The director may authorize removal, relocation, reconstruction, or other modification of an inadequate fishway or fish protective device required by *RCW
77.55.320 which device was in existence on September 1, 1963, without cost to the owner for materials and labor. The modification may not materially alter the amount of water flowing through the fishway or fish protective device. Following modification, the fishway or fish protective device shall be maintained at the expense of the person or governmental agency owning the obstruction or water diversion device.