Croton Water Filtration Plant Activated

Largest Underground DAF Filtration Plant in the United States has the Capacity to Filter up to 290 Million Gallons of Drinking Water Each Day; Will Protect the City against the Possibility of Drought and the Effects of Climate Change

Hazen and Sawyer, in joint venture, prepared conceptual designs, performed environmental impacts studies, prepared preliminary and final designs, and provided start-up operational services for this landmark plant, located in the Bronx’s Van Cortlandt Park. (Photo by NYCDEP)

(NEW YORK, NY – May 8, 2015) – New York City Department of Environmental Protection (DEP) Commissioner Emily Lloyd today announced that the $3.2 billion Croton Filtration Plant was recently activated and water from the Croton water supply system has been reintroduced into the city’s distribution network for the first time since 2008.

Built underground beneath Van Cortlandt Park in the Bronx, preparatory site work and excavation for the 400,000 square foot facility began in 2004. Construction commenced in 2007 and, at the height of the work, roughly 1,300 laborers were on-site. In addition to building the plant, the 33-mile long New Croton Aqueduct was rehabilitated and three new water tunnels were constructed to bring water to the plant, and then from the plant back to the distribution system. With the capacity to filter up to 290 million gallons of water a day, the state of the art facility can provide roughly 30 percent of the city’s current daily water needs.

New York City has three upstate water supply systems – Croton, Catskill and Delaware. The Croton System, located primarily in Westchester and Putnam Counties, is the oldest of the three systems and is composed of 12 reservoirs and three controlled lakes. As population density increased around the watershed, the quality of the water diminished and DEP did not supply Croton water during several summers over the 1990s. The Croton system provides critical flexibility and redundancy to the overall water supply system and, in the 1990s, DEP, federal and state regulators agreed that a filtration plant must be built.

Before construction could begin, more than 1 million cubic yards of rock and soil was excavated from the site, which now reaches a depth of roughly 100 feet below grade. Construction of the 830-foot long by 555-foot wide facility began in 2007 and work included laying nearly 250,000 cubic yards of concrete and 27,000 tons of re-inforced steel, the addition of 160,000 feet of pipe and over 200 pumps, and the installation of more than 10 million feet of low and high-voltage wire, nearly 2 million pounds of duct work and 20 ultra-violet light disinfection units. In 2010, the final roof slab was laid in place and it was covered with dirt and reseeded. The Mosholu Golf Course driving range is now taking shape on top of the facility.

The New Croton Aqueduct was originally placed into service in 1890 and is a 33-mile-long, 13-foot-diameter, brick-lined tunnel that was engineered to convey drinking water by gravity from the New Croton Reservoir in Westchester County to Jerome Park Reservoir in the Bronx. When DEP stopped using Croton Water for in-city distribution and began planning the construction of the filtration plant, the Aqueduct was drained of water and an extensive inspection of the tunnel took place. Rehabilitation work included re-grouting the brick lining of the tunnel, upgrading 34 shaft site connections that allow crews to access the tunnel from ground level, and repairing valves and pumps that allow certain Westchester communities to pull water from the Aqueduct. In addition, a 58-foot-long and 12-foot-wide concrete plug was built inside the Aqueduct beneath Jerome Park Reservoir in order to divert water to the Croton Filtration Plant.

In order to divert the water from the New Croton Aqueduct to the Filtration Plant, DEP drilled and blasted a 12-foot diameter, 880 foot long tunnel. To view a video of a blast click here. In addition, two new water tunnels were excavated by a tunnel boring machine to bring the filtered water back to the existing distribution network. These two tunnels are 9-feet in diameter and together stretch for more than a mile.

Once the water arrives at the filtration plant it undergoes several processes to remove impurities include dissolved air flotation (DAF) stacked on top of rapid gravity filters (anthracite and sand) and then is exposed to ultraviolet light disinfection to protect against potentially harmful micro-organisms. A state of the art laboratory tests the water as it enters the facility, before it leaves, and at every step throughout the filtration process to ensure it meets or exceeds all state and federal guidelines.

For more information, visit the DEP website.

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