53 Pa. Stat. § 16555
The councils of said city, whenever they shall need ground in the city of Philadelphia for reservoirs, or other purposes connected with its supply of water, shall have power, if they cannot agree with the owner or owners thereof as to the price, or if for any other cause they shall be unable by negotiation to secure a satisfactory title thereto, to appropriate the same by ordinance, and to cause a petition to be filed in the court of quarter sessions of the city and county of Philadelphia, on behalf of said city, setting forth by proper metes and bounds the grounds so selected, and that by ordinance the said councils have appropriated the same for said purposes; whereupon the said court shall appoint a jury to assess the damages in the manner now provided by law, and the proceedings thereupon shall be the same and with the like effect as upon the assessment of damages for the opening of streets in said city: Provided, That the jury in such case may report to the said court at any time not later than the fourth term after that of their appointment, unless the said court, by rule or order, should require or permit a report to be made at an earlier or later term.
53 P.S. § 16555