53 Pa. Stat. § 16489
The owners of the said ground, by the first section of this act appropriated for public purposes, shall be paid for the same, by the city of Philadelphia, according to the value, which shall be ascertained by a jury of twelve disinterested free-holders, to be appointed by the courts of quarter sessions of said city, upon the petition of said commissioners; and if the said commissioners shall delay petitioning, as aforesaid, for the period of sixty days after notice given of their taking possession of said ground, then said jury shall be appointed, upon the petition of any person, whose property shall be so taken: Provided, however, That in any case, the said commissioners may negotiate and agree with the owners of any part of said ground, as to the price thereof, and said price shall be reported to the said court of quarter sessions, and if confirmed and approved by said court, shall be conclusive upon said city: And provided further, that whenever it shall be necessary to have recourse to a jury to assess the damages for any property, to be taken as aforesaid, said jury shall estimate the advantage to property adjoining, or in the vicinity, and said jury shall proceed, and their award shall be reviewed and enforced, in the same manner as provided by law, in the opening of roads, in the city of Philadelphia.
53 P.S. § 16489