LEWISTON – Northern Utilities needs to replace its network of cast-iron natural gas pipes more quickly, according to state officials.

Now it will be up to the state Public Utilities Commission to decide if the company should accelerate its gas pipe replacement program and whether the company can pass along the cost to customers.

“We’re in the middle of the investigation now and we expect it to go before the commission in March,” said Gary Farmer, gas safety manager for the Maine Public Utilities Commission.

In all, Northern Utilities uses about 122 miles of underground pipe to deliver natural gas statewide, and Lewiston has more than half of that – an estimated 77 miles of underground pipe. More than half of it is made of cast iron, buried between 1895 and 1958.

A leaking cast-iron pipe led to an explosion Jan. 12, 2004, on Main Street in Lewiston, according to Farmer. The blast and a subsequent fire demolished Lewiston Radiator Works and the former Hotel Holly. Five people were injured.

“Lewiston and Auburn have the vast majority of cast iron in Maine,” Farmer said. “In all, about 61 miles of pipe there is cast iron, and that’s better than half of Northern’s entire system.”

The company has experienced at least 89 broken cast-iron mains between 1998 and 2002 statewide, he said. The company has been working to replace gas pipes since 1985, at a rate of about 3 miles per year.

“That’s their normal, historical rate, that they’ve managed to do on their own,” Farmer said. “We’ll have to see if the commissioners will order them to do it more quickly.”

Cast iron is susceptible to a kind of corrosion called graphitization, he said. Over time, the iron can leach out of the pipe, leaving behind a much weaker network of graphite and iron oxide.

“When a cast iron pipe fails, it doesn’t just leak – it breaks,” Farmer said. “And the biggest problem is, there is no sure way to predict just where and when these breaks are going to occur. If you could do that, you could just go out and replace that section of pipe. But there is no way of knowing.”

That kind of leak caused the Lewiston explosion, according to a report Farmer filed in June. That report found that Northern Utilities was not in violation of gas-line rules.

According to the report, the bottom part of a 6-inch underground pipe fractured about six months before the explosion. Investigators blamed that on sunken soil under the pipe. The explosion and fire was caused by gas leaking from the pipe and moving through the ground to a disconnected service line in the foundation of the former hotel.

It wasn’t the first time gas leaks have caused problems in Lewiston and Auburn. A similar leak in February 1970 killed Dr. Robert Wiseman and his wife, Helena, and destroyed their 55 Pettingill St. house. In 1972, a house on Dawn Avenue exploded, killing Rita and Amanda Castonguay.

A severe leak on Davis Avenue in Auburn in January 1995 forced firefighters to close the street and evacuate homes. Similar leaks occurred in February 2001 on Cedar and Lincoln streets in Lewiston and on Riverside Street in January 2002. All of them occurred in below-freezing temperatures.