Trenching and excavation are particularly dangerous construction operations; they can result in the crushing or suffocation of workers in the case of a collapse. OSHA provides guidelines for the digging and maintenance of trenches which aim at minimizing the risk of collapse. These, along with other helpful information concerning trenching can be found on their website. Collapses may be caused by the weight of a nearby machine, soil shifting due to rain, improper or insufficient preparation or maintenance of the trench, etc. Trenches should be inspected daily for signs of a collapse. Other dangers associated with trenching include underground gas and electrical lines.