Croton Water Treatment Plant (290 mgd)

Client: New York City Department of Environmental Protection
Location: Bronx, NY

While the Croton system currently meets Federal and State standards, the NYCDEP determined that water treatment was required for the Croton supply to provide for the continued health and safety of the citizens of New York City and to comply with State and Federal water quality standards and regulations. New York City then initiated the design and construction of its first water treatment facility, the 290-mgd Croton Water Treatment Plant. 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.

Project Outcomes and Benefits

  • The tight urban site necessitated a reduced building footprint, accomplished by stacking dissolved air flotation/filtration, sending residuals offsite for treatment, minimizing emergency generator capacity, constructing buttresses inside the plant structure, using single-sided formwork and excavated rock wall for outside form, among other innovative, space-saving measures.
  • Under a separate site preparation contract, Hazen and Sawyer implemented an effective, award-winning approach for concurrent, phased design and construction to deliver timely sitework, thus meeting all mandate-driven deadlines.
  • The project called for environmental conservation efforts, including constructing an infiltration trench to protect a nearby forested wetland from possible migration of water toward the excavation, and initiating a tree protection and monitoring program.
  • The political nature of the project demanded a comprehensive public outreach program, to allay public concerns, and ensure minimal construction impacts to the surrounding community.

The state of the art facility, located under a driving range, can provide roughly 30 percent of the City’s current daily water needs, providing critical system flexibility and redundancy (photo by NYCDEP).

NYCDEP awarded a separate Site Preparation contract for the Croton WTP, which enabled the excavation work to proceed while the complex final design for the WTP was completed, reducing the overall project schedule. Over 1 million cubic yards of soil and rock were removed from the 700' x 575' excavation at this site, on a golf course in the Van Cortlandt Park, Bronx. The excavation depth averaged 80 feet and reached a maximum of 110 feet.

A visually-appealing ornamental wall, featuring climbing vines and a water theme, was erected to shield construction activities from area residents.

The magnitude of the work required a large contingent of heavy equipment to work in concert, including jack hammers, backhoes, dump trucks, and other excavation machinery. This photo also depicts the massive size of the excavation relative to the various types of equipment.

Several measures were implemented to reduce the noise, dust, and vibrations from rock blasting activities, to minimize impacts on the surrounding residential community. A test blasting program was first conducted under NYC Fire Department direction, to ensure that the appropriate procedures were followed. Blasting and hauling continued for over 18 months. The photo shows one of the many blasts conducted during that period. Approximately 900,000 cubic yards of rock were ultimately removed from the site. To reduce dust, trucks were washed down, and truck beds were covered.

In addition to the excavation work, the Site Preparation contract included the start of construction of the tunnels required to bring raw water to the plant and deliver treated water to the distribution system. The photo depicts the areas where the tunnels enter the site.

The Croton Water Treatment plant, which went into service in 2015, will produce up to 290 mgd of finished water. The plant includes a raw water and treated water pumping station and raw and treated water connections to the City’s distribution system through new tunnels constructed as part of this project. The treatment processes consisting of flotation for large solids removal, filtration for finer solids removal, ultraviolet and hypochlorite disinfection, as well as supplemental chemical conditioning is housed within the main treatment building. Water treated at the plant meets all current and anticipated water quality goals and standards.

NYCDEP authored a comprehensive Environmental Impact Statement comparing three sites for construction of the Croton WTP. Through detailed environmental, socio-economic and engineering analysis, as well as public involvement and the need to address issues related to security and water distribution, the Mosholu Golf Course site was selected for construction of the Croton WTP.

The completed plant is situated largely under a portion of the 13-acre driving range. In addition to the underground structure, the plant includes two small above ground buildings to access the facility and to receive deliveries.

For more information on this project, or to discuss a similar project in your area, contact

William Becker, P.E. at