Baltimore transportation officials expect Howard Street sinkholes to be repaired Tuesday

Work to fill in sinkholes beneath the pavement at North Howard and West Lexington streets in Baltimore is expected to be finished Tuesday, transportation officials said.

Several blocks of both streets were closed Sunday and Light Rail service was suspended Sunday after Maryland Transit Administration crews discovered depressions in the pavement while performing track work along the light rail’s Howard Street corridor.

Contractors were brought in Monday afternoon to fill the sinkholes with material known as flowable fill, said Frank Murphy, senior adviser in the city transportation department. They were expected to finish applying the substance within about 24 hours, he said.

“It’s like concrete but not as hard, so you can dig through it if you have to,” Murphy said. “It flows in and fills up nooks and crannies.”

Officials have not determined what caused the sinkhole, but ruled out any broken infrastructure that may have leaked and washed away dirt beneath the street. Asked if record precipitation this year might have been a factor, Murphy said heavy rain “often” is to blame for sinkholes.

There has been more than 65 inches of precipitation at Baltimore-Washington International Thurgood Marshall Airport so far this year, 3 inches more than the region’s previous record-wettest year and more than 20 inches above normal.

The Howard Street sinkholes are the latest example of heavy rain challenging efforts to maintain infrastructure. Last month, a portion of East 26th Street in Charles Village sagged amid heavy rain as a retaining wall failed. A section of the Light Rail was out of service for weeks this summer after erosion caused by July flooding.

Sinkholes occur when water — whether groundwater, stormwater or leaking pipes — dissolves rock or soil underground, creating holes or caverns that sometimes lead to dramatic collapse of the land above. In this case, the MTA crews detected the sinkhole before any such collapse could occur.

Murphy said officials rely on such early warning signs to detect sinkholes. Unless they know of an area that might be prone to sinkholes, it’s otherwise not clear where to inspect or monitor, he said.

He said heavy rains like those the region has experienced this year can sometimes lead to sinkholes because they scour away stream banks and erode soils, changing flow patterns.

“Nature being what it is, it changes conditions all the time,” he said.

Ben Schafer, a professor of civil engineering at Johns Hopkins University, called it “reasonable” to expect more sinkholes as heavy rain inundates infrastructure.

“If our sewer and drainage systems cannot handle such rainfall then we will be compromising the soil in undesirable ways — leading to greater occurrences of sinkholes,” he said.

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