A 120-year-old water main that broke and flooded downtown streets will disrupt traffic for at least three weeks, said city officials who reminded residents that such disruptions are frequent because of the aging infrastructure beneath Baltimore.

As crews surveyed a gaping hole caused in part by a water main that burst under Light Street, other workers had been dispatched to Fells Point where another pipe broke, forcing the city to close part of Fleet Street and cutting water service for a time to about 30 businesses and homes.

The incidents underscored a reality in Baltimore: The city sees two to three water main breaks a day. Mayor Stephanie Rawlings-Blake said Tuesday that preventing water main breaks in a city as old as Baltimore is financially impossible. The mayor said billions of dollars are needed to overhaul all of the old pipes that could burst at any moment.

"You'd be hard pressed to find an aging city in the United States that has the money to keep pace with its water infrastructure projects," she said.

The pipe under Light Street had previously been identified as a "high-risk" piece of the city's infrastructure, though that's a common designation for water mains in Baltimore, city officials said.

The replacement efforts will keep Light Street closed between Baltimore and Lombard streets through the second week of August. The right lane of Lombard between South Calvert and Light streets also will remain closed as crews repair water damage to the road, officials said.

The downtown break disrupted workplaces and commutes. Some city workers were forced to leave their cars Monday night in a parking garage that exited to a street that was closed. Several businesses shut because they didn't have water service. And after traffic snarled for hours Monday night, workers were encouraged to take public transportation and avoid affected areas.

The 20-inch-wide pipe, which dates to 1889, ruptured near Light and Redwood streets about 5 p.m. Monday, crumbling the roadway and sending water through downtown streets. Commuters were diverted from Light and Lombard streets in the city center.

On Tuesday, officials said about 700 feet of the pipe will have to be replaced, as will a parallel 10-inch pipe that dates to 1914 and also was identified as "high risk" in a city assessment three years ago.

"The logical thing, while the street is open, while the street has been undermined like that, is to take out the other old line," said Kurt Kocher, a city public works spokesman, noting that the pipes were installed during the presidential administrations of Benjamin Harrison and Woodrow Wilson, respectively.

City officials at a news conference Tuesday on Light Street said they did not recall how much pipe was considered high risk.

Alfred Foxx, director of the city's Public Works Department, called such breaks frustrating, but said the city is trying to be smart about the way it approaches the monumental task of updating infrastructure. He said the city is trying to be more proactive in addressing problems on a systemwide basis, expanding an effort to install technology on major water mains that alerts the department to potential ruptures.

Foxx said his department has decided it will begin increasing the amount of aged piping it replaces each year. "We're going to commit ourselves to doing that," he said.

According to Kocher, there are about 3,800 miles of water lines in the city, with much of the pipe 75 to 100 years old.

The department now replaces less than five miles of water pipe a year but hopes to replace about 20 miles of pipeline in the next fiscal year and to increase that to 40 miles per year within five years, Kocher said.

Increasing the pace at that rate over the next five years would cost $300 million dollars, Foxx said.

Even if met, that goal would not erase the city's water infrastructure problems.

Rawlings-Blake, who is co-chair of the U.S. Conference of Mayors Water Council, pointed to her recent Board of Estimates vote for a 9 percent rate increase for water and wastewater bills. She said such efforts to raise revenue are needed to fund continued infrastructure repair and to modernize the city system.

"When you have infrastructure that's over 150 years old in some places, you have to make the tough choices," she said. "It's extremely unpopular to talk about raising water rates. None of this is popular, but it's necessary. We try to keep a pace that makes sense based on what we can afford."