Hydrel Lights Hoover Dam
Named for Herbert Hoover, the 31st president of the United States, Hoover Dam (on the Colorado River 30 miles southeast of Las Vegas on US Highway 93 at the Nevada-Arizona border) includes a hydroelectric plant that provides power for the states of Nevada, Arizona, and California. Built 1933-1935, this is one of the world's tallest dams, and features a massive off-white concrete wall more than 700' (210m) high and equally as wide. Unfortunately, for many years this wall was badly lit with 64 high-pressure sodium 400W lamps that gave the concrete a sickly glow.
Fortunately, the US Department of the Interior's Bureau of Reclamation (which is in charge of the dam) decided to see what could be done to relight the structure. The end result is a new lighting system with 32 Hydrel 7200 MH1000 spot and flood fixtures with 1,000W metal-halide lamps by Osram Sylvania. The 7200 series fixtures have heavy-walled die-cast aluminum housings with stainless steel fasteners and a precision optical reflector system. The lenses are tempered borosilicate glass, a type of shatter-resistant glass that can withstand tremendous changes in temperature.
“The question was how to bathe the dam in light,” says Dan Roth, the Western states marketing development manager for Hydrel, now part of Lithonia. “The metal-halide makes the concrete sparkle. It has a much cooler color temperature than the old high-pressure sodium lamps.” Although Hydrel does make underwater fixtures (which cannot be used in the open air like this), this model needed to be placed where there isn't too much abuse from the water that floods through the dam. The lights are actually 30' (9m) above the water.
The fixtures are mounted as uplights on the roof of the dam base building that contains the turbines for the power plant. There are 13 flood reflectors for the lower sections of the wall, and 19 spot reflectors to light the upper reaches. “The trick was blending them so there are no dark spots,” indicates Ken Acampora, part of Hydrel's tech support and engineering team that did the job (and has since gone back to add additional 1,000W metal-halide floods on the after bay where the water flows through the dam). Adjustable knuckles allow the fixtures to be tuned in order to provide an even wash to the light.
“We did a photometrics layout in advance to determine the wattage and spacing of the fixtures to light the wall based on the desired number of lumens,” Acampora explains. “We were out there one night fighting the bugs and aiming the fixtures. But in the end, when we backed off a mile downstream, it was amazing to see a perfectly lit surface against all the darkness. The result is spectacular. Truly magnificent.”