Wash. Rev. Code § 79.135.020
Upon an application to purchase the reserved and reversionary rights of the state in any tidelands sold under the provisions of chapter 24, Laws of 1895, or chapter 25, Laws of 1895, or chapter 165, Laws of 1919, or either the reserved or reversionary right if only one exists, being filed in the department's Olympia office by the owner of the tidelands, accompanied by an abstracter's certificate, or other evidence of the applicant's title to the lands, the department, if it finds the applicant is the owner of the tidelands, is authorized to inspect, appraise, and sell, if otherwise permitted under RCW 79.125.200, for not less than the appraised value, such reserved or reversionary rights of the state to the applicant, and upon payment of the purchase price to cause a deed to be issued as in the case of the sale of state lands, or upon the payment of one-fifth of the purchase price, to issue a contract of sale, providing that the remainder of the purchase price may be paid in four equal annual installments, with interest on deferred payments at the rate of six percent per annum, or sooner at the election of the contract holder, which contract shall be subject to cancellation by the department for failure to comply with its provisions, and upon the completion of the payments as provided in the contract to cause a deed to the lands described in the contract to be issued to the holder as in the case of the sale of state lands.
RCW 79.135.020