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New York City's newest power source could be its sewers and reservoirs

More than a billion gallons of water travel through New York State every day, starting upstate and journeying down to the city and the sea, and driven almost entirely by gravity alone. The city’s watershed includes 19 reservoirs, three lakes, 7,000 miles of water pipes, tunnels and aqueducts, and 7,400 miles of sewer lines — and perhaps many megawatts of untapped energy.

Through Thursday, the city Department of Environmental Protection (DEP) is collecting proposals from consultants interested in assessing the hydroelectric energy pent up in the city’s water system. Legislation passed by the City Council last spring directed the agency to conduct a study of hydropower possibilities.

The Croton Reservoir is just one of many parts of the New York City water supply system that could power hydroelectric generation. Photo: Alexis Lamster/Flickr

At the time, City Council Speaker Christine Quinn stressed the urgency of getting New York City up to speed on hydroelectric technology.

“There are other cities in the country, such as Boulder, Colorado, that are generating a significant amount of the city’s power using hydroelectric power,” she said. “And it’s kind of odd, if you think about it, as a city that is made up in significant part of islands, a city that is a ‘river city,’ a city whose greatness began as a significant port, that we are behind the curve — or behind the tide, if you will — as it relates to hydroelectric power.”

The law calls on the city environmental agency to examine the potential for energy-generating facilities and ways to transmit power from the water supply, wastewater treatment systems and natural bodies of water that fall within the city’s jurisdiction. Future reviews are to then identify specific hydropower technologies appropriate for different sites — from installing turbines to simply adding electricity-generating equipment to existing lines and aqueducts. Last but not least, DEP would analyze the economic viability of these options.

Hydroelectric power isn’t unkown to the city’s water system. For decades, city water facilities have generated moderate amounts of electricity from turbines in five upstate locations. And New York State overall is a major producer, ranking third nationwide thanks largely to a cluster of pumps and turbines located downstream of Niagara Falls. But these are only part of the state’s power potential. One of the few comprehensive studies of New York’s hydroelectric potential, from the Idaho National Engineering and Environmental Laboratory in 1998, identified 25 percent of New York State’s underutilized hydropower resources as sitting in the Hudson River Valley.

And increased focus on hydropower is part of PlaNYC 2030 which details the Bloomberg administration’s sustainability schemes and vows to “investigate how to generate energy from the large volumes of water that flow through our water distribution and wastewater treatment systems.”

While adding more hydroelectricity to the city’s energy portfolio could bring environmental benefits, it also poses challenges to the natural environments it enters. Introducing a hydroelectric system can disrupt normal stream flows and the habitats that depend on them, lowering levels of dissolved oxygen in the water. Fish are often the victims of those changes, and they sometimes get caught in turbines and killed.

The city should pay attention to such impacts as it explores its hydroelectric options, suggests Phillip Musegaas, the Hudson River Program Director for Riverkeeper, an environmental advocacy group. He noted that the group has expressed concern about a project placing a large electric turbine in the East River because of the negative effects it could have on the fish populations there.

He added that any adaptations to the city’s wastewater treatment system to promote hydropower should take care not to interfere with the city’s ability to update its existing infrastructure — an antiquated system that combines wastewater and storm water collection and cause raw sewage to flow directly into waterways at times of heavy rain.

Overall, Musegaas said, Riverkeeper supports any effort by the city to explore alternative energy sources.

“That’s always good, to have local generation of power,” he said.