By Roz Hamlett, Portfolio Editor
As the planet pauses for Earth Day 2017, now’s a good time to consider how one green campus – the leafy and canopied World Trade Center (WTC) site – manages to be a relatively stress-free zone for some trees in a city that can be tough for even the hardiest plants.
Part of the answer lies 25 feet above Liberty Street, atop the WTC’s Vehicular Security Center (VSC) and adjacent to the 9/11 Memorial Plaza. There, an 18-zone irrigation drip system sustains 19 planters filled with trees, shrubs, perennials and ground cover in Liberty Park. The system also provides water to more than 20,000 plants on the vertical face of the Living Wall and to the Anne Frank tree, planted last May as a living monument to the young Holocaust victim and renowned diarist.
“It’s amazing when you think how trees in large settings used to be maintained. Today, advanced technology is available in a phone app that allows landscapers to access information remotely from moisture sensors in the ground,” said Christine Weydig, director of the Port Authority’s Office of Environmental and Energy Programs (OEEP). “They can pinpoint the needs of a specific tree quickly and respond from almost anywhere.”
The care and feeding of the Anne Frank tree — a descendant of the tree she saw from her window in Amsterdam during World War II – as well as other Liberty Park plantings are controlled from a windowless, bunker-like room behind a nondescript steel door known as the “Irrigation Room.” It’s a kind of war room specially equipped with computerized water lines, pumps and gauges. From this location, water is dispatched to hundreds of different plant varieties through a subway-like labyrinth of tubing.
Liberty Park acts as a green roof for the VSC. Rainwater is collected in storm detention tanks located strategically throughout the park and then is released slowly back into the city storm water system.
The 9/11 Memorial Plaza has its own separate irrigation system. The 416 white swamp oaks that border the memorial fountains are watered locally by irrigation systems in each building. Some of the rainwater is collected in the large reflecting pools that mark the “footprints” of the original towers, where it’s stored in high-efficiency evaporative cooling towers and then circulated to meet the landscaping needs of the memorial plaza.
The plaza is designed to channel rainwater into drainage troughs that feed into underground cisterns. The water is then pulled into an underground drip irrigation system that waters the trees. The plaza also includes underground aeration pipes to supply air to the roots, and the tree roots are braced to prevent them from buckling the pavement. To further ensure viability, each tree has a monitoring system within its root zone that sends reports on conditions and the tree’s overall health and growth.
Bernice Malione, OEEP’s deputy director, said new technology is helping the agency preserve and sustain “a beautiful and healthy landscape” as spring arrives and new plant life blossoms around the WTC.
“Internet-based platforms and smart devices are allowing the Port Authority to achieve state-of-the-art irrigation,” added Malione.