BOSTON—An independent panel investigating a massive 2010 water main break in the Boston area has found the most likely cause was the progressive failure of bolts that held together two sections of the 10-foot-wide pipe.
The panel appointed by the Massachusetts Water Resources Authority looked at two possible causes and concluded the failure of the bolts was the most likely.
The report released Wednesday said cracks in the bolts' threads likely were created during or shortly after installation and the bolts were then loaded beyond acceptable levels. The panel said the cracks likely grew until one or more failed, transferring the load to the remaining bolts.
The cascading effect caused a blow-out of the O-ring joining the two sections of pipe.
The water main break led to a boil water order for about 2 million residents.