2005 – ENVIRONMENTAL INVOLVEMENT
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.
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Papers 2005
2004 – Communicating Dam Safety Practices to the Community for a 60km Long Canal Hydro Development in New Zealand
Learn morePeter D Amos, Pip Nicolson, M Grant Webby, Murray D Gillon
To obtain a resource consent to build and operate any new water resource or hydro-electric development in New Zealand, the developer is required by the Resource Management Act (RMA) to consult with the community over the effects that the development could have, including describing how public safety risks will be avoided, remedied or mitigated. The community has the opportunity to respond to the authorities issuing the resource consent and influence the conditions attached to the consent.
The proposed Project Aqua Scheme in the South Island, New Zealand, comprised a 60 km long canal system to convey 340 cumecs flow from the Waitaki River across alluvial river terraces and through a chain of six hydro-power stations before returning the water back to the river. Each section of canal between stations would have contained between 4 and 6 million m3 of water within embankments up to 20m high. A breach of any one of these canals had the potential to flood farmland, residential buildings, highways, and other infrastructure, thereby posing a safety risk to local residents together with the potential for significant economic loss.
The paper describes the methodologies that were developed and used to assess the impacts, the measures proposed to avoid, remedy or mitigate safety risks and the public reaction to the associated report that was provided for public consultation prior to abandonment of the project. The methodologies used required adaptation of dam safety and consequence assessment practices usually applied to in-river dams, and applied here to the 60 km long length of canal embankment.
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Papers 2005
2005 – Revised Extreme Floods in Tropical Regions
Learn moreR.A. Ayre and T. L. McGrath
SunWater as an owner of 25 major dams in Queensland has completed a programme to update the design flood hydrology of all of its referable structures in accordance with the latest methodology for estimating extreme design floods. This programme ensures the adequacy of existing spillways is included in an overall dam safety portfolio risk assessment in a consistent fashion.
This paper describes the methodology adopted in the re-assessment of the design flood hydrology of the storages. Principally this has meant the use of a design hydrograph approach utilising runoff-routing methods as described in Australian Rainfall and Runoff (1999). Design rainfall inputs have been based on generalised techniques derived by the Bureau of Meteorology such as the Revised Generalised Tropical Storm Method and the Generalised Short Duration Method for the estimation of Probable Maximum Precipitation. These estimates, coupled with the use of a regional design rainfall estimation technique known as CRC-Forge that is used for determining large to rare design rainfall estimates, have been used to derive a complete estimate of the inflow/outflow flood frequency curve for each dam.
The paper also provides an insight into the significant factors and relationships that are involved in the changes resulting from this process. Overall, there has been an increase in design rainfall depth estimates for the extreme events, and a general reduction to neutral change in the large to rare rainfall range. These changes plus the influence of temporal effects and the assignment of Annual Exceedance Probability (AEP) has led to substantial changes from previous estimates of design floods. The implication of these changes is profound for
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an organisation such as SunWater. -
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Papers 2005
2005 – Risk Management – Public Policy vs Corporate Liability
Learn moreJ S Marsden, P H Jacob, R Nathan and L A McDonald
This paper relates to the conference sub-themes of Dam Safety Upgrades – Management of Risk and Due Diligence and Dam Construction.Specifically, it relates to the changing willingness of governments to fund risk reduction indams compared with risk reduction in other areas.
The cost of dam safety upgrades is just one of a portfolio of risk reduction strategies affecting the general community that governments are required to underwrite.
This paper examines the variation in acceptable risk standards between dam safety and other areas. This may be explained in terms of what is acceptable to the community and the courts. For instance, a corporation is likely to attempt to minimise its liability (which may differ to minimising risk for the community).
We also examine:
- a portfolio approach to safety expenditure and the implicit cost-benefit relationship;
- the impact of the asymmetric relationship between expenditure and absolute size of potential loss; and
- the importance of a whole-of-government approach and reviewing apparent inconsistencies in approach to risk.
There is an increasingly well-established literature on the value of a human life and increasingly systematic approaches to the evaluation of risk and the setting of risk standards. Risk standards are particularly explicit in the area of dam safety – they set limits of tolerable risks for large-scale loss of life (eg. for existing dams, a loss of life of more than 10 persons with a probability of more than one in a ten thousand per annum is regarded as unacceptable under the Australian guidelines).
However, there are significant contrasts in what is tolerated as acceptable risk between different areas of government activity. To date,there appears to be no systematic evaluation of the portfolio of risks or a common view on what is acceptable levels.
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Papers 2005
2005 – LAKE BUFFALO DAM RISK REDUCTION UPGRADE
Learn moreConstruction 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.
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Papers 2005
2005 – Pykes Creek Reservoir; Upgrading the Outlet Works for a 95 year old Dam
Learn moreMike Taylor, Jonathan Jensen and Greg Branson
Pykes Creek Dam is a 33 m high, 22,120 ML embankment dam, 72 km west of Melbourne owned and operated by Southern Rural Water.
The outlet works include a 30 m high “wet” outlet tower near the upstream toe of the dam on the right
abutment with its lower half comprising a concrete lined shaft excavated in rock. A 1.5 m diameter
concrete lined tunnel extends 30 m upstream from the base of the tower to a reinforced concrete inlet structure.The only controls upstream of the downstream toe of the dam comprised 2 guard gates located on the downstream side of the tower, operated manually by means of handwheels from the top of the tower.
Major deficiencies with the outlet works included:
- No facility to de-water the tower to maintain the gates located at the base of the tower. The
gates had become partially inoperable as a result. - The gates in any case were extremely laborious and time consuming to operate.
- No facility to inspect and maintain the upstream tunnel and inlet structure.
- No facility to select variable drawoff levels to control water quality and temperature for river
releases. - The access footbridge to the tower was structurally inadequate to safely accommodate loads for remedial works on the tower.
A major constraint in addressing these deficiencies was that any remedial works needed to be
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undertaken without draining the reservoir or interfering with the releases required for downstream
consumers, including irrigators in Werribee and Bacchus Marsh.The paper describes how all of the deficiencies have been addressed with no interruption to supply, by means of a collaborative effort between the dam owner, the consulting engineer, and 5 separate contractors, with the dam owner playing a leading role. - No facility to de-water the tower to maintain the gates located at the base of the tower. The