Of the 1330 properties zoned orange for further investigation in June, some 860 properties in Kaiapoi and 80 in Pines Beach were today reclassified in the red zone, meaning they will need to be abandoned.
A further 220 properties in northern Kaiapoi have been rezoned green, or safe to rebuild, while another 70 in western Kaiapoi remain in the orange zone and require further investigation.
The Government will offer to buy the 940 properties reclassified into the red zone, while a decision on the 70 orange zoned properties would be made within the next few weeks.
Mr Brownlee said today's decision was not an easy one given the size of the town and the incredible patience shown by its residents since the first earthquake in September.
"Many options have been exhaustively considered, however, in full evaluation of the facts today's decision was also clear cut," he said.
Mr Brownlee said a "huge amount" of geotechnical engineering advice and a range of other factors were considered.
"One inescapable fact was that the land and critical infrastructure beneath the hardest hit parts of Kaiapoi and Pines Beach was so badly damaged that any remediation solution would have required the complete removal of all homes we're zoning red today."
Repair in all the red zone areas would not only require raising the height of the land, but also a complete reconstruction of essential infrastructure like sewage, water, electricity and roading.
"This, like other areas we've zoned red, would have meant residents would have been forced off their land for a period of years," Mr Brownlee said.
"There were also no guarantees that the remediation solutions available, regardless of cost, would have worked."
Significant Government-funded land remediation works were due to begin in the Waimakariri District at the end of June, but these were put on hold so assessment of the impact of the quakes could take place.
"That impact was significant," Mr Brownlee said.
Homeowners in the red zone would receive a Government offer to buy their properties at the 2008 valuation that was in place before the September quake struck last year.
Personalised packs had been due to arrive today to coincide with the announcement, but disruptions to postal services had prevented that, so packs would arrive in the next few days.
Mr Brownlee said it was important to release the information as soon as possible.
"Today's news will be difficult for many people who've bravely hung on for nearly a year in the hope their property could be built on," he said.
"While the news will disappoint some it also provides a clear, and we believe fair path ahead for the hardest hit residents of the Waimakariri District."
