Deepening the Delaware River to 45 feet could begin as early as January or February, even as officials from New Jersey and Delaware threatened lawsuits yesterday to block the U.S. Army Corps of Engineers from proceeding without approval from state environmental regulators.

"It's moving - the train's left the station," said U.S. Sen. Arlen Specter (D., Pa.), who led an effort by Pennsylvania's top elected leaders to persuade the corps to act immediately based on "federal supremacy" over navigable waterways.

Delaware denied a permit for the work in July, six years after the Army applied for it, but Assistant Army Secretary for Civil Works Jo-Ellen Darcy decided Friday to proceed anyway, concluding, as her predecessor John Woodley had in April, that state approval was not required.

Gov. Rendell hailed the decision as a boon for the economies of all three states and "a sound environmental decision as well." He noted that dozens of studies have found dredge spoils to be safe and pledged that if New Jersey and Delaware do not want any of the 16 million cubic yards of material, Pennsylvania will "take it all."

Specter said that 10 million cubic yards of the spoils would go to fill an abandoned mine in Hazleton. Other dredge material will be sent to Fort Mifflin, in Philadelphia.

No sooner had Rendell and Specter spoken at a news conference in Center City than New Jersey Gov. Corzine declared he was directing his attorney general to "prepare legal action to stop this irresponsible move." He said he was "extremely disappointed" with the corps' decision to "plow blindly ahead."

Corzine is locked in a tight race for reelection and faces the voters next Tuesday; the proposed dredging project has been controversial for years in South Jersey.

For Delaware Attorney General Beau Biden, who is weighing that state's legal response, the issue represents an excruciating political challenge. State and national Democrats are urging the vice president's son to run next year to fill the remainder of his father's Senate term, and powerful constituencies - environmental groups and business lobbies - are lined up on opposite sides of the dredging issue in Delaware.

Beau Biden said in a statement that his office was consulting with Delaware environment officials and Gov. Jack Markell and "remains ready to take the necessary legal action to ensure that the Army Corps of Engineers applies for, and obtains, the required Delaware permits before it attempts to dredge the Delaware River."

Rendell and Specter have been pushing hard for the project for years. Specter, a close friend of Vice President Biden, switched to the Democratic Party to run for reelection in 2010, and the White House is backing him, hoping to keep the Pennsylvania Senate seat in party hands.

White House contacts did not hurt in getting the decision, Rendell and Specter said. It was not done as a favor to boost Specter's reelection, they added.

"I've had contact off and on since the Obama administration took office with people in the White Hosue on this issue," Rendell said.

"We always argued this on the economic development and the environmental merits," he said. "I think that's why we prevailed."

"We argued it on the merits, but to argue on the merits you have to have access," Specter said.

The push culminated in a meeting Wednesday in Specter's Capitol Hill office with Darcy. U.S. Sen. Bob Casey (D., Pa.) was also there, and Rendell participated by speakerphone. They argued forcefully that a failure to move forward with the deepening project would deal what one official called a "deadly" blow to Pennsylvania's economy.

Asked if he asked the vice president for help, Specter said, "All I will say is those were confidential communications."

John Estey, chairman of the Philadelphia Regional Port Authority, said ports in the region "are at a competitive disadvantage if we don't deepen the river. Every major shipping line I've sat with over the past 21/2 years asks: 'Are you going to deepen the river?' We are in a very competitive environment. If we don't deepen the river, these lines will not come to Philadelphia."

Rendell acknowledged "there will be lawsuits from some advocacy groups, but they are going to have a heavy burden to go forward and stop this project."

Delaware officials denied the corps' application in July.

Craig Schmauder, deputy general counsel to Darcy, said a contract for routine maintenance dredging was awarded Oct. 9 to maintain the river's current depth of 40 feet.

Under that contract, the corps has up to 60 days to exercise an option to begin the deepening work. A notice to proceed could come after Dec. 25, he said.

The first part of the river to be deepened is an 11-mile stretch in State of Delaware waters.

The Army Corps intends to reapply for a Delaware permit, but because that process could take nine to 12 months, the corps will begin without a permit, Schmauder said.

By the time the corps is ready to deepen the remainder of the main navigation channel in Delaware waters, the corps would hope to have secured a state permit, he said.

"We'll do the first phase without a permit. We intend to go forward unless we are somehow barred through litigation."

Contact staff writer Linda Loyd at 215-854-2831 or lloyd@phillynews.com.