GEORGIA authorities have been given the go-ahead to deepen the port of Savannah's channel from 38 feet to 42 feet at a cost of US$57 million. The port, which has signed an agreement with the US government to allow the deepening work to begin in March, expects the project to be completed in 13 months. The Local Co-operative Agreement (LCA), which formally spells out the responsibility between the Georgia Ports Authority (GPA) and Washington on the deepening project, specifically covers issues relating to funding, easements and disposal sites. Describing the signing of the agreement as a ''historic day for all Georgians'', GPA executive director George Nichols said: ''Deepening the Savannah River channel to 42 feet will give us one of the deepest channels in the South Atlantic. ''This will allow us to continue to develop, stimulate and encourage the water-borne commerce of this state.'' Without such harbour improvements, Mr Nichols added, new larger container ships calling on the port of Savannah would have to lighten loads or wait for high tide before using the harbour, a cost which could cause them to avoid the port. ''Either of these choices would be prohibitively expensive for our customers and ultimately for us,'' he said. The federal government will share the cost of the project with the state of Georgia. The Savannah harbour deepening is the third navigational improvement made at the port. In 1991, a new bridge was built across the Savannah River raising the vertical clearance to 185 feet and late last year the Savannah River channel was widened from 400 to 500 feet.