CEDAR RAPIDS — An Office of the State Archaeologist report estimates as many as 14 beer caves — not three as previously detected — are located underground near access ramps to Interstate 380 in Cedar Rapids.

The report estimates five to eight beer caves — subterranean rooms used for cooling and aging beer before refrigeration — were connected to the Magnus Eagle Brewery, which was built in 1857 and demolished in 1937.

An April 2014 article called “The Original Breweries” by The Gazette’s Time Machine, reported the Magnus brewery had five cellars and the Williams brewery had six.

The report also identifies a second brewery called Williams Cedar Rapids Brewery, built in 1860. It had six caves located immediately southwest of Magnus, according to the report.

“They actually found more openings then they thought they would, up to 11 and possibly 14,” said Cathy Cutler, a district 6 transportation planner for the Iowa DOT. “Further investigation will help inform that number.”

The 45-page report was submitted to the Iowa Department of Transportation this month. The Iowa DOT contracted the study for $19,000 after a staff member noticed a 30-inch diameter sinkhole in a grassy shoulder during a routine bridge inspection in July.

The inspector lowered a camera underground to find man-made structures, at which point the archaeologist’s office was hired.

Marlin R. Ingalls, an architectural historian for the archaeologist office, said the objective of the report was to identify what was below ground near the interchange at Seventh Street NE.

Initially, investigators detected three Magnus beer caves with ground penetrating radar, but historical research revealed the larger extent of the network of caves in the immediate area.

The report estimates at least some of the caves are 20 feet long and 10 or 12 feet tall.

Ingalls climbed into the sinkhole to explore the one cave to which he had access. The caves are constructed with stone archway ceilings, he said.

Debris is piled several feet high, such that it reaches where the arched ceiling begins to curve, and Ingalls had to navigate on his stomach in some places, he said, Steel pilings supporting the interstate are “pincushioned” through the caves in many places and large dislodged rocks make for precarious exploring, he said.

“I did get down in the caves,” Ingalls said. “I’ll probably be the last person to ever do so. It was an interesting experience.”

The environment is “impossibly dangerous,” he said adding that he came back above ground after about 15 minutes.

Ingalls said the city had filled in the caves in the 1950s or 1960s in response to inappropriate use, and they were fully covered by dirt and roads during the building of Interstate 380 in the 1970s.

Ingalls said he found no artifacts during his brief tour of the cave.

The bigger questions the DOT is hoping to answer is if there’s historical significance, and if the caves should be filled in completely, and if so, with what.

The report did not provide resolution on that matter and instead recommended more evaluation.

The report recommended additional surveys to determine the exact dimensions and location of all the caves and the historical significance with respect to the National Register.

The report stated the ground penetrating radar had difficulty delineating voids, so more sensitive remote sensing techniques that can penetrate to a greater depth, such as electromagnetic resonance, should be used.

Electromagnetic resonance has been successful in the past in detecting the measurements of voids, Ingalls said. The tool sends strong electronic pulses into the ground and bounces back at intervals set by the operator, he said.

Cutler said the DOT will continue working with the archaeologists office on the follow up surveys to determine how to proceed. She said the matter is considered a maintenance issue at this point and the roadways are structurally sound.

“It will really depend on the further work we plan to do with the resource agency, the archaeologist’s office, and what they recommend,” she said.