The department shall investigate each activity or project conducted under RCW
90.56.350 to determine, if possible, the circumstances surrounding the entry of oil into waters of the state and the person or persons allowing said entry or responsible for the act or acts which result in said entry. Whenever it appears to the department, after investigation, that a specific person or persons are responsible for the necessary expenses incurred by the state pertaining to a project or activity as specified in RCW
90.56.360, the department shall notify said person or persons by appropriate order. The department may not issue an order pertaining to a project or activity which was completed more than five years prior to the date of the proposed issuance of the order. The order shall state the findings of the department, the amount of necessary expenses incurred in conducting the project or activity, and a notice that said amount is due and payable immediately upon receipt of said order. The department may, upon application from the recipient of an order received within thirty days from the receipt of the order, reduce or set aside in its entirety the amount due and payable, when it appears from the application, and from any further investigation the department may desire to undertake, that a reduction or setting aside is just and fair under all the circumstances. If the amount specified in the order issued by the department notifying said person or persons is not paid within thirty days after receipt of notice imposing the same, or if an application has been made within thirty days as herein provided and the amount provided in the order issued by the department subsequent to such application is not paid within fifteen days after receipt thereof, the attorney general, upon request of the department, shall bring an action on behalf of the state in the superior court of Thurston county or any county in which the person to which the order is directed does business, or in any other court of competent jurisdiction, to recover the amount specified in the final order of the department. No order issued under this section shall be construed as an order within the meaning of RCW
43.21B.310 and shall not be appealable to the hearings board. In any action to recover necessary expenses as herein provided said person shall be relieved from liability for necessary expenses if the person can prove that the oil to which the necessary expenses relate entered the waters of the state by causes set forth in *RCW
90.56.370(2).