 The builders then laid down permanent steel struts to hold back the cofferdam; not only was this likely the first such use of steel bracing, it saved $30,000 compared to the temporary wood bracing that had been used in previous projects.During construction, almost 700 workers were employed for the project at any given time; tradesmen, such as plumbers and electricians, worked with concrete and steel contractors in overlapping shifts, in order to reduce delays.The superstructure incorporated of steel across its above-ground and below-ground sections, and the builders used six derricks to lift the girders from the street.