Nearly 36 Miles of Pipeline Replaced after Mass. Gas Explosions

BOSTON — The utility company involved in last month’s explosions and fires in Massachusetts said it has replaced nearly 36 miles of main pipeline in the area.

NiSource subsidiary Columbia Gas said it’s 80% through work replacing 45 miles of main pipeline, and about halfway through its work replacing 6,100 service lines to homes and businesses.

The company said 151 construction crews are expected to continue work in Lawrence, Andover and North Andover.

The Sept. 13 explosions and fires killed a teenager and injured at least 25 other people. The company says it has paid $23 million in claims from customers.

Federal authorities say natural gas lines became over-pressurized after Columbia Gas failed to account for critical pressure sensors as workers replaced century-old, cast-iron pipes in Lawrence.

In a preliminary report released Oct. 11, the National Transportation Safety Board (NTSB) said Columbia Gas failed to require contract repair crews to relocate pressure sensors during natural-gas pipeline work.  That resulted in over-pressured lines that caused the explosions and fires.

Critical valves controlling the gas flow were not shut for nearly 3 1/2 hours after the first alarm was raised at Columbia Gas’ monitoring center, according to the NTSB report. The center had no ability to remotely open or close valves on its own, but did notify technicians, it added.

Crews were working in Lawrence, a city northwest of Boston, to replace an aged cast-iron main with a new plastic distribution main line. The abandoned main had regulator sensing lines used to detect pressure in the system.  After that main line was disconnected, the sensing lines lost pressure and the regulators fully opened, “allowing the full flow of high-pressure gas into the distribution system supplying the neighborhood,” the report said.

Minutes before the explosion, Columbia Gas’ monitoring center in Columbus, Ohio, received high-pressure alarms for its South Lawrence gas pressure system. The company shut down the regulator at issue about 25 minutes later, at about 4:30 p.m, the NTSB said.

Columbia Gas has said all cast iron and bare steel piping in affected neighborhoods will be replaced with high pressure plastic mains that have regulators at each service meter.

From AP and Reuters reports

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