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 Post subject: Russian city monitored 24 hours day for mining sink holes
PostPosted: Sat Apr 14, 2012 11:14 am 
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Joined: Thu Jul 27, 2006 10:18 pm
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Location: NJ
Dmitry Rybolovlev, the Russian fertilizer tycoon who in February bought the most expensive apartment ever sold in New York City — the $88 million penthouse at 15 Central Park West — may have done a lot for real estate values there. But here in this old mining city in the Ural Mountains, where he made his fortune, not just property values, but properties too, have been plunging.

Sinkholes are common hazards in mining regions, plaguing areas where miners have burrowed into layers of soluble minerals and accidental floods have followed. But in Berezniki, as often happens in Russia, the problem has been magnified by past practices in which safety was not always the foremost concern.

In the West, mines are usually located far from populous areas, to reduce the risks of sinkholes to homes and other buildings. But Berezniki, a city of 154,000 that began as a labor camp, was built directly over the mine — a legacy of the Soviet policy of placing camps within marching distance of work areas.

And so Berezniki is afflicted by sinkholes, yawning chasms hundreds of feet deep that can open at a moment’s notice. So grave is the danger that the entire city is under 24-hour video surveillance. On a screen in the command center late last year, one such hole appeared as a small dark spot in a snowy field in the predawn hours, immediately threatening to suck in a building, a road and a gas station.

“I looked and said, ‘Wow, a hole is forming,’ ” recalled Olga V. Chekhova, an emergency services worker who monitors the video. This was a small one by the standards of Berezniki, which has had three in the past four years. In fact, it has since been called “The Tiny One.”

While scientists have so far successfully predicted each sinkhole, the chasms can open with astonishing speed. On Dec. 4, as Ms. Chekhova watched the dark spot on her screen expand, witnesses began calling an emergency number for reporting sinkholes. They had heard a loud swooshing noise.

As the police cordoned off the area that day, dirt and snow tumbled in. Before noon, the sinkhole was 25 yards across.

Berezniki’s problems have been traced to October 2006, when a freshwater spring began flowing into the mine, where potash fertilizer is extracted from salt lying 720 to 1,500 feet below the surface. The problem is that the walls and pillars of salt that miners had left to support the ceilings of huge underground caverns began to dissolve.

“Imagine putting a sugar cube in a cup of tea,” Mikhail A. Permyakov, the chief land surveyor for Uralkali, the company that owns the mine, said in an interview. “That is what happened under Berezniki.”
...

http://www.nytimes.com/2012/04/11/world ... .html?_r=1


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