Preserving oceans and shorelines with HDD ocean outfalls

As a country that frequently experiences drought, Australia has been undergoing various projects to diversify its water supplies. One such aspect of this is the increasing construction and use of desalination plants, which are used to remove salt and impurities from seawater to produce a supply of fresh water. In a conventional desalination plant, water is piped from the ocean to the plant via an intake pipeline, before the desalination process is completed via methods such as distillation and reverse osmosis. The fresh water is harvested, and an outlet pipeline transfers the brine byproduct back to the ocean for diffusion.

While modern desalination plants are designed to impact as minimally as possible on the environment, their construction still contributes to environmental harm. Intake/outlet pipelines must be placed particular distances from shore, and this can potentially mean significant destruction of coastal dunes, bushland, coral reefs, and sea floor in order to excavate and place the pipes. However, one way of minimising this harm – as well as the likelihood of damage and degradation to inlet/outlet pipelines over time – is by installing them via HDD. So since today is World Ocean Day, let’s take a closer look at ocean outfalls.

Trenchless can help

Using an ocean outfall technique – also known as a shore approach – horizontal directional drilling is used to bore from the pipe start point, to its planned point of exit under the ocean. The pipe is pulled through the bored hole (usually with help from a specialist marine vessels), and voila – the pipe is in place, with no need to dig up the span of the pipeline and significantly damage vulnerable ecosystems. Other trenchless technologies, such as microtunneling, can also be used.

Ocean outfalls: a proven concept

While the technique might sound unconventional, HDD ocean outfalls have been being performed to great success for decades, for various applications other than desalination plants – namely, wastewater pipelines and communications conduits are also commonly placed via outfalls. Here’s a sample of some that we have designed and assisted with:

  • Onslow Desalination Plant: FPS completed preliminary and feasibility design for 2 x HDPE inflow/discharge ocean outfalls up to 950m and 500mm for this new desalination plant in Western Australia.
  • GSP Offshore Landfall: FPS provided for-construction trenchless engineering for this stage of the Midia major gas pipeline project, which incorporated Romania’s first ocean outfall. This outfall was 1514m long and 270m deep, under the Black Sea.
  • Tuas HDD Outfalls: FPS provided for-construction design and onsite project management for the delivery of two 7” threaded cable landing outfalls in Singapore. The bores were up to 420m long for new international fibre optic solutions.
  • Eyre Peninsula: Specialised FEED design and construction evaluation was completed by FPS for the drilling and installation of 4 x ocean outfalls for this new desalination plant in South Australia.
  • 2MON-27: FPS undertook specialised for-construction design for the drilling and installation of 4 x 100mm telecommunications (NBN) ocean outfalls of varying lengths in the picturesque bays of the NSW Northern Beaches.

We’ve also got several ocean outfall projects in process, including for wastewater discharge and communications – stay posted on our Experience page for more details.