According to the university's latest finance committee report, the ground conditions had cost it $1million by the end of February.
However, chief operating officer Stephen Willis said that was not expected to add to the overall budget of the project, which included a contingency for such risks.
The ground conditions were particularly inconsistent under the old west wing of the building, and could be assessed only after it was demolished to make way for a new structure, which will be linked to the existing Walsh building.
The conditions meant smaller piles were needed, which took longer to install.
The total cost of the delay and whether it would cause the project to be completed later than scheduled was still being assessed, Mr Willis said.
It was possible other parts of the project could be sped up to make up for the delay, he said.
