A. Ahmed-Zeki, G. Roads
South East Queensland Water Corporation (SEQWater) as owner and operator is proceeding with an upgrade of the flood capacity of Wivenhoe Dam. SEQWater has formed an Alliance with Leighton Contractors, Coffey Geosciences, Montgomery Watson Harza (MWH) and the Department of Commerce-NSW (formerly DPWS, NSW) to upgrade Wivenhoe Dam. This paper presents feasibility level investigation and design activities for an upgrade option, comprising a large labyrinth auxiliary spillway at the right abutment of the dam, for supplementing the existing gated spillway in handling the Probable Maximum Flood (PMF) event. This right abutment auxiliary spillway option incorporates Hydroplus type concrete fuse gates. The investigation so far has proved the technical viability of this option, however, ranking along with the other three options against various criteria will lead to the selection of the preferred upgrade option.
Hydro Tasmania has recently developed a Dam Safety Emergency Plan, which covers 54 referable dams throughout Tasmania. A major contribution was the development of the Pieman River flood warning system. The flood warning system is a computer-based model that forecasts the hydrological situation of the catchment up to 48 hours into the future and alarms the appropriate personnel when a flood event is imminent. The Pieman River catchment experiences some of the highest average annual rainfalls in Tasmania and contains dams in the High Hazard category. The flood warning system was developed using Hydstra Modelling™ (formerly TimeStudio), which links directly to the Hydstra TSM™ database. This package offers powerful automation tools that enable the Pieman River flood warning system to operate, alert personnel and display results on Hydro Tasmania’s internal website with no manual involvement. With its maintenance free operation and user-friendly interfaces, the Pieman River flood warning system is an effective contribution towards the overall risk management package of the Pieman River Power Development.
Karin Xuereb, Garry Moore and Brian Taylor
Assessment of dam safety requires estimates of extreme rainfall together with the temporal and spatial distributions of extreme rainfall. In order to satisfy dam safety requirements for dams in the west coast of Tasmania, the Bureau of Meteorology has developed the method of storm transposition and maximisation for application in this region.
Daily, as well as continuously recorded rainfall data for all Bureau of Meteorology and Hydro Tasmania sites in western Tasmania have been analysed and the most outstanding rainfall events over one, two and three-day durations in the region have been identified. Meteorological analysis of these events reveals that the most significant rainfall events in the west coast of Tasmania are caused by the passage of fronts, which are sometimes associated with an intense extratropical cyclone, with a westerly or southwesterly airstream.
A database of isohyetal analyses of the most significant rainfall events in western Tasmania has been established. These can be used either ‘in situ’ or transposed to estimate mean catchment rainfall. Storm dewpoint temperatures for the purpose of moisture maximisation have been determined.
Cumulative and incremental three-hourly temporal distributions for sites having continuous rainfall data or three-hourly meteorological observations have been constructed and design temporal distributions of extreme rainfall have been derived.
An objective method for adjusting for differences in the topography between the storm and target locations is proposed.
Bellfield dam is a 78,500 ML drought reserve storage for the Wimmera-Mallee Stock and Domestic System. The 800m long by 57m high zoned earth and rockfill dam is located on Fyans Creek upstream of the Grampians tourist town of Halls Gap in north western Victoria. The dam was built in the period 1963-67. Later in 2002-03 as part of a flood security upgrading (FSU) program, had its rock chute spillway deepened by 3.4m and its embankment crest raised by 1.9m to withstand a PMF.
To manage the FSU’s likely construction constraints and risks, Wimmera Mallee Water’s Headworks Group successfully undertook the upgrading by a mix of schedule of rates contracts and direct management.
This paper complements a companion paper by WMW’s design consultants, URS and describes why and how direct management was used, plus unconventional aspects of spillway deepening and the raising of a narrow dam crest with earthworks and a pre-cast parapet wall.
Keywords: Drill and blast, pre-cast parapet wall, narrow embankment crest, direct management, construction.
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.
M G Webby
Investigations of damaging blowback incidents at the headrace tunnel intake to Rangipo Power Station in the Central North Island of New Zealand are described. The blowback phenomenon is explained theoretically based on evaluation of the evidence available from the incidents and information obtained from the literature. A physical hydraulic model study is described in which this explanation of the blowback phenomenon was verified. The model was also used to devise a solution for the blowback problem.