Sonny Connors, Shaun Nugent, Brett Taylor, Brian Walford
The Tarong coal-fired power station near Kingaroy in southern Queensland discharges ash to a storage facility of 42,000 ML capacity, impounded by a 48 m high-zoned earth and rockfill dam embankment. The embankment was constructed in 1980–81. In recent years, Tarong Energy Corporation (TEC) has investigated a number of options for a new storage facility as the remaining capacity of the existing ash dam storage diminishes. TEC determined that the existing facility should be upgraded to provide additional storage capacity for the short term. At the same time, there emerged a requirement to improve the long-term seismic resistance of the embankment. Enlarging the existing spillway cut provided the material for a 400,000 m3 weighting zone and, by reducing the design flood freeboard, extended the ash disposal capacity by several years without a need to raise the embankment. Challenges included significant foundation seepage and deteriorated riprap. The paper describes the issues, risks, adopted criteria, investigation undertaken, and implementation of the upgrading works. Innovative approaches to the provision of future storage capacity are outlined.
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Stephen Newman, Mark Foster
Construction of the Lake Buffalo Dam was completed in 1965. It was to be a temporary dam, required to operate for several years, then act as a cofferdam for the construction of a much larger dam downstream. This larger dam was never built and a risk assessment completed by Goulburn Murray Water (G-MW) in 2001 identified several dam safety deficiencies at Lake Buffalo were among the highest priorities for risk reduction measures across the G-MW dams portfolio. Specifically it identified Lake Buffalo as having inadequate flood capacity and there were also concerns about transverse cracking within the embankment.
This paper describes the detailed investigation and analysis of the embankment cracking including assessing the potential for piping through an embankment having deficient filters and known transverse cracking. The design features of the upgrade are also described including the design of the a filter buttress, a parapet wall raise, Computational Fluid Dynamics (CFD) modelling and spillway anchoring. Construction was completed in 2003.
Stuart Macnish, Nikki Bennett
The $70 million upgrade of Wivenhoe Dam is being undertaken by the Wivenhoe Alliance, in close
proximity to the town of Fernvale, Queensland. As part of the Alliance’s commitment to delivering positive outcomes for the local community, it was decided part way through the project, to commit to delivering a ‘signature’ community legacy project. The team brainstormed a range of options and a decision-making matrix was used to choose the project that would best meet its objectives.
A partnership has been formed between the Alliance, Esk Shire Council and SEQWater to deliver a
master-planned project which incorporates elements such as a community information/service facility,upgrade of Fernvale Memorial Park, streetscape enhancements, improved parking and installation of shelters along the adjacent rail trail. These major partners, together with representatives of the local community, constitute the steering committee, which oversees planning of the project.
The project aims to encourage visitors to the area, to provide improved amenity and sense of pride for the region, and in turn encourage strong relationships for SEQWater in the area in which they operate. Due to tight time frames the partnership is managing the fund raising activities, community consultation and design processes in parallel.
This paper discusses the process by which the Alliance was able to deliver this remarkable project, within a short timeframe. It also discusses how the local community has been involved and the benefits, which have resulted.
David S. Bowles, Loren R. Anderson, Terry F. Glover, Sanjay S. Chauhan, Ronn S. Rose
A risk assessment was performed for the Sacramento District of the U.S. Army Corps of Engineers to explore the justification for imposing an operating restriction on Lake Success to reduce the probability and consequences of an Earthquake-induced dam failure. The potential for both a sudden overtopping failure and a delayed “seepage erosion through cracks” failure were considered.
The risk assessment focused on the seismic performance of the dam, the potential life loss and economic consequences of Earthquake-induced dam failure, and the estimated residual risk and degree of risk-based justification for the Existing operating regime, a range of Potential Operating Restrictions, and an Indicative Improved Warning and Evacuation System. Risk assessment inputswere supported by seismic deformation analyses under various Earthquake loadings and pool elevations, dam break-inundation modelling, and reservoir simulation.
Evaluations against tolerable risk guidelines from the USBR, ANCOLD, and the UK HSE, together with insights into the relationship between pool elevation and dam failure risk, provided important inputs for the decision to implement an operating restriction.
Stuart Macnish, Natarsha Woods, Michael Dixon
What happens when the people that undertake early environmental investigation stay on as part of the delivery team throughout the design and construction phases of a major project such as the Wivenhoe Alliance?
Often, the early investigation for projects, particularly in the case of environmental impact assessments and approvals processes, is carried out independently of the construction team. In the case of the Wivenhoe Alliance, these issues were set out in the scope of the project itself and delivered by the same team during construction.
The benefits and outcomes have been impressive not only for the project, but for SEQWater and the local community into the future. Improved biodiversity values, increased water quality protection, safety improvements, and value for money are only some of the key benefits experienced.
Individuals within the team also benefit. Environmental professionals are able to implement their
knowledge ‘on-ground’ and progressively improve practices in an area of constant change due to
construction initiatives and timeframes.
This paper explores the specific areas in which the involvement of environmental professionals throughout early investigation and planning, design and construction have benefited the Wivenhoe Alliance and the outcomes that have resulted from this innovative approach.
Howard and Opper
Dam safety planning is a team game. There are many players involved and there is a need for information to be shared and actions to be properly coordinated. The State Emergency Service is the legislated combat agency for flooding in New South Wales and is responsible for planning for and conducting the warning and evacuation of communities at risk from floods, including floods affected by dams. The successful execution of these responsibilities is dependent upon the continuing development of a strong, cooperative relationship between the dam owners and managers, dam regulators and emergency managers and the effective incorporation of community expectations in dam safety planning.
This paper explores some of the ways that this relationship can help to meet well accepted community expectations in respect of risk to life and property and outlines progress made in dam safety planning to date. The emergency response aspect of dam failure planning is still a relatively immature field in Australia, and it follows that there are lessons to be learned as we proceed. In that context, the paper also describes some of the difficulties the State Emergency Service has encountered in its role as the response planning agency and suggests some guiding principles to enhance future interactions between the key stakeholders.