In the few short weeks he has lived in his Ramona Street home, Nick Thumma has been unable to shake a sinking feeling.
It started one day in early March, just after he and his wife moved into their new neighborhood. Thumma noticed the pavement in front of his neighbor's driveway had dipped 6 or 7 inches.
City road crews quickly arrived, patched up the street and moved on, according to Thumma. But the sinkhole didn't stay away long.
"(The patch) lasted maybe a couple of weeks," he said. "I came home from work a couple of Thursdays ago, and there was a giant sinkhole. My car could have fit in it."
Another failed patch job, a broken water line and the discovery of a collapsed mine shaft later, and Thumma said he's ready to take his fight to City Hall, and the Statehouse, if necessary.
He said information about the locations of the city's many abandoned mines and tunnels should be readily available, and homeowners should have insurance options available to insulate themselves against damage from an unexpected sinkhole.
"What I think needs to be done is the citizens of Dubuque need to be informed if these mine shafts are (nearby)," Thumma said. "I don't know if there's one under our house. I have no idea."
Dubuque was heavily mined in the mid-1800s, according to retired university professor and geologist Jim Dockal. He said at least 500, and maybe as many as 1,000, mine shafts and tunnels hide beneath the city's surface.
"When the gold rush happened in the 1850s, everyone took off and just left them," Dockal said, noting they often were not filled in or holed up properly. "They were used many times as ways to dispose of yard waste, tree branches, stuff like that. That's going to decay."
Worse yet, 19th-century miners weren't the most diligent record keepers, Dockal said. Very few inventories of Dubuque's complex mine system exist.
City Engineer Gus Psihoyos said sinkholes pop up in the public right-of-way a few times per year. While the city will attempt to stabilize the area and repair any damaged utilities, like Thumma's water line, Psihoyos said it is virtually impossible to know when and where a sinkhole will occur.
Aside from a few ancient and unreliable maps scavenged by a hobbyist employee, no up-to-date records are available.
"We don't really have any city records of any mine shafts," Psihoyos said.
Plus, mine shafts are not the only underground hazard in eastern Iowa.
"We live on the bluffs of Dubuque, and there are caves and cave crevices that run all over the place because of the ... underlying soil types we have in this region," said Civil Engineer Jon Dienst. "There are fissures, there are caves, there are some shafts. That's just part of living in this region."
In addition to more access to mine shaft records, Thumma said state law should be modified to allow homeowners to purchase insurance for sinkhole-related damages. While legislators in some states have mandated the creation of such risk pools, Thumma said no options are available in Iowa.
"If we have a mine shaft under our house, and our house collapses, what? We don't have that insurance," he said.
Thumma said he already has reached out to city officials and state legislators with his requests. Rep. Pat Murphy, of Dubuque, confirmed he has spoken with Thumma and said the two likely will have additional conversations about the issue in the future.
City road crews will take a third crack at Ramona Street this week. Psihoyos said the street will be excavated, and workers will attempt to find the source of the resilient sinkhole.
"Somehow, we'll bridge the crevice or shaft and make our repairs above ground," he said. "We just basically cap the crevice with concrete usually, reinforce and then we go make the repairs."
City workers also have rigged Thumma's water line to a neighbor's, ensuring a steady supply while repairs are made. But Thumma said the uncertainty will linger after the street and his utilities are restored.
"It's just something that is upsetting to me that we don't know what's down there," he said.