NEW YORK (CBS Local/AP) — The waterfalls at the 9/11 memorial are the two largest man-made waterfalls in the country, but memorial president Joe Daniels says it’s not the size of the waterfalls, it’s the sound.

“That white noise separation that the waterfall creates I think is a signifier that you’re in a very special place,” said Daniels.

Architect Michael Arad first imagined the twin reflecting pools with cascading waterfalls — he calls them voids — as two empty spaces in the Hudson River, west of the smoldering World Trade Center.

Crews have been testing the waterfalls in preparation for the memorial’s official opening on the 10th anniversary of the Sept. 11 attacks, reports WCBS 880’s Peter Haskell in lower Manhattan.

“To get it right, to make sure it works, to make sure they can be turned on and off,” said Daniels. “That of course, there’s no leaks which fortunately there are no leaks at all.”

When Arad entered a competition for a trade center memorial in 2003, the voids were in the footprints of the towers themselves, and manmade waterfalls replaced the churning river.

LISTEN: WCBS 880’s Peter Haskell reports

A jury including Vietnam Veterans Memorial designer Maya Lin chose Arad’s twin waterfalls out of 5,201 entries, saying it embodied the grief and the desire for healing that the terrorist attacks inspired.

The 42-year-old Arad’s 9/11 moment is arriving on the 10th anniversary of the attacks, culminating a journey for the son of an Israeli diplomat and unknown city architect whose poster board sketch became a touchstone for post-Sept. 11 battles over how to mourn and how to remember the dead.

Financial, practical and political considerations forced design changes; hundreds of trees were added to Arad’s original vision. The puzzle of how to list the dead has not been solved to everyone’s satisfaction.

Arad says the core of his original plan remains.

“We’ve gone through an eight yearlong editing process of sort of parsing it down,” he said in an interview in the Manhattan offices of Handel Architects. “But I didn’t end up with a whole other unintended direction to this. Is it exactly as it was eight years ago? No. But is it the same in nature? Yes.”

After terrorists killed nearly 3,000 people and toppled two 110-story skyscrapers, some New Yorkers said the entire 16-acre trade center site should be a memorial or a park. Others said the towers should be rebuilt just as they were before.

In the end, Daniel Libeskind’s master plan set aside eight acres — half the site — for a memorial.

Arad’s design, “Reflecting Absence,” features waterfalls cascading into reflecting pools where the towers stood. The names of all those killed on Sept. 11, 2001 and in the earlier World Trade Center attack on Feb. 26, 1993, are inscribed on bronze parapets surrounding the waterfalls.

In a change from the bare design Arad submitted, the waterfalls are nestled within a grove of swamp white oak trees that will grow as tall as 60 feet.

A museum showcasing remnants of the original trade center will open next year.

Interviewed at the memorial site, Arad referred to the pools as “voids” and said they will evoke the lives lost in the terror attacks.

“These voids that you see behind me — as you approach them as a pedestrian they’re not readily visible,” he said. “And it’s really only when you’re a few feet away from them that all of a sudden the ground opens up in front of you and you see this enormous expanse, these voids which are ringed with these waterfalls and the reflecting pool below them.”

And then the visitors come to the edge and start circling the pools, “following this river of names” around the perimeter.

Members of the jury — Lin was said to be one of Arad’s strongest supporters — said the nearly completed memorial has vindicated their choice.

Paula Grant Berry, a Sept. 11 widow and the lone victims’ family member on the jury, said the falling water “will cut out the sound of the city.”

She added, “The beauty of the design is that it maintains the footprints of the buildings. It gives you a sense of how large the buildings were.”

Arad was an unknown architect working for the New York City Housing Authority when his design was chosen.

Arad grew up in Israel, the United States and Mexico, and served in the Israeli military. A Dartmouth graduate who got his master’s at George Institute of Technology, Arad came to New York two years before the attacks.

Arad was thinking about a Sept. 11 memorial before the competition was announced. He built an acrylic model of his cavernous holes in the Hudson and brought it up to his apartment rooftop to photograph it against the skyline.

“This idea of the surface of the river being torn open and the water flowing into this hole. … I kept sketching it and thinking, could it be realized?” he recalled. “Could you actually create that effect? Could you cut a hole in the river?”

The answer, seemingly, was no. But the idea morphed into Arad’s twin voids in the towers’ footprints.

Not everyone loved the design. Arad keeps a digital New York Post front page —”IT STINKS!” — in his computer.

He appears to take criticism in stride.

“When I entered the competition it was a very private act,” he said. “It was something that I did by myself, sketching in my study, imagining the kind of memorial that I might want to visit someday. But when the design was selected all of a sudden it went from a constituency of one to a constituency of thousands.”

Arad said working on the memorial has been “exhausting and exhaustive” but also “a huge privilege.”

Construction of the memorial began in 2006, and it will be the first component of the rebuilt trade center site to be completed. New office towers, meanwhile, are rising rapidly to the memorial’s north and east.

According to the National September 11 Memorial & Museum, the combined cost of the memorial and museum is about $700 million with an annual operations budget between $50 million and $60 million.

A memorial to the 1995 Oklahoma City bombing that opened in 2000 cost $29.1 million.

The Sept. 11 board has raised about $400 million from private donations and is seeking federal funds so that the memorial and the museum can be free of charge — although it also said it’s considering a voluntary fee of up

Arad said every detail of the memorial has been carefully vetted, from the Virginia-quarried granite that lines the tower footprints to the hand-brushed patina that protects the bronze.

Placement of the nearly 3,000 victims’ names was always contentious.

An alphabetical list “would not have been the right move,” Arad said. “You had married families who shared the same last name and married families who didn’t share the same last name. And if you did an alphabetical listing it would privilege some over others.”

Mayor Michael Bloomberg’s proposal to list the names randomly pleased few. Victims’ family members wanted to list the dead by their employers. Relatives of the firefighters and police officers who died trying to save others pushed for their rank and ladder company to be listed.

The solution was to group people’s names near the names of their friends, family members and co-workers, and first responders were identified. Over 1,200 requests were made, and granted to list the names.

Families who died on the airplanes will be listed together, as will office colleagues who shared lunch every day.

Donald James McIntyre, a Port Authority police officer who died as he tried to make his way to the 84th floor of the south tower, will be listed next to his cousin John Anthony Sherry, who worked there.

Edie Lutnick, who heads a relief fund at Cantor Fitzgerald, the financial services firm that lost 658 people including her brother on Sept. 11, said age and affiliation “could so easily be added.”

“You would be able to know that a 2 1/2-year-old died on the plane,” Lutnick said. “You would learn a story from the memorial and not from a telephone or a kiosk.”

Arad said every choice had consequences. If a victim didn’t work for a company at the trade center, they would have been listed as unaffiliated, which is why no company name will appear anywhere.

“Again,” he says, “everything you did had issues of equity.”

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