Case study

Orford Sewer Outfall Project

In May 2016, Dunstans aligned with Jemrok on behalf of TasWater to design and construct an ocean outfall to service their Water Reclamation Plant at Quarry Point Orford, Tasmania.

  • The brief was to design and install a 225mm HDPE outfall pipe from the Water Reclamation Plant, underneath the sandstone cliff and exiting in 9m of water approximately 230m off shore.
  • The Quarry Point mine provided the sandstone used to construct the Melbourne GPO built over a period of 48 years between 1859 and 1907.
  • This was the first HDD outfall project undertaken by the newly formed TasWater Corporation.
  • Due to the limited space available for site set up at the plant, the Dunstans D100 HDD Rig Spread was chosen as the most capable package to successfully complete the installation.
  • This package consists of our Vermeer D100 x 120 HDD rig and our in-house designed and constructed DCS450 cleaning system. This spread is compact and self-contained allowing for easy mobilisation and a minimal site footprint.
  • The outfall was constructed by drilling the pilot hole with a wireline survey tool out to the seabed, plugging the pilot after verifying the exit location and then forward reaming using a state of the art PDC cutter. This minimised the amount of cuttings and drill fluid being released into the sensitive marine environment.
  • Mobilisation of equipment from the mainland, completion of works and demobilisation back to the mainland were carried out in a single rotation of one month

Dunstans successfully completed the project well within the programmed time frame without incident in an extremely constricted workspace and environmentally and culturally sensitive location.

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Project quick facts

Client

Jemrok/TasWater

Description

Installation of a 225mm HDPE pipe to serve as an outfall for the Quarry Point Water Reclamation Plant

Project date

May-June 2016

Project location

Orford, Tasmania

Pipe type

225mm SDR 9 HDPE

Crossing length

500m

Project cost

$750,000

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