Validating HDD Pull Force Predictions Through Real-Time Monitoring: CDS New Zealand’s Taihiki River Crossings

Abstract

Specialist HDD contractor CDS New Zealand Limited recently completed the successful installation of three polyethylene water pipelines beneath the Taihiki River, linking Glenbrook Beach and Clarks Beach in Auckland. Commissioned by Watercare Services Limited, the project replaced a failed marine-laid watermain serving the rapidly growing Glenbrook Beach community. The design comprised three horizontal directional drilling (HDD) crossings over a 760-metre alignment, incorporating one 140mm OD SDR7.4 PE100 pipeline and two 280mm OD SDR7.4 PE100 pipelines. To minimise environmental and cultural impacts, including erosion-prone cliffs and the historically significant Waiau Pa area, the alignment was shifted west of the original alignment. Drill profiles were designed to depths reaching RL -19m, targeting sandstone and siltstone units of the East Coast Bays Formation. Given the 45-minute one-way travel between the HDD compound and pipe sites, the installed 140mm pipeline was utilised as a drilling fluid return line during subsequent installations. A key challenge was the pullback of small-diameter polyethylene pipes over long distances, which introduced risk of stress-related damage. Initial calculations based on ASTM F1962 informed pipe selection, with additional modelling using the PRCI method for academic comparison. Differences between the two prompted CDS to deploy a smart strain gauge between the pulling head and swivel. This allowed real-time monitoring of pull forces and annular pressures. 1 No-Dig Down Under 2025 Validating HDD Pull Force Predictions Through Real-Time Monitoring: CDS New Zealand’s Taihiki River Crossings Sam Rowdon The resulting data enabled responsive pullback adjustments and provided valuable comparative insights into the accuracy of HDD force prediction models. This project offers a unique case study in both installation practice and data-driven pipeline stress evaluation.

Techniques