P. J. N. Pells and M. Hunter
The potential for generating acid leachate from waste dumps is a major consideration in many metalliferous and coal mines. This paper describes the construction of the highest embankment dam in Indonesia for the sole purpose of storing potentially acid producing waste under water. The paper discusses the features of embankment dam design peculiar to an open pit mining environment which involves moving more than three times the total volume of earth and rock than in the whole of the Snowy Mountains Scheme.
Canning Dam is a mass concrete curved gravity structure 466m long and 70m high and is a primary peaking source for the Perth Metropolitan water supply system.
A safety review of Canning Dam concluded that the existing structure does not possess adequate margins of safety under static and dynamic loadings using contemporary dam engineering practices. Given the location and strategic importance of the Canning source, it is imperative that the dam be upgraded to comply with moder standards.
After investigation of alternative remedial measures to strengthen the dam, a permanent post- tensioned anchoring system was chosen.
Of the total of 165 permanent, monitorable and restressable ground anchors to be installed, 70 will consist of 91 x 15.2 mm strands. These are the highest capacity anchors to be installed anywhere in the world. A proving test for this size of anchor was carried out by VSL in September 1998. The results of the test confirmed that the use of 91 x 15.2 mm strand permanent anchors is feasible and that the corrosion protection is assured.
S. Knight, B. Cooper and P. van Breda
Warragamba Dam was completed in 1960 and impounds Sydney’s main water supply storage. Hydrological studies in the 1980’s showed the existing spillway to be significantly undersized by modern standards. Considering the dam’s High Incremental Flood Hazard category, the current risk of dambreak is unacceptably high. This has resulted in a two-stage program to upgrade the dam to full Probable Maximum Flood (PMF) capability.
The interim (first stage) measures were completed in 1990 and involved a 5.1 metre raising of the dam crest and significant post-tensioning of the dam wall. Following many feasibility/option studies and detailed technical and environmental studies, a contract was let by Sydney Water Corporation (SWC) in late 1998 for the construction of an auxiliary spillway as the major (second stage) component of the flood security upgrading. The spillway will be a large capacity (about 18,000m*/s) concrete lined chute 700 metres long around the dam’s right abutment. In the upper curved section will be the largest fuse plug embankments in Australia (up to 14.5 metres high). The lower straight section will terminate with a flip bucket structure.
The NSW Department of Public Works and Services (DPWS) designed the earlier Interim Works, undertook the subsequent engineering option studies for the Major Works and carried out the concept design and technical specification for the new auxiliary spillway and associated dam modification works. This paper summarises the project, describes the main features of the concept design of the spillway and outlines the associated dam modifications.
Garry Meinck, Chris Elliott and Tony Moulds
This paper describes the experiences of a former state statutory authority in the almost four years since it became corporatised to form a water utility with a fully commercial orientation and with a new board of management with a clear awareness of the responsibilities of corporate governance.
The need to commit to major remedial work at one of the principal dams focussed the Board’s attention on the safety status of all of the Corporation’s 56 referable dams.
In the absence of external dam safety regulation the Corporation has moved to satisfy its corporate governance responsibilities by adopting current best practice in dam safety. Key elements in this process were:
Gary Hargraves, Russ McConnell and John Ruffini
The acceptance of the use of generalised methods for estimating extreme rainfall has resulted in a growth of the Probable Maximum Flood (PMF) estimates that spillways of dams are required to pass. In many cases spillways were not designed with spare capacity and are incapable of safely passing the new PMF estimates. Dealing effectively with the potential for dams to cause damage and loss requires a risk management approach. Such an approach requires more reliable tools for estimation of rainfall. This paper examines the issues, the progress made, and outlines further work and options for clarifying risk.
Robert E Saunders
The vast majority of dams in Australia are relatively small affairs. For example, approximately 90% of Queensland’ referable dams are less than 15 m in height. Most of these dams are owned by small communities, mining companies or farmers, many of which have smaller operations than those of Australia’s larger dam owners. In many cases the dam represents the owner’s sole source of water supply.
Many smaller dam owners are unaware of the key factors affecting the safety and best management of their facilities. Added to this is a general lack of understanding of dam related issues by the community at large. This often leads to significant owner and community concerns (and conflicts) that have the potential to jeopardise the viability, or worse, the safety of a project. The relative importance of the dam to the smaller dam owner often exacerbates these issues.
This paper serves to illustrate, by way of example, a consultant’s viewpoint of some of the issues encountered on small dam projects and suggests actions that the dams industry as whole could take to improve the situation.