Insufficient Restraint Caused Water Main Break, SFPUC Says

Insufficient restraint on water pipes caused the November 25 water main burst on Elm Court, the San Francisco Public Utilities Commission told the South San Francisco City Council in a presentation Wednesday night.

Assistant General Manager Steve Ritchie explained the process of how a 12-inch water main branch, or “turnout," came to release more than a million gallons of water.

“The expert review told us things we didn’t want to hear,” Ritchie said.

The referred experts, Exponent Failure Analysis, Inc., conducted the investigation that found a 12-inch-nominal-size Smith-Blair 41 bolted coupling separated because of insufficient restraint.

Restraints are often concrete blocks, but this particular coupling of two 12-inch pipes had no restraint, leaving the joint vulnerable to breakage.

In a 20-page report, Exponent said axial movement against the improperly restrained coupling caused the two pipes to separate.

“Smith-Blair warns in their product literature that the subject coupling does not restrain axial pipe movement,” the report said.

The report also indicated that the SFPUC had specified the joint’s bend to be a 37-degree angle. A 70-degree angle was used.

Exponent has not yet determined whether the incident could have been avoided had the right bend been used.

“We regret very much that this incident occurred,” Ritchie said. “And we want to make steps to make sure it doesn’t happen in the future.”

Ritchie said SFPUC is in conversation with contractors, Ranger Pipelines, Inc., in order to pinpoint the exact moment of error.

“We’ve been through discussions with all staff involved to find out who did what and when,” Ritchie said.

SFPUC has received 17 claims of damage from South City residents and have responded to 10 claims thus far.

All claims will be paid out fairly rapidly, Ritchie said, and residents can continue to make claims if they discover property damage.

Members of the council questioned the poor communication efforts of the SFPUC and city officials.

Ritchie said this is a vital issue that will be addressed in order to maintain sufficient communication.

“One of the flaws we had was we didn’t have active enough communication,” Ritchie said. “It’s critical to keep everyone informed.”