In every proceeding in which land and property additional to those required for the improvement are acquired, the council shall have power by ordinance to provide that the whole of the expense of any such improvements be assessed upon the property benefited, or that the whole or a portion of such expense (which shall be specified in such ordinance) be borne by the city at large, and the remainder, if any, assessed upon the property benefited.
53 P.S. § 13809