The Savannah port — already the fourth-busiest in the United States — is poised for exponential growth that should spur more economic development in Hall County and the rest of the state, a ports leader told Hall County business leaders Thursday. “Our role is to be an enabler of local commerce to spur economic development,” said Clifford Pyron, chief commercial officer for the Georgia Ports Authority, during a presentation at the Greater Hall Chamber of Commerce’s board of directors meeting at the Gainesville Civic Center. The statewide economic impact of GPA already is major — facilitating $84 billion in sales, adding $33 billion to the state gross domestic product and 370,000 direct and indirect jobs — according to statistics compiled by the Terry College of Business at the University of Georgia.