By Julie Shapiro
DNAinfo Reporter/Producer
LOWER MANHATTAN — The 9/11 Memorial moved one step closer to completion this week when the first mound of soil arrived at the World Trade Center site.
Workers began spreading the soil onto the plaza Monday evening, filling in an area between the tower footprints.
A dozen swamp white oak trees will be planted in the dirt at the beginning of September, the first of the more than 400 swamp white oak and sweetgum trees that will eventually fill the plaza. The plaza will ultimately hold 18,000 cubic yards of soil.
“It’s an important milestone for the project,” said Steve Coleman, spokesman for the Port Authority. “People want to see the plaza take shape, and the dirt is an important component of that.”
Ronaldo Vega, director of design for the memorial, said the soil is no ordinary dirt. It is mostly made of gravel, so that it will support the plaza above and the millions of people expected to visit the memorial each year.
The rocky soil will allow air and water to reach the roots through an irrigation system similar to a rooftop garden, Vega said. To nourish the trees, worm skin and excrement is mixed into the gravel.
The trees’ roots will be able to reach out to each other and spread all across the plaza without limit, Vega said.
“They’ll help each other survive and stay strong,” he said.
The National September 11 Memorial & Museum plans to open most of the tree-dotted memorial plaza by the 10-year anniversary of 9/11, with waterfalls in the original Twin Towers footrpints.
Many of the memorial trees are now growing on a New Jersey farm, while others will come from locations in Pennsylvania and near Washington, DC, that were affected by the attacks.
The memorial foundation picked the trees partly because they will blanket the plaza in an array of colors each fall on the anniversary of 9/11. The swamp white oaks turn amber, golden brown and pink, and the sweetgums turn orange with hints of red, purple and gold.
