The Port of Savannah has leapfrogged ahead of Charleston to become one of the nation's busiest ports, and some fear that deepening the Savannah River could tip the scales further in Georgia's favor.

An Army Corps of Engineers study said "the proposed deepening of the Savannah harbor would not take business from another port," and that increased shipping will require deepening both the Savannah and Charleston ports.

But when the S.C. Department of Health and Environmental Control's board on Nov. 10 approved permits to deepen the Savannah River -- which South Carolina and Georgia share -- critics said the decision would harm the environment and the Port of Charleston.

"It's an attack on South Carolina's economy and our workers," said Liana Orr, executive director of Conservatives for Truth In Politics, which is running a TV advertisement this

weekend criticizing Republican Gov. Nikki Haley.

Haley has taken heat from Republicans and Democrats, who decry the DHEC vote and allege Haley played a role. The governor denies influencing the DHEC board and has said the permit was appropriate.

Environmental groups and South Carolina's Savannah River Maritime Commission plan to challenge the permit. Meanwhile, the Corps of Engineers is pushing toward completing a plan for the deepening next year.

Here's a look at what's going on, and what's at stake:

Question: What does the Georgia Ports Authority want to do at the Port of Savannah, and how does it affect South Carolina?

Answer: The authority wants to deepen 36 miles of the Savannah River to 48 feet, at an estimated cost of more than $600 million. The river is currently dredged to 42 feet.

The proposal would allow larger ships to call at Savannah's port in Garden City. It would make the authorized depth of the channel 3 feet deeper than Charleston's 45 feet, although those depths are not exactly comparable due to the influence of tides and salinity.

The Savannah port can currently handle container ships carrying up to about 6,500 TEUs (a TEU is the equivalent of a 20-foot-long container). Charleston, with its deeper water, in August received the cargo ship MSC Sindy, which can hold 9,580 TEUs. Both ports depend on high tides to accommodate the largest ships and are racing to deepen their channels as an expansion of the Panama Canal draws closer. The canal expansion is expected to bring more cargo traffic from Asia on larger, heavier ships to the U.S. East Coast.

The Savannah dredging would also alter the environment in such a way that machinery would be needed to inject oxygen into parts of the river. It would affect adjoining marsh areas, most of which are located in South Carolina.

Bill Sapp, senior attorney for the Southern Environmental Law Center, put it this way: "In Georgia you have the economic impacts with a fair amount of environmental harm, while in S.C. you have significant environmental harm with limited economic benefit."

Q: Are the Georgia and South Carolina ports rivals whose gains come at each other's expense or allies, as both states seek federal funding for port improvements that could boost commerce across the region?

A: South Carolina is seeking federal money to dredge the Port of Charleston to at least 50 feet, while Georgia wants to dredge the Savannah River to 48 feet. Charleston's proposed deepening is at the beginning of a multiyear study process, while Savannah's began in 1996 and is due for a final decision next year. Both need funding.

Charleston and Savannah do compete for shipping business, and it's a race the Georgia port has been winning in recent years. Charleston has deeper water and can handle much larger container ships, while Georgia's port enjoys proximity to distribution facilities and to Atlanta.

Both ports need hundreds of millions of dollars to deepen their channels. With a congressional ban on earmarks in place and pressure to reduce the federal deficit, there's little federal funding available.

Senators from both states -- along with S.C. Gov. Nikki Haley and the Georgia Ports Authority -- said coastal states need to work together to secure federal funds for port projects.

The Georgia Ports Authority passed a resolution in January supporting Charleston's deepening project, and this month, Georgia Gov. Nathan Deal and U.S. Sens. Saxby Chambliss and Johnny Isakson pledged to support efforts to deepen both the Port of Savannah and the Port of Charleston. U.S. Sen. Lindsey Graham has also said both states need to work together.

In contrast, South Carolina's General Assembly in February passed a resolution opposing the Savannah deepening, and this month, Charleston's legislative delegation voted to back the state's Savannah River Maritime Commission in a challenge to the DHEC decision to allow the dredging.

Q: What about the proposed Jasper Ocean Terminal on the South Carolina side of the Savannah River? Would the Georgia deepening project help or hurt Jasper?

A: The Jasper terminal is a plan that Georgia and South Carolina have been jointly pursuing to eventually build a multibillion-dollar port in economically deprived Jasper County. The location is about six miles closer to the ocean than Garden City. It is now a dredge disposal site with little infrastructure and no utility lines.

South Carolina port officials have said repeatedly that in order for the Jasper port to be viable, it would need to be served by a shipping channel at least 50 feet deep and capable of handling ship traffic in both directions at once.

If the plan to deepen the Savannah River to 48 feet goes ahead, the prospect for a 50-foot-deep channel to serve Jasper would be remote, and the fate of Jasper in doubt, said State Ports Authority officials, including Chief Executive Jim Newsome.

"I don't think a terminal will be built in Jasper County, with a $5 billion investment, unless there is 50 feet and two-way traffic," Newsome said in a recent interview.

Georgia port officials said the Savannah River deepening project would be a boon for the Jasper project, because the dredge material could be used to build up the Jasper site to a height needed for a port. The use of dredge spoils as fill material would save $300 million, in Georgia's view.

Billy Birdwell, spokesman for the U.S. Army Corps of Engineers' Savannah office, said the Savannah River deepening is designed to handle the large container ships that will come with the widening of the Panama Canal, and with the Jasper site also located on the Savannah River, "that means the deeper channel to the ocean would already be there."

Q: The S.C. Department of Health and Environmental Control's board reversed a DHEC staff decision by approving the Savannah River dredging. Why?

A: The board's decision came after Georgia agreed to protect nearly 1,700 acres of marsh in South Carolina, and guaranteed 50 years of funding for oxygen-injecting machines in sections of the river where dredging will reduce levels of dissolved oxygen. Haley said Georgia "met the benchmarks" necessary for the approval.

"I stand behind my DHEC board," Haley said at a Charleston maritime industry event this month. "They did what's right."

The governor also said the Corps of Engineers informed the state that the project would go ahead with or without the DHEC approval. As a result, any concessions from Georgia were a bonus for the state, she said.

Q: Was DHEC's approval needed or, as Haley has suggested, would the Savannah dredging have gone ahead regardless?

A: The idea that the project could proceed without approval from South Carolina is more of a legal theory than a fact.

The federal Clean Water Act gives states a role in certifying whether a project would be damaging to waters within their boundaries. The Army Corps, which sought the DHEC's approval, takes the position that it will comply with state requirements and federal law "whenever practical."

An attempt to move the project forward without DHEC's OK would likely have set the stage for legal challenges.

Q: What happens next?

A: The Corps of Engineers is moving ahead with the deepening project, and the final environmental impact statement is expected next year.

Meanwhile, South Carolina's Savannah River Maritime Commission, which includes state lawmakers, is challenging DHEC's authority to issue the water quality permit. The S.C. attorney general has agreed to represent the commission in the dispute, but work on the Georgia deepening plan is moving ahead.

As the regulatory process and legal challenges proceed, the issues have also become highly politicized.

Some critics of the DHEC's decision have suggested Haley steered her appointed board's vote, after raising $15,000 at a fundraising event in Georgia less than two weeks earlier. The criticism has been bipartisan, with Democrats and Republicans both criticizing the governor for the DHEC decision, which Haley denies influencing.

Senate Majority Leader Harvey Peeler, R-Gaffney, scheduled a Senate committee hearing Tuesday to probe the matter, but Haley said she would not attend. The governor has scheduled a press conference for Monday to address the controversy.