When the Regional Industrial Development Corporation (RIDC) took over Mill 19 at Hazelwood Green and transformed it into a symbol of Pittsburgh’s tech-driven turnaround, it was the only project underway on that site. Now, years later, Hazelwood Green is alive with activity, with Carnegie Mellon University’s Robotics Innovation Center and the University of Pittsburgh’s BioForge under construction and plans announced for a new community sports complex and residential development. “Taking these…