Balickera Tunnel Remediation

Hunter Water
2021 - 2022

tunnel length


rock bolt installation per 12-hr shift


year deisgn life


bats safely removed

Abergeldie was awarded the remediation upgrade of the Balickera Tunnel for Hunter Water, a critical component of the Hunter Valley's water supply infrastructure. The tunnel forms part of the Balickera Canal which contributes over 50% of the water yield from the Williams River to the Grahamstown Dam. 

Completed during the Summer and Autumn seasons of 2021-2022, the upgrade extends the tunnel's design life by an additional 100 years, ensuring continued water supply from the Williams River to the Grahamstown Dam.

Scope of works

The works included:

  • Construction of a cofferdam at the downstream end of the tunnel to facilitate dewatering. 
  • Internal remediation works, including replacing existing bolts, spot bolting as needed with dental concrete at specific locations, and applying fibre-reinforced shotcrete from the tunnel roof to its base.
  • Establishment of equipment laydown areas. 
  • Upgrades to the existing access roads to accommodate construction and maintenance vehicles. 

Overcoming environmental and La Nina challenges

The Balickera Tunnel is a known roosting site for several threatened microbat species and the construction work was deemed to have a biodiversity impact on these colonies due to the temporary exclusion from the tunnel. The remediation works were carried out following a species impact management plan. Further, major flooding due to recurrent wet weather also presented significant challenges to the construction team with constant monitoring of water ingress compared to achievable dewatering rates needed to ensure safety during construction.

The project team, in close collaboration with the Geotechnical Engineer and Hunter Water, developed a new methodology to install rock bolts within the tunnel. This doubled the productivity of rock bolt installation, achieving a 4m/12-hour shift, saving significant costs for the client.


The remediation was completed on time and within budget and now ensures the ongoing reliable transfer of water from the Williams River to Grahamstown Dam through the Balickera Pump Station which holds over 65% of the total water storage for the Lower Hunter Region.

It is estimated that over 6,500 bats were successfully removed for the duration of the works with no impact on the health of the population. Ongoing bat monitoring continues to show these bats are returning in strong numbers.

The project was completed with zero non-conformances.