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Discussion Starter · #1 ·
Mexico City seen faces 'high possibility' of major floods due to drainage problems
19 June 2007

MEXICO CITY (AP) - There is a "high possibility" a huge underground drainage tunnel could soon fail, flooding parts of this mountain-ringed metropolis 5 meters (yards) deep in sewage, the national water agency said Tuesday.

Officials have been puzzled for years by the gradual decrease in capacity of the 6.5-meter-wide (7-yard-wide) tunnel built in the 1970s to drain waste water from the valley, which is home to 20 million people and has no natural outlet. They have speculated that the tunnel may be partially clogged or that its walls could be decaying.

But because it is constantly filled with water, officials have not been able to travel through the structure to inspect it -- or perform much-needed maintenance.

"Because of a lack of maintenance in Mexico City's deep drain over the last 15 years, there is a high possibility that it could fail," according to a National Water Commission statement.

"A failure ... could cause severe floods reaching five meters in the city's historic center, the international airport" and other boroughs on the city's east side, the statement said.

Poor drainage and flooding has been a historical problem for the city, especially during the rainy season that runs typically from late May through October.

Experts say a number of solutions could be used to solve the drainage problem, including unblocking the tunnel, building another branch of deep drainage, or pumping water out through a previously dug drainage ditch. But extremely heavy rainfall could temporarily overwhelm such systems.

The Mexico Valley, where the city is located, was largely covered by lakes when the Aztecs founded the city on an island in 1325. The Aztecs built dikes to try to keep out flood waters. The Spaniards who conquered Mexico in 1521 tried to drain the lakes, which have disappeared under the urban sprawl.
 

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Fortunately the govn't has just made a plan of several million dollars to resolve this issue before it is too late.

Mexico City is set over a lake so it's kind of a floating city...
 

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What the flood...
I thought that Mexico City was laid on sand/silt that makes the city surface quite permeable.
As far as I know, permeability can only do so much. You need up-to-date drainage / sewer systems to prevent floods, which is why you see small towns flooded more often than not. Correct me if I'm wrong though.
 

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In that case they should be REALLY scared about having earthquakes. Surface settlement plus the instantaneous surge of pore water pressures would do lots of damage.
I recall an earthquake in the mid 1980s that had its epicenter about 300 km outside of Mexico City, was barely felt everywhere else but shook the city like a bowl of 'Jello' gelatin. There was MAJOR damage in large sections of the city itself with significant loss of life.

Much like New Orleans, LA, Mexico City is a major city that for all logical intents and purposes should never have been built where it was.

Mike
 

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Discussion Starter · #10 ·
Mexico announces $1.27 billion drainage tunnel for sinking capital
14 August 2008

MEXICO CITY (AP) - Mexico announced on Wednesday it will build a $1.27 billion tunnel that will be almost 39 miles long and more than 20 feet in diameter, to help solve the centuries-old drainage problem of the nation's capital.

Mexico City is sinking because of groundwater extraction, and is vulnerable to flooding because it sits in a mountain-ringed valley with no natural exit for rainwater.

President Felipe Calderon said that the tunnel will be the largest of its type in Mexico, and one of the biggest and most expensive public works projects of his administration.

The city already has some large underground drainage tunnels, but they are aging and vulnerable to heavy storms.

Mexico City is largely built on the soft soil of a former lake bed, and has been hit by periodic floods since it was founded by the Aztecs in 1325.

The Aztecs built dikes to try to keep out flood waters. After the Spaniards conquered Mexico in 1521, the lakes were drained and the first rudimentary drainage channels were built.

Because the city is sinking, the existing tunnels no longer dislodge water by gravity. Instead, the waste water -- a mixture of raw sewage and runoff -- must be pumped out of the valley. The new system would help to remedy that.
 

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I can't believe this: a former Olympic host city sinking. It shouldn't do that, and I will have to put most of the blame on the dumb soil Mexico City is built upon. Can't something be done to prevent the city from sinking even further?
 

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Discussion Starter · #13 ·
I think once the water table is gone below the surface, you can't pump water back in to stabilize it. Hence, sinkholes will continue to appear.
 

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But have there been any sinkholes in Mexico City already?
 

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^^ there have been lots but not only sinkholes but subterraneal caves and when earthquakes occur it's worse than any other city because the terrain of the city is very inestable as it's wet ¬¬ , we have about 10 volcanoes around the city (2 are active) that make the earthquake to be both trepidatory and oscilatory movements and our city receives lots of aerthquakes a year normally the biggest of 6 - 7 degrees Richter scale
 

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Sinking, earthquakes, soft bed lake, floodings, active volcanoes, killer pollution, been destroyed twice, worst land to build atop, no way out.
So.... can we call Mx city a survivor on it's own?
 

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Discussion Starter · #20 ·
Well, many cities are prone to natural disasters, such as Tokyo, Taipei, and LA for earthquakes. These don't happen everyday, and people cope. I doubt there are that many places where these factors are non-existent.

Then there are the freak events that happen once in a century or half century.
 
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