'Once-Lowly' Piece of Infrastructure Honored as a Hero of 9-11

David W. Dunlap recounts how the slurry wall built around the World Trade Center's foundations prevented the devastation to Lower Manhattan from becoming much worse, and "became a symbol of resilience in the months and years after the attack."

1 minute read

September 11, 2013, 10:00 AM PDT

By Jonathan Nettler @nettsj


After it was built over nine months beginning in 1967 "using jury-rigged tools, on a site that brimmed with uncharted obstacles and unhappy surprises", engineer Arturo Lamberto Ressi di Cervia never thought he'd see the retaining wall he helped construct again in his life. But the events of Sept. 11, 2001 changed that. 

"Because the slurry wall held, the 70-foot-deep foundation did not fill with groundwater [when the towers fell]. And because of that, the PATH tubes were not submerged. And because of that, the subway tunnels below the PATH tubes were not inundated," explains Dunlap. "How much worse could Sept. 11 have been? Imagine if Hurricane Sandy had followed the terrorist attack by a few hours."

"Thirty-five years later, in 2002, the architect Daniel Libeskind drew the world’s attention to the symbolic significance of the wall, when he proposed its preservation and exposure as part of the redevelopment of the trade center."

Wednesday, September 11, 2013 in The New York Times

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Wastewater pouring out from a pipe.

Alabama: Trump Terminates Settlements for Black Communities Harmed By Raw Sewage

Trump deemed the landmark civil rights agreement “illegal DEI and environmental justice policy.”

April 13, 2025 - Inside Climate News

High-rise apartment buildings in Waikiki, Hawaii with steep green mountains in background.

Study: Maui’s Plan to Convert Vacation Rentals to Long-Term Housing Could Cause Nearly $1 Billion Economic Loss

The plan would reduce visitor accommodation by 25% resulting in 1,900 jobs lost.

April 6, 2025 - Honolulu Civil Beat

Blue and white Seattle Link light rail train exiting concrete Downtown Bellevue Tunnel in Bellevue, WA.

Why Should We Subsidize Public Transportation?

Many public transit agencies face financial stress due to rising costs, declining fare revenue, and declining subsidies. Transit advocates must provide a strong business case for increasing public transit funding.

April 7, 2025 - Todd Litman

Silhouette of man holding on to back of bicycle ridden by woman with Eiffel Tower in background.

Paris Bike Boom Leads to Steep Drop in Air Pollution

The French city’s air quality has improved dramatically in the past 20 years, coinciding with a growth in cycling.

April 14 - Momentum Magazine

Multifamily housing under construction.

Why Housing Costs More to Build in California Than in Texas

Hard costs like labor and materials combined with ‘soft’ costs such as permitting make building in the San Francisco Bay Area almost three times as costly as in Texas cities.

April 14 - San Francisco Chronicle

Western coyote looking at camera in grassy field.

San Diego County Sees a Rise in Urban Coyotes

San Diego County experiences a rise in urban coyotes, as sightings become prevalent throughout its urban neighbourhoods and surrounding areas.

April 14 - Fox 5