Monday, February 9, 2009

That Sinking Feeling May Be...Karst

The East-West Gateway has just published a map showing sinkhole and karst areas across the metro region, a precursor to their first edition of a regional Environmental Atlas which is currently nearing completion. To appreciate the importance of this information, one has to know something about karst areas and how they are integral to resource management in Monroe County.

As defined by the U.S. Environmental Protection Agency, a karst area is a geologic formation of irregular limestone deposits with sinks, underground streams, and caverns. These karst areas can be hazardous, according to the U.S. Geological Survey (USGS): “Though often considered a benign nuisance, sudden, catastrophic collapses can destroy property, delay construction projects, and contaminate ground water resources.” Karst areas are susceptible to aquifer
contamination and may also lack the stability required for certain land uses.

The thin soil and porous limestone bedrock present challenges for effective operation of septic tanks as a means of waste disposal, especially in the southern half of the region. The caves of the Sinkhole Plain in Monroe and St. Clair counties--found in areas with major limestone and dolomite outcrops--are the most numerous and interesting in the state of Illinois.

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