Frank W. O’Callaghan, Todd Randell
5 minute posters # 2014 Chicago
Building new pipeline infrastructure in highly congested urban environments is causing some interesting challenges for New Zealand engineers and construction companies, demanding innovative new pipeline solutions.
The Birkdale area in the former North Shore City, now part of Greater Auckland City, New Zealand presented such a challenge. The North Shore City Council (NSCC) needed to install a complex new gravity sewer main under residential suburbs at Birkdale to increase flow capacity of undersized discharge pipes from the sewerage network. The new pipeline was drilled at shallow grades through a range of challenging ground conditions including sandstone and soft organic soils. Complicating the planned installation were protected wetlands and vegetation in the Ridgewood Reserve and Eskdale Reserve, a crossing under the Eskdale stream and pipe invert depth of 28 metres or 92 feet from ground surface, under a developed residential subdivision. This heavily populated area has high traffic loading, minimal construction space and many existing buried pipe services with variable knowledge of their location. The continuous 1,048 metre or 3438 feet length drill shot represents one of the longest HDD drill shots completed within New Zealand.
This paper focuses on critical design elements of the project, and evaluation of the plastics pipeline material selection process, arising from the limited capacity HDD drilling equipment available to the contractor. The paper also explores estimated pull forces calculated during the bid phase, vs. actual pull forces recorded during the pullback.
