Environmental interests have sought to block the Port of Miami from dredging its harbor and channel to accommodate larger vessels transiting an expanded Panama Canal. The move potentially deals a setback to the port's efforts to compete with other East Coast ports for the mega-containerships sailing through the widened and deepened canal when it opens in less than three years.

The port had already received approval from the state's Department of Environmental Protection (DEP) to begin the $150 million dredging project, which would deepen the port's harbor and channel to 50 feet from 42 feet, and widen it by as much as 300 feet in certain places.

However, a petition filed Monday with the department by the Biscayne Bay Waterkeeper; the Tropical Audubon Society, and Dan Kipnis, a charter boat captain, said the ecological damage to adjacent Biscayne Bay would outweigh the project's purported economic benefits.

The groups, which beat a Nov. 28 deadline for filing comments on the project, also questioned whether the DEP followed proper procedures in determining the negative impacts of the project on water quality and on the various forms of marine life that inhabit the bay.

"The permit issued by the state of Florida falls short on environmental safeguards for fragile Biscayne Bay and gives multiple exemptions to state rules in place to protect the water quality," said Alexis Segal, executive director of Biscayne Bay Waterkeeper.

Segal added that Biscayne Bay would be subject to "years of blasting and dredging, which will foul the waters and damage ecosystems. And there is no consensus that the project will yield the economic results promised, but the burdens on taxpayers and the environment are sure things."

The filing of the petition means the proposed permit must be reviewed by a state judge in a formal hearing, a process that could take up to a year, according to the petitioners. Another source not affiliated with the port or the environmental groups confirmed the process and the timetable.

The source added that the port and the DEP might have their hands full with the groups. "The folks that filed the petition have a history of not being pushovers," the source said.

For now, the environmentalists' petition prevents the agency from giving the U.S. Army Corps of Engineers final approval for the project, scheduled to begin next year. The project has received $77 million in funding from the state, with Gov. Rick Scott personally involved in reallocating the funds to pay for the work, scheduled to begin next year. Congress has authorized the project but has not provided any funding for it.

Miami, like other East and Gulf Coast ports, is racing to complete dredging projects by the time the expanded canal opens in August 2014. Port executives from New York and Miami want to have their harbors and channels deepened before then to be positioned to handle the big "post-Panamax" ships expected to transit the canal with massive amounts of Asian import cargoes.

The $5.2 billion project will deepen the canal by as much as 10 feet, while new lock construction will enable it to accommodate ships built to carry a maximum of 12,600 twenty-foot equivalent unit (TEU) containers, up from a current maximum of 5,100 TEUs.

The stakes are especially high for Miami, which is competing with the ports of Los Angeles and Long Beach, as well as the Port of Savannah, for cargoes bound for Florida destinations. Only 38 percent of Asian import traffic destined for Florida actually enters Florida ports, according to Port of Miami data. About 13 percent enters Savannah, 500 miles to the north. From there, shipments are moved by truck or rail into Florida.

The agency is reviewing the environmentalists' petition, a spokeswoman told the Associated Press. In a statement, port officials said the project "has undergone extensive studies and reviews by numerous agencies to ensure that stringent environmental safeguards are in place to preserve the surrounding waters, ecosystems and marine life."

A source close to the port said it had expected a legal challenge from environmental groups.