(1) A member who separates or has separated after having completed at least five years of service may remain a member during the period of such member's absence from service for the exclusive purpose only of receiving a retirement allowance under the provisions of RCW
41.26.430 if such member maintains the member's accumulated contributions intact.
(2) The retirement allowance payable under the provisions of RCW
41.26.430 to a member who separates after having completed at least twenty years of service, and remains a member during the period of his or her absence from service by maintaining his or her accumulated contributions intact, shall be increased by twenty-five one-hundredths of one percent, compounded for each month from the date of separation to the date the retirement allowance commences as provided in RCW
41.26.490.