+ Heysen Tunnels - Saccardo Constructions (SA) Pty LtdSaccardo Constructions (SA) Pty Ltd

Heysen Tunnels

This project required innovative concrete placement methods.


Sector: Transportation

Location: Adelaide-Crafers Highway

Client: Federal and State Government joint venture

Project Value: $151 million

Construction period: 1998 – May 2000


  • Each of the 2 tunnels are 500 metres long and 10.5 metres wide
  • Each tunnel has 3 lanes, each 3.5 meters wide
  • Each tunnel has a 90km/hour speed limit and takes about 20 seconds to drive through

The Heysen Tunnels and Mount Osmond Overpass are the centrepiece of a multi-million dollar upgrade of National Highway One through the Adelaide Hills.

The project, funded by Federal and State governments, saw a narrow and dangerous road – which followed the path of bullock tracks made more than a century before – upgraded to the latest National Highway safety standards.

At the heart of the project, two 3-lane tunnels were dug through solid rock to eliminate the worst of the old road and remove dangerous hair-pin corners and steep gradients which resulted in increasing numbers of serious accidents.

Saccardo Constructions were the chosen contractor to lay the concrete road base and pour the portals for the tunnels. Daily pours for two months were needed to keep to the project’s tight program. A total of 14,000 square metres of concrete were laid, involving some 4,000 cubic metres of concrete.

It is with great pride that the main gateway into Adelaide showcases the excellent work of Saccardo Constructions.

Mount Osmond Overpass

In conjunction with the Heysen Tunnel project, a major overpass had to be constructed over National Highway One to provide access and egress to an area of the Adelaide Hills not otherwise easily accessible.

Known as the Mount Osmond Overpass, this project was particularly difficult as the existing turn-off had to remain open during construction and because of the natural topography of the area, access to the site was not easy.

Further, tens of thousands of vehicles – from light cars to double-length semi-trailers passed by each day as part of traffic on the National highway system. In conjunction with the tunnel project and because of their expertise, Saccardo Constructions was awarded the contract to construct the support abutments and bridge for the overpass.

The one-meter thick, nine-meter high abutments required Saccardo personnel to climb into the structure to guide the concrete placement hose through the labyrinth of reinforcement to ensure correct placement and vibration of the concrete.

This structure is one of the many civil projects undertaken by Saccardo Constructions requiring innovative concrete placement methods.