Fluor's engineering and construction management expertise opened the largest hydroelectric power station in New Zealand. Manapouri Power Station, which opened in 1971, generates power by diverting the outflow of two large lakes to a powerhouse 700 feet under the earth.

The initial contract was awarded in the summer of 1963 to Utah Construction & Mining Company, later purchased by Fluor. Project work commenced the following year with excavation work on the six-mile-long tunnel, opening an outlet channel about a half-mile long, and laying out a 13.5-mile gravel-surfaced road connecting the lake to the hydroelectric power station site.

Construction began from the fjord inward. As the shoreline was hilly and waterlogged, a former ocean liner was purchased, refitted and docked at Doubtful Sound to provide worker accommodations.

As the tunnel was excavated inward, round-the-clock pumping operations went on to channel out water pushed into the tunnel from high pressure caused by surrounding mountains. The water's flow reached a peak of 12,000 gallons a minute.

The powerhouse at Lake Manapouri as built was enormous for an underground structure, 364 feet long, 59 feet wide and 127 feet high. Housing seven turbines, each capable of producing 100,000 kilowatts, the powerhouse's construction required excavation work from solid rock.