Now that Boston-area residents are drinking tap water again, the Massachusetts Water Resources Authority is trying to figure out why the coupling that held two pipes together failed.
If you go down to your basement and your pipes aren't all covered up with insulation, you can see couplings holding your pipes together. They're also called collars. If they go, your pipes leak big time, and that's what happened to the water main that carries most of Boston's water. Only in this case, said Fred Laskey, the executive director of the MWRA, the coupling that blew was huge.
"This is a 15-foot-long curved piece of steel, or two pieces, one on the top, and one on the bottom, so it's a big thing," Laskey said.
Investigators have found eight MWRA projects using similar couplings. But Laskey indicated that there is little chance of a catastrophic break like last weekend's.
"First off, where this broke was a 10-foot pipe," Laskey said. "We do have a lot of 10-foot pipes, but we probably don't have any with this kind of coupling under that kind of pressure, so I don't want to leave the impression with the public that we have eight locations with ticking time bombs. We don't know, as we sit here, the details of it, and that's why we're going to do the assessment."
To find out why the coupling failed in a pipe in Shaft 5A this weekend, investigators have to find the pieces of the coupling.
"We hope we find it, obviously, because it would be critical," Laskey said. "It's a critical piece to the study of what happened. It allows the experts to go in and study the metal and look at the bolts, and a whole bunch of things that will get us the answer that we really need."
The MWRA is continuing to dredge the Charles River to find the coupling, but Laskey said there is a chance they may never find it, because it could be buried under the concrete poured under the burst pipe before it was repaired.
Laskey said the MWRA had a brief conversation with the manufacturer of the coupling, which found out by reading the newspapers that their coupling had failed.
The coupling was not the one originally planned for the design. Records show it was modified twice when it was installed seven years ago. The MWRA's chief operating officer says engineers often have to change the design of a coupling in the field during installation.
After a board meeting yesterday, Laskey was describing — in detail — how the coupling was put together when the chairman of the MWRA board, Secretary of Energy and Environmental Affairs Ian Bowles, interrupted:
"At this stage, this level of detail is probably hard for us to give good answers on," Bowles said.
In order to get answers, the board will rely on a special commission that could be formed next week.
This program aired on May 6, 2010.