Mikany Dam Upgrade

What's this project all about? 

Mikany Dam is located six kilometres south-east of Smithton in the state’s north west. It is referred to by local residents as Lake Mikany.

The dam was originally built in 1972 and has two main embankments, as well as a smaller embankment which provides access to an island in the centre of the lake. The dam is gravity-fed from Deep Creek and Muckeye Creek catchments and is the primary source of potable water for Smithton, Stanley and Irishtown. Water is supplied to these towns via Deep Creek to an off-take downstream, where it is pumped to a treatment plant at Smithton prior to distribution.

Project description

TasWater identified a need for upgrades to meet improving Dam Safety standards and associated Australian National Committee on Large Dams (ANCOLD) guidelines. As a result, a substantial investment is required to reduce the risk the dam poses, while also providing a sustainable water supply for customers.

The major features of this upgrade include:

  • Increasing the strength of both embankments by constructing filter and rock-fill berms
  • Minor improvements to spillway
  • A small increase in the height of the dam wall to provide protection in the event of an extreme significant flood
  • The result of the upgrade will be a dam which meets modern standards, is safe, improves water security, and can provide flood protection for much larger floods.

For more information

If you have any questions or would like to know more about this project, please contact Nani Clark, TasWater Community and Stakeholder Engagement, on 13 6992 or email enquiries@taswater.com.au

Q & A

Why is the Mikany site restricted for access by the public for the duration of the project?

This work involves major works on the dam wall which will require operation of heavy machinery in restricted areas. Due to safety concerns for the public and our contractors, access to the reservoir needs be restricted until the project is completed.

When will the site be open to the public again?

The Mikany Dam safety upgrade project is currently scheduled for completion by the end of October 2022. We will keep you updated on progress throughout the works.

Will the cost of my water bill go up?

This project is fully funded by the TasWater capital works program. Water service charges, as detailed in the current Price and Service Plan 2018-21 Pricing Manual, will not be affected.

Why has the project cost increased?

In the early phases of project investigation, limited historical information was available for flood modelling and suitability of locally sourced construction materials. This required a number of assumptions to be made during early cost estimates. As the project developed, some of these assumptions were found to be incorrect. Additional data was gathered to ensure the best outcome for the Mikany Dam safety upgrade, resulting in a redesign of the spillway and more suitable construction materials being sourced from further afield rather than at the dam site itself.

Why has the project been delayed for so long?

A full review of the business case was initiated when the cost increase was identified. The review considered alternate strategic options and spillway designs to ensure we identified the best solution. Following completion of the review, the project was transferred to the Capital Delivery Office (CDO) where the design and execution strategy was progressed to the delivery phase.

What dam construction works are being done?

Construction works will include raising the dam wall and minor improvements to the spillway. These works will improve the dam’s ability to withstand flooding from a 1 in 100 year event to a 1 in 10,000 year event.

Are we increasing the capacity of the dam?

No. The upgrade is required to improve the safety of the dam and to provide long term reliable water supply for our customers.

Will water supply to Circular Head township be affected?

No. The existing water supply to the region will not be affected.

Is the dam unsafe?

Mikany Dam has an estimated flood capacity of 1 in 100 year Annual Exceedance Probability (AEP) before the dam overtops. Once construction is complete, the flood capacity will be improved to 1 in 10,000 AEP, complying with the latest Australian national dam safety standards.

What kind of construction impacts can residents expect during this period?

Access to the dam site will be closed to the public for approximately 18 months. Reservoir Road access will be restricted to local residents and construction vehicles only during this time with construction taking place on TasWater property. Local residents will notice increased movements of trucks and heavy vehicles on the road. There may be some noise generated from rock breaking at the construction site. There will also be some dust generated from additional traffic on Reservoir Road, however water carts will be used to help suppress dust on a regular basis.

What are the construction hours and days?

Monday to Friday, from 6.30am to 6pm. If work is necessary outside of these hours, local residents will be notified.

What sort of public consultation has taken place for this project?

This project has been in development over several years and its planning has been discussed with Circular Head Council and key stakeholders. TasWater is committed to keeping local residents informed of any impacts and mitigation measures during the project. TasWater will regularly supply project updates to the community through the local newspaper, newsletters, Council Facebook pages and the TasWater CDO web site.

Are you planning to use local contractors and suppliers?

Northern Tasmanian construction company Gradco has been contracted to deliver the safety upgrade project. It is anticipated they will engage with regional businesses to supply construction materials throughout the project.

Will the boat ramp be affected by the upgrade?

Yes. Access to the reservoir via the boat ramp will not be possible during construction for safety reasons. TasWater will assess options in consultation with local council, community groups and recreational users regarding the future of this important community facility.

Will the water quality be affected during the construction?

A number of mitigation strategies have been put in place to avoid affecting water quality during the construction process.

There are eagles that frequent the Mikany Dam area. How will you prevent impacts to them?

A natural values assessment completed by an independent ecologist identified wedgetail and white bellied sea eagle nests in the vicinity of the dam, however these are outside of the impacted area. Should nesting eagles be found in the area of the works, mitigation measures have been developed and will be implemented as needed.

Have a question?

We'd love to hear from you.

Please contact Nani Clark, TasWater Community & Stakeholder Engagement. 

Phone: 13 6992
Email: enquiries@taswater.com.au