Snowy Hydro is currently seeking approval for an initial program of Snowy 2.0 exploratory works that would be carried out in the Lobs Hole area of Kosciuszko National Park.
The purpose of these 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 multiple large caverns, approximately 850m below ground level. The largest cavern (for the machine hall) is likely to be about 190m long, 30m wide and 55m high.
The underground 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 exploratory works, the same process would occur - an exploratory tunnel would be excavated to the top of the cavern complex to enable investigation holes to be drilled, allowing further examination of the rock conditions at the likely site of the underground power station.
Exploratory works also includes:
- 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 proposed construction areas.
- The establishment of barge access infrastructure on Talbingo Reservoir.
- Excavated rock management including subaqueous placement in Talbingo Reservoir.
During construction, the Lobs Hole area would not be safe for public access and would be temporarily closed to the public. After construction, it would be rehabilitated and returned to its current use.
As part of the approvals process, an exploratory works Environmental Impact Statement has been submitted to the NSW Department of Planning and Environment and is available online for the public to review.
The exploratory tunnel to the site of the proposed underground power station would be 3-4 kilometres in length. It would be dome-shaped, 8m high by 8m wide, and constructed using drill and blast methods in the same way that the original Snowy Scheme was constructed.
If the main Snowy 2.0 project is approved to proceed, the exploratory tunnel is intended to ultimately form the main access tunnel to the underground power station during the operation of Snowy 2.0.
Construction pad and portal
The portal or entrance to the exploratory tunnel and associated construction pad would be established with a footprint of between 10,000 and 16,000㎡. The construction pad would contain equipment and structures including:
- ventilation system
- diesel generator sets
- air compressors
- office huts
- laydown area for equipment, materials and refuelling
- temporary stockpile for excavated rock
- water supply storage
- dirty water storage for treatment
A construction compound would provide all supporting infrastructure for the exploratory works. The compound would include facilities like an accommodation camp, project office, workshops, concrete batching plant, fuel farm, laydown areas for equipment, water treatment plant, and sewage treatment plant. A construction compound would provide all supporting infrastructure for the exploratory works. The compound would include facilities like an accommodation camp, project office, workshops, concrete batching plant, fuel farm, laydown areas for equipment, water treatment plant, and sewage treatment plant.
Access to the work areas will be provided via both vehicle and barge. Vehicle access would be via Lobs Hole Ravine Road for the movement of personnel and light equipment, while bulky and heavy equipment would be transported via barge access on Talbingo Reservoir.
Upgrades to roads and tracks in the area, including Lobs Hole Ravine Road, are required to facilitate access, including some road widening, gravel pavement overlay and installation of guideposts.
Barge access will require the provision of wharf facilities on Talbingo Reservoir, both near the dam wall and near Lobs Hole.
For safety reasons, public usage of Lobs Hole Ravine Road would be restricted and then returned to public use after construction.
Excavated rock management
It is estimated that approximately 500,000 to 750,000㎥ of rock would 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 scientific and technical investigations being conducted, including a trial during exploratory works for a small portion of the excavated rock to be placed in Talbingo Reservoir. Options being considered include beneficial reuse, as well as placement outside Kosciuszko National Park, or within Scheme reservoirs.
Exploratory works are expected to be completed within 18 to 34 months. Road and access works would begin first which, subject to approvals, is targeted for late 2018 or early 2019.