"The deepening will cut transportation costs by reducing transit delays for larger, more efficient post-panamax vessels," Georgia ports authority executive director Curtis Foltz said.
"Cost reductions of about 30 per cent are expected, saving billions over the 50-year life of the project."
The bill officially lifts the spending limit set when lawmakers first authorised the project in 1999, which will allow both state and federal dollars to flow into dredging.
According to GPA board chairman Robert Jepson the harbour deepening will not only enable the port to handle today's big ships but will also lower shipping costs by $213 million a year, for a "return on investment of $5.50 for every dollar spent to construct and maintain this project".
Initial contracts will include dredging to extend the entrance channel from the mouth of the Savannah River by seven miles further into the Atlantic Ocean.