Center an environmentally friendly building because they would save an extra of water a year. The plumbers union opposed the waterless urinals, claiming they were unsanitary and would provide less work for the plumbers. Philadelphia's Plumbing Advisory Board approved the waterless urinals on April 5 after a compromise, which stated that the building's owners and city officials would monitor the performance of the waterless urinals, was reached. Piping that would allow water to flow to the urinals in case they needed to be converted was installed in the Comcast Center, which Liberty Property Trust says was always part of the building's plan. A week later, on April 13, Liberty Property Trust sold an 80-percent interest in the Comcast Center to German real estate firm CommerzLeasing & Immobilien AG, a subsidiary of Commerzbank AG. The deal completed Liberty Property Trust's planned recapitalization of the anticipated cost of the building, and the value of the joint venture, called Liberty/Commerz 1701 JFK Boulevard L.P., included mortgage debt and equity. On June 18, 2007, the Comcast Center was topped out. The ceremony, which was held in the building's future plaza, featured the raising of a steel beam to the skyscraper's highest point. The beam was signed by workers and guests and as it was raised, on account of tradition, an American flag and a tree sat on the beam. Also sitting on the beam was a statue of Philadelphia-founder William Penn. The statue was there to counteract the 1980s "curse" of Billy Penn, which prevented Philadelphia's sports teams from winning a championship following the construction of buildings taller than the statue of William Penn on top of the Philadelphia City Hall. The statue of William Penn remained on the beam until it was stolen. The statue was replaced and the "curse" ended when the Philadelphia Phillies won the 2008 World Series. Even though the building had not officially opened, Comcast office workers began moving in early December 2007, ahead of the scheduled completion in March 2008. The Comcast Center officially opened on June 6, 2008. A study sponsored by Comcast and Liberty Property Trust said the construction of the Comcast Center created 17,200 jobs and generated US$2 billion of economic activity for Pennsylvania. Despite opposition by other building owners to construction of the Comcast Center, by the time most space in the Comcast Center had been leased vacancy rates in Center City offices were