Blenheim Urban Growth Study Geotechnical Evaluations

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Blenheim Urban Growth Study Geotechnical Evaluations

Through its Growing Marlborough project, Council has been undertaking investigation of areas having potential for urban expansion and considering the issues associated with that process. Part of those considerations is the geo-technical make-up of the soils and the potential for those soils to liquefy in the event of an earthquake. For that purpose tests were carried out on the periphery of Blenheim to generally characterise the soil properties.

Blenheim Urban Growth Study Geotechnical Evaluation Stage 2 Site Investigations

Geotechnical investigations and assessment of proposed growth areas to the north, east and southeast of the city were previously carried out in early 2012 ((pus, 2011;2012a). The investigations showed the areas to the east and southeast are underlain by significant thicknesses (> 15 m) of loose materials which are susceptible to liquefaction. Consequently, these areas would require considerable cost and resources to develop.

The geotechnical appraisal of the ground conditions and suitability of the land for development recommended that land which is more stable to earthquake hazards be developed (Opus, 2012b). The Council therefore developed five new areas to the northwest, west and southwest of the city for possible urban growth and engaged Opus to carry out investigations in the new areas to assess the geotechnical issues there, particularly relating to the hazard posed by liquefaction.

Blenheim Urban Growth Study Geotechnical Evaluation Stage 1 Site Investigations

The project comprised an evaluation of the overall seismic character of the district, a series of specific sub-soil tests then an assessment of the test results.
The objective of the project was to obtain an indication of the development potential of specified areas and an indication, if required, of the scale of further investigations.

The investigation was carried out in three parts:

  • A general review of seismic hazards
  • Sub-soil investigation
  • Interpretation of the field results.

Below is the Interpretation Report. Council’s Environment Committee has considered the Interpretation Report. The Committee resolved:

  • That the growth areas E1 (Dillons Point Road), E2 (State Highway 1/Alabama Road) and SE (Tavera Street/Alabama Road) be excluded from the Growth Strategy and from further Council rezoning consideration
  • That further geotechnical investigation of growth area Na-Nb (Old Renwick Road) be undertaken to create a representative risk profile for development in this growth area.
  • That the implications of the above on the Southern Marlborough Growth Strategy be referred to the Resource Management Plan Review Sub-committee for further consideration
  • That the landowners of the growth areas be supplied with a copy of the report
  • That the report be publicly released once notification of landowners is completed

The reason for the decision is that the sub-soils in the localities identified as E1, E2 and SE have significant development constraints due to the presence of soils having the potential to liquefy during major seismic events. It would therefore be inappropriate for Council to propose zoning this land. Further work is being undertaken to test the ground conditions at site Na-Nb.

  • For more information on the Na-Nb proposals see pages 125-126 of the Southern Marlborough Urban Growth Strategy
  • For more information on the E1 and E2, proposals see pages 129-133 of the Southern Marlborough Urban Growth Strategy
  • For more information on the SE proposals see page 134 of the Southern Marlborough Urban Growth Strategy

Go to Southern Marlborough Urban Growth Strategy