Holland Tunnel

Holland Tunnel. National Historic Civil And Mechanical Engineering Landmark. , The first long mechanically ventilated underwater tunnel in the world designed for motor vehicle use, The 29.5 ft. diameter 3,500 ft. long twin tubes of this tunnel were shield driven by the pneumatic method through extremely difficult river bottom conditions that were overcome by the ingenuity and determination of the engineers, Clifford M. Holland, Milton H. Freeman and Ole Singstad. The tubes were the largest in the U.S. when built., The unprecedented length was a bold step forward in subsequent tunnel engineering., The principal feature of the cast iron-lined tunnel is the ventilating system. Its design was based on elaborate theories of physiological and mechanical tests conducted mainly by the U.S. Bureau of Mines., The resulting system - forcing fresh air in at roadway level and drawing off the exhaust-laden air at the ceiling over the entire tunnel length – has been the model for all succeeding vehicular tunnels. The air is moved by 42 blowing and 42 exhaust fans of 6000 total horsepower, arranged in 4 ventilation buildings., The tunnel is operated by The Port Authority of New York and New Jersey, Presented 1934 by the American Society of Mechanical Engineers and the American Society of Civil Engineers