On his walk from the Inner Harbor Marriott to Camden Yards Tuesday, Tom Murphy was focused on the Orioles game against the Cleveland Indians.
He wasn't thinking about the 15-mile network of pipes that ran below his feet, pumping steam throughout downtown Baltimore. But after the steam pipe explosion that blew a hole in the street Murphy had recently walked down — the underground system was at the forefront of his mind.
Murphy, 50, surveyed the damage Wednesday morning.
"It's sobering to see," he said. "There's all this infrastructure we depend on, and we don't even know we depend on it."
The day after the explosion injured five people and blasted chunks of Eutaw Street pavement into the air, streets remained closed and few answers had emerged about what went wrong.
Veolia North America, which has operated the city's steam pipe network since 2007, said the cause of the explosion remains under investigation.
Crews worked Wednesday to clean up the site of the blast and excavate the affected steam line, company spokeswoman Karole Colangelo said. She said the cleanup will likely take several days.
Initial environmental testing showed low levels of asbestos, Colangelo said, but air quality is normal at the site. Asbestos was once used to insulate pipes.
"We're still awaiting results related to pollutants in the mud and debris in the affected area," Colangelo said. "Out of abundance of caution and in order to expedite the cleaning of the area, we're treating the situation as a remediation action, which requires specialized cleaning techniques, until we can confirm the area is not contaminated."
Joseph Kane researches infrastructure at the Brookings Institution. Steam pipe networks are typically "out of sight, out of mind," he said, "until there's a situation like this."
Because infrastructure is hidden, problems can develop unseen: Pressure can build up, or a pipe can rupture, become corroded or spring a leak.
"These are systems in need of continued oversight to identify where the pinch points may be," Kane said.
Donald Fry, president and CEO of the Greater Baltimore Committee, said the city should learn from the explosion.
"Without knowing the cause of the explosion, this type of incident should serve as reminder to the city's leaders to ensure that they have a full assessment of all the condition of types of infrastructure and a long-range plan to invest in its maintenance and upkeep," Fry said in a statement.
The city has suffered water main breaks and sinkholes in recent years. But Mayor Catherine Pugh said those problems shouldn't be conflated with challenges confronting the city's steam-pumping apparatus.
"This is not that old of a system that's carrying the steam, so I don't feel that we're in danger of steam pipes exploding all over the city," she said.
In March, a broken steam line in South Baltimore closed down Charles Street between Montgomery and Lee streets.
"To have two in a row like that is a little odd," said Mike Evitts, a spokesman for the Downtown Partnership of Baltimore. "But most of our constituents understand the system, so we're not hearing a lot of concern. ... Steam is safe and cost-effective, and that's why so many downtown buildings use it."
Pugh said Tuesday there were no plans to investigate other steam pipes downtown.
"We have to see what the cause of this is first," she said.
Pugh said it was fortunate that the Orioles were playing, because it meant one side of the street was cleared of parked cars.
"This could have been a really severe problem," Pugh said.
Veolia supplies steam, hot water and chilled water to more than 255 customers in downtown Baltimore, according to its website. The steam is used to heat large buildings, such as the Baltimore Convention Center, to sterilize hospital equipment and to clean laundry.
In 2014, some city officials said they wanted some of the revenue from Horseshoe Casino to go toward replacing part of the steam pipe system that runs under the main entrance to the casino. Officials worried that increased traffic would cause the line to break.
The casino and Veolia agreed to contribute a combined $1.5 million to relocate the steam pipe, supplementing funds from the city.
Sunil Sinha is director of the Sustainable Water Infrastructure Management Center at Virginia Tech.
He said Tuesday's explosion points to the need to spend more money on infrastructure.
"In a country like this," he said, "we shouldn't be waiting for things to fail."
Baltimore Sun reporters Ian Duncan and Luke Broadwater contributed to this article.