The sinking city: Dozens of buildings in Milwaukee...sinking! There's a problem and it's deep underground

MILWAUKEE (WITI) -- If you ever look up in Milwaukee, even just a little bit, you can't help but notice we have some amazing architecture here -- buildings that were built to last. But some of them may not last much longer. There's a problem...and it's deep underground.

On Milwaukee food tours, hungry walkers can feast their eyes on a strange phenomenon.

"As we're walking through the Third Ward -- how the bricks are starting to crumble a little bit, and the buildings are beginning to lean," Theresa Nemetz said.

You can even feel the problem under your feet.

"You see the sidewalk is beginning to settle. The city has actually come through and shaved down the sidewalk," Nemetz said.

So what's happening here?

Dennis Barthenheier has dug a giant hole in his basement to find out.

"I noticed this large crack that`s along the wall line here. It's coming apart...and I know why," Barthenheier said.

Much of Milwaukee was built on a marsh. Around the turn of the century, for stability under foundations, contractors used steam-powered pile drivers to sink into the soggy land below thousands of wood pilings -- tree trunks stripped of their branches and bark.

A concrete gap -- basically the building foundation, was placed on top.

Milwaukee landmarks were made this way. Among them: Milwaukee's City Hall, the Mitchell Building. the Button Block, the Pabst, and the Riverfront Building that houses the Milwaukee Repertory Theater.

"A couple years ago we started seeing cracks, basically -- in the walls,"  Chad Bauman, Managing Director of the Milwaukee Repertory Theater said.

Floors are no longer level. There are growing gaps under the doors -- and a tell-tale sign of the source: wharf borer beetles.

"This wall has come down almost two-and-a-half inches," Milwaukee Repertory Theater's Chief Building Engineer Mark Uhrman said.

Signs of the building sinking are everywhere. Wood wedges temporarily support the floor above.

The technique of setting foundations on wood pilings was nothing new. It had been done in Europe for centuries.

However...

"The pilings need to be kept wet. This sounds counter-intuitive, but things that are wet permanently rot slower," UW-Milwaukee Professor of Geosciences Doug Cherkauer said.

In parts of Milwaukee, the water table has fluctuated -- and pilings have been exposed to air.

"They're starting to rot," Cherkauer said.

How long they've been rotting, nobody knows. And why the water table has gone down is disputed. Cherkauer, a hydro-geologist says he isn't even sure it has.

"As far as I know, there are no monitoring wells anywhere in the downtown area, so we don`t know what the groundwater conditions in Milwaukee actually are," Cherkauer said.

But we do know the buildings are sinking -- dozens of them.

In the basement of the Milwaukee Repertory Theater, they're getting ready to remove the rotten wood and replace it with a new foundation.

That brings us back to Dennis Barthenheier -- and the large hole he's dug in his own basement. Fixing sinking buildings is his specialty. The repair at the Repertory Theater will be one of his big projects this year. In his basement, he's just discovering the depth of the problem.

"That wood that you see should be all the way up and into the bottom of that concrete -- but it is gone. It's rotted away," Barthenheier said.

So here's how Barthenheier stops the sinking. He digs down, and each rotted piling is cut off below the water level. One by one, steel jacks are installed. Then, a new concrete form is filled to close the gap between the old cap and the new piling top below.

"All we`re doing is extending the concrete down further to make sure the wood is submerged in water," Barthenheier said.

But with potentially thousands of pilings rotting under buildings in Milwaukee, it's a big job.

"We have water in our basement and we WANT water in our basement," Milwaukee Repertory Theater Chief Building Engineer Mark Uhrman said.

You might be wondering: What if the water table goes down? Won't the pilings rot again?

As part of the repair, they're often installing reverse sump pumps. In your basement, the sump pump kicks in when the water gets high. Here, it kicks in when the water gets low, and pumps water in from the city system to keep the pilings wet.