SAVANNAH — The expansion of the Savannah harbor is authorized to begin and state officials must now form an agreement with the U.S. Army Corps of Engineers to determine how costs of the anticipated $706 million project will be split with the federal government, Georgia Ports Authority officials said Tuesday. The plan can move forward now that President Barack Obama has signed the Water Resources Reform and Development Act of 2014. The expansion is expected to make room for larger cargo ships at Savannah, which has the fourth-busiest container port in the U.S. Hall County manufacturers have said the port deepening is important for their business.