Lt. Governor Jim Cawley and Philadelphia Mayor Michael Nutter are expected to be on hand for the ceremony.
The initial structure will include 160,000 square feet of retail space on two levels, topped by a 325-unit apartment building.
Phase I will also renovate the 200,000-square-foot family court building into retail and office space.
"We're going to have grocers, we're going to have restaurants, entertainment, fashion," said Jeff Kanne, CEO of National Real Estate Advisors, the $2.2 billion-asset, Washington-based firm backing the project.
The project will be built with 100% union labor, including IBEW electricians. The development team was glad to note that union crews delivered the NREA-backed tower at 2116 Chestnut Street ahead of schedule.
The $500 million-plus project is aimed at upgrading Philadelphia's worn downtown retail district and spreading Center City's apartment revival east of Broad Street.
NREA counts the International Brotherhood of Electrical Workers and other labor unions among its investors.
Planned are new store buildings facing Market Street, lit by Times Square-style signs, that will be topped by 325 apartments - at $2,300 a month for a one-bedroom unit - with underground parking.
The builders will strip and replace the outside walls of the eight-story former Snellenburg warehouse facing 11th Street, now used by the city's Family Court. The developers are talking to office tenants, but could end up putting more apartments there.
Retail stores are planned for the first floor of the nearby 12-story Girard office building, with the upper floors upgraded for office, hotel, or apartments, depending on market demand.
"We're going to make Market Street cool again," said Daniel Killinger, director at NREA Development Services.
If the initial space sells well, the group plans to replace buildings in the 1100 block of Chestnut Street with new stores and apartments - bringing the residential count for the entire project to as many as 1,000 units.
