If, incidental to the construction or maintenance of a state highway, the department determines and orders that an encroachment previously authorized by written permit must be changed, relocated, or removed, the owner of the encroachment shall change, relocate, or remove it at no expense to the state, except as provided in AS 19.25.020, within a reasonable time set by the department. If the owner does not change, relocate, or remove an encroachment within the time set by the department, the encroachment shall be considered an unauthorized encroachment and subject to the provisions of AS 19.25.220 - 19.25.250.