Tarraleah FAQ

• What is the feasibility study looking at?

  • We’re assessing two scenarios – refurbishing or redeveloping the scheme:
    1. 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.
    2. 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 energy demand).
       • This will involve a lot of new infrastructure that will boost the scheme capacity and delivery more energy annually – essentially getting more value from the same water resource.
  • The main parts of the scheme we’re talking about are the power stations at Tarraleah and Butlers Gorge and the water conveyances that run from Lake King William. Conveyances are the parts of the system that transport water.
  • The feasibility study will identify the preferred future strategy for the scheme.

  
  

• What would the benefits be?

  • The future energy market that 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; up to an extra 200 GWh each year, which is enough to power 25,000 homes.

  
  

• 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, should it no longer be needed for power generation, and other parts of the scheme that may hold value. That’s all part of the feasibility study.

  

  The future of the station will depend on the outcome of the feasibility study and which scenario is the preferred option.

  • If we choose to redevelop the scheme…
    • This will mean the construction of a new power station, with more capacity, in a nearby / adjacent 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.
  • If we choose to refurbish the scheme…
    • There are a couple of possible outcomes under this scenario.
    • We could choose to maintain the existing station and do the work needed so it can continue to operate safely and reliably. One example is that the six turbines and generators are at the end of their life and will need to be replaced with brand new machines.
    • The study may also show that it’s just as economical, or more economical, to build a separate, new station with similar capability to what we have now. If we did this, we’d take the existing station out of service.

  
  

• What is proposed for the water conveyances?

  • The Tarraleah scheme has two complex water transfer systems from Lake King William to the Tarraleah station – totalling about 30 kilometres of open canals, flumes (a type of water channel), tunnels, siphons (pipes) and ponds.
  • Most of the components are now 60-80 years old and nearing the end of their asset life.
  • If we choose to redevelop the scheme
    • This could mean a single new conveyance which 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.
  • If we choose to refurbish the scheme…
    • The conveyances would stay in their current configuration but we’d need to do work to either refurbish them or, in some cases, replace the existing infrastructure with new conveyances where it’s economically viable to do so.
    • If it’s determined that it’s more economical to build a new station than retain the old one, we’d also need some new pipelines to transfer water. Nothing would change with the size of the existing storages so we’d still be limited in our ability to respond quickly to demand changes in the electricity market.

  
  

   

   

  
  

• 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. As part of the feasibility study, we’re 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, terrestrial 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.

  
  

  
  

• How long will the study take?

  • The study is expected to take around 18 months to complete, wrapping up around the end of 2019. Once we have all the information, we expect to be able to confirm our preferred strategy for the scheme early in 2020. 

  
  

• 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 was a preliminary assessment to give us an early understanding.
  • We’re now taking a close look at:
    • what’s under the surface of the ground where we would be tunnelling and digging – geotechnical investigations
    • what’s growing and living in the waterways – aquatic surveys
    • what’s growing and living in and around the scheme – terrestrial surveys
    • the area and scheme history including Aboriginal and built heritage assessments and field surveys.
  • This information helps our team make decisions about where new assets and infrastructure might go and how they are best constructed.
  • It also provides valuable information that will help us make plans to minimise impacts on the plants, animals, river life and heritage values as the project progresses.

  
  

• Can I provide feedback?

  Of course!

  We welcome views from the Tasmanian community and will continue to keep you informed as studies progress. 

  We welcome your suggestions on the best way to provide project updates or for you to contact us with questions you may have.