The Oven Mountain Pumped Hydro Storage Project is an off-river development in New South Wales, Australia. The project is owned and will be developed by Alinta Energy.
With an estimated base cost of approximately A$1.97bn ($1.29bn), the construction of the project will commence at the end of 2024 creating 600 jobs during construction.
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The targeted year for the commencement of commercial operations is 2029. Oven Mountain will have an operational life of over 100 years.
Once operational, the off-river development will produce up to 900MW of renewable electricity and between eight to 12 hours of dispatchable energy for storage and distribution to the National Electricity Market.
Oven Mountain Location Details
The Oven Mountain Pumped Hydro Storage Project will be located approximately 60km southeast of Armidale and 70km northwest of Kempsey through the Kempsey-Armidale Road on private land.
The project will be situated at the southeastern corner of the Armidale Regional Local Government Area (LGA) close to the Kempsey Shire LGA within the New England Regional Economic Zone (REZ).
The project will be developed within Australia’s Thunggutti Aboriginal Community area.
The Macleay River borders the project from the west and the Carrai Tablelands surround the project from the east.
Oven Mountain Key Infrastructure
The Oven Mountain Pumped Hydro Storage Project will consist of an underground power station, dams and reservoirs, water intake structures, spillways, a Macleay River pump facility, tunnels, and a power waterway.
The project will have two concrete-faced rockfill dams with an upper and a lower reservoir. The upper dam and reservoir will be approximately 780m long and 70m high.
The upper reservoir will cover approximately 20 hectares (ha) area with an inundation extent of approximately 16.7ha.
At the Full Supply Level (FSL), the upper reservoir will have a storage capacity of around 5.1 gigalitres (GL) and a height of approximately 881mAHD.
At the Minimum Operating Level (MOL), the upper reservoir will have a height of approximately 830mAHD.
The lower dam and reservoir will have a storage capacity of around 6.5GL at FSL and will be approximately 280m long and 70m high.
The lower reservoir will cover approximately 24.7ha and an inundation extent of approximately 21.6ha. At FSL, the lower reservoir will be 250mAHD high, 215mAHD MOL and 205mAHD at the Lowest Operating Level (LOL).
Both reservoirs will have water intake structures and two concrete-lined spillway chutes. A pump facility will be developed on the edge of the Macleay River. The pump facility will include an access road, duty pumps, and standby pumps.
Three main tunnels, consisting of two Main Access Tunnels MAT1, MAT2 and an Emergency Cable Ventilation Tunnel (ECVT), will be developed for the project.
The power station complex will receive loop access from the MAT portal via MAT1 and MAT2. The switchyard portal and the transformer hall will receive services access and egress via the ECVT.
The ECVT portal will consist of a station switchyard, control rooms, ventilation, blast walls, and firefighting equipment.
The power waterway of the project will include a vertical pressure shaft, a high-pressure headrace tunnel, a high-pressure tailrace tunnel, penstocks, and draft tube tunnels inside the power station.
Associated Facilities Details
The associated facilities of the Oven Mountain Pumped Hydro Storage Project will include access roads, tracks and bridges, Surface work pads and facilities, communication facilities, and utilities for construction and operation.
The water diversion and treatment facilities, laydown/stockpile areas, spoil emplacement areas, and ancillary operational facilities will be a part of the associated infrastructure of the project.
Out of a total of approximately 40km of permanent, approximately 25km will be newly constructed roads and the rest will be the existing ones.
In addition to surface portals, four main construction pads will be temporarily used during the construction phase.
The communication infrastructure like fibre optic cables will be needed during the operation of the project.
The communication infrastructure will be located on an overhead line connecting the upper and lower dams and reservoirs and electrical lines.
The utilities for construction will include construction water supplied from the Macleay River and for operations, the utilities like water, electricity etc will be combined into a single corridor of about 5.4km in length.
Three permanent spoil emplacement areas will be developed to store around 2.9 million cubic metres (Mm3).
A dead storage area of storage capacity of approximately 300,000 to 400,000m3 within both reservoirs will be used for the placement of spoil.
The ancillary operational facilities will include maintenance housing, a work area, a car parking, a workshop, storage, switchgear etc.
Oven Mountain Project Details
The underground power station of the project will connect the upper and lower reservoirs of the Oven Mountain Pumped Hydro Storage Project.
The underground water intake and pipe facility built on the Macleay River will supply water to the lower reservoir.
The water from the lower reservoir will pass the gate shaft and enter the tailrace and headrace tunnels. The headrace tunnel connects the upper reservoir.
The upper reservoir will release water falling over 600m through the high-pressure headrace tunnel to the underground power station.
The reversible Francis turbines of the underground power station will generate up to 900MW of power and feed it to the NEM via ECVT.
Power Infrastructure and Transmission
The underground power station complex will be located below the upstream end of the system of the project. The power station complex will consist of two main caverns and many interconnecting tunnels.
For power supply and infrastructure, an approximately 15km-long transmission alignment will be developed.
The transmission alignment will consist of a 330kV double circuit single tower overhead infrastructure and a 132kV single circuit single tower overhead infrastructure.
The tower infrastructure will lie within tower sites (maximum 25 in number) of approximately 50m*50m. The maximum width of the transmission easement will be approximately 105m.
A substation will be built with associated infrastructure of up to 330kV rating for the project. A high-voltage switchyard will connect the transmission lines and cables exiting from the underground power station.
Key Contractors
In December 2023, WSP was selected by Alinta Energy to conduct geotechnical studies for the Oven Mountain Pumped Hydro Storage Project.
EMM was awarded the contract to prepare the Environmental Impact Assessment (EIA) for the project.
AECOM, supported by Lombardi Engineering, was appointed as the owner engineer for the project by Alinta Energy.
AECOM and Lombardi will provide engineering, procurement, scoping, monitoring, and assessment of the geotechnical results for the project.
Both companies will prepare reference design, Original Equipment Manufacturer (OEM) and Early Contractor Involvement (ECI) procurement support, and technical support for the project.
Project Timeline
September 2020: Critical state significant infrastructure designation.
January 2021: Scoping report.
February 2021: Secretary’s Environmental Assessment Requirements (SEARs) issued.
2021-2022: Site and field investigations as a part of Environmental Impact Statement (EIS).
August 2023: EIS submission to the Department of Planning and Environment (DPE).
September-October 2023: Formal exhibition of the EIS by DPE.
End of 2023: Response to submissions.
Mid-2024: Ministerial determination.
End of 2024: Start of construction.
2029: Targeted operations.
