53 Pa. Stat. § 1721
Every municipal corporation shall have power to lay out, establish, or re-establish grades of streets and alleys, or parts thereof, and to construct bridges, piers, and abutments therefor, and sewers and drains in any street or alley, or through, or on, or over private property. Every municipal corporation shall also have power, upon the petition of a majority of property owners in interest and number abutting the line of the proposed improvement, to be verified by affidavit of one or more parties to said petition (a majority in interest of owners of undivided interests in any piece of property to be deemed and treated as one person for the purposes of petition), to grade, pave, curb, macadamize, and otherwise improve any public street or public alley, or part thereof, within its corporate limits, or which they may be, in whole or in part, boundaries thereof. And also including the improvement of any street, road, lane, or alley, and any sections or parts thereof in length in the space between the curb, gutter, or actual carriage-way line and the property line, either by an original work or improvement thereon, or by a change, repair, renewal, or alteration in the said highway space, by the spacing and constructing of a footwalk, curb, parking space, or shadetrees, or by changing, altering, renewing, replanting, pruning, or otherwise improving the same in any or all of said particulars. On petition, viewers shall be appointed as provided in the first section of this act, who shall assess the costs and expenses of the sewer, or grading, paving, curbing, macadamizing, footwalks, parking, shadetree planting, or changing, altering, renewing, replanting, pruning, or other improvement of each street or alley, or part thereof, within its corporate limits, upon the property benefited, according to benefits, if sufficient can be found, but, if not, then the deficiency, when finally ascertained, shall be paid by the municipal corporation, and the proceedings of said viewers, and the proceedings on their report, shall be as provided in this act for viewers and reports of viewers in cases of property taken, injured or destroyed.
Upon petition, as aforesaid, of a majority of property owners in interest and number abutting the line of a proposed temporary improvement or paving, the municipal corporation shall have the right to make the same, the costs and expenses thereof being assessed against the property benefited in the manner heretofore provided. Thereafter, the municipal corporation may replace said improvement or paving with a permanent improvement or paving in the manner provided by law, with the right to have the costs and expenses thereof assessed against the property benefited in the manner heretofore provided, but only if the costs and expenses first assessed shall be allowed as a credit or set-off against the costs and expenses assessed for such subsequent permanent improvement of paving.
53 P.S. § 1721