"It [Chapel St building] was around eight or nine per cent and we deemed that to be quite a significant harm [risk], both to our staff and nearby public so we made the decision to demolish it," Mr O'Donnell said.
Work began on Monday and Mr O'Donnell expected it to be completed by the end of yesterday or sometime today .
The first GWRC building to be demolished was in Victoria St and was due to a "risky" brick wall.
"That was on the pedestrian side so we were quite concerned about how that would fare in a reasonable earthquake."
Mr O'Donnell was unsure of the demolition cost but said an effort to minimise it had been made by recycling shed material.