| 21. | The city is home to a gravel mining area owned by Tiller Corporation and C . S . McCrossan.
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| 22. | Because sand and gravel mining cause lowering of ground water, as rainwater can cannot percolate in the aquifer.
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| 23. | Excessive erosion caused by logging, grazing and gravel mining is the most serious issue facing the Garcia River.
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| 24. | Roads are maintained with gravel mined locally next to the current Mahwelereng Stadium, known as " Lekgethe ".
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| 25. | The lakes were built as a result of the sand and gravel mining efforts of Overland Sand and Gravel.
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| 26. | The island passed through a succession of private owners during the following years, including several gravel mining corporations.
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| 27. | Much of Cave Creek Wash lies in state trust land, where there has been some gravel mining in the past.
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| 28. | At the same time, Taylor has petitioned the zoning board to ban gravel mining altogether, except at existing operations.
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| 29. | Threats to the survival of the species include gravel mining, off-road vehicle use, grazing, and development.
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| 30. | Gravel mining was a threat to the species but since the area was designated a national monument these operations have ceased.
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