ENGINEERS AT the World Trade Center site have discovered a 30m long gash in one of the walls of the 'bathtub' structure underneath the collapsed towers.
The huge crescent-shaped hole runs along the top of the slurry wall which retains the River Hudson flowing alongside.
Before the September 11 terrorist attacks the walls were secured by the buildings above, but since then they have been held in position largely by debris which fell into the basement.
Engineers, fearing inundation by the Hudson if the walls failed, have been gradually excavating the debris and installing ties to secure them (GE March).
George Tamaro, a partner at consultant Mueser Rutledge, is leading the excavation and stabilisation work. He said pumping around the hole at the south east corner of the site near the junction of Greenwich Street and Liberty Street was ensuring that water did not flood the basement.
'We knew the hole was there and believe it was caused by the top of Tower Two crashing into the basement, ' he said. 'However we did not know the extent of the damage. '
Tamaro said work to uncover debris near the hole was proceeding very gently. It is intended to rebuild the lost section of wall and the top level of ties near the hole cannot be installed until this is completed.
A new access bridge into the excavation has now been finished. This has allowed searching of debris below the original access road to begin.
Tamaro said it was hoped that the bulk of the bathtub work would be completed by the end of this month.