If the certifying officer certifies that the petition bears the signatures of owners of taxable property within the proposed district, representing 60 percent or more of the total assessed valuation of all taxable property therein, the board of supervisors may determine and order, by a four-fifths vote, that the proceedings required by the District Investigation Law of 1933 are unnecessary and that said law shall not apply. The petition shall thereupon be filed without an accompanying bond or other undertaking. If said determination and order is made, the notice of hearing on the petition shall so state.