Tarraleah FAQ

• What did the feasibility study look at?

  • We assessed two scenarios to identify the preferred future strategy for the scheme.
    1. Redevelopment
       • This is about transforming the scheme’s capability to better suit the anticipated needs of the future energy market (by making it more flexible and responsive to changes in demand).
       • This would involve a lot of new infrastructure - a new power station and potentially new water conveyances (the parts of the system that transport water). This will boost the scheme's capacity and ability to deliver more energy annually – essentially getting more value from the same water resource.
       • An initial 2 machines (110MW) in a new station could replace the capacity of the existing power station.
       • Capacity for the installation of a further 2 machines (another 110MW) timed to take advantage of the market opportunity created by Marinus Link.
       • Changes to the current small headponds to allow the delivery of 24 hours of continuous operation at full capacity (220MW) when the market needs it.

  2. Refurbishment

  • This is about maintaining the existing scheme capability. The scheme assets would be refurbished and in some cases replaced, to ensure they continue to operate safely and reliably well into the future.
  • In this scenario, the scheme will continue to operate as ‘baseload’ with similar capacity and annual energy production. Baseload refers to a generation resource that generally runs continuously throughout the year and operates at stable output levels.

  
  

• What would the benefits be?

  • The future energy market will need supply options that can be quickly switched on when needed. Repurposing the scheme would allow it to deliver more renewable energy, more flexibly in the future.
  • What that actually means is….
    • More than doubling the current scheme capacity up to 220 MW - it’s like having a bigger engine in your car!
    • Generating more renewable energy annually.
    • Allowing faster and more flexible operation that is better suited to supporting the growth of wind and solar power.
    • Allowing the delivery of 24 hours of continuous operation at full capacity (220MW) when the market needs it, through changes to the current small headponds.

  
  

• What is proposed for the existing Tarraleah Power Station?

  The Tarraleah station is iconic and has a rich history. It’s important that we understand those heritage values and make a plan for managing and preserving the historic station, and other parts of the scheme that may have value, should they no longer be needed for power generation.

  

  A redevelopment of the scheme would mean the construction of a new power station in a nearby location.

  • The existing station would continue to operate while the construction work is underway so that we don’t impact on our ability to generate energy.
  • When the new station is completed, the existing station would be taken out of service and managed in line with what’s recommended in our heritage study.

  Refurbishment  of the scheme means we'd maintain the existing station and do the work needed so it can continue to operate safely and reliably. The six turbines and generators are near the end of their life and will need to be replaced with brand new machines, along with replacement or refurbishment of other parts of the station.

  
  

• What is proposed for the water conveyances?

  • The Tarraleah scheme has two complex water transfer systems from Lake King William to the Tarraleah Power Station – totalling about 30 kilometres of open canals, flumes (a type of water channel), tunnels, pipelines and ponds.
  • Most of the components are now 60-80 years old and nearing the end of their asset life.
  • Under both scenarios, there could be a new water conveyance replacing the existing infrastructure.
  • Redeveloping the scheme would see a single conveyance that would allow water to be transferred more efficiently to an enlarged storage pond on a plateau above a new power station.
    • Being able to store more water closer to the station, and transfer that water more quickly and efficiently, would increase the flexibility of the station. This would allow it to produce more power and respond more quickly to changes in electricity demand.
    • In fact, changes to current small headponds would allow the delivery of 24 hours of continuous operation at full capacity (220MW) when the market needs it.

  
  

   

   

  
  

• What is proposed for the current water storages?

  • The scheme has a large headwater storage at Lake King William, and several smaller storages: Mossy Marsh Pond, and what we call No. 1 Pond and No. 2 Pond.
  • We’re looking at what role those smaller storages could play in the future, including assessing options to increase the storage volume of No. 2 Pond which is located to the west of Tarraleah Village.
  • This assessment involves environmental studies (aquatic and terrestrial ecology, geomorphology, water quality and heritage) to understand any potential impacts of an increased water storage area.
  • Increasing the storage volume (also called ‘capacity’) will increase the flexibility of station operations. It means we can store more water closer to the station and better control how that water is released and conveyed to a power station for electricity generation. We won’t have to worry about first moving that water all the way from Lake King William, many kilometres away, before it can be used.
    • Being able to store more water closer to the station, and transfer that water more quickly and efficiently, would increase the flexibility of the station. This would allow it to produce more power and respond more quickly to changes in electricity demand.
    • In fact, changes to current small headponds to allow the delivery of 24 hours of continuous operation at full capacity (220MW) when the market needs it. 

  
  

  Image: The diagram depicts what a full proposed redevelopment of the scheme could look like.

  
  

  
  

• How long will the study take?

  • We’ve now wrapped up the technical part of our study which took 18 months to complete.  The next step is determining the asset management strategy to set Tarraleah up for long term success in a future energy market.
  • In March 2021, ARENA and Hydro Tasmania released a knowledge sharing report that presents a framework for making hydropower asset management decisions in a future energy market context, using Tarraleah as a case study. You can access the report here - Repurposing hydropower assets for future market. 

  
  

• What are the impacts of changing the scheme?

  • The good news is that when we did a pre-feasibility study in early 2018, we looked at possible environmental and social impacts and didn’t find any potential high risks or impacts. This has been confirmed through our ongoing assessments which show that risks and impacts remain low. 
  • As part of the feasibility study, we've now:
    • Identified environmental and social values and what will be needed to maintain or enhance those values
    • Established 'baseline' conditions for environmental and social aspects of the scheme and its surrounds
      • surveyed what’s growing and living in the waterways – hydrological modelling and aquatic ecology surveys
      • surveyed what’s growing and living in and around the scheme – terrestrial ecology surveys
      • surveyed the area and scheme history including Aboriginal and built heritage assessments and field surveys.

  • Determined the nature and extent of any likely impacts based on the two scenarios, so that we can formulate mitigation measures to address these.

  
  

• Can I provide feedback?

  Of course!

   

  We welcome feedback from the Tasmanian community and will continue to keep you informed. We welcome your suggestions on the best way to provide project updates or for you to contact us with questions you may have.