53 Pa. Stat. § 16509
The Fairmount park commissioners shall have power, on behalf of the city of Philadelphia, to adjust the boundaries of said park with any railroad or canal company whose track, tow-path, or canal navigation lies within or is bordering upon said park, and with any other owner bounding upon the park, and to receive and make the proper conveyances or releases in adjusting said boundaries as now provided by law; and if an increase of width be conceded to any company or companies, or individuals, or an exchange of property be made, it shall be at a rate of compensation not less than a just and proportionate share of the cost of the whole property paid at any time by the city of Philadelphia, with lawful interest thereon; which compensation shall be paid into the sinking fund of said city for the extinguishment of the park loan.
53 P.S. § 16509