Whenever any local or public improvements shall be ordered by the council, which are to be paid for in whole or in part by special assessment or special taxation or otherwise, it shall be the duty of the city engineer to prepare a plan or profile of the proposed improvement and specifications for the construction of the same, which shall be kept on file in his office, and be open to the inspection of city officers and other persons interested therein. (R.O. 1959, Ch. 36, Art. 5, Sec. 2)