Firefighters created of fireline by hand and with mechanized equipment such as bulldozers. Most of the bulldozer work was done on the North Fork fire. Some other fires were too remote or in too steep terrain for the safe operation of heavy equipment, and bulldozers were prohibited from many areas because of the impact they have on surface features. Additionally, the thin, unstable ground near the park's geothermal features could not be trusted to support the weight of heavy equipment. Bulldozers are rarely used on fires in U.S. National Parks.