Columbia Gas on Friday plans to announce details of its plan for replacing all 48 miles of pipeline in the Merrimack Valley, according to a spokesperson for the town of Andover. This includes areas affected by last week's gas explosions.
One person died and more than 20 people were injured after the explosions and resulting fires last Thursday in parts of Lawrence, Andover and North Andover.
Thousands of people are now without gas in the area, and it could be months before gas service is fully restored to the affected 8,600 customers.
The aging existing pipes — some over 100 years old — are made of cast iron and bare steel, and will be replaced by plastic pipes made from PVC.
Installing new main distribution pipelines is the easy part and will go relatively quickly, says Gene Palermo, a plastic pipe consultant in Tennessee.
According to Palermo, new PVC pipes do not corrode or crack, even at temperatures well below zero, and can be put in place without digging up streets.
There are several “trenchless” methods. In one method, workers thread new plastic pipe through existing metal pipe. In another, workers use a metal cutting tool to crack old pipe and install new plastic pipe as the tool works its way underground.
The more difficult aspect of the work will be installing smaller service lines that run from the mains to homes and businesses. These require carefully digging through sidewalks and lawns, heat-sealing connectors to the main, and installing pressure sensors as the line enters a building.
John Buonpone, a gas worker with 29 years of experience, says “tying in the service line and hooking it up to a house is dangerous, costly and time consuming.”
He predicts that is what will take months for Columbia Gas to provide service to the 8,600 affected customers.
Buonopone says every gas pipe in every building in the affected areas needs to be inspected and tested. So do consumer gas appliances — hot water heaters, boilers and stoves.
According to Andover officials who met with Columbia parent company NiSource this week, NiSource has committed to replacing all damaged infrastructure and appliances and completely reimbursing residents for any out of pocket expenses.
The National Transportation Safety Board, which is investigating the disaster, believes the cause of the explosions was overpressurization in the pipelines.
According to a letter from Massachusetts' U.S. senators to Columbia Gas and NiSource, the pressure in the gas pipelines was 12 times what it should have been.
This segment aired on September 20, 2018.