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Engineers face chicken-or-egg-like question in Mount Adams landslide

Which slid first, the hill or the retaining wall?
Which slid first, the hill or retaining wall?
Posted at 4:44 PM, May 04, 2017

CINCINNATI -- Engineers are still trying to determine what caused a Mount Adams landslide that damaged two houses Wednesday.

Their main question: did the hillside begin slipping and knock over the retaining wall, or did a retaining wall fail, allowing the hillside to slide down?

Residents were ordered out of the two Baum Street homes after dirt and pieces of retaining wall from between Baum and Oregon Street crashed into them, causing serious damage. The buildings department also ordered decks on Oregon, above Baum, stay closed until the city could check they were safe.

All the decks, except at the City View Tavern which needs unrelated maintenance work, have been cleared, according to Art Dahlberg, director of the buildings department. 

Matt Fenik of Metropolitan Design and Development, the company building the wall and the homes, said it was the hillside that failed first, causing the wall to buckle.

Dahlberg wasn't sure of the cause yet.

"Clearly, we could see there had been movement on the slope, but at this point we don't know if the wall failed and the dirt moved," he said. "Or, was there movement in the dirt that overpowered the wall and had the collapse?"

Residents still want to know what caused the landslide and that their homes will be safe.

"I'm pretty shook right now," Oregon Street resident Kyle Gilligan said. "Kind of nervous that the foundation to our deck might fall loose and we'll lose our beautiful view. That's what we pay for up here and that's what we love about living up here in Mount Adams."

From Gilligan's deck Thursday, a sea of blue tarps were visible. They were keeping rain from further saturating the hillside where the landslide happened early Wednesday.

 

Dahlberg said everything was done by the book when the retaining wall was installed.

"As part of this process, not only was it permitted, but it was required to have special inspections by a professional engineer," he said. "A professional engineer designed, was involved in that process. They evaluated the soil before the wall started to be installed. They evaluated the backfill as the wall was going on up and they evaluated the construction of the wall with signed reports."

But something was missed, and that's what investigators want to find. Cincinnati hillsides are often limestone and shale from glaciers moving through the area centuries ago. That's being checked as a possible cause.

There is also a combined storm and sanitary sewer line running between Baum and Oregon streets that MSD has been checking for possible problems.

Oregon Street resident David Berwanger said he was optimistic the issue could be fixed.

"Up on the hill year, it always seems like kind of a living thing," he said. "There's always something that seems to be going on."

The section of wall that failed is part of a single, long wall behind multiple properties on Baum. According to Dahlberg, the entire wall has been under construction since September 2012.

The city issued a permit in August 2015 for the section that collapsed, and work finished in November 2016. The wall is privately-owned, according to city officials.

Not the first slippage

Mount Adams has a long history of slippage problems. 

The 1974 landslide

Back in 1974, there was a much bigger landslide related to work done on ramps connecting the Dan Beard Bridge with Downtown. 

Attorney C. Francis Barrett represented people in a Baum Street building that was damaged then. 

"As a result of that construction, the Ohio Department of Transportation had to cut away the toe of that hill," Barrett said. "Once they cut away the toe of the hill, the entire hillside started to slip."

A $22 million retaining wall was built to stabilize things. Cables were tied to an underground tunnel to handle the load. But Barrett said building the wall caused even more problems.

"The entire parking lot started to move. The entire building started to move and eventually the building had to be closed," Barrett said. "All the residents had to be vacated for safety purposes because of that massive landslide."

That wall is now the reason new development is possible in Mount Adams. If it hadn't been installed, the entire hillside up to the Highland Towers apartment building would have slipped to the bottom, according to Barrett.