Another layer of concrete is poured, creating a composite flooring structure about 10 inches thick.
A layer of concrete separates many of the new homes from toxic soil, a legacy of the area's industrial past.
He added that the cracks affected only the top layer of concrete and did not pose a structural problem.
A triple layer of concrete and steel has to deal with this perilous circumstance, a job that the old dock wall might otherwise have done until doomsday.
"But when there's not enough air space for the freezing water to expand into, it can pop off the top layer of concrete".
In Minneapolis, the bridge, parts of which were getting a new top layer of concrete at the time of the collapse, was carrying tons of equipment and material.
Spalling or scaling occurs, Mr. Roman said, when water that has seeped into the top layer of concrete freezes and the surface breaks off in layers.
In 1995, it was reported that a layer of concrete had been discovered under the stage floor, one to four inches thick.
Gary Bucci, the general contractor, said that upgrading the building to meet current electrical and plumbing codes has at times required drilling through the thick layer of concrete.
Yesterday, another investigator said the work was in its preliminary stages, with the backhoes hacking through a layer of concrete before they can begin digging in earnest.
The foundations and first layer of concrete, incorporating rubble from an old patio, have gone in, and there will be insulation and more concrete.
