Latest sinkhole is 14th in Cape Girardeau since July

March 2008

U.S. Water News Online

CAPE GIRARDEAU, Mo. — Two more sinkholes have emerged in Cape Girardeau — bringing to 14 the number of collapses in the southeast Missouri town since July.

Ken Eftink, the city's director of development services, said the soil collapses on the city's south side are not yet a crisis, but are serious problems.

"Most of these sinkholes have collapsed suddenly," Eftink said. It's not safe to be down there walking around."

Eftink said the problem is the banks of Cape LaCroix Creek are dropping into the creek. The U.S. Army Corps of Engineers and the Missouri Department of Natural Resources have been brought in to help.

The city has spent more than $30,000 to address land collapses on municipal property. The wastewater and sewage treatment plant is in the area and considered potentially threatened. But most of the sinkholes have appeared on land owned by SEMO Stone, Buzzi Unicem, AmerenUE, SEMO Port Authority and the Burlington Northern Santa Fe Railroad.

State geologists have made 14 surveys of the area to identify bedrock depths and locate rock fractures, sand and gravel deposits, as well as underground caverns or similar hollow areas. Sinkholes are more likely to form along the weak zones and in vertical fractures of underlying rock.

Sinkholes form in areas called karst regions when the uppermost bedrock, typically limestone or dolomite, is dissolved by groundwater. Rainwater seeping into the ground also washes away weaker areas of bedrock. The ground collapses as soil washes into the underground voids. The most recent collapses occurred Feb. 22.

Burlington Northern Santa Fe Railroad spokesman Steve Forsberg said the holes are "a challenge for everybody involved." Cables and sensors have been installed near the tracks — the same technology used for detecting rock slides on or near tracks in mountain and canyon areas.

"If a sinkhole is encroaching on the track, we would get notification," he said.

AmerenUE had to relocate gas lines and some utility poles. Buzzi Unicem has been working with the city to prevent underground springs from filling its quarry.

Mayor Jay Knudtson said the city does not have the money to handle the full scope of sinkhole investigation and repair, and he's seeking state and federal help. U.S. Sen. Kit Bond, R-Mo., visited the site recently; other lawmakers, including U.S. Rep. Jo Ann Emerson, R-Mo., and U.S. Sen. Claire McCaskill, D-Mo., have toured or sent staff members to inspect the sinkhole region.