Monitoring to continue on Hunter Expressway project

20 April 2012

Gas was detected on the $1.7 billion Hunter Expressway project this afternoon during routine drilling.

The gas has since dissipated but monitoring will continue across the weekend as a safety precaution.

The Hunter Expressway project is the largest road infrastructure project under way in NSW.

The project site has been subject to extensive coal mining since the 1900s.

To build the road the project team must stabilise the mine voids where major structures such as viaducts and interchanges for the expressway will be located. 

Mine maps were analysed and drilling investigations carried out to confirm locations of mines. Tunnels up to 110 metres underground were found along the project alignment.

To ensure the stability of the expressway all mine voids must be filled.

Around 3.30pm this afternoon, hydrogen sulphide gas was detected during routine drilling near Stanford Road Kurri Kurri. The gas had dissipated again by 5pm.

Drilling gear used on the project contained gas monitoring equipment which detected the presence of gas.

Contractors immediately set up a 50m exclusion zone and vacated the area. No workers were affected.

The gas was contained within the exclusion zone. While present levels are zero, further monitoring will continue throughout the weekend and further mitigation measures investigated if required.


The Hunter Expressway is being built in two sections. The 13 kilometre eastern section from the F3 Freeway to Kurri Kurri is being built by an alliance between Roads and Maritime Services (RMS), Thiess, Parsons Brinckerhoff and Hyder Consulting.  The 27 kilometre western section from Kurri Kurri to Branxton is being built by Abigroup.

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