Apparently in response, the final version described the "box beam column footings that outline the space where the twin towers stood."

Construction is underway for abutments and column footings of the bridge as of early 2011.

Excavation of 18,000 cubic yards of bedrock for the column footings will begin in February, he said.

While their column footings reached bedrock, a foundation wall had to be built around them to resist the tremendous inward pressure from the riverside soil.

It is a type of combined footing, consisting of two or more column footings connected by a concrete beam.

Their exterior walls will align with the remnants of the towers' original column footings, preserved at a level just above bedrock.

It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.

Column footings will be placed in 19 locations, and steel will be driven down as much as 15 feet into the bedrock.

At the bottom of the 70-foot-deep foundations are many steel column footings defining the full outline of the north tower and much of the south tower.

Perhaps the most important new element will be the provision of access to the base of the tower outlines, which are still marked by remnants of column footings.

No simple structure, this skyscraper will rise directly over the outbound PATH tracks and over utility lines that must be relocated around the tower's column footings.

NELSON DE MILLE place where the bedrock met the hewn and mortared stone of the column footing.

NELSON DE MILLE Gallagher's light swung up and focused on the column footing, then probed the space where she was hiding.

Most important, Mr. Arad's original design did not provide access to structural remnants of the twin towers, like the perimeter column footings that can still be found at the bottom of the foundation.

The Coalition of 9/11 Families, which has championed the preservation of the column footings, said yesterday that it was encouraged by the new plan, though not wholly satisfied, since it failed to address the south tower footprint.

Those remains include column footings from the twin towers, the foundation wall, smoke-scarred ruins of the underground parking garage, the tubes and terminal of the Hudson & Manhattan Railroad and a stairway leading to the vanished plaza.

The basement, which is closed to the public, contains an archeological surprise: the original 1875 station platforms and column footings for the 1897 station above, made up of dressed stone copings salavaged from the original wall of the open cut.

Irene Chang, the vice president for legal affairs and counsel to the development corporation, said the agency was committed to keeping parts of the slurry wall visible, allowing access to the column footings and preserving the tower footprints as voids.

Severed during the clearing of ground zero, many steel and concrete column footings that still outline the perimeters of the twin towers will be made part of the memorial itself, as will a 70-foot-tall, 250-foot-long section of the original slurry wall.

In the review, for instance, a balance may have to be found between preserving the remnants of the towers' footprints, which are still partly visible as rusted steel column footings around the base of the site, and accommodating a permanent PATH terminal.

Typically, columns are centered on column footings, but in conditions where columns are located directly adjacent to the property line, the column footings may be offset so that they do not encroach onto the adjacent property.