As part of Wellington Water’s work to improve the earthquake resilience of the water supply network across the region, the first phase of an exploratory drilling program was recently undertaken within the harbour to assess the confined freshwater aquifer present below the sea floor. The project will ultimately involve a sub-sea water well installation on the harbour floor into an artesian aquifer – something that has never been constructed before.
ENGEO were appointed by the Griffiths McMillan Joint Venture team as Design Manager and Geotechnical Engineer for the project.
Variable and inclement weather conditions in the Capital meant conducting a delicate drilling programme over water was challenging at times. Health and Safety was paramount and significant systems and processes were put in place to ensure workers were safe and well informed.
The aim was to prove the presence and capacity of the aquifers beneath the harbour at two strategic locations and then collect samples to test the fresh water for chemical composition.
Working with the project structural and mechanical engineers, ENGEO undertook state of the art liquefaction and lateral deformation analysis to model the water well beneath the harbour floor. The presence of mapped faults in the vicinity of the well sites added a strong seismic dimension to our work.
ENGEO fostered a strong collaborative approach when working with the project structural engineers and GNS Science to determine key geological and seismic risks during the detailed design phase of the works.