Eric J Lesleighter and Peter F Foster
The Ross River Dam was constructed in 1974 following design by the State Government, including hydraulic model testing, by SMEC. The maximum spillway discharge at that time was 1100 m3/s.Latterly, the dam and spillway have come up for a comprehensive review given that the dam is in an extreme hazard category because of its location only a short distance upstream of the city ofTownsville. The revised hydrology has produced outflow hydrographs peaking at over 4 000 m3/s –more than three and a half times the original – to be passed through the 130 ft (39.62 m) widespillway.
The paper describes the hydraulic modelling planned and carried out to determine changes needed to handle such high discharges. The modelling was to provide for the installation of radial gates and piers, and study of the water level, pressure and dissipation conditions in the dissipator for several key discharges through the range to PMF. Pressure measurements included transients, consideration of the potential for uplift of the basin floor slabs, the integrity of the walls to handle the differential loads, and, as a major consideration, the energy conditions in the flow exiting the dissipator and the integrity of the rock downstream to avoid erosion.Each of these aspects will be addressed in the paperboth from the modelling and interpretation standpoint and from the civil structural analysis standpoint, together with a description of the strengthening works required to achieve a satisfactory outcome.
Brett Jones, Brian Mayhew
In preparation for the Corporatisation of the former Snowy Mountains Hydro-electric Authority, an
enquiry was held into the health of the Snowy River below Jindabyne Dam. This enquiry has led to a
range of environmental release requirements being placed on the new entity Snowy Hydro, including
requirements for variable release patterns (daily base flows and periodic flushing flows) and water
Construction works are currently underway to modify the existing Jindabyne Dam structures so that
these releases can be provided. The works include a new intake channel and control structure, a new environmental release tunnel and modifications to the existing spillway, including a concrete lined chute and plunge pool. Provision is also being made for a future mini-hydro power station, which would generate using waters released to provide environmental flows.
This paper discusses the history and background of Jindabyne Dam including the Snowy River
inquiry, details of the environmental flow requirements; design to meet the required capabilities and
the current status of the project.
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.
Peter 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.
Wellington Dam is an extreme hazard concrete gravity dam located on the Collie River approximately
170km south of Perth. Originally constructed to a height of 19m in 1933, the dam was raised to its
present height of 34m in 1960 by placing significant additional concrete against the downstream face
of the original dam. To ensure a lasting bond along the interface between the original and secondary
concrete, an open slot was formed and later grouted once the temperature of the secondary concrete
was similar to that of the original dam.
A recently completed stability analysis identified that Wellington Dam falls well short of contemporary
dam engineering standards for flood loading. Several assumptions were made during the preliminary
analysis relating to concrete shear strength parameters, bonding between the original and secondary
concrete and drain effectiveness that generated a significant range of results. On this basis, further
investigation was carried out to define the concrete parameters and drain condition at Wellington
Exploratory drilling found that Wellington Dam is cracked from the upper gallery through to the
downstream face. The drilling programme also confirmed that the interface between the original and
secondary concrete has become unbonded and that the gravity dam is behaving like an unbonded
short composite beam. The mechanism causing the observed behaviour of Wellington Dam can largely
be explained by external temperature effects and Alkali Aggregate Reaction, (AAR).
This paper explores the techniques used to investigate the condition of the concrete and illustrates the
relationship between concrete behaviour and temperature and AAR effects within a composite
concrete gravity dam.
Changes to the Regulatory and legal environment have resulted in an increased focus on the
importance of proficient management of dams. Operation and maintenance manuals are now a
Regulatory requirement in Tasmania for all but very low hazard dams and are also required to ensure that dams are managed efficiently and safely. To meet these requirements Hydro Tasmania has developed the ‘Smart’ operations and maintenance manual.
Hydro Tasmania has a large portfolio of dams and as a result requires a large number of operations and maintenance manuals. This would result in an overwhelming array of information that is subject to evolving change if the traditional approach to the manual was adopted. To overcome this burden, a controlled electronic manual was developed to enable:
• Critical operation and maintenance information to be collated with minimal effort;
• Electronic hyperlinks to key existing operation and maintenance documents, reference
materials, and portals into operational data bases; and
• A means of updating and controlling information that is subject to change.
This paper will discuss how Hydro Tasmania developed its user-friendly operation and maintenance manuals in an innovative, unique and controlled manner to ensure prudent management of dams and to comply with Regulatory change.