All objections or protests relating to the validity of the proceedings had under this division, and not otherwise provided for in this division, shall be made in writing and filed in the manner and not later than the time at which protests or objections may be filed for the hearing designated in the resolution or ordinance of intention, and any protest or objection relating to the validity of the proceedings had under this division not made at such time and in such manner shall be waived and may not thereafter be urged, pleaded or raised in any action or proceeding, and the adoption of a resolution or ordinance finally ordering the acquisition or improvement shall be conclusive evidence that the proceedings prior thereto under this division are valid and sufficient.

(Added by Stats. 1941, Ch. 79.)