(Trent Nelson | The Salt Lake Tribune) Homes at Traverse Ridge near a mining operation, Friday, Nov. 23, 2018. The city of Lehi has sent a letter of assurance to residents saying there are no health risks from the gravel mining and construction on Point of the Mountain. They cite a health department study showing the operation is not causing health-damaging air pollution. The health department tells a different story — and can't say there are no health risks from the mining.