What next after the 2nd Geotech report – Zone C Processes

The main report contains outlines on the processes to be followed in remediating land according the zone in which a property is located. These are reproduced below:

Zone C is Retreat Road and many of the streets closer to the river.
2.3 Zone C
Zone C is the land which has generally suffered very severe or major land damage, or is close to the areas of major remedial works. It includes a buffer area, where required, to provide adequate space to undertake the works and protect neighbouring buildings. Zone C also includes some areas of moderate land damage which require a wider-scale, coordinated remediation programme than the land in Zone B. Land remediation and building work in Zone C will require suburb-specific geotechnical reporting, engineering design and major remediation works. These will differ from suburb to suburb to meet the target land performance standard as adopted by the Government. Repair or rebuilding of houses in this area will need to be staged so that repairs and rebuilding work can be undertaken in association with land and infrastructure remediation.
2.3.1 Process
• Suburb-specific geotechnical reporting is being undertaken and will provide engineering guidance for the coordinated land repair strategies.
• Where buildings do not need to be rebuilt but can be repaired, cracks located on accessible land should be filled with sand or gravel (depending on crack width) and the land lightly compacted with a plate compactor or small roller. Additional works may be required where cracks or significant volumes of ejected sand are present beneath dwellings.
• Demolish buildings and damaged hard surfacing where re-levelling or repairing is not economically practical. Where land cracking is severe, sub-excavate the ground and recompact the upper 1-2 m to achieve a hardfill raft beneath the building platform and main access way, and as much land beyond the building platform and main access way as is practical.
• Where perimeter treatment works are undertaken to reduce the extent of lateral spreading under a similar sized earthquake event, building foundations can be constructed subject to simple shallow soil testing confirming suitable foundation conditions.
• Where perimeter treatment works are not practical, consideration could be given to constructing specific foundations that can accommodate similar levels of ground movement, as experienced from the Darfield Earthquake sequence, without structural collapse.
2.3.2 Programme outline
It is recommended that works within Zone C in any individual suburb be staged to allow the maximum number of people to remain in their homes for the longest period possible. Staging of works will allow rebuilding to commence as soon as one portion of land remediation work is completed.
The actual timeframe and number of stages involved will depend on a number of factors including detailed design and location of the land remediation works, obtaining necessary regulatory approvals, and co-ordination with infrastructure works. Once each stage of the land remediation works is complete, rebuilding works in that stage will be coordinated by the private residential insurance companies. It is likely that land remediation works will occur concurrently in a number of areas to ensure the works can be completed as quickly as possible.
A flowchart demonstrating the indicative programme is provided in Figure 5.3 (page 14).

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