Allan King & Sons has an impressive portfolio of successfully carrying out both remote and local contracts – from major road intersection upgrades, prawn farm ponds, flood immunity works, constructing multiple bridges from Dundee as far as Timber Creek, to manufacturing construction materials, and the operation of fixed and mobile concrete batching plants.

But constructing more than six kilometres of the Arnhem Highway – a large portion of which was a new alignment; in effect, building a two-lane, raised road, including culvert installation, intersection works either end of the project, simultaneously with the construction of 13 bridges – was tough even by the Territory’s standards.

The stretch of road crosses the formidable Adelaide River floodplains – blacksoil plains that flood every monsoon, often closing the highway for up to 10 days at a time, disrupting the lives of residents, tourists and businesses in Arnhem Land and Jabiru.

“It was a tricky job carried out in tough conditions,” says operations manager Mitch King. “There were construction elements that were new to the NT, which made it interesting, but we’ve got a good depth of technical support internally and years of experience in this kind of work.”

Challenges included:

• Working on a “blacksoil” plain where soft soils deposits ranged in depth from 5 metres to 22 metres, making the entire work zone subject to settlement and movement. Once the black soil is saturated, it becomes inaccessible for machines, trucks and even light vehicles. Temporary accesses had to be constructed to get to and from the work zone.

• Constructing of a special working platform and drainage rock layer, suitable for ‘wick installation machines’.

• The installation of over 60,000 individual wicks which totaled approximately 700,000 lineal metres, with two modified drill rigs, – a first for the Territory.

• Multiple plates installed throughout the alignment to monitor and assess the settlement data of embankments.

• Employing a complex traffic management system to maintain public access across the Adelaide River Bridge during the work, including allowing access to a jumping crocs attraction.

The work has reduced flooding on the highway to less than four hours a year.

The $35 million contract won the $30-75 million category at the 2022 NT Civil Contractors Federation awards.

Works included building 13 new bridges, which was carried out by another born-and-bred Territory company, Advance Civil.

The Federal Government contributed $62.3 million and the Territory Government $15.58 million to the cost of the overall project.

Allan King & Sons employed 25-30 workers directly and used 12 local subcontractors and 117 suppliers on the job, which took more than two years, including a nine-month “settlement” period where only monitoring occurred.

“All of the workers were local, except a few specialists, such as the wick installers, who had to be brought in from interstate,” says Mitch.

Allan King, who has more than 40 years’ experience in road construction, oversaw the project from beginning to end.

The project manager was John Klaas, supported by Xinsike “Cisco” Ao, Kieran Blackburn in the office and Troy King on the ground.

Mitch says the success of the project was not the management team but everyone onboard – the “experienced and hardworking” men and women in the Allan King & Sons team, as well as subcontractors and suppliers.

He says building strong, transparent relationships raises confidence on all sides.

“Sound business practices and experience, subcontractor management and a high level of communication were a strong part of the successful completion of this project, safely and to a high standard.”

Allan King & Sons employs 80-100 full-time equivalent staff and has in more than 350 pieces of plant and equipment, including dozers, laserequipped graders, loaders, excavators, compactors, rollers, body trucks, agi trucks, dump trucks, moxies, mobile crushers and screens, reclaimers, side-tippers, water trucks, prime movers and floats.

Services include civil construction and engineering, bulk and detailed excavation, plant and equipment hire, manufacturing of construction materials, mobile crushing and screening, fix and mobile concrete supply, bridge construction, and subdivision works.

The company has grown since being established by Allan and his wife Sandra 27 years ago, with three sons, Luke, Troy and Mitch, forming part of the family business, which is now one of the most successful civil construction companies in Northern Australia.