Glenbrook Estuary Crossing

Location:

Glenbrook Beach and Clarkes Beach, Auckland

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Project Overview:

This HDD project required the installation of a 140mmOD PE100 SDR 7.4 pipe (mud return line) and two separate 280mmOD PE100 SDR7.4 water pipelines to be installed over 740m at depths in excess of 20m under the Taihiki River.

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Challenges:

Due to cliff erosion CDS worked with the client to develop an alternative HDD design alignment and profile that would avoid long term risk to the new pipelines.

The installation forces required to install small diameter PE pipelines over long installation length required accurate pull force and stress calculations. The methodology for pipeline pullback was carefully planned to consider capstan forces, pipe roller positioning and buoyancy control. Additionally, real time data logging of forces applied to the pipeline using a smart downhole stress gauge were captured in the field to ensure the pipes were not overstressed.

Due to the sensitive marine environment, hydraulic modelling and a hydro-fracture assessment was undertaken by CDS. This including modelling of drilling pressures considering the proposed equipment and methodology and drilling fluid rheology. Formation fracture pressures were calculated using cavity expansion theory and data captured in the project geotechnical investigation.

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