"It's an ancient line that dates back 50 years," Director Pam Tuft said. "They occasionally fail, and we'll put a valve in and re-establish the connection."
Firefighters responded to the break in front of 119 Petaluma Boulevard North at about 8:40 p.m. Monday, according to the Petaluma Fire Department.
Water was seen leaking from under the asphalt along a stretch of roadway approximately 100 feet long. The break caused several mounds to form in the street.
Police shut down the street in both directions between Western Avenue and East Washington Street while a water department representative responded to assess the possibility of sinkholes.
The flow of water was shut off, according to the fire department.
Repair work should be completed Wednesday, Tuft said. Petaluma Boulevard North reopened at 7 a.m. today.