None of the provisions of this division shall apply to proceedings heretofore or hereafter commenced for the construction or acquisition, or the construction and acquisition, of sanitary sewers, sewage disposal works, and storm water drains, including the acquisition of sewer and storm water drain rights-of-way and easements necessary in connection with such improvement, when such proceedings have been recommended by the health officer of the city or county in which such proceedings are instituted as necessary as a health measure, if such recommendation is given in writing and spread upon the minutes of the legislative body conducting such proceedings, and such necessity is found to exist by resolution adopted by the affirmative vote of four-fifths of the members thereof. The findings and determinations made by the legislative body pursuant to this section shall be final and conclusive upon all persons in the absence of actual fraud.