• The Catskill-Delaware ultraviolet disinfection facility provides water for nearly 9 million New York City and upstate residents.

file under: 3D/4D Design, Energy, Facilities, Government, North America, Sustainability, United States, Water

Advancing Large-Scale Drinking Water Treatment

New York City's Catskill-Delaware UV Disinfection Facility

Part of the world’s largest unfiltered surface supply, the Catskill-Delaware system conveys water from an expansive watershed in upstate New York through dozens of miles of tunnels to Kensico Reservoir, approximately 12 miles north of New York City in Westchester County. Here, the Catskill-Delaware ultraviolet (UV) disinfection facility treats and controls the flow of nearly 90 percent of the city’s drinking water.

This project demonstrates that UV technology is both a feasible and cost-effective disinfection alternative for large-scale potable water facilities. 

The largest of its kind in the world, with a design capacity of 2 billion gallons per day, the innovative Catskill-Delaware facility has been recognized by the American Council of Engineering Companies as a national Grand Award winner for 2013. The facility provides enhanced disinfection of the drinking water supply for nearly 9 million New York City and upstate residents—setting a new standard in UV technology. Completed by a joint venture team led by CDM Smith and Hazen and Sawyer, the facility has been fully operational and treating the entire flow from the Catskill-Delaware supply since December 2012.

Setting the standard
Due to the watershed’s high-quality water, the New York City Department of Environmental Protection (NYCDEP), with the joint venture’s help, obtained a filtration waiver from the U.S. Environmental Protection Agency (EPA). However, changing regulations for unfiltered surface water systems require enhanced disinfection to inactivate Cryptosporidium (an organism that can cause gastrointestinal illness), and NYCDEP sought alternatives to compliance that would not require a costly filtration plant.

Studies showed that enhanced disinfection with UV would provide at least equivalent protection for the city’s water supply at a much lower cost than filtration. “This project demonstrates that UV technology is both a feasible and cost-effective disinfection alternative for large-scale potable water facilities,” observes Brian Kearney, CDM Smith project manager. Previously, UV systems in the United States were limited to wastewater treatment and much smaller drinking water projects.

Award-Winning SolutionThe Catskill-Delaware facility applies low-pressure, high-output (LPHO) UV disinfection technology on a scale that is unmatched. “The size and capacity of the facility sets Catskill-Delaware apart," says Kearney. “It includes four 12-foot diameter raw water pipes, 11,760 lamps in fifty-six 48-inch diameter UV vessels, and the four 144- by 120-inch venturi flow meters.” The facility also uses sixteen 84-inch-diameter, inline, space-efficient energy dissipation valves—the largest ever built—to control flow through the plant.

Sustainable approaches
Using UV disinfection rather than filtration resulted in significant savings, according to Gary Kroll, CDM Smith senior vice president. “The $1.3 billion Catskill-Delaware facility costs considerably less than the expense of building and operating a filtration plant.”

A holistic approach to design and construction further reduced costs and minimized impacts on the environment. For example, the LPHO lamp technology requires 30 percent less power than the alternative, medium-pressure lamps, reducing energy use and lowering costs. Additionally, the design was carefully developed to maintain gravity flow to the city, avoiding the need for large pumps and associated power use.

Throughout the project, the team carefully limited the facility footprint and construction duration. The surrounding natural areas were also retained and enhanced through extensive wetlands mitigation and visual enhancements at Kensico Reservoir in the town of Mount Pleasant. From start to finish, measures were taken to protect air quality and reduce the facility’s carbon footprint, including using low-sulfur fuels in construction equipment.

Designing for the future
The Catskill-Delaware project team faced numerous challenges, which included selecting the UV system supplier and demonstrating the necessary Crypto log inactivation while the design was ongoing. Meanwhile, to meet the aggressive schedule set forth in the city’s filtration avoidance determination with the EPA, staged construction was used, including a site preparation contract that advanced more than 600,000 cubic yards of mass excavation while the facility’s design was being completed. The UV facility construction was completed on schedule and on budget—meeting the multiple interim milestones established by regulators.

Quality control was ensured using a 3D model of the designed facility, identifying potential conflicts during the early stages of construction that enabled timely action to resolve issues and complete the project on schedule. In addition, 4D modeling used by the general contractor integrated a schedule component to more efficiently sequence work activities across the site. The facility’s innovative design also allows for a future, 2-billion-gallon-per-day filtration plant to be built on the same site if necessary, while maintaining gravity flow and avoiding energy-intensive, costly pumping. It provides a separate UV treatment system for the host community, and a connection for future UV treated water by neighboring communities.

“Implementing UV at Catskill-Delaware advances the application of this technology across the industry, and sets an example in sustainable infrastructure. The facility maintains the city’s legacy for providing safe, clean water to its consumers in an energy-efficient and environmentally responsible way,” says Kroll.