NEW YORK — Standing at the foot of the 9/11 Memorial can be awe inspiring, to say the least. Reflecting upon the events of that day, “Ground Zero” holds a special place in the hearts and minds of each individual who visits this hallowed ground.
9/11 Memorial bronze panels. Photo credit: Ron Gumucio
In the footprints of where the Twin Towers once stood sit two rectangular, reflective pools — the North and South Pools. Measuring close to an acre each and 45 feet in depth, the pools serve as the base of what is now considered North America’s largest manmade waterfalls. Every minute, 50,000 gallons of recycled water slowly surge over the lip of the waterfall ledge creating sheets of cascading water. A total of 152 connecting bronze panels engraved with the 2,983 names of the victims surround the two pools and their respective waterfalls. Millions of people are expected to visit each year to pay their respects.
“The bronze panels are the first thing people see, the first thing they touch, and their first contact with the Memorial,” said Ronald Vega, the Memorial’s director of design and construction. “We want people to be able to connect with it.”
But what you won’t see are the miles of half-inch copper tubing beneath the bronze surfaces. With about 91 tons of bronze in the panels and miles of brackets and tubing, copper and its alloys play a significant role in the memorial’s functionality.
Because of its corrosion resistance, high level of heat transfer ability, durability, workability and reliability, copper was the preferred piping material choice for this project. Andy Kireta Sr., president of the Copper Development Association (CDA), said he was impressed by the amount of copper used at the site, which visitors would be able to see firsthand.
“From the piping to the panels, copper plays a key role in making this Memorial truly unforgettable,” said Kireta, during a recent visit to the hallowed grounds. “To be here and to see it in person is a remarkable experience.”
Beneath the solemnity
KSW Mechanical Services Inc., Long Island City, N.Y., started installation of the 9/11 Memorial mechanical system and copper piping in December 2010 and completed the project in August 2011, in time for the 10-year anniversary of the attacks on the World Trade Center. The 9/11 Memorial copper piping project consists of approximately 12,000 feet of copper brackets and 14,000 feet of copper piping.
“All of the connections were either soldered with 95/5 solder or brazed depending on their location,” said John Boutillier, project executive, KSW Mechanical Services Inc.
A look below the bronze panels. Photo credit: Amy Dreher.
“When it came to the final connections of the plaque’s copper tubing to the seven 1/2-in. and one 3/4–in. flex hoses, which penetrated the plaque supports, we utilized SharkBite fittings.”
Tubing is fastened behind each panel in a closed loop system down into the pedestal, thereby controlling the temperature of the touch surfaces, keeping the panels between 40°F and 70°F, serving as a hydronic system of sorts. To keep the panels at a temperature consistent with the season, a 40% propylene glycol water solution was used to keep the plaques warm in the winter and cool in the hot summer months.
From the mechanical room below, a plate and frame heat exchanger was used to cool the water and a shell and tube heat exchanger was used to heat the water. The water, then, is pumped and recirculated with the aid of two Taco centrifugal pumps — one operating pump and one back-up just in case — per pool.
“We worked together to design and assemble a back-mounted tube system that could work within the parapets and nameplate system,” said Christopher Powers, founder of KC Fabrications, Gardiner, N.Y, who worked to design the system to ensure it would work with the bronze parapet. “A network of copper pipes circulates glycol behind the parapets to heat and cool the bronze panels.”
KSW Mechanical created the mock-up designs to preassembly of the individual plaques, which were then shipped to the site to fit together like a jigsaw puzzle.
Copper tubing is measured and cut onsite. Photo credit: Amy Dreher.
Instrumental in the supply and delivery of all of the piping was Davidson Pipe Supply Co., Brooklyn, N.Y., which furnished all of the piping. Owner Peter Davidson was instrumental in facilitating the delivery of piping on time.
“Davidson was hands-on from the initial order to the delivery,” said Boutillier. “Without his help, we wouldn’t have gotten the job done.”
One minor ‘hiccup’
Project executive Boutillier described a slight obstacle with the design and installation, “Because the name-engraved bronze panels are backlit at night, if someone was to look into the openings, one could see the piping, which was unacceptable to the designers.”
Boutillier looked far and wide for solutions when he found the answer at his daughter’s home, believe it or not. He used her shower rod cover, made the proper size cuts to wrap around the copper stand-offs, and placed the pieces beneath the plaques, which, strangely enough, did the trick. He purchased approximately 100 more curtain rods to finish the scope of the project.
The project, which is United States Green Building Council LEED Gold certified, also uses recycled water for the waterfalls and to irrigate the nearly 400 trees that have been planted on site. “The system is extremely efficient,” said Vega. “It was designed to minimize water and energy costs.”
For more information about copper tubing applications, visit www.copper.org.