NEW YORK -- New York City engineers have begun testing the waterfalls for the Sept. 11 memorial at ground zero.
The cascades are the largest manmade waterfalls in North America. They empty into massive reflecting pools that mark spots where the World Trade Center towers once stood.
Testing of the waterfalls for the north pool began Tuesday morning. The testing included switching on the eight pumps to see how the water will flow into the basin.
More than 350,000 gallons of water streamed into the pool. It circulated at 52,000 gallons per minute.
Testing of the south pool waterfall will begin next spring.
The 176-foot-perimeter pools are the centerpiece of Michael Arad's "Reflecting Absence" memorial.