Edgar Dam Strengthening Project
Project Update – November 2023
EPBC referral submitted
The project was referred to the Department of Climate Change, Energy, Environment and Water (DCCEWW) for assessment under the Environment Protection and Biodiversity Conservation Act 1999 on 21 November 2023.
We will update this page as the project moves through the assessment process, including when it opens for public comment. You can also track this via the EPBC Act Public Portal.
For more information about the assessment process, including key steps and indicative timings, please take a look here.
New Quarry selected
The newly licenced Sunshine Quarry (west of Maydena) contains plentiful durable rockfill, so we recently made the decision to go ahead with this quarry for the project. This is a great outcome as it will reduce truck traffic through Maydena and emissions.
Worker accommodation
We continue to work with PWS to explore the feasibility of refurbishing the PWS canteen. If a joint decision is made to progress with these works, a separate approval will be sought. If this idea is not progressed, workers will be based at Edgar Campground as initially scoped.
Project Update – July 2023
Dam Works Permit
Under the Water Management Act 1999, this project requires a dam works permit. Following assessment by NRE Tasmania’s Water Management and Assessment Branch, a permit was granted on 29 May 2023. A request to review this decision has been lodged. More information about the Dam Works Assessment Decision Framework can be found here. An update on the status of this review is expected in August.
Project Schedule and timings
Dam works will not start until all relevant approvals are in place. The original project timeline (as outlined on this site) is no longer achievable given the dam works permit review. At this stage, we anticipate preparatory works on the washdown facility, staff quarters and road improvements will start late this year but works on site are unlikely. This means Edgar Dam campground is likely to remain open through this upcoming summer period. We will confirm this as soon as possible.
Project Update – May 2023
Edgar preparations continue and we’ve got a couple of interesting updates to share.
Quarry Choice
We recently confirmed that the bulk of hard dolerite materials needed to build the new rock buttresses can be sourced from Halls Quarry, just outside of Maydena. Selecting this nearby quarry is a great outcome as it significantly reduces truck traffic through community centres and reduces the project’s overall carbon footprint. We’ll need to continue to bring a smaller amount of specialised materials from Boral Quarry in Bridgewater.
In finalising our quarry choice, potential environmental impacts were a key consideration and our decision was informed by desktop, field and LIDAR surveys.
Washdown Facility
Robust environmental controls are an important feature in all our projects and were a particular focus in this case, given Edgar Dam’s location within Tasmanian Wilderness World Heritage Area.
To stop the spread of weeds and Phytophthora, we will install (subject to final approvals and consent) a permanent biosecurity washdown station at the junction of Scotts Peak Road. The preliminary design for this facility has been finalised and will be included in the upcoming submission for assessment under the Environment Protection and Biodiversity Act 1999. This facility will be made available to other organisations working in the TWWHA, including Parks and Wildlife Service (PWS) and Tasmanian Fire Service, providing an ongoing, positive impact on management of this unique area.
Upgrading critical infrastructure
In consultation with PWS, we plan to upgrade (subject to final approvals and consent) the original Hydro-Electric Corporation canteen and mess-hall which was built in the 1960s and now sits within the PWS operations base on Scotts Peak Road. It will be great to see a piece of Tasmania’s history restored and project staff will be glad to have kitchen facilities and sheltered lounge areas to enjoy during works. In the longer-term, it will provide a hub for workers accessing the south-west region, including track builders, maintenance crews and emergency services.
Project Background
Edgar Dam is one of three dams edging Lake Pedder. Built in 1972, it is part of the mighty Gordon-Pedder scheme, capturing 40% of the water that supplies Tasmania's largest hydro-power station, Gordon Power Station. This station can generate up to 432 MW of electricity or approximately 13 percent of Tasmania's annual energy needs.
Edgar Dam lies next to Lake Edgar fault (see map below from McCue et al., 2003), a crack in the earth's crust that was formed about 540 million years ago. When the dam was built, engineers knew about the fault but in the Australian context, earthquakes were poorly understood and the fault was deemed inactive. Several high-profile earthquakes, including the devastating 1989 event in Newcastle, changed perceptions around the risk of earthquakes and prompted new research at fault sites across Australia, allowing scientists to develop a much more detailed understanding of past and possible future behaviour.
From this new research, Lake Edgar fault was deemed active, although the chance of movement is extremely low. Scientists now believe the fault has had three significant movements in the past 48–61,000 years, triggered by earthquakes of a magnitude 6 and above. The last significant movement was thought to be 18,000 years ago (Swindon et al., 2007; Clark et al., 2011).
Many dams are built and perform safely in active earthquake areas. The key is to appropriately manage seismic risk. What the research highlighted was a new risk that needed additional management - until now, we've managed this risk using post-event controls (safety planning, in-situ monitoring) and this work will permanently improve the dam's seismic resistance. Learn more about managing dam risks in this section.
Project overview
The concrete face on the existing dam wall will be removed (in stages) and gravel filters and supporting rock added to strengthen the internal structure. Before construction, the toe pond (at the base of the dam wall) will be excavated down to the rock to ensure the new structures are built on a solid foundation which will improve stability and drainage. These features will improve the dam wall's capacity to withstand an earthquake. A wave barrier will be added along the top of the dam wall to deflect seiche waves which can form after an earthquake.
This simple, low-impact engineering solution will deliver immediate safety benefits for the community and environment and ensure we are meeting our responsibilities as owners and managers of this asset.
We're currently in the planning phase - learn more about project design, how we've managing impacts, and our forward timeline by clicking the image below
As we progress through to the approvals and construction phases, we'll publish regular updates on this page. Subscribe to get these straight to your inbox!
Questions?
We recognise that Lake Pedder holds significance for many Tasmanians. This project is about delivering immediate safety benefits and will not impact decisions about the future of Lake Pedder. For more information, please take a look here.
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