Design Flaw Cause of Thanksgiving Water Main Break

Utility officials say that a design flaw in a 60-inch water main in South San Francisco caused it to burst on the morning after Thanksgiving Day, sending more than a million gallons of water into the surrounding neighborhood.

San Francisco Public Utilities Commission Assistant General Manager Steve Ritchie on Tuesday said that a joint coupling holding two different sizes of pipe together failed to contain a restraint part, which could have prevented the joint from bursting.

"Two pieces of pipe literally just came apart where they were joined together," Ritchie said.

On Nov. 25 at about 9:45 a.m., a leak was detected where a 12-inch water supply pipeline connected to a 60-inch pipeline on Elm Street and Park Way, according to the SFPUC.

By 11 a.m., the small leak had turned into a geyser shooting water 60 feet into the air, which flooded half a dozen homes and as many as 10 vehicles parked on nearby streets. Between 1 and 2 million gallons of water poured into the neighborhood before the water was totally shut off at about 12:55 p.m., according to the SFPUC.

A subsequent investigation by a third party indicated that the joint coupling was to blame, Ritchie said.

SFPUC engineers have since analyzed 35 similar joints being installed as part of the utility's $4.6 billion Water System Improvement Program, and ensured that each coupling now contains a restraint part in its design, Ritchie said.

The SFPUC has done "the right thing" by conducting a quick review of the incident to ensure that "it doesn't happen again," Ritchie said.

Officials did not estimate how much damage the mishap cost, but said the utility had already honored six residential claims and was in the process of reviewing nine vehicular claims and estimating cleanup costs incurred by the city of South San Francisco.

-Bay City News