Cal. Sts. & High. Code § 2932

If the acquisition or improvement is for sewerage or drainage facilities only and is deemed by the legislative body conducting the proceedings to be necessary for the inhabitation or use of the property benefited, and such body shall, by a four-fifths vote of all members thereof entered upon its minutes, determine that said project is feasible and that the lands to be assessed will be able to carry the burden of such proposed assessment, it may by like vote overrule a majority protest in the proceedings hereunder or in the improvement proceedings to follow. Such finding and conclusion shall be final and conclusive in the absence of fraud.