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