PHILADELPHIA -- Nearly three decades after Congress directed the U.S. Army Corps of Engineers to investigate deepening the main shipping channel of the Delaware River, the dredging is finally going to happen.

A federal judge on Wednesday gave the green light, denying an injunction to stop the Corps from deepening a 13-mile stretch of river by five additional feet this year, without first obtaining a Delaware state permit.

Opponents - Delaware, New Jersey, and several environmental groups - are assessing the court's decision and planning their next legal moves.

They have several options: appeal the ruling to the U.S. Court of Appeals for the Third Circuit; amend their complaint to raise new issues; or wait for a full airing before the federal court in Wilmington.

U.S. District Judge Sue L. Robinson decided only one thing: to let the deepening begin in a section of river, known as Reach C, in waters off Delaware.

The judge enjoined future stages of the 102.5-mile deepening from its current 40 feet to 45 feet, pending her further orders. Proponents want the deeper river to accommodate bigger commercial vessels and boost the economic vitality of regional ports.

"This way she keeps her finger in the pie and makes sure everybody is doing what they should be doing," said one lawyer in the case.

On Friday, Robinson amended her 31-page opinion to make clear that she intends for the entire project to proceed, not just part of it.

Opponents of deepening the river should give up the fight, the judge said.

"Just to be clear, the deepening project is one that should be completed, consistent with Congressional intent," the judge wrote. "The court does not equate administrative obstacles with proof of insurmountable environmental risks."

"For those who oppose the project in the first instance, the time for that fight has long passed," Robinson said, adding, "The decision to allow deepening in Reach C, therefore, is not a 'bridge to nowhere.' It is a first step in a regulatory process that has worked in the past, and should work here, to accomplish Congress' goals without causing environmental harm as defined by statute."

The N.J. Department of Environmental Protection said it was "extremely disappointed" in the ruling. "We believe there are significant environmental, economic, and state's rights concerns that the decision does not adequately take into account," said acting DEP commissioner Bob Martin.

"All information and scientific analyses of other dredging projects indicate that there will be serious impacts to our natural resources in Delaware waters and an increase in air emissions that will adversely affect public health. We strongly oppose this dredging project," Martin said.

New Jersey has a lawsuit pending in U.S. District Court in Trenton against the deepening, as do several environmental groups.

Delaware Riverkeeper Maya K. van Rossum, on behalf of five environmental plaintiffs in the Delaware case, expressed disappointment that the Corps will be able to "deepen one inch of the river" but said Robinson's refusal to give a blanket approval to later stages "demonstrates the strength and merit" of the environmental plaintiffs' legal claims.

"A concession for limited deepening in Reach C, while perplexing, does not change the import of this finding," van Rossum said, noting that "segmentation of federal projects" - allowing the first stage to proceed but not the others - "is itself a violation of federal law and policy that cannot be remedied with a judge's sanction and is itself grounds for legal challenge."

Environmental groups said they were reviewing the ruling and "assessing their options."

Jason Miller, spokesman for Delaware Attorney General Joseph "Beau" Biden, said Friday that Delaware had not yet made a decision on how to proceed. "Obviously the governor's office is involved, and the Department of Natural Resources is involved in that decision," Miller said.

At the helm of the case is Robinson. On the federal bench in Wilmington since 1991, she was nominated by President George H.W. Bush to fill a seat vacated by Jane R. Roth.

Robinson was born in Mount Carmel, Ill., in 1952, and graduated Phi Beta Kappa from the University of Delaware. She earned a law degree in 1978 from the University of Pennsylvania Law School.

She was in private practice in Wilmington until 1983, when she became an assistant U.S. attorney, a job she held until becoming a U.S. magistrate judge in the District of Delaware from 1988 to 1991. Robinson served as chief judge of the U.S. District Court in Delaware from 2000 to 2007.

Hardworking, deliberate, smart, fair, and a good listener is how several lawyers described Robinson.

"She will routinely do two trials a day," said one Wilmington lawyer. "She'll start at 7:30 in the morning with one case, and she will sit until 7 or 8 o'clock at night sometimes."

David Stratton, managing partner of Pepper Hamilton L.L.P.'s Wilmington office and a former colleague of Robinson's in private practice, described her as "very bright, extremely principled, very hardworking, and very diligent."

"I'm sure she gave a lot of thought to the issues in that case and decided it the way she thought the law and the facts dictated," Stratton said. "She is not swayed by public opinion. She is not afraid to address difficult issues."