News Release 090

DEPARTMENT RESPONDS TO SINKHOLE COLLAPSES
IN CAPE GIRARDEAU

Volume 36-090

Contact: Hylan Beydler

(For immediate release)

573-368-2118

ROLLA, MO, FEB. 28, 2008 -- Geologists with the Missouri Department of Natural Resources' Division of Geology and Land Survey are helping the city of Cape Girardeau to identify what is causing recent sinkhole collapses and likely locations where additional sinkholes may appear in the southeast portion of the city.

The city and Senator Crowell requested the department's assistance to better protect roads, rail transportation corridors and utility infrastructure critical to the energy distribution and sewage treatment in the Cape Girardeau area. 

Collapses have occurred on private property in this part of town for several decades; however, within the last 18 months, the number of ground collapses has dramatically increased, and the threats to sewer and water lines and transportation corridors are becoming more severe. "Two new sinkholes appeared in this area as recently as Feb. 22," said Glen Young, a geologist with the department.

Staff geologists have completed 14 different geophysical surveys in the impacted area. Each survey line is between 270 and 400 feet long. The survey data reaches to depths between 70 and 110 feet. The geophysical surveys identify how deep it is to bedrock and where sinkholes could potentially form because of fractures, faulting and increased weathering of the rock materials along these weaker zones. The field work is not yet complete, but already the geologists are creating cross-sections and maps to look for bedrock fracture trends, unusual bedrock structures and highly weathered zones. A geophysical survey induces small electrical currents in the ground and measures how the earthen materials respond. The geologist can determine where solid rock is located, where sands, gravels and soils are located and where these geologic materials form unusual structures, such as offsets or caverns in the subsurface.   

The U.S. Army Corps of Engineers is coordinating technical investigations by state and federal agencies, including the Department of Natural Resources and the U.S. Geological Survey's Missouri Water Science Center. The Corps of Engineers is looking at possible methods of stabilizing Cape La Croix Creek, and the geophysical data will assist them with their plans. "The Corps of Engineers and the city are encouraged by the results of the geophysical surveys conducted by the Department of Natural Resources, for their potential predictive capabilities, and they are eager to see additional work conducted," said Peter Price, a geologist with the department. "Our staff understand the subsurface bedrock conditions, and these investigations will assist the U.S. Geological Survey, the Corps of Engineers and the city of Cape Girardeau in determining areas that may be susceptible to future collapse."

"We really appreciate Glen's efforts by getting involved early in the process, when the collapses started occurring, by conducting the geophysical surveys and explaining the data with the interested parties," said Ken Eftink, director of Development Services for the city of Cape Girardeau. "His efforts have helped the city prepare mitigation plans in the areas where critical city utilities are potentially threatened."

Sinkholes form in karst regions when the uppermost bedrock, typically limestone or dolomite, is dissolved by groundwater. When water from rainfall moves through the soil and encounters bedrock, the bedrock begins to dissolve and voids form. Soil gradually washes into the voids, eventually causing a collapse or depression to form at the surface.  

For more information about sinkholes and other geologic hazards in Missouri, visit the Division of Geology and Land Survey's Web site: www.dnr.mo.gov/geology/. For news releases on the Web, visit www.dnr.mo.gov/newsrel. A complete listing of the department's upcoming meetings, hearings and events, is online at www.dnr.mo.gov/calendar/search.do.

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Editor: Photo is available at http://www.dnr.mo.gov/newsrel/capecitysinkhole.jpg.

Photo Caption: This photo was taken shortly after a sinkhole collapsed Friday, Feb. 22, in southeast Cape Girardeau. The surface opening is about 25 feet in diameter and at least 20 feet deep. The rock mound on the opposite side of the railroad tracks covers an earlier collapse. Photo courtesy of city of Cape Girardeau.