Case study

Mitcham Stormwater HDD Outfall

In 2014, John Holland on behalf of the Mitcham and Rooks Road Alliance (MRRA) engaged Dunstans Construction Group to complete a storm water outfall as part of the MRRA Rail Separation project.

As part of the project, a storm water retention basin was constructed adjacent to the rail corridor and was connected into an existing storm water drain via a directionally drilled outfall.

  • Dunstans bored along a 1.2m easement between a building, existing sewerage and storm water pipes and the rail corridor to install the new 500mm HDPE storm water outfall.
  • A key aspect of the project included ‘at grade’ targets allowing gravity to drain the retention basin, eliminating the need for pumps.
  • The Horizontal Directional Drilling (HDD) had to be completed quickly to ensure minimal disruption to the construction of the retention basin and the MRRA’s overarching project milestones.
  • Our team designed, engineered and constructed the new storm water outfall, successfully completing the pipe installation on time, using our Vermeer D100x120 Drill Spread.

The Dunstans HDD team overcame many challenges during the project. Harsh weather conditions halted other areas of the project, while reinstated ground conditions made maintaining borehole integrity difficult. Space for our hardstand was only 3m wide at the entry point and access to the site was tight, due to its suburban industrial site.

Despite these potential setbacks, the project was delivered on time, within budget and meeting rigorous quality and safety standards.

Project quick facts


John Holland Group


Installation approximately 100m of 500mm HDPE pipe by HDD

Project date

March – April 2014

Project location

Melbourne, Victoria

Pipe type

500mm OD HDPE SDR11 pipe

Crossing length


Project cost