Cap Blow-Out Cause of Massive Canary Square Flood

The blow-out of a cap on a large pipe under Centre Street is to blame for the spectacular flooding at the corner of Boylston and Centre.

The flood appears to have started sometime after 11 p.m. Friday near the intersection with South Huntington Avenue where work crews had been active well into the evening. As of noon Saturday, 20 residents remained without water, according to Mark Van Dam, spokesperson for the Boston Water & Sewer Commission. Crews expect to have water service restored to those persons by 2 p.m. Saturday, he said.

Water main break at Canary Square, Friday, Sept. 9, 2016.

Claire Miller

Water main break at Canary Square, Friday, Sept. 9, 2016.

Here’s what caused the flooding: Workers from Feeney Brothers removed a “thrust block,” essentially a giant piece of granite from the end of an older water main. The water pressure then blew out a cap at the end of the pipe. That means the incident wasn’t a “water main break” in the sense of a pipe rupturing.

Van Dam said the agency apologizes for the inconvenience to customers.

The Water & Sewer Commission has spent $1 billion in the past 20 years, Van Dam said, repairing Boston’s famously old infrastructure. The result, he said, is that despite the city’s age, it is “well below industry standards” for number of water main breaks.

The incident lit up social media. There have been a series of posts, photos and videos, as well as reports of low water pressure in residents’ homes Saturday morning.

Previous Jamaica Plain News coverage:

Overnight Water Main Break Floods Centre Street