ST. PAUL, Minn. (AP) -- An underground water line ruptured early Saturday in downtown St. Paul, flooding several city blocks, causing a widespread drop in water pressure and prompting city officials to warn against drinking tap water.
Rick Larkin, the city's director of emergency management, said there was "significant street damage" after the 20-inch main broke around midnight, sending thousands of gallons of water coursing through eight to 10 square blocks.
David Wagner, who oversees the underground piping system for St. Paul Regional Water Services, said the pipe appeared to split spontaneously, not as a result of construction or other human activity.
"We get on average 100 water main breaks throughout the system every year. Most are small in size and only cause issues for people in that immediate vicinity," Wagner said. "We typically don't get breaks of this magnitude in a pipe of this size. It's very, very unusual."
When asked whether other parts of the pipeline might be susceptible to similar ruptures, he said investigators would re-examine the system "but I wouldn't anticipate any further problems."
Within a few hours, officials isolated the break and closed the valves to turn off that portion of the water supply. Full water pressure was restored to most of the grid, but Larkin said public works crews would dig up a large section of road to repair the broken part of the line.
Wagner said work could be completed as soon as late Saturday.
The city imposed a no-drink advisory and urged residents in the downtown, West Seventh Street and lower west side neighborhoods to avoid drinking tap water Saturday until officials could confirm the water was clean.
That advisory was lifted about 3 p.m. after lab tests showed no contamination from chemicals. But since tests for bacterial contamination take 18 hours, residents were still advised to boil water for three minutes before drinking it.
The area where the leak occurred is full of apartment and office buildings. Larkin said there didn't appear to be much structural damage beyond the streets themselves.
"It's a hilly area of the city, so it all just ran down the hill," he said.
With water pressure dropping for much of the area overnight, some hospitals switched temporarily to reserve water supplies.
Officials closed several downtown streets after the break, but Larkin said crews were working to reopen many of them before dawn. Part of the work involved clearing away the ice from the ruptured line that had made it to street level.
"Once the street is cleaned up and the ice dealt with, it'll shrink back to a one-block area,'' Larkin said. "It really becomes a construction project."
The flooding comes a month after a break in a 3-foot water main in downtown Minneapolis spilled millions of gallons of water and flooded streets. The rupture occurred after a contractor struck the pipe with a backhoe.