The U.S. Coast Guard has ruled that the Chesapeake Bay is a suitable shipping channel for an energy company planning to unload liquefied natural gas from foreign tankers at its Cove Point plant in southern Calvert County.

The decision, after 18 months of study, is not a definitive green light for plant owner Dominion Resources Inc. But with the Coast Guard's recommendation, the Richmond-based company clears a major regulatory hurdle in its plan to reactivate the offshore terminal.

The Coast Guard will develop an operating plan outlining specific security measures for foreign tankers entering the bay, said Lt. Cmdr. Brendan McPherson, a spokesman. Dominion officials say they hope to begin shipments in May.

Security is the major issue surrounding the $120 million project. Maryland lawmakers and Calvert residents questioned whether allowing more large tankers into the bay would increase the risk of a terrorist attack -- possibly involving the natural gas facility and nearby Calvert Cliffs Nuclear Power Plant.

Sen. Barbara A. Mikulski (D-Md.), one of the project's most vocal critics, released a statement Monday in support of the Coast Guard's recommendation. She praised the "rigorous review," which included three meetings with experts from law enforcement, security, energy and shipping, and said she would continue to monitor the plans.

"I accept the view of the Coast Guard and these experts that the risk of [liquefied natural gas] shipments into Cove Point can be managed by strong security measures," Mikulski said. "I know the Coast Guard will be vigorous in their efforts."

Arrival procedures, which were tightened after Sept. 11, 2001, require ships to provide the Coast Guard with a list of cargo, crew members and places traveled. Additional security measures under consideration for tankers coming into the Chesapeake include four-day notification of arrival, inspections at sea, vessel escorts to the plant, facility security inspections and water patrols.

Officials also may require a buffer zone around the offshore terminal and traveling tankers, which would force other vessels to stay clear, McPherson said.

"No maritime operation is risk-free," he said yesterday. "What we're trying to do here is balance the free flow of vital commerce with our responsibility and need to ensure public safety and security."

The plant stores natural gas shipped from domestic points during summer and high-demand winter months. Dominion wants to refurbish and reactivate a pier 1 1/4 miles offshore to remove liquefied gas from oceangoing foreign tankers. Natural gas in vapor form then would be transported through a pipeline that runs 87 miles from Calvert to utilities in Prince George's, Charles, Fairfax and Loudoun counties.

The offshore facility has been idle since 1980, when falling domestic natural gas prices and a dispute with foreign suppliers caused its former owners, Columbia Gas and Consolidated Natural Gas, to end the import operation.

In its letter of recommendation to Dominion, Coast Guard officials said the size and characteristics of tankers transporting liquefied natural gas would not have a significant impact on the density of marine traffic in the bay. The average carriers are 930 feet long and 136 feet wide, and they carry 34 million gallons.

No apparent obstructions for the tankers exist in the waterway between Cove Point and Cape Henry, Va., where the vessels would enter the bay, the Coast Guard said. The channel was found to be wide enough for large vessels to travel.

On Tuesday, Dominion spokesman Dan Genest said the company was pleased with the Coast Guard's ruling. Various state and local agencies must grant final approval before the company can begin importing its product.

Genest added that the ruling probably would hasten the closing of Cove Point to fishermen.

Mikulski has asked the Coast Guard to meet with fishermen to find a way to accommodate both security concerns and the fishermen's economic needs.

Dominion Resources wants to reactivate a 2,500-foot pier 1 1/4 miles off Calvert's Cove Point to remove liquefied natural gas from foreign tankers. The Coast Guard has ruled that the Chesapeake Bay is suitable for shipping.The Cove Point plant's 16 million-gallon tanks store natural gas shipped from domestic points during summer and high-demand winter months.