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...blasts that killed one person and injured at least 25.  The lawsuit in Essex County Superior Court is the first to be filed...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...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...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...