Cold weather and time may have contributed to a natural-gas leak.
LEWISTON – Old pipe and deep frost likely contributed to a natural gas leak in January that destroyed the former Hotel Holly in a fiery explosion.
The state is continuing its investigation into the causes of the Main Street gas leak, Farmer said. A section of cracked cast-iron pipe was sent to a metal-testing lab in Massachusetts on Monday, two weeks after the explosion next door to Lewiston Radiator Works. That business was destroyed in the blast.
The cracked pipe appears to be old, said Gary P. Farmer, gas safety manager for the Maine Public Utilities Commission. It was buried beneath several layers of cobblestone, meaning it hadn’t been dug up since Main Street was paved with asphalt.
Farmer is looking for answers to two questions: why the break occurred and when it occurred.
“First, they’ll try to determine if the temperatures had an effect on the cast iron or if load was a factor,” he said. He added that he is most concerned about when the break occurred. “It is possible that it started several months ago.”
It’s not 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. At the time, experts said stress from the frozen ground caused the line to break.
In 1972, a house on Dawn Avenue exploded, killing Rita and Amanda Castonguay. The cause of the blast was said to be gas that had collected in a sewer near the house.
Although an exact figure was not available Friday, Fire Chief Michel Lajoie recalled that there were several explosions blamed on natural gas in the early 1970s.
Other gas leaks have driven people from their homes while crews worked to repair the leak.
A severe leak on Davis Avenue in Auburn in January 1995 forced firefighters to close off 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 the leaks occurred in below-freezing temperatures.
“Cold can upset the ground as the frost goes down, and frost just goes deeper when there is no snow covering the ground,” Farmer said. “That’s why lines buried under streets are a concern. The frost does go deeper there.”
Cast iron
Lewiston’s natural gas delivery depends on 77 miles of underground pipe. More than half of it is made of cast iron, buried between 1895 and 1958. The oldest pipes initially were used to transport manufactured coal gas, Farmer said.
Cast iron isn’t bad, Farmer said. In fact, it’s proven to be a great way to move natural gas. It’s strong, durable, resists corrosion and was a big improvement on pipe materials before 1895, which included wood and wrought iron.
Cast iron does have drawbacks, however. It’s a brittle material that can crack when stressed, and it is susceptible to changes in temperature and ground movements.
“That’s why you’ve seen much of it replaced by plastic pipe,” Farmer said.
Plastic pipe is lighter, more flexible and easier to install – and it doesn’t corrode. Ground movements don’t affect it as much as they do cast iron.
Cast-iron reacts very much like concrete, Farmer said. “It doesn’t handle tension well, and cracks start to form.”
In the summer, construction digging is a concern – not because crews might accidentally break a pipe but because they might not bury it properly when they’re finished. If part of the pipe is left unsupported or covered with lighter soil, the pipe can start to bow.
In the winter, changes in temperature can cause the ground to shift, putting new stresses on the brittle pipe.
Leaks need to vent
In the summer, leaking natural gas can move through warm ground easily, venting itself in open areas. But when the ground over the pipe is capped with 3 feet of frost, the gas needs to find a place to escape.
That can be a sidewalk, another utility line or a building.
“That’s why it appears winter time is a bigger problem for gas leaks,” he said. “You can have a leak buried under a field go undetected for weeks, and it’s never a threat. But when the ground freezes, that gas builds up and it has to go someplace.”
The state requires Northern Utilities, the gas provider for Lewiston, Auburn and the Portland area, to sweep through all city streets with special gas-sniffing machines both at the beginning of frost season and at the end, looking for hidden leaks.
“It’s only required for cast iron lines because of the historic issue,” Farmer said.
Farmer said he didn’t know when to expect results from the metals tests on the pipe, but his investigation is continuing. Part of it includes an audit of Northern Utilities’ records to make sure they are up to date on testing and maintenance.
“Northern Utilities should not be too concerned,” Farmer said. “They’ve turned out to be competent operators in the past, and I’d be surprised to find out differently.
“But we have been concerned with the cast iron in the system. It is rational to have cast iron. It’s been an excellent solution for years. But now, it makes sense to watch it a little more carefully.”
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