Several steps away from the crumbling edge of East 26th Street in Charles Village, a construction worker slowly unrolled a long yellow measuring tape into a circular hole about the size of a sewer manhole lid.
Foot after foot of the tape disappeared as he sought to learn the depth of the hole being bored straight down into the earth by a hulking orange drilling machine anchored not far from St. Paul Street.
Another worker at the block-long construction site Tuesday said the hole is the first of many that will be cut into the street as part of a new design to keep East 26th Street and the earth beneath it from spilling down onto the railroad tracks, which run parallel to the street, as they did last week when a century-old retaining wall collapsed amid heavy rain.
Adrienne Barnes, a city Transportation Department spokeswoman, said the city hired contractors to replace the retaining wall and repair the street. She said that 65 "borings" or "piles" are being inserted into the street by contractors hired by the city.
Such holes can be filled with steel beams or underground caissons to bolster ground stability and anchor retaining walls, experts said.
Barnes said the contract for the work is not finalized and there is no estimate of the cost or other specifics about the project.
"This is an emergency. It wasn't anything we planned for or anything that was projected. It was something we had to do," Barnes said. "We don't have any final numbers yet. Our job is to restore the neighborhood. We need to do whatever we need to do."
Jack Temple, who lives at the corner of East 26th and St. Paul, said residents were told at an informational meeting Sunday that "barring setbacks," the project could take as little as three weeks, far shorter than the 40 days they were told they might be displaced from their homes. In the meantime, Temple — who said he "absolutely" appreciates the quick start to repairs — is staying in a Towson hotel room provided by the city.
The city is proceeding with the work despite questions about who may be responsible for the accident, which sent the masonry wall, tons of earth and asphalt as well as eight cars tumbling onto the railroad tracks below. The city and CSX Transportation, which owns the tracks, have tussled in the past about who is responsible for maintaining the walls.
Bryan Rhode, CSX's regional vice president for state government affairs, said in a statement that the city is "leading the efforts in stabilizing the site, supporting the needs of residents and developing plans for reconstruction," and that the railroad is "grateful and supportive of the city's actions in focusing on those immediate requirements."
Neither city nor railroad officials have answered questions about where the company's right-of-way ends along East 26th Street or who had responsibility for the wall.
CSX repaired the rail bed and reopened the busy line to trains about a day and a half after the collapse.
One expert on retaining walls said the tab for replacing the wall, especially under rushed circumstances, could easily be more than $1 million.
"When time is of the essence … you usually will end up constructing something more expensive," said Steve Wendland, head of geotechnical and geological engineering at Kleinfelder, a San Diego-based engineering firm with offices in Hanover. "That's very quick that they've got back out there to rebuild things."
Still, a more modern retention system based on support pilings would be cheaper than a new stone masonry wall, because stone walls are so labor-intensive to create that costs are driven up, he said.
Barnes said the city hired Concrete General of Gaithersburg as the prime contractor. The firm could not be reached for comment. The engineering firm is Baltimore-based Whitman, Requardt and Associates, she said.
Jeremy Kargon, an assistant architecture professor at Morgan State University who has studied infrastructure issues in Baltimore, said it is not uncommon for the city to respond to a disaster by footing the cost for initial repairs, then billing the party ultimately deemed responsible.
"Typically in disasters, that's how the city works," Kargon said. Even when homes collapse, he said, "the city goes ahead and sends in the demolition crew, and then bills the owner."
Experts in soil retention and retaining wall construction said the century-old wall that collapsed was likely a simple "gravity wall" — mainly drawing strength from its own sheer mass — and almost certainly was undermined by saturation of the earth behind it.
Wendland said statistics show about 75 percent of major wall collapses across the country are caused by water, when drainage systems built into the walls clog or otherwise fail to flush out standing water. He also said that despite their appearance as permanent pieces of a city landscape, even major retaining walls have a limited lifespan.
"It's 100 years old, and that's often how long we design our new retaining walls to last for," said Wendland, who advises on construction of retaining walls around the country. "With highway projects we're working on right now, that's often the life span we aim for."
Charles Schwartz, chair of the civil and environmental engineering department at the University of Maryland's A. James Clark School of Engineering in College Park, said soil saturated by rain can exert three times more pressure on a wall than dry soil. Water also erodes the natural cohesive strength of the soil itself, he said.
"It had to be the water," Schwartz said of what caused the collapse. "Almost all the time these things happen after periods of heavy rain, because you get those water pressures in there that decrease the soil strength."
Several inches of rain fell on Baltimore in the days prior to the collapse.
City officials have said the street was inspected for stability as recently as one year ago, and that cameras were sent into underground pipes to check for damage. But officials have not provided any documentation of the inspection.
Because retaining walls often have relatively simple designs, they don't require as much regular maintenance as other pieces of infrastructure, such as bridges and dams, experts said. That is good for cost containment, but also can lead to neglect of important aspects of walls, such as their drainage, while bridges and dams receive regular inspections, they said.
Kargon said the wall's failure is not all that surprising, given the vast amount of infrastructure maintenance that has piled up in Baltimore after years of austerity in transportation spending.
The hometown of the Baltimore & Ohio Railroad, Baltimore is built on a vast transportation infrastructure for a much larger population than now resides in the city, and its limited tax base today doesn't provide nearly enough funding to keep up with maintenance demands, he said.
"We simply don't have the human and fiscal capital to maintain the infrastructure that we have," Kargon said.