With the introduction of the geotechnical assessment guidelines in 2011, the Council has been requiring geotechnical reports for all subdivision applications.

Geotechnical requirements for subdivision applications

With the introduction of the geotechnical assessment guidelines in 2011, the Council has been requiring geotechnical reports for all subdivision applications.

More information is now available about liquefaction risks including Environment Canterbury’s recent liquefaction hazards study.

Recent changes made to the subdivision guidelines in light of that Environment Canterbury study mean that the Council now has more discretion about what sort of geotechnical information it will require with subdivision applications.

At the subdivision consent stage, the Council has a duty to ensure that there is a stable building platform on all new newly created lots. For a large part of Selwyn district the additional information now available has demonstrated that the land is stable without the need for a geotechnical investigation.

The Partially Operative District Plan has a liquefaction damage unlikely overlay for the purposes of risk assessment. Please refer to this in the context to your proposal.

Smaller Subdivisions

For smaller subdivisions in this overlay the Council is not going to require, in the first instance (there may be some special circumstances that result in the need for some geotechnical investigations), geotechnical investigation reports for the smaller subdivision consent applications from 1 August 2013.

Larger Subdivisions

For larger subdivisions within this overlay, ie those exceeding 15 lots, a geotechnical investigation will still be required, given the scale of development and size of investment.

In other parts of the district

Geotechnical reporting is still required for all subdivisions outside the overlay.

Potential Liquefaction Zones and Ground Stability Issues

There is potential liquefaction hazard in the eastern areas of the district (Lincoln, Tai Tapu and Prebbleton area), possible slope stability issues along the high terrace faces on the Rakaia and Waimakariri Rivers, and potential slope stability and foundation bearing issues within the foothills and mountainous areas. Geotechnical investigations to address these and any other ground associated issues are needed.

Plan Change Stage

A geotechnical report is also necessary at the plan change stage in any part of the district.

Geotechnical reporting should follow the requirements of the current Ministry of Business Innovation and Employment guidelines and include subsurface testing.