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China started building walls because the seven Kingdoms were at war in 800 B.C.E.
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Emperor Quin Shi Huang built a north wall to defend against the Mongols in 220 B.C.E.
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The length of the norther wall was 3,100 in 210 B.C.E., 10 years later.
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The Chinese got rid of the Mongols and made stronger walls in 1368.
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China's state owned Coal Mines used Openpit Mining starting in 1949.
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The real planning for the Three GOrges Dam started in 1955. Many people had concerns and they delayed work for 40 years.
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China's state owned Coal Mines stopped using Openpit Mining in 1980.
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Area Type Mining was used in surface coal mines after 1980.
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The Three Gorges Dam began in 1994.
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In 2003, the hydroelectric power started.
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The main wall on the Three Gorges Dam was complete in 2006.
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As of 2006, the Three Gorges Dam was the largest dam structure in the world.
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Coal production was 3.24 billion tons in 2010 and surface mining was about 9% of that.