There is increased pressure from stakeholders for projects to include evaluation of emerging broader development issues within the environmental assessment process. These emerging issues are not well documented or understood and at the forefront of untested preliminary government policy positions.
Agencies expect proponents to invest in evaluating these matters outside of typical assessment practices. Requests are made late in the evaluation and approval process.Assessmen involves matters not directly related to the project or within the proponent’s control and occurs late in the project development cycle.
The Lower Fitzroy River Infrastructure Project (LFRIP) was identified through the Central Queensland Regional Water Supply Study in 2006, as a solution to secure future water supplies for the Rockhampton, Capricorn Coast and Gladstone regions. The Gladstone Area Water Board and SunWater Limited, as proponents, propose to raise the existing Eden Bann Weir and construct a new weir at Rookwood on the Fitzroy River in Central Queensland.
The LFRIP environmental impact statement (EIS) was approved, subject to conditions, by the Queensland Coordinator-General in December 2016 and the Commonwealth Minister for the Environment and Energy in February 2017. Achieving conditions that will realise positive environmental outcomes while simultaneously achieving project objectives, particularly with regard to timeframes and costs, was not without its challenges.
The EIS was developed in accordance with the requirements of the State Development Public Works Organisation Act 1971 (Qld) and the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999, including an extensive stakeholder consultation programme. These regulatory requirements are well understood and applied to projects as normal accepted practice. They ensured that potential project impacts and benefits were identified, that appropriate levels of effort were applied to investigations to establish baseline conditions and that risks to and impacts on environmental (including social and cultural) matters were adequately mitigated and managed.
The environment is not static. Emerging issues and perceptions results in regulation and policy changes in response to political and social drivers. During the development of the EIS both new legislation and new policies were imposed on the project.New legislation resulted in additional assessment around matters previously considered mitigated and managed (fish passage). New legislation introduced new matters for assessment (connectivity). Collaboration and engagement with stakeholders were key to understanding the applicability of these elements to the project and for developing an approach to address the legislative requirements late in the project’s development and assessment process.
In Queensland,policy is emerging to mitigate and manage impacts of development on the Great Barrier Reef World Heritage Area’s universal values. The EIS was required to address the direct project impacts on water quality and the impacts arising because of the LFRIP (facilitated development). Water secured by the LFRIP is for urban, industrial and agricultural purposes. Urban and industrial developments are well regulated and subject to specific environmental approvals processes. Use of water for agricultural purposes, intensive irrigated agriculture in particular,is less regulated. Policies developed are reactive and require individual projects to address these impacts.In the absence of regulatory guidelines for assessment of consequential impacts, the project adopted a collaborative approach. The proponents established a working group, including State and Commonwealth technical agencies. This allowed for robust and scientifically defendable methodologies to be developed and agreed upfront. Streamlining the approach by including key decision makers assisted in managing expectations and focused the assessment on realistic and achievable outcomes relative to the project. The result was defendable outcomes allowing timely decision making and avoided rework as much as possible.
This paper describes developments in environmental assessment relating to new and augmented weirs.
M. A. Hariri Ardebili, M. Akbari and H. Mirzabozorg
This paper presents a study on the effects of incoherence (considering the Harichandran and Vanmarcke coherency model) and wave-passage (considering various wave velocities) on the nonlinear responses of concrete arch dams . A double curvature arch dam was selected as numerical example, the reservoir was modeled as incompressible material and the foundation was modeled as a mass-less medium. Ground motion time-histories were artificially generated based on a Monte Carlo simulation approach. Four different models were considered in the generation of ground motions; Uniform excitation; Just incoherence effect; Just wave passage effect; and finally take into account both incoherence and wave passage effects. It was revealed that modeling incoherency can have significant effect on the structural response of the dam by modifying the dynamic response of uniform excitation and inducing pseudo-static response. Also, it was concluded that incoherency effect overshadow wave passage effect and results caused by wave passage effect are close to the results of uniform excitation.
2011 – Comparison of wave passage and incoherence effects on nonlinear non-uniform excitation of concrete arch dams
Krey Price, Mike Harvey, Bob Mussetter, Stuart Trabant
The California Department of Water Resources, Division of Dam Safety (DWR-DSD), has determined that San Clemente Dam on the Carmel River in Monterey County, California, does not meet seismic safety standards. Several alternatives have been considered to decommission the dam and eliminate the hazard, including thickening of the 25-m-high, concrete arch structure, lowering the dam, and complete removal. At the present time, the upstream reservoir that had an original storage capacity of about 1.8 GL, is essentially filled with sediment. The 29-km reach of the Carmel River between the dam and the Pacific Ocean passes through urbanised areas within the upscale Carmel Valley; flooding and channel stability in these areas are significant concerns. The Carmel River also contains habitat for the endangered steelhead and red-legged frog that could be positively or negatively affected by the decommissioning.
After an extensive series of hydraulic and sediment transport modelling studies, two actions remain under consideration: (1) dam thickening, which will require reconstruction of the existing fish ladder and construction of an adjacent, 3-metre diameter sluice gate to prevent sediment build-up from blocking the ladder outlet, and (2) removal of the dam and rerouting the river into a tributary branch of the reservoir, which would isolate approximately 65 percent of the existing sediment deposits from future river flows and eliminate a significant fish-passage problem. Both options were modelled extensively in hydrologic, hydraulic, and sediment transport applications. Since available models do not adequately represent sediment dynamics at the sluice gate, a special sediment routing model was formulated to evaluate this aspect of Option 1. Option 2 is currently preferred by the resource agencies, since it would optimise endangered species habitat; however, this option would be three to four times more expensive than Option 1, and funding limitations may impact the alternative selection. Evaluation efforts are ongoing, along with approaches to address liability issues associated with the decommissioning actions for the privately owned facility, while optimising the benefits and costs of the selected action.
Modelling Studies to Design and Assess Decommissioning Actions for a Seismically Unsafe, Concrete Arch Dam
David R Jeffery
In 2004 the Victorian Government announced the decision to proceed with Australia’s largest dam decommissioning project, the return of the 365,000ML capacity Lake Mokoan to a wetland.
The project has been completed and has resulted in significant river health benefits through liberating environmental flows in the Broken, Goulburn, Murray and Snowy Rivers. Decommissioning has allowed the recovery of water savings for return as environmental flow to the River Murray (30,000 ML/year) and Snowy River (21,000 ML/year).
With decommissioning complete, development of a significant wetland complex across the 8100 hectare site has commenced.
This project has been undertaken at a time when the Broken River basin was exposed to its worst drought conditions in over 100 years and within 11 years of the worst flooding experienced in the nearby Rural City of Benalla. These extremes of climatic conditions and their impacts on the local and irrigation communities have ensured considerable community and stakeholder interest in the decision to proceed with decommissioning and in the subsequent delivery of each of the project elements.
This paper provides an explanation of the drivers for the project, describes the process followed and some of the challenges experienced over the projects seven year life and presents some of the lessons learned along the way.
2011 – MOKOAN – RETURN TO WETLAND PROJECT
Craig Messer, Francisco Lopez, and Manoj Laxman
The Enlarged Cotter Dam is a new 80m high Roller Compacted Concrete Dam being constructed to augment the water supply for the Canberra region. Due to the size of the main dam and the extreme climatic variations in the ACT, where temperatures range from sub zero in winter to in excess of forty degrees in summer, it is expected that significant stresses will be generated during the cooling of the structure. For this reason it is essential that an understanding of the magnitude of these stresses is developed through the initial strength development period and at critical periods such as the first and second winter when the temperature differential between ambient conditions and the core of the structure may be greatest. The development of thermal stress within the structure has critical impacts on both the RCC mix design and the dam construction equipment and methodology.
For the Enlarged Cotter Dam, thermal stresses were investigated using both two and three dimensional finite element transient heat transfer analyses, making use of the thermal properties derived from laboratory testing including instrumented thermal blocks, as well as established literature. Modelling of the thermal stresses in the dam required the development of time dependent concrete properties, such as strength, stiffness and heat generation, with the latter based on test results and calibrated to actual measured values. Additionally, site dependent conditions for ambient temperature, external conduction, convection and radiation factors, dam foundation temperatures and restraint, dam construction sequence, formwork, joint spacing, insulation and timing of reservoir filling were also modelled.
Initial thermal modelling of the dam demonstrated that significant tensile stresses and potential cracking could develop within the structure, at both early and mature concrete ages. Subsequent analyses were developed to investigate methods of reducing these stresses to within acceptable limits. This paper presents the results of the thermal analyses, including the methods to be employed during and after construction to minimise cracking without impacting construction costs and even optimising the speed of construction.
Finite Element Transient Thermal Analysis of the Enlarged Cotter Dam