| 11. | The three deep-pit mines were Thoresby in Nottinghamshire.
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| 12. | Initially, it operated as an open-pit mine.
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| 13. | Pit mining was instituted, but it, too, had its dangers.
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| 14. | Exhausted open pit mines may be refilled with tailings.
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| 15. | The present-day open-pit mining operation was begun in 1910.
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| 16. | Both men examined Wall's properties and recommended open-pit mining.
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| 17. | The first open pit mine was located in Lac-Jeanine, Quebec.
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| 18. | Since it is an open pit mine it would disturb the natural environment.
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| 19. | This can happen in open pit mines as well as in underground mines.
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| 20. | The open-pit mine that Williams oversees spreads over nearly 15 square miles.
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