TYBEE ISLAND, Georgia -- Crews working round-the-clock have begun deepening the waterway cargo ships use to reach Savannah's port after 16 years waiting for studies and funding. It takes that long to balance the countless economic, engineering and environmental impacts of dredging nearly 24 million cubic yards of material from the harbor channel to lower it by 5 feet to allow super-sized container ships to access Savannah year-round.

The Army Corps of Engineers says the project could be done in January 2022 if no delays occur. But that is already being challenged by South Carolina's environmental regulators who filed documents Friday accusing the federal agency of doing unacceptable harm to the Savannah River, which forms a shared border between the two states.

For the first time since it opened in 1895, the inland waterway linking Savannah to the Atlantic Ocean will have a mean low-water depth of 47 feet. That depth is needed to make room for larger cargo ships that began arriving via an expanded Panama Canal last year.

The Corps of Engineers has partnered with the state of Georgia and Georgia Ports Authority to share the cost of the $652 million Savannah Harbor Expansion Project, or SHEP. Congress provides money for the Corps to study potential harbor improvements across the country, and it decides which ones are warranted and will best serve the nation's economy. It also sets budgets to fund them. In addition to dredging the shipping channel, the Corps will build dissolved oxygen injection systems at Plant McIntosh and downstream of Hutchinson Island. Those plants will remove water from the river, inject it with oxygen inside two-story devices called Speece cones and return it to the river.