(1) Upon receipt of perpetual care and maintenance fee payments, the department shall transmit such payments to the state treasurer for deposit in the perpetual maintenance account authorized by chapter 19, Laws of 1983 1st ex. sess.

(2) Moneys in the perpetual maintenance account shall be invested by the state investment board in the same manner as other state moneys. Any interest accruing as a result of investment shall accrue to the perpetual maintenance account.

(3) The department shall maintain a segregated account of perpetual care and maintenance fee payments which are deposited in the perpetual maintenance account.

(4) The department, in consultation with the state radiation control agency, shall periodically evaluate the perpetual care and maintenance fee to determine whether it will provide adequate financing to assure perpetual care and maintenance of a closed facility. Any adjustments to the fees shall be made by rule adopted pursuant to chapter 34.04 RCW.