9/11 A Decade Later: Memorial Pools’ Waterfalls Are A True Engineering FeatJul 07, 2011
The September 11th memorial, which opens on the 10th anniversary of the attack on the World Trade Center, is a feat of engineering due to the powerful machinery that powers the site’s signature waterfalls. NY1’s Bobby Cuza took an exclusive behind-the-scenes tour of the site and filed the following report.
A little more than two months from now, visitors to the September 11th Memorial will be greeted by sheets of water cascading 30 feet down into twin reflecting pools set in the footprints of the Twin Towers. These manmade waterfalls have a scale that is unmatched.
“We haven’t had any fountains this large in one place anywhere else in the country,” said Port Authority Senior Engineer Edward McGinley.What visitors won’t see may be just as impressive. Massive pump rooms make up a mechanical marvel that collects all that water, treats it and sends it back to the top at a rate of 24,000 gallons per minute.
“It’s a very complicated, swimming pool-type system, but it requires a lot of maintenance,” says McGinley. “There’s a lot of pumps, there’s filters, there’s mechanical filters to take sediment out, there’s UV lights that take bacterial control, there’s chemical additives.”
A heating system will keep the water from freezing in winter and the waterfalls will be carefully regulated, particularly when there is heavy winds.
“You’re going to have blowoff, and you’re going to have turbulence on top of the water,” says McGinley. “So you may need to speed up or slow down the pumps, so that you can get the aesthetic look that you’re looking for off the weir, a nice, steady stream of water with a nice, even flow.”
Testing on the north pool is well underway, but the south pool was lagging behind until Wednesday, when it began filling with water.
LED lights at the base of the pools will illuminate the water at night. There are also filters on that level to catch objects like coins and flowers, many of which are likely to be tossed there on September 11, when family members gather at the memorial for the official dedication.
The memorial’s online reservation system goes live on Monday, at 911memorial.org.