If the city’s total share of the costs equals or exceeds fifty percent of the entire cost of the project, the governing body may initiate, carry out, and construct the project, and special assessments may be levied against the benefited property in the manner provided by law, unless within thirty days after the first publication of the resolution declaring the work to be necessary, the owners of seventy-five percent or more, by area, of the property liable to be specially assessed for the improvement, shall file written protest against said improvement with the city auditor.