A survey of spillway gate systems and operations has recently been completed by dam organisations in Nth America, Australia and New Zealand. The survey sought to identify typical arrangements for spillway gate systems and common features pertaining to reliability such as system redundancy, actuation methods and back-up systems, gate and hoist types, remote and local operation, gate testing programmes, and human factors.
Sixteen organizations responded, covering sixty two dams and nearly four hundred gates. This Paper reports on the preliminary analysis of the data, providing an overview of the industries’ approach to spillway gate operation and control.
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An energy and water company spends $8 million on maintenance each year. This work is defined and scheduled through a maintenance management system, part of an enterprise solution that cost the company over $2 million for licence fees, management consulting and installation.
The company has an ageing asset base and has been spending $18 million annually on capital improvements. The work activities are selected to meet safety requirements, enhance reliability, improve plant and upgrade customer service, and are defined, prioritised and scheduled on Word and Excel, which are standard applications on the desks of the company’s engineers and accountants.
This company is a composite (typical) of many in the energy and water business.
The most significant business decisions that owners usually have to make are capital spending commitments to modernise energy and water assets. To be successful, strategies have to be devised to meet the overall strategic objectives of the business, and processes adopted based on a fully functional and integrated asset planning system.
‘Aptus’ is a web-based planning application built specifically for asset intensive businesses. It enables a consistent analytical framework using engineering knowledge and the dam owner’s financial criteria, to provide new perspectives and support strategic planning and decision making with triple bottom line reporting. Aptus is a proven resource to maximize the value of the asset portfolio and sustain the business into the future.
John Grimston, Robin Dawson, Maurice Fraser
Water supply for irrigation of horticulture and agriculture in New Zealand has gained considerable momentum since the mid 1990’s. The rapid growth of the wine industry in areas such as Marlborough (located at the top of the South Island) and dairy conversions in many areas of South Canterbury are prime examples of the pressure being applied to existing water supplies and sources and the increasing need for new irrigation supplies and security of supply.
The larger irrigation projects of the past were implemented by the government – schemes such as the Rangitata Diversion race and the Lower Waitaki irrigation project both on the east coast of the South Island. The 1990’s and early 2000’s has seen a largely hands off government approach to potential irrigation projects with the shift towards leaving it to market forces to build irrigation schemes. The result has been that due to significant larger project risks and capital cost requirements with often multi party stakeholder groups, only relatively small schemes have been implemented – the Waimakariri irrigation scheme and Opuha irrigation dam are a few examples. However, in recent years with the value of water increasing several significant irrigation projects promoted by private enterprise or progressive district councils with farmer groups are being investigated and a few may be close to implementation.
The recent drought conditions have focussed attention on the need for storages to maintain security of supply and, together with the balance with sustainability, the consenting environment in New Zealand and existing river/aquifer allocations, significant challenges to development are presented.
Specific case examples include the proposed Delta dam near Blenheim being developed by a private group of irrigators and the Bankhouse development being implemented by a private owner in the same Marlborough region.
This paper provides a background to irrigation in the South Island and describes these two proposed schemes and associated storage dams, together with an insight into the key issues related to the proposed projects.
Hydro Tasmania has recently upgraded the control systems for the spillway gates of three of its dams, Clark Dam, Meadowbank Dam and Liapootah Dam. The upgrades followed internal reliability assessments that highlighted high reliance on operator attendance, single points of failure and operational difficulties on each of the three gate systems.
The three gates are of contrasting types. Clark Dam Spillway Gates are submerged orifice type radial gates, operated by wire rope hoists. Meadowbank Crest Gates are flap type gates, held by 10 hydraulic cylinders per gate, a design that has had a difficult operating history. Liapootah is a floating drum gate. The upgrades for each gate therefore required different solutions, albeit within a common basis of design framework. The solutions arrived at are innovative, and meet or exceed worlds best practice.
All three gates are now fully automatic, with PLC control. The use of PLC’s significantly enhances the reliability of the gates. Extensive use is also made of the PLC in monitoring key systems. For example, an impossibly rapid lake level rise detected by one transducer, but not its duplicate, will be alarmed but ignored to avoid unnecessary discharge. All systems incorporate appropriate redundancy. The PLC systems also provide some automatic functional testing functionality and enhance remote alarms and local fault finding.
Mechanical systems were modified to facilitate automation and increase reliability. Stand by power sources used include auto-start diesel genset, DC batteries and a micro hydro generator.
The design and implementation of each of the upgrades was carried out by the Electrical and Mechanical Group of Hydro Tasmania’s Consulting Division, in conjunction with Generation Division’s Project Management Group.
Steven Fox and Mark Tansley
Yarrawonga Weir was constructed in the 1930’s and is located on the Victoria / New South Wales border, between the towns of Yarrawonga and Mulwala. Dam safety investigations revealed that the main embankment was founded on a very loose layer of sand that would be vulnerable to liquefaction even under the operating basis earthquake.
This paper details the statutory approvals and community consultation processes that were employed and the benefits that they provided to the $13 million remedial works project.
Local communities can assist, be neutral or obstruct a project. By engaging the community in a positive manner it is possible to deliver excellent results without increasing costs.
Gregg Barker B.E. (Hons.) GradIEAust
Dam safety emergency plans (DSEPs) are typically produced for individual dams. For owners of a large portfolio of dams, this approach creates document control difficulties, requires excessive time and effort and can lead to confusion when a single emergency affects multiple dams having individual DSEPs. Hydro Tasmania has developed a single DSEP which is applicable to its portfolio of 54 referable dams. The DSEP contains generic emergency response procedures, is applicable to a whole range of generic dam safety incidents, uses a simple colour-coded flowchart-action list format, has a two-stage emergency response, retains all necessary dam-specific information and can be easily adapted to any organisational structure. This approach was found to have benefits in document control, flexibility in the management of the emergency response and short lead time in terms of having DSEPs which cover an entire portfolio of dams.