Hardesty & Hanover designed two fixed bridges: the 950-foot steel arch Rainbow Bridge and the 1,000-foot steel arch Lewiston-Queenston Bridge, the longest fixed spandrel arch bridge in the world at its time of completion. The 1897 Whirlpool Rapids Bridge, an 800-foot arch bridge carrying both highway and railroad traffic, was purchased by the Niagara Falls Bridge Commission (NFBC) in the 1960s and rehabilitated by Hardesty & Hanover to provide the NFBC with three international toll crossings over the Niagara River between the US and Canada. Since 1963, Hardesty & Hanover has been the Consulting Engineer responsible for planning, budgets, inspection, special designs, maintenance, and repairs for the three international bridges and facilities. Hardesty & Hanover provided annual bridge inspections and major repairs and rehabilitations on these bridges for nearly fifty years.

In 2003, the NFBC began planning for the future expanded facilities at the three international crossings. Hardesty & Hanover developed a 30-Year-Plan for the Commission, which involved traffic and financial studies and projections and detailed development for the expansion of the facilities at each bridge. In 2005, Hardesty & Hanover performed a detailed inspection, evaluation and load rating of the deck of the Whirlpool Rapids Bridge.

In 2008, Hardesty & Hanover was selected to perform the general and detailed inspections as required, for the Rainbow, Lewiston/Queenston, and Whirlpool Bridges including the approach span bridges, adjoining plazas, the NFBC Administration Building, and associated roadways for the years 2008, 2009, 2010, 2011.