UPDATE 1-Transco gas line says force majeure on Miss. storage

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NEW YORK Feb 22 (Reuters) - Williams' Transco gas pipeline unit said it has declared force majeure due to the closure of two of its seven underground natural gas storage caverns at the Eminence Storage Field in Covington County, Mississippi after leaks were discovered.

The company said in a website posting late Friday that it discovered gas escaping from the ground around the wellhead of cavern 1 after found a leak at cavern 3.

A prior posting said cavern 3 had a capacity of 3 billion cubic feet. The size of cavern 1 was not known.

The company said it intends to file an application with the Federal Energy Regulatory Commission to abandon the caverns.

Due to the force majeure event, the Eminence field was capable of providing approximately 70 percent of contracted capacity and 92 percent of contracted deliverability, the posting said.

The daily injection capability was not affected.

The company was not immediately available for comment.

The 10,000-mile (16,090-km) Transco system is a major provider of natural gas to northeastern and southeastern states, moving gas from the Gulf Coast to major metropolitan areas in New York, New Jersey and Pennsylvania with a peak capacity of 8.6 billion cubic feet per day.

Williams Partners LP (WPZ.N) owns 100 percent of the Transco gas pipeline. Williams Cos (WMB.N) owns approximately 75 percent of Williams Partners.

Natural gas is held in inventory underground in depleted reservoirs in oil or gas fields, in aquifers or in salt cavern formations. Salt caverns typically provide very high withdrawal and injection rates relative to their working gas capacity with the large majority of salt cavern storage facilities developed in salt dome formations in Gulf Coast states. (Reporting by Eileen Moustakis; Editing by Marguerita Choy)