Gov. Mark Sanford and four S.C. members of Congress have asked the U.S. Department of Transportation to launch an in-depth study of a proposal to build an $83 million bridge in a remote, swampy area.

Sanford and the congressional members say they want a "cost-benefit study" to examine whether the bridge is needed, how much development the bridge will generate and whether that development would harm the swamp and Shaw Air Force Base, 18 miles north.

A new study could delay or kill the $83 million project, which has been given top priority by U.S. Rep. Jim Clyburn, D-S.C.

The proposed 9-mile bridge and road is on the northern edge of Lake Marion and would link the Orangeburg community of Lone Star with the Clarendon County community of Rimini.

Friday, Clyburn fired off his own letter to the U.S. Department of Transportation, accusing the four white S.C. members of applying a different standard to his bridge project, which would serve largely black communities.

"I am sure my Republican colleagues did not intend to single out my district and priorities for disparate treatment. But they have," wrote Clyburn, who is black.

Most of the money for the bridge would come from federal sources.

In his letter, Clyburn said if the Republicans are going to request a cost-benefit study of his project, he will request the same kind of analyses for their federal projects.

Ordinarily in Congress, members from one state don't oppose each other's special pork projects.

In asking for a study, Sanford and the congressional members -- who include Sen. Lindsey Graham, R-S.C. -- are siding with major environmental groups in the state.

In recent weeks, environmentalists have lobbied the Republicans to send the letter. Environmentalists also say they will sue to stop Clyburn's project if it goes forward. The project will damage one of the most beautiful and untouched spots in South Carolina, 40 miles south of Columbia, they say.

To Clyburn, a former civil rights activist, the bridge is a long overdue way to reunite black communities torn asunder by the creation of Lake Marion years ago. It will also bring economic development to low-income areas, Clyburn said.

The Republicans' request last week is sure to escalate a political war that now involves racial issues. The dispute has caused a deep rift between Clyburn and the state's environmentalists, for years staunch allies.

And in an ironic turn of events, environmentalists find themselves working with Republicans -- not generally known for being pro-environment -- against Clyburn to stop his bridge.

"This project has been surrounded by controversy since the day it was proposed," wrote Sanford in his letter.

"One of the central points of debate has been whether or not the road project will actually generate economic development ‘.‘.‘. (or) be an unwise expenditure of public funds that will have negative impacts on the Upper Santee Swamp," Sanford wrote.

The letter to Transportation Secretary Norm Mineta from the four S.C. members of Congress -- Graham and Reps. Joe Wilson, Jim DeMint and Gresham Barrett -- made essentially the same points as Sanford's.

In his letter to Mineta, sent Friday, Clyburn said that to say he was astonished by the request for a cost-benefit study "is probably the biggest understatement of my 10-year career in the U.S. Congress."

In his 10 years, Clyburn said, no member of Congress has ever written such a "bizarre and unprecedented letter about another member's district priorities."

Sanford's letter went into more detail than the letter from the members of Congress.

"We believe that a cost-benefit study is necessary before an informed decision can be made on the merits of this project," Sanford wrote.

"The analysis should cover a variety of issues ‘.‘.‘. actual traffic counts and projections, the likelihood of any employment and development beyond actual road construction ‘.‘.‘. negative or positive impacts on tourism in the area; and a host of other issues that thus far have not been fully addressed," Sanford wrote.

Clyburn said major issues surrounding the proposed project have been addressed.

Earlier this year, all six S.C. House members signed letters saying they would support each other's projects, including Clyburn's bridge, Clyburn wrote.

And a recently finished Environmental Impact Study has concluded that "this project can be accomplished without harm to the environment and wildlife in the area," Clyburn wrote.

But Jane Lareau, an official with the S.C. Coastal Conservation League, said the Environmental Impact Study -- overseen by the S.C. Department of Transportation -- is superficial and flawed.

"The DOT has never met a road or bridge it didn't love," Lareau said. She said the Environmental Impact Study ignored such fundamental concerns as how much the development spawned by the bridge would hurt the Santee Swamp area.

Elizabeth Mabry, executive director of the S.C. Department of Transportation, had no comment Friday on the matter.

Clyburn said he will not give up. "I will not allow partisanship or bullying by powerful interests to deter me from my duties and responsibilities to my constituents," he wrote.

A spokesman for the U.S. Department of Transportation said Friday the request for a cost-benefit study is "under review."