CHARLESTON, S.C. (AP) — Former South Carolina U.S. Rep. John Spratt was appointed Wednesday to mediate a lawsuit challenging the $650 million deepening of the Savannah River shipping channel.

Spratt, from York, was chairman of the House Budget Committee and a member of the House Armed Services Committee during his 28 years in the U.S. House representing South Carolina's 5th Congressional District. He lost his re-election bid to Republican Mick Mulvaney two years ago.

Spratt was appointed by U.S. District Judge Richard Gergel to mediate environmental groups' complaints that the U.S. Army Corps of Engineers needs a South Carolina pollution permit for the project.

The lawsuit was brought by the Southern Environmental Law Center on behalf of the Savannah Riverkeeper, based in Augusta, Ga., as well as the South Carolina Coastal Conservation League and the South Carolina Wildlife Federation.

It contends that because toxic cadmium from river silt will be dumped on the South Carolina side of the river, a state permit is required. Gergel this week allowed both South Carolina's Savannah River Maritime Commission, which oversees state interests on the river, and the Georgia Ports Authority to enter the lawsuit.

The authority wants the river deepened so Georgia ports can handled the larger containerships that will routinely be calling when the Panama Canal expansion is completed in 2014.

In his order, Gergle noted federal civil cases are subject to mediation and the selection of a mediator is usually up to the attorneys involved. But he said in this case, appointing a skilled mediator is important to the success of the process.

"The issues in this litigation are complex and involve the interests of various state agencies in at least two states, the responsibilities of the national government to maintain the navigable waters of the United States and significant environmental challenges in one of the most environmentally sensitive areas of the country," the judge wrote.

He also said that time is a factor because work on the deepening is scheduled to begin next spring.

"The Court regards Mr. Spratt's prior exemplary service as a member of the leadership of the United States House of Representatives and his understanding of the complex and competing interests in play in this dispute as making him uniquely qualified to serve as the mediator," Gergle wrote.

There was no answer at Spratt's office in York on Wednesday.

Gergle also appointed United States Magistrate Judge Bruce Howe Hendricks to assist in the mediation.