"There is growing interest in hydropower, because it is one of the potential solutions to global warming," said Linda Church Ciocci, director of the National Hydropower Association.
The addition of a second powerhouse at the Holtwood dam requires approval from the Federal Energy Regulatory Commission and the Pennsylvania Department of Environmental Protection, among other government agencies. If the project is approved, construction could begin early next year and be finished by 2011.
The proposal has drawn no major protests from environmental groups, although American Rivers urged the FERC to consider the impact of blasting during construction on wildlife in the area, according to agency records. But officials with the U.S. Fish and Wildlife Service and the Maryland Department of Natural Resources have suggested that improved flow through the rebuilt dam might actually help migratory fish.
The Holtwood expansion would transplant a second heart into a workhorse that has been clomping away steadily since before the Titanic was launched.
Construction on the Holtwood dam started in 1905 and finished in 1910. The five-story-high wall of concrete stretches for nearly a half-mile across the Susquehanna in a wooded valley.
The dam transformed the rocky, shallow river into a deep blue reservoir, called Lake Aldred, which is eight miles long. It's the second of four hydroelectric dams (after the Conowingo Dam in Maryland) that radically transformed the Lower Susquehanna from a natural river into a stepped series of artificial lakes.
Attached to the Holtwood dam is a rectangular building, 500 feet long, 100 feet wide and 150 feet tall, with ornate neoclassical decorations and rows of grand arches. Inside hum 10 hydroelectric generators, each about 20 feet in diameter.
About 240,000 gallons of water per second from the river rush through a screen that catches floating sticks (and often water snakes). The current pushes blades on wheels, making turbines spin. This generates 109 megawatts of electricity, enough to light up about 90,000 homes.
Some of the machinery is so old that it has been designated an International Historic Mechanical Engineering Landmark.
"The architecture is pretty amazing," said Chris Porse, manager of the Holtwood dam. "The arches are reminiscent of Roman architecture. It's a reminder that water power has been around for centuries, with the Egyptians, Romans and Greeks all using it."
