In case the property or any portion thereof described in the notice is not removed from the right-of-way within ten days after the date of the posting, exclusive of the date of posting, all such property upon the right-of-way of the state highway or portion thereof becomes unlawful, and the department shall commence proceedings in the name of the state of Washington for the removal thereof by court action. The department shall thereupon prepare two original copies of the order together with two copies each of the notice posted and of the affidavits in proof of posting thereof and duplicate copies of a certificate by the department describing with reasonable certainty and with due reference to the center line stationing of the state highway and to proper legal subdivisional points, each structure, building, improvement, encroachment, or other means of occupancy, other than pole lines, pipe lines, or other structures maintained for public and quasi-public utilities, on the state highway or portion thereof specified in the order that remain upon the right-of-way as aforesaid. Thereupon action shall be commenced in rem for the purpose of removal of all such unlawful property, in the superior court of the county in which the state highway or portion thereof containing the structures is situated, entitled and in the name of the state of Washington as plaintiff and describing each unlawful structure, building, improvement, encroachment, or other means of occupancy, which structures, buildings, improvements, encroachments, or other means of occupancy shall be briefly named as defendants.