After receiving such reports, the board shall determine and declare by resolution whether or not the proposed plan of work is feasible and whether or not the project, as set forth in said reports, is necessary, and if so, shall make an order determining the amount of bonds that should be issued in order to raise the amount of money necessary therefor, and in determining such amount, sufficient shall be included to cover the cost of inspection of works in course of construction. Such determination by the board shall constitute a conclusive determination that the reports then on file with the board are adequate and sufficient to enable the board to make the determination as

set forth in such resolution.