Rising above the sinkholes: City is getting ahead of the problem

After months of work, Cape Girardeau may finally be getting ahead of the sinkhole problem on South Sprigg Street.

Since January, Sprigg Street has been closed to through traffic from Southern Expressway almost to Interstate 55. But the last work to shore up the banks of Cape La Croix Creek will begin Monday and city officials hope the road can be reopened by Friday.

A contractor will drill holes through the concrete slabs that form the embankment of the creek and pump a concrete grout into any voids, public works director Tim Gramling said. "They will come in and help determine what is there," he said. "Hopefully it will be minor."

Sinkholes have regularly been a problem along South Sprigg Street but the problem became especially severe in the last 12 months. More than 20 holes have opened up, forcing the relocation of a natural gas line owned by AmerenUE, imposing expenses on Buzzi Unicem to pump grout underground to stop water seeping into its quarry and causing headaches for the city. Burlington Northern Santa Fe Railroad has installed sensors on the tracks to issue alerts if the ground shifts under or near the tracks.

The city, the private businesses, the U.S. Army Corps of Engineers and the Missouri Department of Natural Resources have all played a role in trying to understand why the sinkholes came so quickly and in such large numbers. The only good news about the sinkholes is that the problem seems to have abated for now, Gramling said.

No one has a firm answer for why the problem was so severe, Gramling said. "The conclusion was that it is a lot of karst topography and last summer was a dry summer," he said. "There were a variety of issues coming together at the same time and I don't know that anyone can pinpoint one reason."

The repairs to Sprigg Street have included removing fill material put in place to raise the roadbed following the Great Flood of 1993, material that had deteriorated badly, Gramling said.

FRED LYNCH ~ flynch@semissourian.com Repairs are almost complete on the South Sprigg Street bridge over Cape LaCroix Creek. The sinkhole that threatened the bridge has been filled and a contractor will pump concrete into any weak spots next week.

FRED LYNCH ~ flynch@semissourian.com Repairs are almost complete on the South Sprigg Street bridge over Cape LaCroix Creek. The sinkhole that threatened the bridge has been filled and a contractor will pump concrete into any weak spots next week.

"It was just kind of a mud instead of soil," Gramling said. "It looked like it was acting more like a sponge than a support for the pavement."

Along with repairing the roadbed and stabilizing the banks of Cape La Croix Creek, the city has filled with rock some of the sinkholes threatening the roadway. Buzzi provided the rock as part of the partnership to deal with the sinkholes, Gramling said.

"It was kind of a trade-off," he said. "On the whole thing we were working together. [Buzzi] used some equipment of ours to do things for them, and they have been good enough to turn around and let us have some rock."

Most of the sinkholes are just west and south of the city's wastewater treatment plant. The holes are concentrated within an area totalling about 100 acres.

The most recent hole opened in April and was 20 feet wide and about 20 feet deep.

The cost of the work to be done next week won't be known until the contractor is able to make the test drillings, Gramling said. The city pays on a per-truckload basis for the process known as mudjacking.

Regaining the use of Sprigg Street will help the businesses along the road as well as the city, said Doug Leslie, city manager. Trucks will have better access to Buzzi's quarry and city solid waste trucks will have a shorter route to the transfer station, Leslie said.

"We have had to run our solid waste trucks on a detour route that is much longer, so the fuel savings should be considerable, not to mention the convenience," he said.

rkeller@semissourian.com

335-6611, extension 126

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