CHARLESTON, S.C. (AP) — A federal judge ruled Tuesday that both the Georgia Ports Authority and South Carolina's Savannah River Maritime Commission may take part in a lawsuit challenging the $650 million deepening of the river shipping channel.

But U.S. District Judge Richard Gergel denied a motion to expand the lawsuit to rule on what South Carolina environmental laws pertain to the project. So the suit will now center solely on the issue of whether the work needs a South Carolina pollution permit.

Environmental groups in both South Carolina and Georgia originally sued the U.S. Army Corps of Engineers, charging a permit is needed because the deepening work will mean toxic cadmium from river silt will be dumped on the South Carolina side of the river.

The suit 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.

The Georgia Ports Authority had asked to intervene on the side of the corps; the Maritime Commission on the side of the plaintiffs.

Supporters of the deepening project say it is needed so the river can handle the larger container ships that will routinely call at the Georgia ports when the Panama Canal is expanded in 2014.

The plaintiffs wanted the suit amended so the court would decide if other South Carolina environmental law applies. They noted that the corps has said repeatedly it can proceed without South Carolina approval under exemptions in the Clean Water Act.

They argued both the Department of Health and Environmental Control and Gov. Nikki Haley cited the corps' position as part of the rationale for giving state approval to the project. Their filing quoted Haley speaking last fall at the Charleston Propeller Club.

"I have in writing, your DHEC board had in writing, a letter from the Corps of Engineers saying we don't need a permit from DHEC to give Georgia their dredging," Haley was quoted as saying. "It's not they didn't need it. They were gonna do it anyway."

But both the corps and the Georgia Ports Authority — in court filings Monday opposing amending the suit — said no final decision has been made on whether the exemptions will be used.

"It is clear that none of the corps' statements — much less those of third-party politicians — can be characterized as final" under the federal Administrative Procedures Act, attorneys for the Georgia Ports Authority wrote. They added that, at most, the corps' positions stated in state courts and the media "are reservations of its potential rights."

"The court lacks jurisdiction because there is no waiver of the United States' sovereign immunity applicable to the proposed amendment complaint. There has been no final action by the corps that is reviewable," Assistant U.S. Attorney James Leventis wrote on behalf of the corps.

The plaintiffs have said a ruling that other South Carolina environmental law applies will allow a fairer review by state regulators.

Because the corps indicated South Carolina permits aren't needed, state regulators have been operating under the "mistaken impression" that resistance to the deepening project "is futile," the plaintiffs said. Because of those statements regulators concluded "approving the project with meager mitigation is preferable to more aggressive review or conditions," they added.

But attorneys for Georgia Ports Authority responded that "contrary to overstatements from the plaintiff environmental groups, the environmental consequences ... will be fully mitigated under a plan developed through extensive consultation with all of the stakeholders, just as Congress required."

Gergel's denial of the motion to amend was without prejudice, which means the plaintiffs can bring it up again later.