What is a grayfield?

A grayfield is a former retail or office facility.  The good news?  The ground was protected throughout the former use and uses were generally low-impact.  The bad news?  Finding new users for purpose-built facilities is difficult to impossible (everyone has their own footprint), and the vast areas of pavement load storm sewers and create heat islands.  Worst of all, these facilities are often centrally located (got the first location next to the interstate, for example), and new businesses end up sprawling out further.