CEDAR RAPIDS — A bridge inspector thought he'd found a potentially hazardous sinkhole near an Interstate 380 access ramp late last month, but a preliminary investigation suggests it's 150-year old beer caves, a remnant of a long closed brewery, officials said.

During a routine bridge inspection on July 31, an Iowa Department of Transportation staff member noticed an 18-inch void in a grassy shoulder off the Seventh/Eighth Street access ramps to I-380 southbound.

The ramp was closed to evaluate possible safety concerns, but they found more than they bargained for.

Cathy Cutler, a transportation planner with the Iowa Department of Transportation District 6 office, said the inspector lowered a camera underground revealing a structure beneath the earth.

Cutler said an older staffer in the District 6 office in Cedar Rapids suspected it was beer caves, which he said was a consideration when the interstate was built in the 1970s.

Beer caves were fairly common for breweries before refrigeration, and there's several in Iowa, including under the north side of Iowa City. These subterranean caverns, some big enough to fit a truck, were typically constructed out of limestone or brick.

An article in The Gazette on Aug. 6, 1977, reported that excavators had unexpectedly pierced a beer cave during construction of this stretch of I-380 when they were digging to lay a culvert north of Eighth Street.

The local DOT office informed the DOT's Location and Environment office, which studies historical and environmental impacts.

After examining historical data and old atlases, staff contacted the University of Iowa's Office of the State Archaeologist to continue the investigation, which has been going on this week.

“When it looked like it was going to take more research to figure out, we called in our partner agency,” said Brennan Dolan, with the Location and Environment office.

An archaeologist and an architectural historian were part of a team that visited the site on Monday, and detected three-to-four underground limestone caverns using ground penetrating radar.

The archaeologist's office also suspects the caverns are beer caves connected to the former Eagle Brewing Company/Magnus Brewing Company near Cedar Lake.

“Everything is very preliminary at this point,” said Carl Merry, the research director at the state archaeologist's office. “Right now it's a hypothesis. We are trying to identify as best we can what is down there. It could be more than one thing.”

Merry said the caverns are 20 to 30 feet below ground, and they still are trying to determine their size. He said they are structurally sound, but people should not try to enter because they don't know for sure what is down there.

Merry's team will conclude its investigation with archival work and then submit a report to the DOT.

Cedar Rapids historian Mark Stoffer Hunter is a bit more certain of the findings.

“They are the Magnus beer caves. That's exactly what they are,” Hunter said after hearing of the discovery. “This is very exciting as an historian.”

The brewery was constructed by Jacob Wetzel in 1859.

Wetzel hired an old world brewer from Germany named Christian Magnus as his brewmaster and foreman, according to The Gazette's Time Machine. Beer caves were essential to Magnus' vision for the beer cooling and aging process. The brewery was a five-story complex overlooking Cedar Lake, but the back ran into a hill where the caves were located.

The brewery had five cellars that could hold 2,000 barrels, two ice houses that held up to 2,300 tons of ice, and a capacity to produce 60 barrels of beer in 12 hours.

Magnus bought out Wetzel in 1868, and at the height of production, the Christian Magnus Eagle Brewery and Bottling Works put out 25,000 barrels of 4.5 percent beer in the late 1800s and early 1900s.

Hunter said the brewery was possibly best known for Eagle Brewing, a popular beer with a logo of an eagle perched on a beer keg with its wings stretched wide and a man tapping the keg.

The brewery closed because of prohibition in 1915, although it operated for several more years producing soft drinks, among other items, before entirely shutting down in the 1920 and being demolished in 1937, Hunter said.

Hunter said in later years homeless people would use the caves, and they were later boarded up. However, children would break through the boards with “skull and cross bone — do not enter warning” to explore.

A neighborhood then was built on top of the beer caves, before being torn down for I-380, he said.

Cutler said the DOT will seal the 18-inch void, but because they don't believe there is a safety risk to motorists, additional work is not expected, she said.

“We will fill it in to make sure the void isn't there. but traffic has been running on it for years, so it's obviously safe to drive on,” Cutler said.

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