The demolition work served as a backdrop for a noon ceremony, hosted by Willard G. Rouse 3d, Liberty chairman, at which Mayor Street signed an ordinance cutting the city wage and business gross-receipts taxes.
Standing on a portable stage on the construction site, Rouse declared: "The companies that will occupy the building we build on this site will add to the job count and the vitality of the city. We are very optimistic about Philadelphia's future."
The last tenant on the site, the city's Public Defender Association, will move to its new quarters in the Packard Building on 15th Street by June 15.
"Then we will begin final demolition work . . . which will take about 45 days," said John Gattuso, the Liberty senior vice president in charge of the skyscraper project, which is called One Pennsylvania Plaza.
Liberty has announced no lease signings, but Gattuso said he remained confident that it would have enough leases signed to begin construction by August. Site preparation, which is expected to cost $25 million, began late last summer. Construction is scheduled to be completed in late 2004.
The nine city art commissioners were treated like prospective tenants for the 1.25-million-square-foot building. They got the full multimedia sales presentation before discussing the building's public art, which requires their approval.
Liberty has proposed a water sculpture - a high-tech fountain designed by Claire Kahn Tuttle of San Francisco and Wet Design of Los Angeles - for the half-acre outdoor plaza.
Tuttle showed pictures of fountains she has created for the World Trade Center in Barcelona, Spain, and the Performing Arts Center of Los Angeles.
The choreographed and brightly lit fountain will have displays that change to "reflect many moods" of the city - from quiet and contemplative to vibrant and playful, she said. Using computer technology, heated water and wind sensors, it will be a showpiece of the plaza, even in winter.
Liberty has proposed large murals for the interior lobby.