This project consisted of the design and construction of a new HVAC Duct at the Parker Dam on the Lower Colorado River. The newly installed high-pressure insulated duct was designed to connect to the existing 60,000cfm air handler unit which had previously been installed within the Parker Dam generator room. The new duct spans the distance of the power plant, 260 feet long, and is secured to existing vertical concrete columns using custom designed and fabricated structural supports. The main trunk is equipped with twelve (12) registers which are adjusted to provide cooling between each of the four hydroelectric generator units. One of the major challenges of this project involved the installation of large prefabricated duct sections, as large as 72in x 72in x 24ft long. Clearance was extremely tight due to the proximity of the hydroelectric generators, as well as the existing electrical raceways and switchgear which are critical for the distribution of local power. The duct was successfully installed on schedule without interrupting power generation.