NEW YORK—At the World Trade Center site in New York, the architects responsible for the planned skyscrapers, memorial plaza and museum sought to commemorate the events of Sept. 11, 2001, aesthetically by restoring the site's dominance of the Manhattan skyline while paying tribute to what was lost 10 years ago.

The builders of those projects—the Port Authority of New York and New Jersey and Silverstein Properties Inc.—have sought to honor the events of that day in a different way: by using the lessons learned from the original World Trade Center's collapse to manage construction and occupancy risks associated with the new projects at the site.

One of the most significant ways in which the events of 9/11 have informed risk management at the Trade Center site, say risk managers and safety experts involved with the rebuilding, has been in the engineering and construction of the new high-rise towers. Silverstein Properties' reconstructed 52-story 7 World Trade Center, which was built across the street from the actual Trade Center site in 2005, served as the model for how the four Trade Center site towers would be designed from the standpoint of safety and security.

“We recognized two important challenges: that (building) codes would be changing; and our design needed to anticipate this and, in fact, exceed the potential code changes,” said Shari Natovitz, vp of risk management for Silverstein Properties. The design also would need to “exhibit the life-safety features required to assure tenants that this would be among the safest buildings in the world. We and our design consultants met that challenge by designing above code.”

All four of the World Trade Center site's new towers will be constructed around reinforced, monolithic concrete cores that span each building from top to bottom, which risk managers for the Port Authority and Silverstein said provide increased capability to withstand a violent impact similar to the 9/11 attacks. Additionally, each tower's base, particularly that of the flagship 1 World Trade Center, will be made of high-density steel and concrete to protect against ground-based catastrophes or attacks. In 2005, the New York Police Department insisted the Port Authority make additional safety and security adjustments to the base of 1 WTC, resulting in the removal of nearly all the windows and the use of even heavier, 14,000psi concrete—seven times the density of sidewalk pavement.

“It's a much different type of construction” than the original World Trade Center, said James Keane, general manager of operations, safety and risk management for the Port Authority. Mr. Keane said the original twin towers were built around segmented concrete cores and relied more heavily on perimeter steel columns to support their weight.

In addition to the solid, reinforced core columns and higher-density perimeter steel construction, Mr. Keane said designers incorporated several other safety and security elements that took their cues from the difficulties workers and emergency responders had in evacuating the twin towers on Sept. 11. The new towers all will feature widened, pressurized stairwells—with a dedicated stairway for emergency responders—concrete-protected sprinklers, emergency risers and communication systems, and protected tenant collection points on each floor.

“A lot of lessons from Sept. 11 were put into the design of the new buildings to best protect occupants and emergency responders,” Mr. Keane said, “and the result is a set of very robust towers.”

The events of Sept. 11 also informed to a large extent both developers' experiences in the insurance marketplace when the time came to seek coverage for their respective projects.

Silverstein Properties had just endured a complex and bitter dispute over insurance payouts from the first World Trade Center's collapse at the time it brought its projects to the marketplace in 2007. Though she was not with the company when it purchased coverage for the original towers, Ms. Natovitz said she was well acquainted with the “areas that required improvement either in strategy or execution.”

Paramount among them was contract certainty, she said, especially in consideration of the company's insurance dispute.

“Silverstein and Willis North America worked together to assure that a complete coverage form was part of the submission for each line of coverage,” Ms. Natovitz said. ”Willis then managed the process of assuring concurrency, and Silverstein rechecked the finalized contracts.”

While much of what happened at the World Trade Center on Sept. 11 has lent insight into reducing the risks of rebuilding the site, some lingering effects of the attacks have proven less helpful. In 2005 and 2006, when the Port Authority first brought its projects to the insurance market, there was little interest generated among U.S.-based insurers in the program, Mr. Keane said.

“The domestic market wasn't really ready for the World Trade Center construction,” Mr. Keane said. “Part of it was an overall market fear of terrorism, but the complexity of the project itself would involve hundreds of contractors working in close quarters together, and that all had to be protected as well.”

“We also had to rebuild a lot of relationships with the marketplace post-9/11,” he added.

Given the physical, emotional and political complexity of the work, Ms. Natovitz and Mr. Keane said working in concert to provide near-constant communication and detailed information to their brokers and underwriters was crucial to overcoming market nervousness about rebuilding on the site.

“Once you worked your way through the communication challenges, eliminating redundancies and eliminating any potential gaps, what we had was a profile that we could present to the insurance marketplace that demonstrated an across-the-board commitment to building out these projects as safely as possible,” Ms. Natovitz said.