The governing body of any municipality may, by ordinance, include in the special assessment for the paving, macadamizing or constructing sidewalks on any street, avenue or alley the cost of bringing to the established grade said street, avenue or alley, or part thereof, proposed to be improved; provided, that the resolution declaring the paving and macadamizing necessary to be done shall also declare that the street, avenue or alley, or part thereof, shall be brought to the established grade, and that the cost thereof shall be included in the special assessment for paying for the paving or macadamizing.