The Freedom Tower

The New York Times says the National September 11 Memorial and Museum at the World Trade Center will not open for at least three years. But on his visit last week, Pope Benedict XVI was able to see — in situ — the largest single exhibit that the museum will offer.
The original slurry wall of the World Trade Center, the left side of which will remain on display in the September 11 museum.
A 62-by-64-foot section of the trade center’s original foundation wall, called a slurry wall, preserved and exposed, will occupy the heart of the enormous West Chamber of the underground museum. This wall section is identifiable because it looks much the way it did seven years ago. It was clearly visible from the spot where the pope blessed ground zero on April 20.

Elsewhere along the slurry wall, steel caisson cores have been erected where a new concrete liner will be poured in front of the old wall. The liner wall system will strengthen the slurry wall against caving in or leaking. Floor slabs in the trade center’s basement once provided that extra bracing. High-strength steel cables, known as tiebacks, do so now.

“We are confident that it is safe at this stage,” said Raymond E. Sandiford, chief geotechnical engineer for the Port Authority of New York and New Jersey, which is constructing the museum. “But we wouldn’t want to rely on it for 100 years. We have to either line the slurry wall or reinforce the exposed wall so that the loads on it are very minimal.”

The idea of displaying the slurry wall can be traced to a proposal in 2002 by the architect Daniel Libeskind, who was designated master planner of the trade center site. He said then that the walls around the site had “withstood the unimaginable trauma of the destruction and stand as eloquent as the Constitution itself, asserting the durability of democracy and the value of individual life.”

Six years later, the idea has survived.