You can always go to
www.phila.gov/map and click on zoning when the menu of maps pops up to look at zoning across the city. The entire area between 2nd and 6th, Callowhill to Spring Garden is now CMX-3. The details of the additional bonuses available in this area through the overlay are laid out here:
http://planphilly.com/articles/2015/...hern-liberties
Those extra bonuses are what allow this project to achieve that height and density which would appear to exceed what would be allowed under normal CMX-3 conditions.