With approval for the Exploratory Works stage granted in early 2019, Snowy Hydro has now commenced work on the Snowy 2.0 project in the Lobs Hole area of Kosciuszko National Park. The purpose of Exploratory Works is to gain a greater understanding of the underground geological conditions at the proposed location of the new power station. The underground power station consists of two large caverns, approximately 800m below ground level.
The cavern complex is one of, if not the most, challenging areas for the design of Snowy 2.0.
It is common practice internationally for hydro-electric power projects, particularly with large underground caverns, to establish an exploratory tunnel to the top of the power station cavern and drill numerous horizontal investigation probes. The associated testing includes in-situ stress testing to confirm that the power station complex location and orientation are suitable for the stress conditions at depth. During Snowy 2.0 Exploratory Works, the same process will occur - an exploratory tunnel will be excavated to the top of the cavern complex to enable investigation holes to be drilled, allowing further examination of the rock conditions deep underground. Exploratory Works also include:
- The establishment of a construction pad and portal at the Lobs Hole Ravine area.
- The establishment of a construction compound, including accommodation camp and supporting services infrastructure such as power and communications.
- The upgrade and establishment of roads to provide access to the construction areas.
- Excavated rock management including a trial of placement in Talbingo Dam.
The Lobs Hole area has been closed to the public for safety reasons. After construction, it will be rehabilitated and returned to its current use.
The exploratory tunnel to the site of the underground power station will be about 3 kilometres in length, dome-shaped, 8m high by 8m wide. The tunnel will be constructed using a combination of the drill and blast (similar to the Snowy Scheme tunnel shown above) as well as tunnel boring machines. The exploratory tunnel is intended to ultimately form the main access tunnel to the underground power station during the operation of Snowy 2.0. The tunnel portal or entrance will be a permanent structure at Lobs Hole, similar to the Tumut 2 Power Station portal.
The program of Exploratory Works will require the establishment of construction facilities at Lobs Hole which will include equipment and temporary structures such as:
- concrete batching plant,
- ventilation system,
- laydown area for equipment, materials and refuelling,
- a temporary stockpile for excavated rock,
- water supply treatment and storage,
- project offices.
The workforce for Exploratory Works will be housed in purpose-built temporary accommodation. The camp will be fully self-contained with dining and recreational facilities. At the peak of works, approximately 200 people will live on-site.
Access to the work areas will be provided via Lobs Hole Ravine Road. Upgrades to roads and tracks in the area are required to facilitate movement of large vehicles and all weather access. For safety reasons, Lobs Hole Ravine Road and the Lobs Hole camping area are now closed to the public for the duration of construction and will be reopened when project works are completed.
Excavated rock management
It is estimated that approximately 500,000 to 750,000㎥ of rock will be excavated during Exploratory Works. This excavated rock is expected to be temporarily stored in designated areas at Lobs Hole. Final excavated rock placement and management will be determined following the results of scientific and technical investigations being conducted, including a proposed trial during Exploratory Works for a small portion of the excavated rock to be placed in Talbingo Dam. Options being considered include beneficial reuse, as well as placement outside Kosciuszko National Park, or within the dams.
Exploratory Works are expected to be completed within 18 to 34 months.