Wash. Rev. Code § 35.43.188
A city or town ordering a local improvement upon which special assessments on property specifically benefited by the improvement are levied and collected, may provide as part of the ordinance creating the local improvement district that the payment of an assessment levied for the district on underdeveloped properties may be made by owners of other properties within the district, if they so elect, subject to terms of reimbursement set forth in the ordinance. The terms for reimbursement shall require the owners of underdeveloped properties on whose behalf payments of assessments have been made to reimburse all such assessment payments to the party who made them when those properties are developed or redeveloped, together with interest at a rate specified in the ordinance. The ordinance may provide that reimbursement shall be made on a one-time, lump sum basis, or may provide that reimbursement shall be made over a period not to exceed five years. The ordinance may provide that reimbursement shall be made no later than the time of dissolution of the district, or may provide that no reimbursement is due if the underdeveloped properties are not developed or redeveloped before the dissolution of the district. Reimbursement amounts due from underdeveloped properties under this section are liens upon the underdeveloped properties in the same manner and with like effect as assessments made under this chapter. For the purposes of this section, "underdeveloped properties" may include those properties that, in the discretion of the legislative body of the city or town, (1) are undeveloped or are not developed to their highest and best use, and (2) are likely to be developed or redeveloped before the dissolution of the district.
RCW 35.43.188
Severability-Prospective application-Section captions-1988 c 179: See RCW 39.92.900 and 39.92.901.