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Baseline Keeps the 9/11 Memorial Plaza’s Green Infrastructure Adaptable and Sustainable


  • Two-wire technology that prevents having to run new wires back to irrigation controllers
  • Soil moisture sensors’ ability to collect data 24/7 on irrigation and precipitation impact
  • Flexibility to change, relocate, add, or remove irrigation components
  • Thriving tree population with zero removals / failures to establish

Landing the design of the 9/11 memorial is no small feat. PWP Landscape Architecture won this bid, with the goal of completing the memorial by the 10-year anniversary of 9/11. PWP brought on Northern Designs as a specialist irrigation consultant since trees were a critical component of the site plan. The top of mind questions were — could the trees at the memorial survive and thrive? And how could they be efficiently irrigated in a crowded urban landscape?

Baseline’s involvement in the memorial began at a tree farm in Millstone Township, New Jersey, where the trees for the memorial were grown. 400 prime specimens were selected after intensive evaluations of 2,000 swamp white oak trees.

Along with the new trees planted, an older one was included: the Survivor Tree — a tree found badly burned at Ground Zero on the day of the attacks. It was nursed back to health in Brooklyn and replanted at the 9/11 memorial site, irrigated by Baseline controllers and soil moisture sensors, along with the other 400 trees. The second chance at life for this tree is a symbol of resilience and survival and captures the somber but hopeful spirit of the memorial.

This project required intensive planning that anticipated milestones years down the line. For example, all the trees were grown in the permanent container that would be used onsite. The same soil and containers that started off on the farm were transplanted with the trees to the memorial site. Even the rotation of the trees was planned prior to planting, based on projections about canopy placement and light sourcing.

One major challenge of this project was that it was unstructured. There isn’t much of a soil base in New York City, which means the memorial was essentially built on a concrete structure. Northern Designs had to incorporate irrigation piping in corridors beneath the platform. A complex series of valves were mounted to the walls and water was brought up through a slab to the soil portion of the project.

Any mistake was severe. Having to excavate a failing tree would mean concrete removal and a bill running into the tens or hundreds of thousands of dollars.

Turning Miles of Underground Irrigation Into A Streamlined System 

Northern Designs set out to create a streamlined watering system amidst incredibly complex, high-stakes conditions.

“What caught my attention about Baseline was the moisture sensors. Now, we can look back and see how they work, but at the time, moisture sensors weren’t thought of as a viable product,” said Mike Astram, founder and principal at Northern Designs.

Mike’s team placed sensors at several points along each tree’s roots. They also included backup sensors in case of the original sensors’ failure. These placements were baked into the long-term plan, because once tree roots were covered up with concrete, it would be a huge undertaking to access them.

The project used a combination of reclaimed stormwater and city water. Northern Designs worked to supply bubblers and drip irrigation to all trees across the entire platform – about five miles of drip irrigation in total, with drips spaced out every 16 inches in PVC sleeves that irrigate sand-based soils.

After the trees matured, bubblers were turned off and everything began to run off of drip irrigation. Sod and ground cover is irrigated with pop-up, high-efficiency nozzles, and rotators. According to Astram, “Baseline’s two-wire technology was optimal for the application of this irrigation system.”

One of Northern Designs’ main goals was to limit the valve locations along the corridors. At each valve manifold, the team clustered three or four individual valves. With this set-up, anyone who needs valve access won’t have a difficult time gaining entry. With standard wiring, the memorial would require miles and miles of wiring, but the two-wire system is far easier and more efficient. People can add valves, move zones, or relocate an existing valve to a new location without having to go back to the controller and get wire to the valve.

“Baseline’s two-wire system made installation a lot easier as far as any changes on the project,” Astram noted.

Technology That Adapts As Time Goes On

As with any project in an urban setting, there’s a lot of pre-existing infrastructure involved, including plumbing, electrical, lighting, and security equipment running through. Irrigation is one factor, but trying to figure out how a specific pipe will get where it needs to go with plumbing, drainage, and site utilities is a multi-faceted problem to solve.

“The irrigation system itself is complicated, but the coordination with everything else involved went smoothly,” said Astram. Sensors collect data 24/7 so they can see how irrigation cycles and natural precipitation are impacting the grow boxes where the trees reside, as well as other landscape assets.

Despite the many challenges and pressures, the project was completed by the ten-year anniversary of 9/11.

“As far as maintenance goes, the system is still working,” said Astram. “The two-wire system is still working well, and with online access, it’s much easier to maintain than having to go to a controller all the time,” he added.

Astram’s team upgrades the irrigation technology periodically,  to stay current with technology that’s available today. They’ve been able to do just that thanks to Baseline’s flexible, adaptable model and Northern Designs’ future-proof irrigation planning.

“As far as Baseline, the two-wire system made it much easier to make changes in the field, add additional irrigation, and relocate things,” said Astram. The controller was set up temporarily in one location and then moved to a permanent one. With the two-wire path, running wire through valve locations is a straightforward process.

Astram’s main concern when the project started was planting the trees onsite. The memorial went up more than a decade ago and to date, no trees have been removed — they’re all still going strong.