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February 5, 2009

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New

Behind the scenes with Out On A Limb –
a tree adventure exhibit at the Morris Arboretum

This summer, when visitors see the exhilarating new Tree Adventure exhibit at the Morris Arboretum, they might not be thinking about what went on behind the scenes and below the surface in the construction of Out on a Limb, a dramatic 275-foot walkway that will soar more than 40 feet above the ground. This project, designed by Metcalfe Architecture & Design, will incorporate the highest level of tree protection and care, which of course, fits perfectly into the central message of the exhibit- We need trees, and trees need us – thus introducing visitors to the critical role trees play in our environment.

Despite bracing winter temperatures, construction of Out on a Limb - a Tree Adventure began in early January with Morris Arboretum arborists supervising the project. The exhibit is designed to showcase trees and educate visitors about our symbiotic relationship with them. To reflect this goal, the maximum preservation of trees and their rooting environment is paramount. Every design and construction decision must balance the excitement factor of building a canopy walkway high into the trees with construction techniques that create the least disturbance to the local environment. And it goes without saying that the structure must also achieve maximum stability and safety.

To accomplish this, considerable pre-planning was gone into studying the root systems of the trees in the exhibit site plan prior to construction.  Arboretum staff, in conjunction with Metcalfe architects, structural engineers and construction staff have surveyed and exposed the roots to determine exactly where points of entry should be placed to minimize the footprint of the foundation. Careful examination has informed exactly how the tree canopy structure will be build among the trees.

Out on a Limb – a Tree Adventure exhibit’s impact is intended to ‘tiptoe’ through the trees using smaller points of entry called micro-piles instead of larger points which would affect a greater portion of the root surface. To further protect the roots, layers of mulch with stabilizing fabric have been installed to cushion the roots.

To safeguard the tree trunks, a protective casing of wood slats has been placed around the tree at base level and six feet upward. This technique is replicated 30 feet up to shield the tree canopy from potential damage by the construction cranes.

As an added element of challenge in creating the smallest footprint for Out on a Limb – a Tree Adventure, the exhibit is built on a ridge that begins the Wissahickon Gorge, on hard bedrock, so that all of the construction must be engineered to accommodate the site’s geology.

When the Tree Adventure exhibit is complete in early summer, visitors will have the opportunity to experience the critical role trees play in our environment. They will gain an informed perspective on how trees develop, grow, and contribute to the biosphere, which will foster a keener understanding of the relationship between people and trees. Most importantly, Tree Adventure will nurture a sense of stewardship toward trees in our communities, many of which are stressful environments where trees depend heavily on people to sustain them. And to accomplish this goal the Morris Arboretum is leading by example and has employed all of the best conservation practices in the construction of Out on a Limb – a Tree Adventure exhibit.

 

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