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Automation Solutions for the World Trade Center Site: Museum Reflecting Pools

The 9/11 Museum and Memorial site covers eight acres and includes two massive reflecting pools with waterfalls. Delta Fountains and Siemens Industry Inc. is providing engineering, automation and pump flow control for these water features.

Delta Fountains co-owner Joe Petry describes the unique requirements of the reflecting pools. Photo: Siemens
Delta Fountains co-owner Joe Petry describes the unique requirements of the reflecting pools. Photo: Siemens

Ten years of work have gone into reclaiming the World Trade Center site in New York City where hundreds of people lost their lives on Sept. 11, 2001. Plans for the site include new World Trade Center towers, a train/subway transportation hub, a museum and a memorial to those who lost their lives. The 9/11 Museum and Memorial site covers 8 acres and includes above- and below-ground exhibits, as well as two massive reflecting pools with waterfalls positioned in the foundations of the former twin towers.

Siemens Industry, Inc—the U.S. affiliate of Siemens’ global Industry Sector business and a supplier of production, transportation and building technology products and services—is providing more than $12 million in building technology, power distribution and automation solutions to the site (See Powering the World Trade Center Site). At the reflecting pools, keeping the water sparkling clean and the acoustic and visual counterpoints consistent minute-to-minute is no small feat. For that, Siemens partnered with Delta Fountains, the Jacksonville, Fla. manufacturer of the pools.

Each pool is almost an acre in size and holds 600,000 gallons of water. Water pours over smooth, stainless steel weirs that stretch horizontally atop the pool’s four walls and then falls vertically down into a catch basin to be recirculated. The falling waters provide a soothing acoustic backdrop to the tranquil, reflective surface of the water in the center of the pool.

The pools’ operating complexities required a master control system with a sophisticated architecture and onboard central processing units (CPUs) for redundancy. When the project began three years ago, one of the challenges facing Delta was the need for a solid, up-to-date, technical solution that could be easily upgraded with the latest features and capabilities as the project evolved. Siemens brought in its top application engineers to work both with its distributor, AWC, and with Delta Fountains’ team to determine specifications and the best hardware and software to meet the project requirements. The result was $180,000 worth of Siemens automation solutions.

Precise flow control
Water is pumped at a rate of up to 30,000 gallons per minute and filtered at a rate of 6,000 gallons per minute in the pools. Variable frequency drives (VFDs) were attached to each pool’s pumps so Delta Fountains engineers could have more precise control over water flow and pressure rates. Such control helps maintain the pool water’s consistency whether it is falling over weirs or resting in the reflective portions of the pools surface.

In addition to providing precision flow control, the VFDs also dramatically reduce energy consumption and CO2 emissions over time because they can continuously drive the 16 pump motors in each pool at optimal speeds. This also saves on motor wear and tear, ensuring a sustainable solution while reducing maintenance costs.

Siemens automation and control components are based on an open architecture called Totally Integrated Automation (TIA), which enables adaptability and flexibility of technology solutions. For such a massive and complex project with long design and approval cycles, TIA provided the Delta Fountain engineers with more options. That meant that, despite it being a fixed-priced project, engineers could make design changes to incorporate new technology. Siemens TIA solution saved Delta Fountains the cost of approximately two technicians, or approximately $150,000 to $200,000 a year. What’s more, because the automation solution allows day-to-day operations to be controlled remotely from Jacksonville, Delta Fountain engineers avoid the additional costs of living in New York.

Renee Robbins Bassett,, is managing editor of Automation World. Reporting for this article was provided by Siemens and Sandra Tigert, Robert Jensen, Chris Lesnik, and Natalie Scannell.

For More Information

More information about the rebuilding of this national landmark can be viewed on the World Trade Center website.

“Engineering Ground Zero” is a Nova special report that aired on PBS stations. It covers the designing and building of One World Trade Center and the National 9/11 Memorial and Museum.

9/11 Memorial website

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