If the agency head determines that the proposed improvements are not specially beneficial to state-owned lands or are not authorized by law or that the amount assessed against state-owned lands is not the just and equitable portion of the cost of the improvements which the state should pay as specified in WAC 82-12-030 and RCW 79.44.020, then it shall be his responsibility to initiate formal action commensurate with his exceptions to said improvements. The agency head shall immediately notify the assessing district and the director by registered or certified mail of his exceptions. When necessary, the agency head shall utilize all legal remedies available to property owners to challenge the amount or validity of any assessment.