Imported Gas Cited In Rash Of Leaks

The company's findings are certain to intensify discussion in the gas industry about "interchangeability" -- the feeding of different natural gases, including imported liquid natural gas, into the U.S. interstate pipeline grid. Cove Point is one of four import terminals operating in the United States; the others are in Georgia, Louisiana and Massachusetts. Federal Energy Regulatory Commission officials have said they expect at least eight new terminals to begin receiving imported gas by 2010.

Until now, the focus has been mainly on how the imported gases, which tend to burn hotter, would affect household appliances, furnaces and gas turbines.

The Washington Gas study could force the industry to look more closely at how imports will affect the millions of miles of mains and service lines used to transport gas to customers.

"Some of the issues are going to be what kind of mechanical seals they're using, and how standard they are in the industry," said Ronald Gist, an analyst with the Houston energy consulting firm Purvin & Gertz.

The company analysis, headed by Environ International Corp., helps explain why the leaks were concentrated in Prince George's and not throughout the region, where Washington Gas serves nearly a million customers in Maryland, Virginia and the District.

Washington Gas relies on three interstate pipelines that supply domestic gas and a fourth that carries imported gas directly from Cove Point. The imported gas blends with domestic fuel by the time it reaches most Washington Gas customers. But about 300,000 customers, mostly in Prince George's, receive gas directly from Cove Point, before it has mixed with other supplies, according to Washington Gas documents.

Environ examined three potential factors in the leakage: winter ground temperatures, aging seals and gas composition.

"The age of the seals and winter ground temperatures also affect other areas of the Washington Gas service territory that employ mechanical couplings," the company said in a statement. "These areas have not experienced increased leak patterns."

Prince George's has a high concentration of the failing couplings, which were used widely from the 1950s through the 1970s -- a period of surging growth and home building in the county. Advances in plastics and fusion welding made the couplings outdated, but there are still thousands in use throughout the region, as well as the country.

An estimated 111,000 couplings are in Prince George's alone, Washington Gas spokesman Tim Sargeant said. He declined to say how many are in use throughout the company's service region.

Natural gas is made up almost entirely of methane, with a small percentage of heavier hydrocarbons such as ethane, propane and butane. The level of heavier hydrocarbons in the gas typically varies depending on where the gas comes from and how it is processed. Those variations in turn can affect a number of factors, including the temperature at which the gas turns to liquid -- known as hydrocarbon dropout -- and how hot the gas burns.