Lawsuit targets Massachusetts utility over deadly gas explosions

BOSTON, Sept 18 (Reuters) - A resident of a Massachusetts city rocked by last week's deadly gas blasts that damaged dozens of homes sued utility operator NiSource Inc on Tuesday, accusing it of inadequately maintaining its distribution system.

The proposed class action lawsuit targets NiSource and its subsidiary Columbia Gas of Massachusetts, which services Andover, North Andover and Lawrence, three communities northwest of Boston that staged large-scale evacuations following the Thursday afternoon blasts that killed one person and injured at least 25.

The lawsuit in Essex County Superior Court is the first to be filed after Thursday's explosions. It claims the gas pipeline system used by Columbia Gas to service those communities was "poorly maintained, antiquated, obsolete, and highly dangerous."

Merrillville, Indiana-based NiSource did not respond to a request for comment. It has set up set up a phone center and an office to accept residents' claims for property damage and costs related to the fires and evacuation.

The lawsuit said the company failed to implement reasonable safety and leak prevention practices and failed to replace obsolete high-risk materials in the system, which used pipelines constructed of cast and wrought iron rather than plastic.

The complaint, filed by Lawrence resident Francely Acosta, who was forced to evacuate, accused NiSource of negligence and creating a public nuisance by failing to maintain gas pressure in its "antiquated" system, which it blamed for Thursday's explosions.

The lawsuit seeks unspecified damages on behalf of residents affected by the incident and an order requiring NiSource to stop operating its system in an unsafe manner.

The blasts on Thursday destroyed as many as 80 houses in the largest natural gas pipeline accident in the United States since 2010.

Some 8,000 people were displaced amid evacuations of entire neighborhoods as firefighters raced for hours from one blaze to another and utility crews rushed to shut off gas and electricity.

The National Transportation Safety Board is investigating the incident, which Columbia Gas has said affected 8,600 of its customers.

NTSB Chairman Robert Sumwalt on Sunday said over-pressurization of the gas distribution system was to blame and that the agency was looking at pressure sensors attached to a line that was taken out of service before the explosions.

In a letter to NiSource on Monday, U.S. Senators Edward Markey and Elizabeth Warren, both Democrats of Massachusetts, said the pressure in the pipeline system had been 12 times greater than it was intended to hold.

(Reporting by Nate Raymond, Editing by Rosalba O'Brien)