Francisco Lopez and Michael McKay
At 36 m high and completed in 1902, Barossa Dam is one of the first true concrete arch dams in the world. During the 1954 Darlington Earthquake the dam sustained some damage, in the form of several vertical cracks on both dam’s abutments. In 2013, GHD conducted a nonlinear time-history seismic assessment of Barossa Dam. The analyses, carried out using finite element techniques, included ground motion loading corresponding to Maximum Design Earthquakes (MDEs) with 1 in 10,000 Annual Exceedance Probability (AEP).
This paper will explain the purpose of the study, the material investigation phase, the methodology, model results, the anticipated seismic behaviour of the dam wall, as well as the predicted level of damage under the MDEs. The paper examines the dam construction practices of the beginning of the 20th century, and how such practices affected the material properties and the structural performance of Barossa Dam.
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Bronson McPherson, David Guest, Barton Maher, Ian Tanner and Amit Chanan
There is significant community interest in the potential for water supply dams to be adapted for flood mitigation, particularly for major dams located upstream of flood vulnerable populations. There may be a number of large dams which have the potential to provide significant flood mitigation benefits to Australian communities if they can be adapted for flood mitigation functionality. Other dams already provide significant flood mitigation benefits, however their limitations are not properly understood by the general public. Two major dams located near a large urban town centre prone to flooding are examined as a case study and some international cases are presented.
Flood mitigation often has a different funding source to water supply. The funding arrangements for flood mitigation dam works can be complex, considering the potential stakeholders and somewhat intangible benefits. If the community wants to use a water supply dam to provide flood mitigation then who provides the funding for the modification works?
Leonard Wiliem, Rob Keogh, and David Thomas
Progressive rope creep on the steel ropes which hold 14 counterweights in tension on the seven spillway gates was monitored regularly. The 2011 annual inspection identified that the creep had taken the lower guide wheels of the suspended counterweights beyond the extent of the wheel guides.
A programed project to extend the guides was delayed due to Workplace Health and Safety concerns on confined access and working under a suspended load. A study was commissioned to deliver a safe method of extending the guides. Because regular testing and two flood events had proved the gates were functioning well, the risk of failure in gate operation during flood event was considered low and a lower priority was assigned to rectification work.
Callide Dam is a SunWater owned dam located in Central Queensland. It has a similar spillway gate mechanism as Coolmunda Dam. The only difference is that Callide Dam gates work in pairs with one counterweight attached to each gate.
In January 2013 due to heavy rainfall caused by the ex-cyclone Oswald, Callide Dam experienced a flood event which triggered a gate operation. During the draining phase, the gates operated abnormally sustaining damage to the structure and to the automatic gate opening mechanism. SunWater undertook investigations to identify the cause of the abnormal operation and found that the primary cause of the gate abnormal operation was due to jamming of the suspended counterweight on the end of the guides. This was due to cable stretched over 26 years of service to the extent that the lower wheel assembly was beyond the guide rails at the time of the flood event.
The event at Callide Dam was a wake up call for SunWater to re-evaluate the risk assessment for Coolmunda Dam. This re-evaluation recommended to assign the highest priority on the rectification of the wire rope creep issue on the radial gate as the risk of failure in gate operation during flood event was high.
This paper discusses the actions in re-evaluating the risks at SunWater’s Coolmunda Dam and the measures taken to quickly undertake remedial action on both dams and the challenges involved with each.
Steven Slarke, Dr Martin Mallen-Cooper and Marcos Guirguis
Keepit Fishway Offsets
Fish passage structures are being provided by State Water Corporation as part of a strategic program to address fish passage barriers that triggered S218 of the Fisheries Management Act 1994 at Mollee Weir, Gunidgera Weir and Weeta Weir in the Namoi River. These sites are an offset for dam safety upgrade works on Keepit and Split Rock dams in the headwaters of the Namoi River. Rather than applying high-level fish lifts at the dams, the three lowland sites represent the top three ecological priorities in the Namoi River for fish passage facilities – a case of less cost for greater ecological outcomes. The objective of the fish passage facilities at these sites is to restore upstream and downstream fish passage for about fifteen native fish species. The key biological objectives are to pass adult and juvenile fish upstream and adult fish and larvae (which drift with the current) downstream.
Mollee Weir was constructed in 1973 on the Namoi River downstream of Keepit Dam, near Narrabri in northern NSW. The nine-metre high weir is used for irrigation and comprises a reinforced concrete structure featuring three bays with undershot gates and two piers. The upstream and downstream water levels are highly variable, with a maximum differential head of about six metres. Fish are unable to pass the weir during regulated and unregulated flows; even when the undershot gates are fully raised in high flows, due to high velocities in the opened weir. The weir’s large undershot gates are also a barrier to safe downstream fish passage during regulated flows. High water pressures and velocities beneath the partially raised gates create a high mortality rate for fish and larvae moving downstream.
Fish Passage and Regulator Structure
Designed for State Water NSW by URS Australia Pty Ltd in cooperation with Dr Martin Mallen-Cooper of Fishway Consulting services, Mollee Weir features a new fish lock for upstream-migrating fish and a dedicated overshot gate with dissipating pools for downstream-migrating fish, and was constructed during 2013 to 2014.
It is the tallest fish lock in Australia that is filled from the top.
The innovative design features two separate downstream fish holding bays and two fish lock entrance gates, to provide optimal entrance conditions at varying river flows and water levels.
To provide safe downstream fish passage at low to moderate river flows, a 4 m wide ‘downstream multi-function migration gate’ has been integrated beside the fish lock structure. This overshot gate also provides an attraction flow to the fish lock entrances, and tracks the upstream water level at high river flows to provide a high discharge pool and weir fishway as a bypass around the weir structure.
The Mollee Weir fish lock provides upstream fish passage for the full range of upstream and downstream water levels.
Lyndon Johnson and Jamie Campbell
Data presentation is an important and much discussed aspect of Dam and asset safety worldwide. We rely on drawings and graphs of instrumentation data to tell us things about our assets that are hidden from the eye and to monitor changes linked to failure modes. It’s common that we look at data gaps for our assets, data quality and data processing but how often do we rethink the fundamentals of data presentation?
Engineers and data analysts, as humans, have evolved in a 3D world with our senses to match match. According to Keller GB, et al (2012) almost 20% of the human brain is dedicated to processing vision with up to 60% involved when locating, scaling and referencing objects in 3D space. As a result, 3D is an extremely efficient platform from which to display and disseminate information.
This paper discusses methods to efficiently transfer asset information into 3D and how to present animated surveillance data against asset models. The paper discusses how these methods work, benefits and limitations in the context of modern dam asset portfolio management and presents some key case studies of where and how these methods have assisted with asset diagnoses.
Wark, Bob; Thomas, Louise
This paper discusses the rating curves developed for several case studies from the Pilbara and Kimberley, including the Harding Dam, Moochalabra Dam and Ophthalmia Dam. The paper will discuss the impact of underestimated rating curves on the design of infrastructure. An example has occurred at Harding Dam where the pump station was designed to be inundated at a 1:100 AEP and this is now estimated to occur at a lower AEP. The paper will also discuss methods to improve the accuracy of rating curves and the challenges associated with determining accurate rating curves.