Indianapolis, Southern Indiana face different sinkhole risks

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Recent heavy rainfall has already led to extensive flooding across Central Indiana, but some are now concerned that the added pressure on storm sewers could lead to sinkholes.

Rainfall contributed to a massive sinkhole in Chicago last week, which swallowed three cars.

“Pretty scary when you looked at what the size of those holes were and the fact that you could fall into it,” said Terry West, a Purdue University professor of geological engineering.

West has written extensively about sinkholes and says the increased rain creates the potential of similar events happening in Indianapolis. Urban areas with aging pipes are always at risk when heavy rains put pressure on storm sewer systems, he said.

“If the storm sewer is very full, the velocity of the water tends to increase and can cause erosion,” West said. “Then if you have any weak spots the sewer could actually collapse and you’d have a problem like they had in Chicago.”

West said Indianapolis residents don’t need to worry about sinkholes like the deadly one that swallowed part of a home in Florida earlier this year. A man died after a large sinkhole opened up beneath his bedroom without any warning. West said the Florida sinkhole was due to slow erosion of limestone bedrock. Though much of Central Indiana is safe from such sinkholes, the sudden events do threaten people who live on Indiana’s Mitchell Plain, a stretch of limestone bedrock running south from Martinsville, through Bloomington and Bedford.

“That’s where the limestones are exposed,” West said. “They’ve had plenty of time to dissolve underground and then the surface can collapse and fall into the opening of the sinkhole.”

West said he believes urban development can contribute to sinkholes because irrigation systems and new wells lower the water table and open up empty pockets just beneath the surface.

Though homes are at risk in several states, he said there is little that can be done to avoid them.

“If you’re in a limestone area then you have a possibility of it happening,” West said. “But trying to guess where it’s going to be located is not an easy thing to do.”

West said the risk of storm sewer sinkholes in Indianapolis will likely decline when the city completes the Deep Rock Tunnell Connector, which will take some of the pressure off the city’s current combined sewer overflow.