Cotter dam one of a kind

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1 Sustainability in Public Works Conference July 2014 Paper<Insert Paper number> Cotter dam one of a kind K. Dickson, S. Wright * ACTEW Water, Canberra, ACT *Corresponding author. sally.wright@actew.com.au ABSTRACT: The construction project to enlarge the Cotter Dam represents one of the most significant projects in Canberra s history. Utilising the Infrastructure Sustainability Council of Australia (ISCA) rating tool to ensure sustainability was threaded through the entire design and construction, this project has managed to deliver long term water security for current and future generations; economic benefits to the local region; significant environmental achievements and two world firsts in construction design. A lengthy drought in the ACT between 1999 and 2010 depleted Canberra s water supply. ACTEW together with Bulk Water Alliance partners commenced the project to enlarge the dam by 20 times its original capacity and future climate-proof the region using first class sustainable design. While securing water was the main purpose, this project, completed in October 2013, had additional benefits: Engineering innovations: Two world firsts in infrastructure design; development of an aeration step in the primary spillway; and use of a paver for roller-compacted-concrete replacement, which at 87m high is the tallest roller-compacted-concrete dam in Australia. Another first was the creation of the 7km artificial freshwater rock-reef within the dam to ensure the survival of the last viable population of endangered Macquarie perch in the ACT. Environmental, economic and social benefits: Meticulous attention was paid to protecting and enhancing the neighbouring environment throughout the design, planning and construction phases of the enlarged Cotter Dam with emissions from all project stages offset to make this a carbon neutral infrastructure project. The construction injected $88m into the local economy and local recreation areas were built attracting over 200,000 visitors. Involvement in the ISCA Infrastructure Sustainability program led to this project being the first to register for a national IS rating. A rating of commendable is anticipated. Using this framework has encouraged innovative thinking and has led to new standards in construction and project management being established. KEYWORDS: Cotter Dam, roller compacted concrete, sustainability, engineering solutions, water security, rock-reef. 1 Introduction The construction project to enlarge the Cotter Dam represents an important community benefit and one of Canberra s most significant sustainable infrastructure projects. Utilising the ISCA rating tool to ensure sustainability was threaded through the entire design and construction, this project has managed to deliver long term water security for current and future generations; economic benefits to the local region; significant environmental achievements and two world firsts in construction design as well as other engineering achievements. A lengthy drought in the ACT region between 1999 and 2010, known as the millennium drought, put significant pressure on the national capital s water supply. After undertaking various climate change studies, ACTEW Water together with Bulk Water Alliance partners (GHD, Abigroup and John Holland) commenced a significant project to enlarge the dam by 20 times its original capacity. This not only improved the security of the ACT s water supply it also put the ACT region in a good position to meet continuing uncertainties of climate change, in particular the risk of water shortage arising from drought and support a growing region. A key element was to ensure that the infrastructure was built incorporating worldclass sustainable design. In line with the ISCA framework and methodology, which helps to focus the design, construction and operation of infrastructure projects to optimize environmental, social and economic outcomes over the long term, sustainability was kept front of mind during all stages of design and construction. The project took six years to complete. Project design commenced in 2008, with construction

2 commencing in October 2009 and the enlarged dam completed in October Some of the key highlights are featured below. 2 Engineering solutions The project included two world firsts in infrastructure design. The first is the development of an aeration step in the primary spillway, designed to prevent fast flowing water from damaging the face of the dam during a 1 in 1000 year rainfall event. The step aerates the water which reduces the cavitation forces produced by fast flowing flood water and redirects the water into a stilling basin at the base of the dam. In the stilling basin energy and speed is removed from the flowing water by the geometry of the basin structure and the specially constructed energy dissipation blocks. Figure 2: Roller compacted concrete wall Another first of its kind was the creation of a seven kilometre intricate artificial freshwater rock reef within the dam to protect the survival of the last viable ACT population of the endangered Macquarie Perch. This feature provides for fish conservation and will help with university research on these fish species and their habitat now and into the future. Recognised for its originality and groundbreaking design, this project received the Australian Water Association National Award for Program Innovation in Figure 1: Aeration spillway The second first is the use of a paver for roller compacted concrete (RCC); at 87 metres high the Cotter Dam is the tallest RCC dam in Australia. All the aggregates and sands used in the concrete production were quarried and crushed onsite. A concrete paver was created for the downstream steps of the dam to improve dam productivity, safety and quality. Up to 200 metres of finished step could be completed in one shift using a team of just three people. The use of the paver reduced labour resources, created a safer working environment, provided cost savings and created a higher quality finish. Figure 3: Fish habitat rock reef Other innovations included the design and development of an electric hydraulic kibble, specifically used to complete the concrete pour on the secondary spillway walls. An automated operating mechanism for opening and closing the concrete kibble was developed to eliminate safety hazards associated with the manual operation of the kibble lever which was often very difficult to reach and used at heights. The final product delivered a low risk electric/hydraulic remote controlled solution which improved efficiency and safety for the dam construction. 3 Local economic benefits Over 2.5 million hours were worked on the Cotter Dam project, with over 60% performed by employees that were sourced locally. This

3 helped to inject $88 million into the local economy. The construction of a dam of this size and type is extremely rare. The construction workers on this project have improved their skill base and many of these vital lessons will be taken onto projects across Australia and around the world. A main purpose of the Cotter Dam enlargement is to provide security against a future water crisis which would otherwise have financial and social implications for this region. The expansion increased the storage capacity of the dam from 4 gigalitres to 76 gigalitres providing an additional 35% volume to the territory s water storage capacity. This has removed the threat of water restrictions. Previously, water restrictions have created flow-on costs to households, commercial activities, water-intensive businesses and the tourism sector. 4 Safety comes first Safety remained the highest priority throughout the construction. By continually challenging accepted practices, ACTEW promoted continuous improvement and set new benchmarks in safety. Working collaboratively with Comcare, WorkSafe ACT and trade unions such as the CFMEU, the management team instilled a culture of safety-first behavior through its Work Safe Dam Safe initiative which provided safety training for all staff and workers. This, coupled with the team-building strategy of Dam Good, Dam Great, Team Dam, provided an engaging platform for all stakeholders. Nearly 12,000 hours of formal safety training was undertaken with over 220,000 hours of identifiable safety specific activities were delivered. 5 Sustainability indicators The project s Sustainability Policy governed decision-making and the practices used to design and build the dam. The policy was based on the ISCA Infrastructure Sustainability requirements to embed sustainable management and governance; resource use; emissions, pollution and waste management; ecology management; people and place; plus delivering innovation into the project. Key performance indicators (KPI s) were developed to help drive the project team towards outstanding sustainability performance and to respond to key elements in the environmental impact assessment [1]. Table 1: Project key performance indicators Key Area Result Environment Legacy Key Performance Indicators KPI s were developed to improve environmental management performance, build in sustainable project management, and protect the endangered Macquarie Perch and the Cotter and Murrumbidgee Rivers so that neither was negatively impacted. The Legacy KPI s were focused on lasting economic, operational and community benefits including contributing to the local construction industry through employment and knowledge. Quality Avoiding unplanned cracking is crucial to water retaining structures. Therefore effective concrete temperature management for RCC was a key outcome supported by other Quality KPIs. Operability Community engagement and stakeholder management Maintaining supply from the Cotter reservoir was a high priority for ACTEW, reflected by this KPI. Impact on the local community was a significant concern for ACTEW requiring effective community and stakeholder management. KPI s were focused on the time and effectiveness of responses to community complaints and information provided to the local community. Safety Continuous real time evaluation of safety of the project was incorporated in the safety KPI s.

4 To ensure success a range of sustainability related management plans were developed to align with the policy, and performance showcased in annual sustainability reports. 6 Environmental considerations In line with the IS rating tool, a major consideration was to protect and enhance the neighbouring environment throughout the design, planning and construction phases. Environmental highlights included: 6.1 Reuse of resources Approximately 1 million tonnes of foundation bedrock was quarried and retained on-site to be crushed and used in the construction of the dam wall. Processing and crushing this bedrock into aggregate for 360,000 cubic metres of roller compacted concrete use saved nearly 3 million kilometres of construction vehicle journeys, equivalent to circumnavigating the equator 71 times, as well as saving valuable materials. 6.2 Biodiversity offsets Management and rehabilitation of 420 hectares of native land in the Cotter Dam catchment area was used to offset the biodiversity impact of constructing the new dam. 6.3 Carbon neutrality The project team committed to offset all carbon emissions associated with the construction and operation of the project, through securing 900,000 tonnes of carbon dioxide equivalent of carbon forestry offsets over 30 years. 6.4 Tree replanting Relocation took place of more than 120 Grass Trees (Xanthorrea) from the inundation zone. These were replanted on the Cotter Dam Discovery Trail, at the Australian National Botanic Gardens Canberra, at the National Arboretum and in rehabilitated areas of the Cotter catchment. 6.5 Native bush plantings In consultation with the Yurung Dhaura Indigenous work group, more than 2000 indigenous bush medicine plants and traditional food species endemic to the Cotter Region were planted. 6.6 Sustainable procurement Throughout construction, preference was given to suppliers with a sound environmental reputation and life cycle and sustainability credentials. 7 Heritage program The Cotter catchment was a traditional dwelling point for Aboriginal people and hosts an abundance of Aboriginal cultural history. To ensure that the Cotter s indigenous history was recorded for present and future generations, a comprehensive heritage program was undertaken as part of this project. Approximately 4,000 Aboriginal and European heritage artefacts were collected by Aboriginal representatives and others over the Cotter Dam construction and inundation site, ranging from stone cutting tools and axe heads to grinding stones. In addition, both Aboriginal and European artefact material including artworks, photography and films of the past and the present were recorded. In August 2013 a Return to Country ceremony was conducted with the Aboriginal artefacts placed in a carefully selected site overlooking a reach of the dam. This has provided a lasting legacy of the archaeological significance of the Cotter area. A separate celebration of the cultural heritage of the area was constructed at the site through the Cotter Dam Discovery Trail, a 1.4 kilometre trail built to showcase the history and heritage of the area and its significance to the Canberra community as well as providing direct views of the Cotter Dam. Figure 4: Cotter Dam Discovery Trail Since opening in September 2010, the trail has received over 200,000 visitors and around 1,600 students participating in education programs relating to the dam. 8 Community benefit This infrastructure project has been important to the people of Canberra. It has secured water for future growth of the region. It has

5 generated educational and recreational facilities such as the Cotter Dam Discovery Trail and the upgrade of the well used recreation facilities at Cotter Avenue. A school education program has been delivered by ACTEW Water aimed at increasing awareness about the project and explaining the engineering and sustainability achievements of the project. Figure 5: Viewing platform 9 Lessons learnt and conclusions The ISCA IS rating tool provided the framework for a wide range of sustainability elements to be considered throughout the various stages of the project; from design, to construction through to operation. It has encouraged innovation and ingenuity to overcome complex challenges and improve upon existing best industry practice to establish new standards of construction and project management. Involvement in the IS program led to this project being the first to register for a national IS rating. It is anticipated that this project will score a commendable rating once final verification has taken place against the IS rating tool. Acknowledgements ACTEW Water would like to acknowledge the Bulk Water Alliance in the development of the enlarged Cotter Dam. Bulk Water Alliance partners comprise ACTEW Water, GHD, Abigroup and John Holland. References 1. ACTEW Corporation, 2009, Enlargement of the Cotter Reservoir and associated works. Water Security Major Projects, Environmental Impact Statement, vol 1.