or anticipated delinquencies of assessments or both levied or to be levied against the lands in the district for said purposes, in excess of fifty percent of its regular normal assessment for said bonds.
RCW 87.22.230