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.
The 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.
Using UV disinfection rather than filtration resulted in significant savings. 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.