87.15 Repairs, replacements and extensions; procedure. Whenever the flood control board shall determine and certify that repairs or replacements are necessary to such an extent as to amount to a partial reconstruction of the improvement rather than ordinary maintenance, or whenever said board shall determine that material additions, extensions or betterments to said improvement are necessary, the board shall file a petition with the department setting forth the necessity for such repairs, replacements, additions, extensions or betterments, and thereupon the department shall proceed to make the same determinations and certifications as in the case of an original petition for the construction of the improvement, except that the enumeration of lands or other property benefited and of the political subdivisions included within the drainage area shall be the same as in the original order for the construction of the improvement, unless the department shall affirmatively find that changes in such enumeration are necessary because of errors in the original findings.