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Microtunnelling the Ocean Outfall Pipeline, Christchurch, New Zealand


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Author J Moore, R Fleming and G Jones


An ocean outfall is currently under construction in Christchurch, New Zealand
to transfer treated wastewater from the existing treatment ponds at the city
wastewater treatment plant to diffusers located 3 km offshore. The New Zealand
$85 million project comprises a new pump station and 5 km of 1800 mm diameter
pipeline with a design capacity of 6.0 cumecs. The pipeline comprises 2.3 km of
concrete pipe installed by microtunnelling and 2.7 km of polyethene marine pipe
installed by dredge and lay.

This paper describes the consent process, key environmental and community
constraints, the tender process, risk provisions included in the contract, the
type of contract, partnering provisions, geotechnical design issues and the
pipejacking construction activities and issues.