In August 2017, as part of our regular and routine safety checks we observed increased seepage from the dam wall. After further investigation we found evidence of internal embankment erosion (piping) within the upper section of the dam wall. This situation was considered to be unsafe for the dam and water was released from the reservoir to prevent any further deterioration in the dam wall. We then informed the Waratah-Wynyard Council and informed the community and other key stakeholders. We have continued to manage the water level of the reservoir.
We recognise that Waratah Dam is of great importance to the community, particularly in terms of recreation and environmental values, however, despite our ongoing maintenance of this ageing infrastructure the Waratah Dam is not currently safe and as the dam owner our primary concern is to ensure that it is. If it failed it could be a risk to life and property, which is a risk which we must address. To replace the dam is expensive, with an independent assessment putting the cost in the order of $3.8 million. It is not economic to repair the dam.
Additionally, the dam is not a required water supply asset for TasWater, as the water supply for Waratah is able to be provided year-round by the run of the Waratah River. Our modelling has shown that there is enough water in the river to supply the needs of the township, given the water needed to supply Waratah is about ten percent of the dry weather flow.
Expression of Interest Process
Given these issues our options are to divest or decommission the dam. We undertook two Expression of Interest (EOI) processes where we sought interest from the community and other stakeholders in relation to taking over the ownership of the dam:
- The first ran from mid December 2017 to the end of January 2018. No responses were received.
- The second ran from late March to 22 May 2019.
Following this extensive search to find a new owner for the Waratah Dam, including the two Expression of Interest processes, one could not be found.
TasWater investigations – summary
We have undertaken a number of investigations into various aspects of the dam with independent consultants. The most recent investigations in 2018 were completed and are summarised below (see the document library for more detailed summaries and the individual reports).
The environmental study found that no threatened flora species were discovered, while none of the four threatened fauna species within 5km of the dam (Tasmanian devil; spotted-tailed Quoll; wedge-tailed eagle; swift parrot) are considered to be affected by the lowering of the dam.
Due in part to the 1975 dam failure and subsequent rebuild that impacted the potential historic heritage value of the dam, decommissioning will not have a major impact on historic heritage values. The Aboriginal heritage survey did not locate any Aboriginal relics during the survey of the Waratah Dam and adjacent area.
The hydrology study showed that with its spillway in its pre-2017 condition, the Waratah Dam does attenuate flood peaks by varying amounts depending on the nature of storms (i.e. their duration and intensity). Nevertheless, the risks associated with flood overtopping failure are considered by Entura to be unacceptably high, and it is recommended that the spillway capacity should be upgraded, or the dam decommissioned as a matter of urgency.
For more information
For more information about this project, please contact Moira Skinner, TasWater Community and Stakeholder Engagement, on 13 6992 or email: firstname.lastname@example.org