Case study

Colac Pipeline – Olangolah Weir HDD Crossing

In 2011 Dunstans Construction Group, working closely with the Barwon Water Alliance, completed two horizontal directionally drilled crossings in the environmentally fragile Otway Ranges to replace multiple sections of the deteriorating Colac Pipeline.

  • Our team was engaged to drill two separate crossings. The first
    of these began at the wall of the Olangolah Weir beside the outlet creek, requiring a 292m installation of 500mm HDPE pipe.
  • Works were undertaken during the winter months when demand
    on the system was at its lowest. Challeneges such as inclement weather and poor access to the site (within a State Forest) were overcome using an extremely mobile and well-maintained D100 Drill Spread.
  • The “pose little or no risk” approach to the project saw us work closely with AMC to engineer a suitable drilling fluid that would have the least possible impact on the delicate Otway Ranges ecosystem. All aspects of the drilling operation were analysed and adapted to ensure best practice in environmental compliance.
  • The Dunstans team completed the design, engineering and construction of the new pipeline and successfully completed the pipe installation on time, using our Vermeer D100x120 Drill Spread.

This was the first project completed by the Vermeer D100 Drill Spread. Dunstans delivered this project on time, budget and with no time lost due to injury – satisfying rigorous safety and quality standards.

Project quick facts


Barwon Water Alliance


Installation of 500mm HDPE pipe by HDD

Project date

May – October 2011

Project location

Olangolah Weir, Otway Ranges, Victoria

Pipe type

500mm OD HDPE pipe

Crossing length


Project cost