MacKenzie Elmer

melmer@dmreg.com

A portion of the riverbank has collapsed near City Hall in downtown Des Moines.

Pam Cooksey, city engineer, said her department noticed Monday that soil between City Hall, 400 Robert D. Ray Drive., and the Des Moines River had shifted, but it has not determined a cause. Cooksey said it "looked kind of like a sinkhole."

"We’re looking into that right now to figure out what’s going on to get a repair," she said. "We became aware of it today. I assume it started it over the weekend."

Cooksey said the slide has not compromised the structural integrity of the historic building, which opened in 1910 and is listed on the National Register of Historic Places. The building has been closed since June while construction crew complete a yearlong renovation project.

The collapse also coincides with the replacement of the Grand Avenue bridge over the Des Moines River. The bridge is located just north of the collapse. Crews have removed the existing bridge deck, which will be replaced this year.

In April, a sinkhole swallowed a 40-foot tree in the front yard of a home on Des Moines’ south side. Officials said an abandoned coal mine underneath the site was likely to blame.

Cooksey said there are no abandoned mines near the latest collapse.