15 October 2014

What’s underneath Auckland’s city centre?

More is known about what lies beneath our city centre with the completion of 127 cored boreholes drilled as part of the City Rail Link (CRL) project.

The boreholes show a piece of Auckland’s history with a mixture of volcanic rock, sandy sediment, reclamation material and groundwater unearthed along different parts of the CRL route.

More than 3000 metres of core samples have been removed which if laid end to end would cross the Auckland Harbour Bridge three times.

The latest series of boreholes were drilled from June to October and covered the entire route of the City Rail Link from Britomart to Mount Eden. Core samples have been removed from each borehole to show the ground make-up underneath. Water monitoring equipment has been installed in a number of these boreholes.

“This round of work concentrated on areas identified as requiring further exploration,” says project director Chris Meale.

“The drilling programme is an important element of progressing and refining design on the CRL over the next 18 months.”

A number of boreholes in the Karangahape Road area investigated the interaction between ground water and the proposed CRL station below Pitt Street and Beresford Square. In Eden Terrace they looked at areas where the CRL tunnels will rise to meet the existing rail line.

“I would like to thank the property owners that allowed drilling in their property and put up with disruption during the drilling programme,” he says.

Ground investigation work for the CRL is continuing. Over the next few months a pump test will be carried out to further investigate underground water near the Karangahape Road station and trenches will be excavated in some sites along Albert Street to determine where utility services are buried.

ENDS

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