NPR Dredging & Reclamation Works
Brisbane Airport is located on an old Brisbane River delta. This means the underlying soils are soft watery mud and silt down to 35 metres.
Significant preparation work was required to remove the water to create a solid base for building on. This was achieved by inserting 330,000 vertical wick drains into the underlying soils and piling 11 million cubic metres of sand on top to compress the soils and squeeze the water out.
The sand was extracted from the Middle Banks in Moreton Bay by the Jan de Nul trailer suction hopper dredge ‘Charles Darwin’ – one of the most modern and powerful dredges of its type in the world. The “Charles Darwin’ pumped the sand ashore through a 1.1 metre diameter pipeline which stretched for 8.5 kilometres to the furthest point of the site.
Use of the dredge eliminated the need for hundreds of thousands of truck movements on Brisbane roads.
The dredge site in Moreton Bay was carefully selected to ensure there was no impact on marine wildlife in the bay. It was 12 kilometres from the nearest sea grass beds frequented by dugongs and turtles and away from other areas with a high abundance of other marine life.
The dredge site was just off Moreton Island adjacent to Brisbane’s main shipping channel and confined to a long, narrow linear footprint with gently sloping batters. The sand is of an extremely high quality with negligible levels of fines, silt or mud.
The Dredging Process:
- The ‘Charles Darwin’ extracted clean marine sand through a suction head similar to that of a vacuum cleaner.
- It did not infringe on the deeper soil layers and took fine marine sand only.
- Dredging did not interfere with marine life such as dolphins, whales, dugongs or turtles.
- No significant noise, visual or landscape issues impacted on Moreton Island residents.
- The site was carefully selected to avoid other users of the bay such as commercial or recreational fisheries or tourism operators.
- A 24/7 real-time water monitoring program was in place to ensure all water quality limits were adhered to.
Delivering the sand to the runway site:
- The sand was mixed with transport water taken from the Brisbane River at the dredge mooring site.
- The sand was pumped through the pipeline in a water/sand slurry at a 5:1 ratio.This meant that for every 30,000 cubic metres of sand delivered, 150,000 cubic metres of water was also delivered to the site.
- The transport water was channelled into holding ponds for management until it reached the required water quality standard for release back into the drainage system.
- The ‘Charles Darwin’ completed pumping the required 11 million cubic metres of sand on 7 December 2014 – almost two months ahead of schedule.
- Further information on the dredging process can be found in the BAC Fact Sheet ‘Dredging and Reclamation’.
The Jan de Nul Trailer Suction Hopper Dredge (TSHD) “Charles Darwin” completed pumping the last of 11 million cubic metres of sand ashore to Brisbane Airport’s New Parallel Runway site on 7 December 2014 – two months ahead of schedule. Working 24/7 and averaging three round trips a day to deliver 30,000 cubic metres of sand at a time, the ship’s powerful engines pumped the sand ashore via a 1.1 metre diameter pipeline which stretched for 8.5 kms to the furthest end of the site.
The use of the pipeline avoided the need for thousands of heavy truck movements on Brisbane roads and contributed to Brisbane Airport Corporation, along with contractor BMD, winning the Excellence Award in the Environmental Category of the 2014 Queensland Engineering Awards. The pipeline was just one of a number of environmental initiatives taken by BAC to protect and enhance the environment during the project.
The reclamation site has now entered its settlement phase and will be left to consolidate for up to four years before it can be built on.
Thank you Jan de Nul for your contribution towards building Brisbane’s New Parallel Runway.
Fact Sheets on the project
Video explaning the Dredging process:
New Parallel Runway - Overview
New Parallel Runway - Reclamation Works
New Parallel Runway - Environment: