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Fixing the broken water main at Howard and Lombard streets - a breach that pushed 60 million gallons of water onto downtown streets Wednesday night - has gotten trickier.
Public works officials now know that the pipe is embedded in the brick arch that forms the top of the 106-year-old Howard Street Tunnel - and that they will have to order critical custom-made pipe parts from Arkansas.
But their repair effort was abruptly stopped after the Fire Department expressed fears that the work could cause the tunnel to fall on firefighters battling the train fire. The pipe rests on bricks nine inches above the tunnel ceiling, officials say.
All of that means the large hole in the middle of a major downtown intersection could be there for days, along with the steady flow of water being channeled from the pipe onto Howard Street and down a storm drain.
"We're basically in a holding pattern," said Robert H. Murrow, spokesman for the city Department of Public Works. "We're doing a lot of planning."
Even plans to shut off the last valve feeding water into the main were deemed too dangerous, said Amar Sokhey, chief of the Public Works' Bureau of Water and Wastewater. To close the valve, workers must first open it further, and fire officials don't want to risk any more water seeping into the tunnel - even if it would then stop flowing entirely.
Once the Fire Department says it is safe to proceed on the pipe repair, it could take two or three days to do the job, Sokhey said.
The delay is acceptable, Murrow said, because area hotels and businesses have had normal water service since a period Wednesday when pressure was weak and the water cloudy. The city's network of pipes includes built-in bypasses to deliver water when a line breaks.
Officials have not been able to inspect the pipe to see what role the fire played in the rupture. But they have said a link seems likely. Murrow said Thursday that "it looks more and more like it's the fire."
The broken main has caused no apparent structural damage to the tunnel, said Warren Williams, the bureau's chief of utility maintenance. Water is seeping down despite round-the-clock effort to pump most of it out of the pipe.
Initially, public works officials put the cast-iron pipe's age at 90 years, but Sokhey said records found yesterday indicate that it dates to the 1880s. If so, it predates the tunnel, which was built between 1890 and 1895. The distance from road surface to tunnel is four or five feet, he said.
The first step after work resumes will be to dig up debris surrounding the pipe. Only then can workers take a precise measurement of the pipe. Its diameter is about 40 inches, but the measurement can't be off by even a fraction of an inch.
At that point, officials will call the Smith-Blair Inc. foundry in Texarkana, Ark., and order clamps that will connect a new pipe section about 18 feet long. If the fit is not exact, it will leak, Williams said. Smith-Blair was chosen because it makes a "proven product," he said, adding, "Particularly when you're doing a repair like this, you want to do the best you can."
The foundry will need 24 hours to make the clamps, which will be flown to Baltimore. Water will flow again when all the pieces are joined together. Even then, Sokhey said, it is likely the tunnel's arch will need to be repaired.
Public works officials now know that the pipe is embedded in the brick arch that forms the top of the 106-year-old Howard Street Tunnel - and that they will have to order critical custom-made pipe parts from Arkansas.
But their repair effort was abruptly stopped after the Fire Department expressed fears that the work could cause the tunnel to fall on firefighters battling the train fire. The pipe rests on bricks nine inches above the tunnel ceiling, officials say.
All of that means the large hole in the middle of a major downtown intersection could be there for days, along with the steady flow of water being channeled from the pipe onto Howard Street and down a storm drain.
"We're basically in a holding pattern," said Robert H. Murrow, spokesman for the city Department of Public Works. "We're doing a lot of planning."
Even plans to shut off the last valve feeding water into the main were deemed too dangerous, said Amar Sokhey, chief of the Public Works' Bureau of Water and Wastewater. To close the valve, workers must first open it further, and fire officials don't want to risk any more water seeping into the tunnel - even if it would then stop flowing entirely.
Once the Fire Department says it is safe to proceed on the pipe repair, it could take two or three days to do the job, Sokhey said.
The delay is acceptable, Murrow said, because area hotels and businesses have had normal water service since a period Wednesday when pressure was weak and the water cloudy. The city's network of pipes includes built-in bypasses to deliver water when a line breaks.
Officials have not been able to inspect the pipe to see what role the fire played in the rupture. But they have said a link seems likely. Murrow said Thursday that "it looks more and more like it's the fire."
The broken main has caused no apparent structural damage to the tunnel, said Warren Williams, the bureau's chief of utility maintenance. Water is seeping down despite round-the-clock effort to pump most of it out of the pipe.
Initially, public works officials put the cast-iron pipe's age at 90 years, but Sokhey said records found yesterday indicate that it dates to the 1880s. If so, it predates the tunnel, which was built between 1890 and 1895. The distance from road surface to tunnel is four or five feet, he said.
The first step after work resumes will be to dig up debris surrounding the pipe. Only then can workers take a precise measurement of the pipe. Its diameter is about 40 inches, but the measurement can't be off by even a fraction of an inch.
At that point, officials will call the Smith-Blair Inc. foundry in Texarkana, Ark., and order clamps that will connect a new pipe section about 18 feet long. If the fit is not exact, it will leak, Williams said. Smith-Blair was chosen because it makes a "proven product," he said, adding, "Particularly when you're doing a repair like this, you want to do the best you can."
The foundry will need 24 hours to make the clamps, which will be flown to Baltimore. Water will flow again when all the pieces are joined together. Even then, Sokhey said, it is likely the tunnel's arch will need to be repaired.
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