Wrong studs led to water main break, report says
A clamp joining two giant water pipes failed last May largely because it was held together by wrong-sized studs, investigators said yesterday in a report on the cause of the massive water main break that cut off clean drinking water to nearly 2 million residents of the Boston area for more than two days.
Those findings — the result of a yearlong forensic examination by a panel of three engineers — would explain why the 1-ton coupling broke apart just eight years after it was installed, and it paves the way for the Massachusetts Water Resources Authority to file a lawsuit to try to recover the approximately $5 million it cost to respond to and repair the break at a critical underground juncture in Weston. The clamp had previously been identified as the probable cause of the water main break, and the report pinpoints the studs, which are similar to bolts, as the culprits in the clamp’s failure.
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.
Victaulic manufactured the pipe coupling system and specified what studs to use, and it had representatives on site during the installation of the clamp in 2002. The report also noted there were other steps that might have added stress to the studs.
For example, two nuts were placed on each end of the studs, double the number called for in the coupling instructions, and the studs were tightened after the initial installation, the report said.
Several parties are also likely to have signed off on each step of the installation. It was unclear last night what companies performed what steps in the installation process.
In a statement, Victaulic’s Luftig said: “We are not surprised by the report. It is consistent with our own findings — the bolts failed.
“However, the questions that remain and must be answered are: what caused the added stress on the bolts that made them fail at this location and why did the MWRA and their installers deviate from the installation guidelines? Our products, including the one installed here, are designed to conform to governing industry standards and have been used successfully for decades.’’
MWRA officials said in a statement that the agency did not install the coupling, but that “we hired design firms, contractors, and a construction manager to select, install, and oversee installation of the coupling.’’ The officials say there will be a myriad of issues that need to be sorted out in the future, such as why there were double nuts.
The water main failure on May 1, 2010, caused a geyser that ultimately sent 265 million gallons of water and tons of soil into the nearby Charles River before workers turned off the flow. It was one of the nation’s most disruptive water main breaks in recent decades.
Once the break was fixed, the MWRA led a massive search for the failed clamp, ultimately finding it twisted below the pipe, with a single intact stud and nuts holding the two sections together. Workers were able to extract the top half of the clamp and a portion of the second half. They also recovered pieces of two other studs, nuts, washers, O-rings, and insulating material, according to the report. There were originally eight studs holding the clamp together.
From an analysis of the recovered pieces, the investigative panel pieced together a play-by-play of what may have happened some 20 feet underground near the Route 128 and Massachusetts Turnpike interchange.
First, already-cracked studs were probably installed with the coupling in 2002. The panel said cracks found in the crowns of the three recovered studs are an indication of a poor manufacturing process. Then, with the studs too weak to withstand the pressure, it is likely cracks developed in their “thread roots’’ during installation of the coupling or shortly after water began flowing through the pipe. Additional fissures grew, exacerbated by the wet underground environment. Eventually, one stud probably failed, transferring the load to the remaining studs until each sequentially failed.
The 24-page report said it is “safe to say that [the unrecovered studs] were fractured as part of the failure process and thus may have been ‘precracked,’ as well.’’
The failed clamp was not the project’s first design choice. The pipes were originally supposed to be much more rigidly connected and encased in concrete, but that method had to be dropped because the pipes did not perfectly align.
That led project designers to shift to the clamp system, which allowed the pipes some freedom of movement. The first clamp installed failed water-pressure tests, and a second slightly different version was then used.
The pro bono panel, selected by the MWRA, hired a company to perform numerous tests and experiments and spent hundreds of hours examining the issue.
Beth Daley can be reached at firstname.lastname@example.org.