The Port Hills has not suffered the same type of area-wide damage (namely liquefaction and subsequent lateral spreading) as the Canterbury Plains area.  Assessment of the area was carried out by the Port Hills Geotechnical Group (PHGG), comprising six geotechnical engineering companies and was led by the Christchurch City Council to collect and review data from geotechnical hazards arising from the earthquakes of 22 February and 13 June.

The primary objective of the PHGG was to assess existing damage to properties, lifelines and infrastructure from recent earthquakes and their aftershocks. The secondary objective was to identify areas that are at heightened risk from large scale geotechnical hazards and to prepare mitigation measures to deal with those hazards.

Rapid site specific assessments were undertaken by the EQC Land Damage Assessment Team (LDAT). Where LDAT observed any life-safety issues, these were notified to the Christchurch City Council. The land damage categories applied to every property were:

The land damage map from PHGG (marco-scale hazards) was combined with the site-specific EQC LDAT land damage map by Tonkin & Taylor to produce one coherent and consistent map to allow decisions to be made regarding zoning.

Green zoning means that homes in this zone can begin the repair and rebuild process.  Remaining white zone  properties means that more information and assessment is required.

Non-residential properties (those properties used for commercial purposes, schools, hospitals, council facilities, parks and reserves) are not included in the residential mapping work undertaken by PHGG and T&T and, therefore, remain white on the map.

At this stage rural residential properties are zoned white as there is no rapid way of identifying them in the land use databases. They will typically be zoned green as they are identified.

The greater Banks Peninsula area from south of Governors Bay, including Diamond Harbour, is not included in this zoning.  Ongoing mapping will continue in this area.  At this stage it is considered that there will be only a few pockets of significant land damage present across the greater Banks Peninsula, however, this is yet to be confirmed.

Within the initial green zone for Port Hills there are properties with Section 124 notices issued to prohibit entry. They have been issued because they have localised geotechnical hazards, the building poses a risk due to structural reasons, or the property is at risk from failure of other property or infrastructure.  The change from white zone to green zone does not change that status of these individual properties.