What’s Causing The Growing Number of Urban Sinkholes?

Last week in Pittsburgh, a Port Authority bus nearly got swallowed up in a downtown sinkhole. While no official data exists, sinkhole incidents are becoming more common, heightening public interest.

Some of these incidents reflect natural causes in a handful of states (like Florida) with underground conditions – especially large limestone deposits, natural springs, and caverns – that are susceptible to massive precipitous soil erosion.

You Might Like

But the incidents in urban centers like Pittsburgh may be masking a more troubling phenomenon:  the ongoing deterioration of outmoded wastewater infrastructure in a growing number of American cities from New York to San Francisco.

In the first quarter of 2017, there were 39 significant sinkhole incidents  related to failing infrastructure—a rate of about one every four days— in places as varied as Chicago, Los Angeles, Hoboken, New Jersey, Sioux City, Iowa, and Seattle, Washington, according to a review conducted by the Associated Press.

While the seepage of underground water is to blame in both natural and man-made causes, the sinkhole collapses in cities like Pittsburgh would have been preventable had their sewer infrastructure been renovated or replaced in a timely fashion.

Urban planners and engineers have been calling for renovations to drain and sewer pipes for years but budget-strapped cities have been dragging their feet.  A lack of federal support and the continuing press of other funding priorities have delayed the onset of repairs.

In Washington, DC the underground infrastructure dates to the American civil war.  It’s considered a minor miracle that no major street collapses have occurred thus far.

In some of the failing infrastructure cases, residents have been killed or injured, utilities have been disrupted and major property damage has occurred.

In a Detroit suburb in 2017 a sinkhole the size of a football field suddenly swallowed parts of three houses and a section of road.

In theory, pro-active inspections of underground pipes and sewer lines should allow urban authorities to predict where collapses might occur, but it’s never so simple.

In Indianapolis 2018, a sinkhole opened up along a major downtown street crossroads on the eve of its annual July 4th celebration.  A local non-profit had been inspecting weaknesses in the city’s sewer lines for years.

But the group failed to inspect the section that collapsed.

Terry West, a Purdue University sinkhole expert says it’s is hard to forecast where major water leaks will develop or where connections between lines will have a problem.

“In cities like Indianapolis, the sinkholes are human-related things but are still very difficult to predict where they are likely to occur,” West argues. “So you don’t have other options than to fix them as they develop.”

What’s really needed, experts say, is a Congressionally-mandated, federally-funded infrastructure survey focused on underground sewage and water systems.

But that means Congress needs to move forward on a major new infrastructure bill – which is unlikely in the current climate of hyper-partisan gridlock

In Florida, the state has developed a sophisticated geological detection system to help authorities anticipate where new sinkhole problems may emerge.

But above-ground forecasting of Nature-made sinkholes is relatively easy.  Human systems, it seems, are far too complex and unpredictable to be assessed with new technology alone.