The volume-of-fluid (VOF) technique was employed to develop a Computational Fluid Dynamics (CFD) model for comparison to physical measurements available from the Eildon Dam model in Australia for validations purposes. The water surface in the downstream chute of the spillway was observed to be mostly comprised of fully developed aerated flow. The free surface is physically measured as located between the mixing and upper zones, thus investigator judgement is critical to achieve reliable measurements. The mixing zone is also characterized by surface waves to complicate matters even further. A challenge arose to develop a post processing methodology that replicates as closely as possible the measuring technique used by the physical modeller for direct comparison of results, using a novel method which utilises Poisson probability of exceedance applied to the free surface.
Trustpower is a New Zealand based hydro generator and retailer. It started off as a business that only owned a few schemes and then during a period of rapid expansion between 1998 and 2002 acquired the bulk of its current schemes. Now it owns and operates 25 hydro schemes across New Zealand ranging from 150kW to 80MW output.
This paper examines how Trustpower’s Dam Safety Management System (DSMS) has evolved over time, taking account of developments in the business environment, proposed regulatory changes, improvements in the NZSOLD guidelines and evolution in international dam safety practice.
The Kumara-Dillmans-Duffers Hydro Electric Power Scheme (HEPS) and in particular its Kapitea Reservoir (high Potential Impact Category) will be used as an example to highlight how the DSMS evolved over this period.
The U.S. Army Corps of Engineers (USACE) is responsible for flood risk management across the United States. USACE has more than 710 dams and is responsible for more than 24,000 kilometres of levees. Since 2008, USACE projects have prevented more than AU$1.2 Trillion (in 2017 dollars) in damages from flooding. Although some of this came as a result of dozens of smaller floods, much of that protection came during three events within the last five years. From 2010 through 2017, the U.S. has had three major inland floods and two coastal events where federal flood protection exists: in 2010 on the Cumberland River, in 2011 on the Missouri, Ohio, White, and Mississippi Rivers, in 2015 on several rivers in Texas and Oklahoma, and in 2017 along the Gulf Coast of the U.S. and its territories in the Caribbean. For many of these locations, these events produced record rainfall and the flood of record. USACE operated many large facilities on these systems and those systems overall performed as expected. However, USACE also experienced some operational issues, did a substantial amount of flood fighting, had several incidents, and several failures. This paper will describe the flooding experienced in those events, the operations of the flood protection systems, the performance overall, and some of the lessons learned.
An assessment of dam failure consequence for Jandowae Water Supply Dam in South-West Queensland was performed using HEC-LifeSim. The purpose of the assessment was to investigate the applicability of the software to inform decisions on an appropriate regulatory pathway for the dam that reflects the consequences of failure. This paper details the development of the hydrologic and hydraulic models behind the HEC-LifeSim simulations, the assignment of key parameters and their sensitivities, and a comparison of predictions to existing procedures for assessing potential loss of life and populations at risk. The paper reflects upon the level of effort required to develop HEC-LifeSim assessments and the relative benefits gained using this information in the regulatory space.
The rehabilitation of wet tailings storages is likely to become of increasing importance. In a setting of increasing environmental regulation and oversight, the environmental issues inherent in wet tailings storages will increase in visibility. This will translate through to increased regulatory attention, rehabilitation standards and costs. This scenario will necessitate increased engineering ingenuity and approaches to develop cost effective and robust/ defensible outcomes.
This case study of a coal fired power station ash dam rehabilitation compares a conventional (baseline) rehabilitation strategy and the development of a higher land use, with potentially beneficial outcomes for the owner, the community and the environment.
The baseline rehabilitation was a conventional fit-for-purpose rehabilitation approach consistent with the proposed final land use comprising the creation of a stable, open greenspace environment. The higher land use was an aspirational target style rehabilitation, with the assessed highest and best use for the site that was determined to be an industrial land development. While there will be limitations due to the low strength tailings foundation, this higher land use is considered an appropriate stretch target and is a feasible outcome for this site.
The As Low As Reasonably Practicable (ALARP) principle was established in the Australian Dams
community in the ANCOLD Guidelines on Risk Assessment in 1994. Since that time, dam owners have been focused on reducing their societal risk to below the ANCOLD Limit of Tolerability (LoT) through dam safety upgrades and are now considering how to justify an ALARP position. This paper presents a framework that provides a systematic approach to assembling the inputs, applying a process and documenting the outcomes of an ALARP assessment. It is a pragmatic approach that aligns with the safety case, which is a legislated requirement for Major Hazard Facilities in Victoria.
The framework has been applied to two dams in Melbourne Water’s portfolio with differing societal risk, size, uses and criticality to the water supply system. It has highlighted the importance of dam safety governance, documentation of procedures, defensible technical analysis and an ongoing engagement with leading industry practice, in demonstrating risks are ALARP.