ENGINEERS WERE this week preparing to shore up a 25m deep, 1km long retaining wall surrounding the World Trade Center (WTC) basement this week to stop it collapsing.
Before the WTC towers collapsed on September 11, the diaphragm wall was supported by a series of horizontal slabs which made up basement floors.
These slabs were destroyed when the twin towers collapsed, and at the moment the wreckage is preventing the wall from falling in instead, said Mueser Rutledge Consulting Engineers partner George J Tamaro. Tarmaro is leading investigations into the foundations at the site.
Hasty removal of the debris by emergency services could cause the wall - known as the 'bathtub' - to collapse, warned Tamaro.
This could destabilise structures built on fill to the west of the wall or allow water from the Hudson River to flood the basement. Flooding would delay clear up work and increase structural damage.
Tamaro has advised that a detailed survey of the wall must be carried out and additional support put in before the emergency services start to clear the debris.
'We need to provide a temporary support of the wall by using anchors, ' said Tamaro, who worked on the original WTC basement construction.
When the wall was built it was temporarily supported with tieback anchors before the basement floors were complete. The anchors were then detensioned, but left in place.
Tamaro said the original anchors may now be retensioned or new anchors put in.
An internal bracing scheme may then also be applied.