Molybdenum and its applications

Stainless steel lets wastewater treatment plant shine

By Catherine Houska, TMR Stainless (Consultants to IMOA)

New York has a new, high profile stainless steel architectural landmark, and it is not a skyscraper. It is the attractive and expanded Newton Creek wastewater treatment plant. This is an example of municipalities around the world retaining architects to transform traditional unsightly infrastructure into attractive urban art and to stimulate redevelopment. Molybdenum-containing stainless steel has played an important role in this worthy project.

Newton Creek Type 316 stainless digester “eggs” displaying their low reflectivity finish in the daytime light.
Photo: NYC Department of Environmental Protection.

The Newton Creek plant is the largest of New York City’s fourteen wastewater treatment facilities, serving approximately 1 million residents and a drainage area of more than 65 km². It is located on Newton Creek, a 5.6 km long polluted waterway on Long Island. The plant began operation in 1967 with a capacity of 1.2 million cubic meters per day during dry weather. Upgrade work began in 1998 and will eventually raise plant capacity by 125%. The completion of Phase 1 in 2008 increased capacity by 50%. Completion of Phase 2 is expected in 2016. In addition to the fundamental need to expand capacity and eliminate odor problems, the city had other requirements.

The facility is visible from vantage points in the Brooklyn, Queens and Manhattan city boroughs, including the Long Island Expressway, the Brooklyn-Queens Expressway and the Kosciusko Bridge, making aesthetic revitalization highly desirable. Hence, the New York Department of Environmental Protection (DEP) engaged the architecture firm Polshek Partnership to work with the engineers to create an attractive facility along the estuary. Since long service life was required, material durability and resistance to the coastal salt-laden air were as important as aesthetics.

Function and form

Eight gracefully curved egg-shaped silver towers rise 44 m above the site like an alien apartment complex in a science fiction movie. These digester “eggs,” which are the project’s most visible component, will process up to 5.7 million liters of sludge every day, using anaerobic technology. At their widest point, the eggs are over 24 m in diameter.

Polshek chose to highlight these towers and make them an important sculptural element by wrapping them in 22,297 m² of 9.5 mm thick Type 316 stainless steel. Using the strong lines of a batten seam roof system and a proprietary low reflectivity finish to softly reflect light further highlighted the elegant shape of the digesters. Type 316 stainless steel with 2% molybdenum has become the standard specification for projects in locations with coastal or deicing salt exposure for Polshek Partnership and some other prominent US architecture firms. The more commonly used Type 304 does not contain molybdenum and can have aesthetically unacceptable surface staining in environments with corrosive salt or pollution, and regular cleaning is required. This stainless steel will not be manually cleaned, making Type 316 the logical choice.

Type 316 stainless steel was also used for numerous other architectural applications including the wall panels and curved batten seam roof on six buildings, canopy cladding, louvers, railings, ladders, and doors (both interior and exterior) and handrails in the facility. In addition, stainless steel was used extensively for plant equipment that is traditionally stainless steel.

Satisfying addition to the neighborhood

George Trakas, a renowned environmental sculptor, designed a new, 0.4 km nature walk that is located next to the plant. The walk offers stunning views of the city and the plant’s unique architectural features. State-of-the-art odor elimination technology made the nature walk possible; it will eventually wrap around three sides of the facility. The walk is a popular addition to the community, providing recreation and a romantic view. Type 316 was used for handrails, gates, and other items along the walk.

Night time view of the digester “eggs” showing their shroud of thin blue light that highlights their unique sculptural appearance.
Photo: NYC Department of Environmental Protection.

The DEP’s Frank Giardina stated, “Facility materials reflect the community’s desire for a clean, modern, and durable presence within the neighborhood. Stainless steel was chosen as one component of a coherent palette of materials used throughout the site as a maintenance-free, glossy, and impervious material, thereby retaining the fresh look of the facility for many years. Specifically, Type 316 stainless steel was chosen as a corrosion resistant material for use within a coastal environment.”

Hervé Descottes of L’Observatoire International, who has worked on other high profile projects by well-known architects, was commissioned to design illumination for the new facility. At night, a thin layer of blue light highlights the unique sculptural appearance of the digesters and active areas of the plant, like the loading docks. The pedestrian walkways in the surrounding park are highlighted with blue and yellow light, and white lights are used to illuminate the plant’s other buildings. The colors were chosen to contrast with the bright orange lights of the city.

“It is thrilling to see form and function beautifully expressed in the structure we are illuminating to night,” said DEP Commissioner Emily Lloyd. “Each evening we will be reminded of the elegant combination of engineering and art in the blue aura of the structure… . This stunning plant demonstrates that with care even the most utilitarian infrastructure can be an exciting and inviting neighbor.”