Environmental groups have asked the Federal Energy Regulatory Commission to rescind its decision approving a new liquefied-natural-gas export terminal in Maryland. The project's cost is estimated at $3.4 billion to $3.8 billion.

In a petition filed on Oct. 15, the groups, which include Earthjustice, asked FERC for a rehearing of its Sept. 29 decision to permit the Cove Point project in Lusby, Md., to go forward. They also want FERC to cancel that ruling and halt construction, arguing that the environmental review it issued doesn't meet National Environmental Policy Act requirements.

The groups say their petition puts them in a position to file a lawsuit challenging the commission's decision.

Parties to the proceeding have 30 days after Sept. 29 to request a rehearing or appeal a decision. FERC has a further 30 days to respond to such filings. But the commission also can issue an order giving itself more time to review the petitions, says Tamara Young-Allen, a FERC spokeswoman.