An employee walks near a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. The Borodinsky colliery, 9 km (5.6 miles) long and more than 100 meters (328 feet) deep, annually produces more than 20 million tons of coal and is considered to be the biggest opencast coal mine in Russia, according to official representatives. (Photo by Ilya Naymushin/Reuters)

A worker walks near train wagons loaded with coal at the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

Machinist Sergei Klushnichenko stand onboard a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A train transports coal at the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A general view shows the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A general view shows the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge loads wagons with coal at the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

Machinist Alexander Kozhakin operates a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)

A rotary dredge works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. (Photo by Ilya Naymushin/Reuters)