Bayou Corne: the Louisiana town that's being swallowed by a sinkhole

The sinkhole in September 2012. Image: US National Nuclear Security Administration.

For those of us who can watch them from behind the protective barrier of a computer screen, sinkholes seem pretty cool. Yes, they cause destruction, but in a world where large objects normally stay where we put them, there's a certain fairytale quality to the way they can just suck away enormous chunks of the earth. They can swallow parked cars:

They can swallow trees with cartoon-like efficiency:

But for the residents and ex-residents of a tiny town in Louisiana, sinkholes are pretty much the worst things ever.

Let's start at the beginning. On 3 August 2012, the residents of Bayou Rouge, Louisiana, noticed a funny, petrol-like smell in the air. Later that day, someone stumbled on a giant hole filled with sludgy water on the western edge of the town, not far from the fork of the Bayou Corne waterway. 

The hole, it was soon established, was caused by the collapse of an underground salt cavern, mined by a company called Texas Brine. On that first day, the hole covered around an acre of land. Here's helicopter footage over Bayou Corne taken another ten days after the hole opened (they reach it around 35 seconds in): 

As sinkholes go, it's not particularly glamorous. If we're completely honest, it looks like a giant pond. But as time went on, it became clear that this sinkhole's work was far from done.

When the walls of the mine collapsed, it turned out, they let natural gas and oil filter up to the surface, to escape into the town's air. As a result, Louisiana Governor Bobby Jindal issued an evacuation order on the day of the hole's discovery. Many left the town; some stayed in defiance of the order. Texas Brine was tasked with investigating the collapse.

Yet things kept getting worse. Texas Brine have burned off millions of cubic feet of escaping gas and oil in an attempt to keep it out of the atmosphere. There are fears that the sinkhole might explode if the escaping gas ignites. Oh, and it's grown to cover around 31 acres. This is the latest satellite image of the town from Google Earth:

Spot the sinkhole! Clue: it's the giant black pit visible from space. Image: Google Earth.


The sinkhole has been swallowing up Texas Brine's revenues, too. From the beginning of the evacuation, the company sent each resident a weekly cheque for $875. In August 2014, a federal judge approved a $48.1m settlement, which Texas Brine will spend on buying up the town's properties and paying residents' damages. It's also paid out to some families as restitution for the "mental anguish" they've experienced since 2012. 

But, three years from the sinkhole's first appearance, the town's residents and ex-residents are still stuck in limbo. As of January, according to the Louisiana Advocate, 12 families of the original 150 remain, though they, too, will leave once they've reached a deal with Texas Brine. And the empty houses? The company has shut off utilities and is stripping out appliances, leaving them as empty shells. It remains to be seen whether they'll be demolished, or whether Bayou Corne will become a ghost town.

Scientists say the sinkhole's growth has slowed (though it's been belching out mini-earthquakes since mid-December), so it seems unlikely it will finish off the town completely. This probably isn't much consolation for Bayou Corne's once close-knit community, though: as ex-resident Nick Romero told the Advocate, the worst thing isn't the sinkhole's destruction – it's "losing all your friends" as they're forced to scatter around the state.  

 
 
 
 

How bad is the air pollution on the average subway network?

The New York Subway. Image: Getty.

Four more major Indian cities will soon have their own metro lines, the country’s government has announced. On the other side of the Himalayas, Shanghai is building its 14th subway line, set to open in 2020, adding 38.5 km and 32 stations to the world’s largest subway network. And New Yorkers can finally enjoy their Second Avenue Subway line after waiting for almost 100 years for it to arrive.

In Europe alone, commuters in more than 60 cities use rail subways. Internationally, more than 120m people commute by them every day. We count around 4.8m riders per day in London, 5.3m in Paris, 6.8m in Tokyo, 9.7m in Moscow and 10m in Beijing.

Subways are vital for commuting in crowded cities, something that will become more and more important over time – according to a United Nations 2014 report, half of the world’s population is now urban. They can also play a part in reducing outdoor air pollution in large metropolises by helping to reduce motor-vehicle use.

Large amounts of breathable particles (particulate matter, or PM) and nitrogen dioxide (NO2), produced in part by industrial emissions and road traffic, are responsible for shortening the lifespans of city dwellers. Public transportation systems such as subways have thus seemed like a solution to reduce air pollution in the urban environment.

But what is the air like that we breathe underground, on the rail platforms and inside trains?

Mixed air quality

Over the last decade, several pioneering studies have monitored subway air quality across a range of cities in Europe, Asia and the Americas. The database is incomplete, but is growing and is already valuable.

Subway, Tokyo, 2016. Image: Mildiou/Flickr/creative commons.

For example, comparing air quality on subway, bus, tram and walking journeys from the same origin to the same destination in Barcelona, revealed that subway air had higher levels of air pollution than in trams or walking in the street, but slightly lower than those in buses. Similar lower values for subway environments compared to other public transport modes have been demonstrated by studies in Hong Kong, Mexico City, Istanbul and Santiago de Chile.

Of wheels and brakes

Such differences have been attributed to different wheel materials and braking mechanisms, as well as to variations in ventilation and air conditioning systems, but may also relate to differences in measurement campaign protocols and choice of sampling sites.

Second Avenue Subway in the making, New York, 2013. Image: MTA Capital Construction/Rehema Trimiew/Wikimedia Commons.

Key factors influencing subway air pollution will include station depth, date of construction, type of ventilation (natural/air conditioning), types of brakes (electromagnetic or conventional brake pads) and wheels (rubber or steel) used on the trains, train frequency and more recently the presence or absence of platform screen-door systems.

In particular, much subway particulate matter is sourced from moving train parts such as wheels and brake pads, as well as from the steel rails and power-supply materials, making the particles dominantly iron-containing.


To date, there is no clear epidemiological indication of abnormal health effects on underground workers and commuters. New York subway workers have been exposed to such air without significant observed impacts on their health, and no increased risk of lung cancer was found among subway train drivers in the Stockholm subway system.

But a note of caution is struck by the observations of scholars who found that employees working on the platforms of Stockholm underground, where PM concentrations were greatest, tended to have higher levels of risk markers for cardiovascular disease than ticket sellers and train drivers.

The dominantly ferrous particles are mixed with particles from a range of other sources, including rock ballast from the track, biological aerosols (such as bacteria and viruses), and air from the outdoors, and driven through the tunnel system on turbulent air currents generated by the trains themselves and ventilation systems.

Comparing platforms

The most extensive measurement programme on subway platforms to date has been carried out in the Barcelona subway system, where 30 stations with differing designs were studied under the frame of IMPROVE LIFE project with additional support from the AXA Research Fund.

It reveals substantial variations in particle-matter concentrations. The stations with just a single tunnel with one rail track separated from the platform by glass barrier systems showed on average half the concentration of such particles in comparison with conventional stations, which have no barrier between the platform and tracks. The use of air-conditioning has been shown to produce lower particle-matter concentrations inside carriages.

In trains where it is possible to open the windows, such as in Athens, concentrations can be shown generally to increase inside the train when passing through tunnels and more specifically when the train enters the tunnel at high speed.

According to their construction material, you may breath different kind of particles on various platforms worldwide. Image: London Tube/Wikimedia Commons.

Monitoring stations

Although there are no existing legal controls on air quality in the subway environment, research should be moving towards realistic methods of mitigating particle pollution. Our experience in the Barcelona subway system, with its considerable range of different station designs and operating ventilation systems, is that each platform has its own specific atmospheric micro environment.

To design solutions, one will need to take into account local conditions of each station. Only then can researchers assess the influences of pollution generated from moving train parts.

The ConversationSuch research is still growing and will increase as subway operating companies are now more aware about how cleaner air leads directly to better health for city commuters.

Fulvio Amato is a tenured scientist at the Spanish National Research CouncilTeresa Moreno is a tenured scientist at the Institute of Environmental Assessment and Water Research (IDAEA), Spanish Scientific Research Council CSIC.

This article was originally published on The Conversation. Read the original article.