Hazen and Sawyer Wins Top Honors in 2008 Engineering Excellence Awards Competition

Croton Water Treatment Plant Site Preparation Project Recognized for Enabling Timely, Efficient Construction of NYC’s First WTP

Croton WTP at Mosholu Golf Course

(NEW YORK, NY-January 16, 2009) – The Croton Water Treatment Plant Site Preparation Project won the Diamond Award from the American Council of Engineering Companies (NY), the highest honor in the 2008 Engineering Excellence Awards program. The project was commissioned by the New York City Department of Environmental Protection (NYCDEP) and carried out by the joint venture of Metcalf & Eddy and Hazen and Sawyer (M&E/H&S).

The Croton water supply is a vital component of New York City’s overall water supply system. Since its development in the late 1840s, the Croton supply has experienced periodic declines in water quality that sometimes necessitate system shutdowns. For decades, the City has actively planned for filtration of the Croton supply. Following a lengthy siting process involving numerous locations and stakeholders, the City obtained approval in 2004 to construct a 290-mgd water treatment plant (WTP) at the Mosholu Golf Course, an active recreational facility within the Bronx’s Van Cortlandt Park. Site approvals were predicated on constructing the plant underground and restoring the land to public use at project completion. This project presented a significant challenge to the City, involving construction of a complex WTP on a tight urban site, while meeting Consent Order deadlines for project completion and addressing public concerns.

This demanding schedule called for concurrent, phased design and construction that delivered timely and efficient sitework to support WTP construction. To streamline the overall project schedule, NYCDEP awarded the joint venture a separate site preparation contract, to commence while the WTP design was being completed. Instrumental to project success, the contract fostered close coordination between stakeholders, allowed preparatory work to be completed ahead of schedule and under budget, and facilitated subsequent WTP construction.

The complex WTP design was complicated by site topography as well as the requirement that the plant be constructed underground. To reduce building footprint and the extent of excavation, the design team implemented numerous innovative measures, including: applying dissolved air flotation/filtration, with residuals treated offsite; constructing buttresses inside the future plant structure; and using single-sided formwork and excavated rock. Walls up to 100 feet high were excavated using blasting within one-foot tolerance. To enable efficient WTP construction, nearly 200,000 cubic yards of soil and 900,000 cubic yards of rock were removed from the 700’ x 575’ x 110’ (max.) excavation over a period of 18 months.

Addressing environmental impacts and public concerns were also important project considerations. An infiltration trench was constructed to protect a nearby forested wetland from possible migration of water toward the excavation. To promote community wellbeing during site construction, the project team initiated a dynamic public outreach program, culminating in several advantages for the community. These included relocation of Mosholu Golf Course; permanent modifications to roadways to improve traffic flow; construction of a granite-faced ornamental wall to obscure site construction; and strict construction practices regarding dust, noise, air emissions, rodent control, and cleanliness.

The end result of this highly efficient, carefully-coordinated project was timely and economical sitework that enabled uninterrupted construction efforts. Once completed (in 2012), the Croton WTP will help ensure the continued health, safety, and prosperity of over 8 million water consumers.

For more than half a century, Hazen and Sawyer has focused on two things: providing safe drinking water and controlling water pollution. Our range of services encompasses the planning, design, and construction management of water and wastewater-related projects – from clean water treatment, storage, and distribution to wastewater collection and treatment. Since our founding in 1951, we have grown in size to over 740 employees in 25 offices.

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