The 150-year old beer caves that captured the imaginations of Cedar Rapids history buffs and beer lovers upon being rediscovered under Interstate 380 a year ago are expected to be sealed up soon, officials say.
Brennan Dolan, an archaeologist with the Iowa Department of Transportation, said this week officials are still determining how and when to seal the void.
“At minimum, they will need to be capped or filled,” Dolan said. “We don’t want the sinkhole to expand.”
On Friday, Dolan will visit the site where a bridge inspector last July discovered an 18-inch-wide sinkhole along the Seventh and Eighth street access ramps to I-380. Further investigation revealed that below were beer caves — subterranean rooms used for cooling and aging beer before refrigeration — connected to two breweries from the 1800s that have been demolished.
A DOT group will use LiDAR, a remote sensing tool, to measure the volume of the void below and create a detailed map assessing attributes such as craftsmanship and materials used in constructing the caves.
The data collected will be provided to the DOT’s local office, which will be responsible for sealing off the caves, he said.
Neither the interstate pavement nor the abutments supporting the interstate have moved, meaning the roadways above are structurally safe, Dolan said.
But the space is already partially filled with debris and poses safety risks if people try to enter. And Dolan said officials don’t want the sinkhole to get bigger.
Dolan said the likely solution will be to either cap the caves with something like a manhole cover or to fill the space with a material that preserves the interior of the caves but can be chipped away in the future, such as hydraulic sand or flowable mortar.
How quickly the void is filled could be dictated by the outcomes of the LiDAR tests. If cave conditions are deteriorating, for example, crews may act more quickly.
The Iowa DOT officials had conceded sealing the caves was an option for safety reasons shortly after the discovery was made, but finalized the decision only recently after the completion of tests and studies.
The DOT hired the Office of the State Archaeologist and the Iowa Geological Survey to study the area for historical significance and to identify the number and scope of caves below.
Based on the tests, which included probing the ground with electric pulses, officials believe three caves are directly under the roads, and the area around Cedar Lake overall had 11 to 14 caves connected to Magnus Eagle Brewery, which was built in 1857, and Williams Cedar Rapids Brewery, which was built in 1860.
In the years after the breweries went belly up in the post-Prohibition era, the caves were used by vagrants and for teenage dares, and later covered over by neighborhoods and then the interstate.
Cedar Rapids historian Mark Stoffer Hunter said it is disappointing to know the caves will be sealed, but he is glad they will be preserved.
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“I still hold out hope that at some point down the road we find a solution to make those available for tours for the public,” he said. “I think there is a really great opportunity for us. It is just a really unique industrial story of Cedar Rapids. We have this great brewing history, and a great history of this old German neighborhood.”
Stoffer Hunter said he hopes the memory of the beer caves stays fresh in mind so the next time the DOT needs to do a redesign of the interstate, there’s a push to excavate and restore them.