Wrong studs led to water main break, report says

The panel also found that some, if not most, of the studs securing the clamp probably cracked during the manufacturing process, weakening them.

“They were the wrong size,’’ said Ronald G. Ballinger, a panel member who is a material science professor at Massachusetts Institute of Technology. He said heftier studs or more of them should have been used to secure the clamp, also known as a coupling.

MWRA officials said yesterday that the clamp and studs were provided by Pennsylvania-based Victaulic. Eric Luftig, a Victaulic spokesman, said in an e-mail yesterday, “We do supply products with studs, but we do not manufacture studs.’’ It was unclear yesterday who manufactured the studs.

Ballinger and the other panel members — chairwoman Zorica Pantic, president of Wentworth Institute of Technology, and John H. Bambei Jr., engineering chief of Denver Water — ruled out other theories for the break, such as an earthquake or other ground movement that could have displaced the two pipes enough for the coupling to fail, or a stray underground electrical current that could have weakened the clamp.

“The panel concludes that progressive stud failure is consistent with the evidence,’’ the report says. “No other scenario better fits the observations.’’

MWRA executive director Fred Laskey declined to say which of the many companies and subcontractors involved in the coupling’s installation would be named in the suit the agency expects to file “expeditiously.’’ The agency’s goal, he said, is “to make the ratepayers whole.’’

Laskey said the agency was re-examining other couplings in the water system — many of the same type of design and some manufactured by Victaulic, although none at such a high-pressure juncture — to see whether the studs are the proper size or could fail.