Preamble. List of contributors

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2 Preamble Providing water to the National Capital was a key consideration in determining the boundary of the Australian Capital Territory and the site for Canberra. The city was planned during the 1901 to 1911 federation drought and the wrangling over the allocation of the waters of the Murray River. The demand for water drove the final decision on the location of the ACT borders, which are based on major water catchments. The main catchments considered were the Cotter, Gudgenby, Naas and Paddys River, which all lie within the Territory. The origins of Canberra and the ACT are linked with water, and our future must be as well. Since the earliest times in the history of the ACT, successive administrations have created a series of dams and water features that distinguish Canberra from other cities. The key challenge for the medium and long term is to build additional water supply assets that can cope with reduced average inflow into the dams and longer, more frequent droughts, without having to impose highlevel water restrictions for extended periods. To have the capability to deal with these longer, drier and more frequent droughts, there is a need for future supply capacity that will be additional to that which is needed in years of average inflow. The cost of this extra capacity does not represent premature investment. It is justified on the grounds of ensuring water security during these times when climate change and climate variability are having a significant impact on the sustainability of supply. ACTEW acknowledges that it is working in Ngunnawal Country. List of contributors This Environmental Impact Statement was prepared by the ACTEW Water Security Major Projects Team with input from the following organisations: Abigroup Ltd ActewAGL Bassett Consulting Engineers Biosis Research Pty Ltd CB Richard Ellis Pty Ltd Ernst & Young Ecowise Environmental GHD John Holland KRM Consulting Pty Ltd Manidis Roberts Navin Officer Heritage Consultants Pty Ltd Tania Parkes Consulting University of Canberra

3 List of photographic contributors The following contributed to the photos used in the Environmental Impact Statement: ActewAGL. Biosis Research Pty Ltd. Col Ellis. Murray-Darling Basin Commission. Territory and Municipal Services. National Archives of Australia. National Library of Australia.

4 Contents EXECUTIVE SUMMARY 1 1 INTRODUCTION Background and need Why the change in recommendations? Criteria for new water supply assets Water security options under various climate change scenarios Alternatives considered Preferred options Government decision major water security projects for the ACT Enlarged Cotter Dam updated report, July The proponent Structure of this EIS 33 2 PROJECT DESCRIPTION Location, context and tenure Existing Cotter Dam (history) Project specifications Construction details Operation Decommissioning Project timeline Compatibility with the principles of the Territory Plan Objectives of the project 71 3 EIS PROCESS AND METHODOLOGY Background to EIS Statutory process The scoping document Potential environmental impacts Potentially significant environmental impacts 88 4 EXISTING CONDITIONS General Climate Geotechnical conditions Demographics Demand for water The status of the land Commonwealth legislation Territory legislation, management plans, guidelines and strategies POTENTIAL ENVIRONMENTAL IMPACTS Infrastructure impacts Construction materials and waste management practices Land values and impacts 146

5 5.4 Water resources values and impacts Microclimate, air quality and emissions, noise and vibration Terrestrial biodiversity and nature conservation Aquatic ecology Aboriginal and European cultural heritage Social impacts Health impacts Economic impacts Whole-of-system impacts POTENTIALLY SIGNIFICANT ENVIRONMENTAL IMPACTS Water quality in the reservoir Cold-water pollution Terrestrial biodiversity and nature conservation Aquatic ecology Impacts on threatened fish Macquarie perch spawning habitat Introduction of pests or pathogens through recreational use Alien fish (expanded populations and upstream invasion) Cultural values Public expectations and understanding Recreation areas Climate change CONSULTATION Consultation on scope Consultation in preparation of draft EIS Consultation activities Summary of consultation outcomes Consideration of community/agency feedback and representation on draft EIS Next steps in community consultation RECOMMENDATIONS AND COMMITMENTS Recommendations Commitments relating to impacts identified as not potentially significant Commitments relating to potentially significant impacts GLOSSARY List of abbreviations Definitions References 301

6 List of Appendices Appendix A Scoping Document Appendix B Document Contents Map Appendix C ACT Government Press Release Water Plan Appendix D ECD Concept Design Appendix E Land Status of Cotter Dam Enlargement Project Area Appendix F Cotter Catchment Landscape Analysis Appendix G Visual Impact Report Appendix H Cotter Dam Acoustic Modelling Appendix I Cotter Dam Enlargement EIS: Terrestrial Flora and Fauna Impact Assessment Appendix J Aquatic Ecology Study Appendix K Fish Management Plan Appendix L Fish Management Plan Phase 1 Assessment Appendix M Cultural Heritage Impact Assessment Appendix N Community Feedback Community Consultation on the Draft EIS for the Enlarged Cotter Dam Appendix O Socio-Economic Impact Assessment Appendix P Greenhouse Gas Assessment Appendix Q Greenhouse Gas Emissions Strategy Appendix R Future Water Options Appendix S Enlarged Cotter Dam Update Report July 2007 Appendix T Employment Impact of the Cotter Dam Enlargement and the Murrumbidgee to Googong Water Transfer Appendix U Traffic Impact Assessment List of figures Figure 1.1 Inflows to Corin, Bendora and Googong Reservoirs Figure 1.2 Annual inflows into Corin, Bendora and Googong Reservoirs Figure 1.3 Projected storage with climate continually repeating 16 Figure 1.4 Projected storages with repeated 2006 climate 17 Figure 2.1 Lower Cotter Catchment land use map and access trails 36 Figure 2.2 Location of Cotter Dam 37 Figure 2.3 Main engineering infrastructure and construction area set-out (concept) 39 Figure 2.4 Indicative construction area at clay borrow sites 40 Figure 2.5 Comparison of Cotter Reservoir and Enlarged Cotter Dam inundation areas 41 Figure 2.6 The Cotter Dam and the Reserve have been a recreational destination for generations of Canberrans and visitors 43 Figure 2.7 Building the original Cotter Dam between 1912 and Figure 2.8 The Cotter Pumping Station in its original configuration, before a two-storey extension was built to house the vertical pumps 44 Figure 2.9 The Cotter Dam after the wall was raised in Figure 2.10 Tunnel and pipeline to Cotter Pumping Station on the banks of the Murrumbidgee River 45 Figure 2.11 Artist s impression of the Enlarged Cotter Dam 46 Figure 2.12 Construction cycle for main dam Generic RCC construction process 54 Figure 2.13 Delivery of roller compacted concrete to the dam via conveyor (concept) 56

7 Figure 2.14 Tower crane layout (concept) 57 Figure 2.15 Probability of time taken to initially fill the Enlarged Cotter Dam to TWL 63 Figure 2.16 Probability of time at various levels after the initial filling 64 Figure 2.17 Probability of duration of drawdown events greater than 1.5m below TWL of Enlarged Cotter Dam 65 Figure 2.18 Downstream of Cotter Dam flow duration curve for existing Cotter Dam and the Enlarged Cotter Dam ( ) 66 Figure 2.19 Project timeline 68 Figure 3.1 Flow chart for impact track approvals in the ACT 77 Figure 3.2 Scoping the environmental impacts 80 Figure 4.1 Average maximum and minimum temperatures for Canberra 92 Figure 4.2 General wind direction and strength at Canberra Airport 93 Figure 4.3 Average monthly rainfall and number of rain days 94 Figure 4.4 Moving average inflows to Corin, Bendora and Googong Reservoirs 96 Figure 4.5 Water use distribution for Canberra and surrounds 101 Figure 4.6 Land potentially affected by the Enlarged Cotter Dam proposal 104 Figure 5.1 Hourly traffic volumes Cotter Road (summer and winter) 126 Figure 5.2 Proposed road access 130 Figure 5.3 Traffic count data 134 Figure 5.4 Cotter River catchment 147 Figure 5.5 Cotter Dam visual catchment 149 Figure 5.6 Sensitive visual receptors and view points 149 Figure 5.7 Sensitive receivers 165 Figure 5.8 Blasting exclusion zones 177 Figure 6.1 Sample locations hydrodynamic modelling 198 Figure 6.2 Terrestrial biodiversity study areas 200 Figure 6.3 Pre-1750 vegetation model 201 Figure 6.4 Vegetation community mapping 203 Figure 6.5 Conservation values mapping 211 Figure 6.6 Aboriginal cultural heritage recordings within or near the proposed inundation area and construction areas 247 Figure 6.7 All European cultural heritage recordings within or near the proposed inundation area and construction areas 247 Figure 6.8 Public amenities and recreation facilities 261 Figure 6.9 Moving average inflows to Corin, Bendora and Googong Dams 270 List of tables Table ES.1 Potentially significant impacts 4 Table 1.1 Previous and revised costs of water restrictions ($million per/year) 15 Table 1.2 Recommendations from the Enlarged Cotter Dam Update Report 2007 with EIS responses 31 Table 1.3 Document structure 34 Table 2.1 Details of the proposed works 49 Table 2.2 Objectives of the project 71 Table 3.1 List of approvals required 79 Table 3.2 Descriptions of likelihood for environmental impacts 81

8 Table 3.3 Elements of consequence 81 Table 3.4 Descriptions of consequence for environmental impacts 82 Table 3.5 Risk assessment likelihood and consequence 83 Table 3.6 Identifies potential impacts and risk assessment (from ACTPLA Scoping Document, the full scoping document is presented in Appendix A.). 84 Table 3.7 Potentially significant impacts and residual risk assessment 89 Table 4.1 Target of and observed reductions from water restrictions since November Table 4.2 Blocks of land that may be affected by the project 103 Table 5.1 Total number of truck movements per day by construction month 132 Table 5.2 Estimated volume of water to be used during the construction 139 Table 5.3 Waste streams, volumes likely to be generated and proposed waste management measures 143 Table 5.4 Visual impact assessment Sensitive visual receptors 150 Table 5.5 Visual impact assessment View points 151 Table 5.6 Adopted criteria for maximum dust fallout 162 Table 5.7 Forecast capital and operating expenditures for Water Security Major Projects 2007/08 to 2012/ Table 5.8 ANCOLD hazard category 187 Table 6.1 Summary of predicted water quality values for the Enlarged Cotter Dam 194 Table 6.2 Table 6.3 Table 6.4 Table 6.5 Indicative pre-1750 vegetation of the lower Cotter catchment modified from the Lower Cotter Catchment Strategic Management Plan Terrestrial flora listed under the EPBC, NC, TSC and FFG Acts that may occur in the locality 208 Estimated vegetation type and loss due to actions relating to the construction of the main dam and two saddle dams (Note: these are approximate). 214 Estimated total vegetation loss by type due to all construction activity and maximum reservoir capacity 215 Table 6.6 Cotter Precinct recreation areas, facilities and function 262 Table 7.1 Consultation with agencies during scoping of EIS 271 Table 7.2 Consultation register government agencies and stakeholders. 274

9 Executive summary Introduction The enlargement of the Cotter Reservoir is needed to deliver a more secure water supply for the Canberra region. The Cotter Dam lies on the Cotter River approximately 18 kilometres (km) west of Canberra City in the ACT. The project will increase the capacity of the Cotter Reservoir from 4 gigalitres (GL) to around 80GL, raising the ACT s overall storage capacity by a third. The project proponent is ACTEW Corporation Limited (ACTEW). ACTEW is an ACT Government owned company whose primary functions are to provide energy, water and waste water services to the ACT. The Enlarged Cotter Dam was chosen as a high priority option because of its relative economic benefit to the community, reliability of water supply and low environmental impacts. ACTEW is committed to the provision of a safe, secure and sustainable water supply for the ACT and Region. Securing supply for an inland city in the driest continent on earth is a big challenge, especially with droughts tipped to get longer, drier and more frequent. The Enlarged Cotter Dam project is a key component in ACTEW s long term plan to ensure this security, leading to a prosperous national capital and a vibrant and healthy community. This Environmental Impact Statement (EIS) provides an overview of the project, assesses the potential impacts and proposes mitigation strategies to address them. Project description The existing Cotter Dam lies on the Cotter River in the Lower Cotter catchment approximately 18km due west of Canberra. It is just upstream of the confluence of the Cotter, Paddys and Murrumbidgee rivers, this area forms a recreational precinct that includes Cotter Avenue, Cotter Campground, Casuarina Sands and Cotter Pumping Station. The Enlarged Cotter Dam will be constructed approximately 125 metres (m) downstream of the existing dam. The project consists of a main dam with two adjacent saddle dams. The new dam will be approximately 80m high and the adjacent saddle dams will be built to an approximate height of 11m and 16m. The storage capacity would increase from currently 4GL to 78GL. Element Main dam Description of works Main dam wall roller compacted concrete structure. Integrate the dam wall aesthetically and thematically into the wider Cotter Precinct landscape and recreational plan. Dam axis to be located approximately 125m downstream of existing Cotter dam wall. Final location subject to geological and geotechnical assessment regarding the adequacy of abutment and foundation conditions. Width of main dam approximately 260m. Height of main dam approximately 80m. Storage capacity of approximately 78GL (at 550.8m AHD). Access to top and base of dam, for maintenance personnel and the public (if permitted). Multi-level intake tower capable of drawing water down to 5 per cent of storage capacity. Internal access to drainage and inspection galleries. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 1

10 Element Mechanical and electrical works, instrumentation and power supply Description of works Provision of trash and fish screens and gantry crane at the intake tower and associated electrical works. Provision of surveillance instrumentation of the dam structure including piezometers, tilt meters, inclinometers and remote monitoring. Power supply and communications to intake and outlet structures. Dam plug valve to permit draining of the reservoir. Quarry site Clay borrow areas Saddle dams Spillway, intake and outlet Investigation and analysis of the quarry site, including suitability, quantity and proximity of in-situ material. Investigation and analysis of clay borrow areas, including suitability, quantity and proximity of in-situ material. Two separate embankments preferentially constructed of earth/rock-fill. Service spillway for floods, designed in response to risk assessment. Overflow crest and apron for flood events designed in response to risk assessment. Energy dissipating structure. Variable level intake capacity with an approximate range between 5ML/d and 1,200ML/d for environmental releases with the dam at 60 per cent full. The pipework required for the delivery of raw water from the river discharge point to the suction side of the existing tunnel be sized to 1,500 mm. Manual and remote controlled valve operation. Intake tower to allow environmental flows and town demand to be sourced from separate levels within the water column. Online water quality sampling for dissolved oxygen, turbidity, and temperature at intake tower valves. Ability to take physical samples from intake valve levels using the online water quality system. Trash racks and fish screens on the intake tower to prevent material being sucked into river discharge valves and Cotter pumps Heavy lift ability for maintenance of intake valves. Low-level intake to access deep storage and allow for flushing. Water supply and environmental release pipelines to be fitted with appropriate meters to measure flow for operational and licence requirements. The discharge point of the stilling basin to incorporate a river flow gauge (wide V notch crest), to allow measurement of the flow below the dam, whether it be overflow or environmental flow release. Spillway flow (water level) measurement. Catchment and precinct management Provision of additional (and/or replacement of) mixers and de-stratifiers to maintain water quality in larger reservoir (subject to findings of hydrodynamic modelling). Extended boat ramp to allow reservoir access over the full range of drawdown. Mixers operation to be linked to weather station at the dam wall. Implementation of fish habitat management plan. Aquatic real-time management system building on hydrodynamic model. 2 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

11 Element Description of works Quarry and borrow sites to be left to agreed standard and profile. Preference for the location of sites is below Full Supply Level for use as fish habitats. Provision of river diversion works. Design must consider implementation sequencing to permit continued operational use during construction. Upgrading and continuous management of access and forestry tracks used to ensure protection of the catchment and water quality General construction Optimisation of the progressive impoundment of water taking account of the continued operational use of the existing Cotter Dam, including access for ActewAGL maintenance personnel for the duration of construction. Obtain all construction works permits and approvals required to execute the works. Ability to meet ongoing abstraction licence conditions, including e-flows. Relocation of existing services as necessary. The existing dam and 231 hectares (ha) of land will be inundated, and a further 38ha of land will be cleared for construction and ancillary works. Most of the land surrounding the Cotter Dam is of low environmental value and is already impacted by the existing reservoir, previous forestry plantations and severe bushfires in ha of the land to be impacted is former pine forest that was destroyed by these fires, the remaining 105 ha is native vegetation. All land within the project area is either unleased Territory land or leased by ACTEW. Subject to approval, construction of the dam is planned to commence in the last quarter of 2009 and is expected to be completed in Project justification and benefits The Enlarged Cotter Dam forms part of ACTEW's continued response to secure water supplies for the ACT. The key challenge for the ACT in the medium and long term is to build additional water supply assets that can cope with reduced average inflow into the dams and longer, more frequent droughts, without having to impose high level water restrictions for extended periods. The Enlarged Cotter Dam was chosen from a range of water supply options as it will: Deliver a net economic benefit to the community. Have minimal impact on threatened fish populations. Result in environmental benefits derived through improved catchment condition and improved understanding and habitat opportunities for endangered species within the dam. Use existing infrastructure via the pump station at Lower Cotter and the Mt Stromlo Water Treatment Plant. Draw water from a reliable catchment in times of drought. Capture environmental flows that are released from the Corin and Bendora reservoirs that often spill over the current Cotter Dam. Catch much of the overflow from storm events that the current dams in the Cotter system cannot store. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 3

12 Generate economic benefits as a result of the construction project itself and the expertise that it will bring to Canberra. Lead to economic and social benefits derived from spending less time subjected to water restrictions. EIS process A project of this magnitude requires the preparation of an EIS under the Planning and Development Act A draft EIS was submitted to ACT Planning and Land Authority in October 2008 and was publically notified. This final EIS addresses the issues raised by the community and regulatory authorities. Potentially significant environmental impacts Potentially significant impacts in relation to the Enlarged Cotter Dam were identified using a risk assessment process that considered the likelihood and consequences of a particular impact occurring. For the purposes of the Scoping Document (Appendix A), this assessment was undertaken without consideration of potential mitigation measures. The uncontrolled risks are listed in Table ES.1 below and the Scoping Document. This EIS considers these potential impacts and identifies commitments necessary to manage the risks. Taking into account the mitigation measures that ACTEW has committed to undertake, the residual risk of these impacts can be assessed. The residual risks are also tabulated below. These potential impacts are addressed in detail in Chapter 6 of this EIS. A range of lesser potential impacts are discussed in Chapter 5 of this draft EIS to ensure all potential impacts have been thoroughly considered. Chapter 8 describes the impact mitigation measures identified by the proponent and the commitments made to implement them. It is considered that, on the basis of the commitments made, the risk of significant environmental impacts of the Cotter Dam Enlargement is low. Table ES.1 Potentially significant impacts L = Likelihood C = Consequence R = Risk Scoping document assessment Residual risk assessment L C R L C R Water resource values and impacts Impacts upon water quality within the reservoir or downstream due to biological or physical processes Thermal stratification of dams leading to the release of cold water to the environment Likely Moderate High Unlikely Minor Very low Possible Moderate Medium Remote Moderate Very low Terrestrial biodiversity and nature conservation Disturbance of protected or environmentally sensitive areas Almost certain Moderate Very high Unlikely Moderate Low Impacts on areas of native vegetation Almost certain Moderate Very high Almost certain Minimal Medium 4 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

13 L = Likelihood C = Consequence R = Risk Scoping document assessment Residual risk assessment L C R L C R Aquatic ecology Changes to the aquatic biology of the reservoir or downstream Likely Moderate High Possible Moderate Medium Impacts to ecosystems caused by changed flow regime below the Cotter Reservoir Almost certain Minor High Unlikely Minor Very low Impacts on endangered fish species Inundation and destruction of Macquarie Perch spawning habitat Introduction of pests or pathogens through recreational use Expanded populations of alien fish Upstream invasion of alien fish species during construction of the new dam Likely Major Very High Unlikely Moderate Low Possible Major High Unlikely Moderate Low Possible Major High Possible Moderate Medium Likely Moderate High Possible Minor Low Possible Major High Unlikely Moderate Low Heritage Impacts on objects or places of cultural heritage value Likely Moderate High Unlikely Moderate Low Social Community misunderstanding about the impact on water supply and the need for the project The loss of recreational opportunities and amenity Likely Moderate High Unlikely Minor Very low Likely Moderate High Unlikely Minor Very low Potential impacts on the project The impact of unavoidable climate change on the project Likely Moderate High Unlikely Minor Very low ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 5

14 Conclusion The proposal to enlarge the Cotter Dam represents a major investment in water supply infrastructure with the objective of increasing the security of Canberra s potable water supply. Construction of the dam and the consequent impoundment of water will have some impacts on the environment. The information presented in this EIS demonstrates that while there are some potentially significant impacts that could occur, appropriate mitigation measures are available to manage the risk of these impacts. A high standard of environmental management will guide this project and the significant economic and social benefits of an Enlarged Cotter Dam will positively impact on this region for many years to come. Considering the potential impacts and benefits, ACTEW believes that the proposal to enlarge the Cotter Dam should be supported by decision makers, stakeholders and the Canberra community. Summary of key findings and recommendations The Enlarged Cotter Dam project represents a significant investment on behalf of the ACT community. Projects of this nature are not undertaken lightly and should not be without due consideration for the potential benefits and impacts across the spectrum of the environment, economy and society. This EIS finds that while significant impacts could occur, there are sufficient mitigation measures available to adequately control the likely risks. It is recommended that: For the long term benefit of Canberra, and based on the ability to successfully mitigate all potentially significant impacts this assessment recommends that the project should proceed. The project should be built in accordance with all commitments proposed to be adopted. Chapter 8 includes a concise summary of all commitments made in this assessment. The commitments should form the basis for development approval. This is best achieved by considering these commitments as conditions for approval along with other conditions which may be relevant. 6 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

15 1 Introduction 1.1 Background and need The proposal to enlarge the Cotter Dam is not new. As Canberra has grown so has the demand for water. In the face of predicted climate change the need for a reliable water supply has been reinforced. Enlarging the Cotter Dam is one of the preferred options for delivering improved security to Canberra s water supply. This project was announced in a press release by the Government in October 2007 (Appendix C) as part of a suite of initiatives to secure the ACT s water supply. The selection of major infrastructure projects was based on more than four years of investigations to identify sustainable future water sources for Canberra and the region. These investigations included: The ACT Government s Think water, act water a strategy for sustainable water resources management (2004a). ACTEW s Future Water Options project 2004/2005 (2005a). ACTEW s Review of Future Water Options Assumptions (2006). ACTEW s Review of Future Water Options based on new information 2006/2007 (2007a). ACTEW s Recommendations to the ACT Government regarding the Security of the ACT s water supply (2007b). The ACT Government decision and announcement of the key initiatives for securing Canberra s Water Supply October 2007, (Appendix C) Think water, act water The ACT Government released its water resources strategy Think water, act water a strategy for sustainable water resources management (ACT Government, 2004a) on 28 April This strategy assessed all aspects of ACT water resources, including water supply, demand management, institutional arrangements, regulation and innovation. Through a comprehensive consultation process, Think water, act water identified a series of objectives to guide sustainable management of water resources in the ACT, including to: Increase the efficiency of water usage. Provide a long-term reliable source of water for the ACT and region. Furthermore the strategy states: A range of water supply options for the future will continue to be considered in case water use efficiency measures are not able to save enough water to avoid the need to construct water supply infrastructure. This planning process is being developed in a strategic manner to ensure there is no risk to the long-term security of water supplies in the ACT. Previous analysis indicated that the ACT would need to augment the water supply by 2017, to meet demand for a population of about 405,000. Several issues emerged that motivated reassessment of this prediction: The current drought was developing into one of the worst on record, with experts concerned about permanent climate change for the region. The Cotter River water supply catchment was almost completely burnt in the bushfires of 2003 and was expected to deliver reduced inflows to water storages as it recovered. The ACT Government announced a population policy in the Canberra Spatial Plan (ACT Government, 2004b) of 500,000 by ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 7

16 The Government s water strategy, Think water, act water, had set water efficiency targets of a reduction in per capita mains water use of 12 per cent by 2013 and 25 per cent by Environmental Flow Guidelines, first introduced in 1999, were under review. As water restrictions continued, the impacts on the community were being realised as significant, requiring a decision about what levels of water restrictions would be acceptable in planning for a long-term reliable water supply. Think water, act water charged ACTEW with the responsibility for assessing the reliability of the existing water supply and recommending options for new water sources for the ACT Government, and set a target of March 2005 to achieve this Future Water Options In response to Think water, act water, ACTEW launched the Future Water Options project on 30 April The project built on earlier work that had identified possible new water sources for the ACT and region as documented in the Options for the next ACT Water Source report (ACTEW, 2004a). Among more than 30 options, the report specifically highlighted and investigated three main water sources for future supply to Canberra and the ACT. These options were as follows: Building a new dam near Mt Tennent, south of Tharwa. Enlarging the existing Cotter Dam. Transferring water from Tantangara Dam in NSW to the ACT. ACTEW established a project team of specialists in water resources management, hydrological modelling, environmental studies, planning analysis, engineering, economics and related areas to conduct this analysis. The project team comprised more than 20 engineers, scientists and other professionals drawn from ACTEW, ActewAGL, other ACT agencies and specialist contractors and consultants. Studies were undertaken to assess and evaluate environmental, social, economic and technical issues and prepare preliminary engineering designs for the various alternatives. After nine months of detailed study and analysis the Future Water Options team provided their findings and recommendations to the ACTEW Board and ACT Government. Two key reports were provided to the ACT Government: An assessment of the need to increase the ACT s water storage (ACTEW, 2004b), predicting the future reliability of the existing supply. Implementation Plan: a recommended strategy to increase the ACT s water supply (ACTEW, 2005a) recommending implementing options to increase the reliability of the ACT s water supply. The final recommendations of Future Water Options were to implement: The Cotter Googong Bulk Transfer, where surplus water from the Cotter water supply catchment in the west is transferred through the existing reticulation network for storage in the Googong Reservoir. The Angle Crossing Option, where water is pumped from the Murrumbidgee River, near Angle Crossing, to Googong Dam via Burra Creek. 8 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

17 Additionally, it was recommended that: The remaining options of an Enlarged Cotter Dam (to 78GL), a small (43GL) or a large (159GL) Tennent Dam, and transferring water from Tantangara Dam down the Murrumbidgee River into the ACT be retained as future viable options. ACTEW undertake the necessary work program to be ready to implement one of these options if required. The work program was to include a regular review of the key assumptions that the studies were based on, and technical studies to support the approval process. Additional technical analysis will be undertaken for each of the dam options, including refining the dam design, further detailed examination of pipeline routes and additional examination of the benefits of building a new water treatment plant near the Tennent Dam versus transferring water from the Tennent Dam into the Mount Stromlo Water Treatment Plant Actions since 2005 The Cotter Googong Bulk Transfer commenced operation in 2005 and has proved successful in transferring up to 12GL per year from the Cotter River storages to Googong Reservoir. Further analysis found that the construction of a Murrumbidgee River pump station at Lower Cotter, in addition to Angle Crossing, could have very similar benefits. This option has also been implemented. The Cotter Dam and Cotter Pumping Station were progressively reintroduced into operation as part of the supply system in A new 80 megalitres (ML) per day pump station was built in the Murrumbidgee River and is now pumping water to the Mount Stromlo Water Treatment Plant. The Cotter River catchment has continued to provide more reliable flows than the Gudgenby and Queanbeyan River catchments during times of reduced rainfall (ACTEW, 2006). This had serious implications for the viability of any Tennent Dam option. ACTEW is implementing a drought contingency program to supplement supplies in the continuing drought and impending Stage 4 Water Restrictions. These measures include: Upgrading the Murrumbidgee River Pump Station. Refurbishing the Cotter Pumping Station. Providing a recycled water pipeline from the Lower Molonglo Water Quality Control Centre. Optimising the North Canberra Water Recycling Scheme. The basis of the drought contingency program is to maximise use of existing water sources, primarily the Murrumbidgee River and Cotter Reservoir, through minor works and adjustments to operational procedures. The planning assumptions that underpinned the Future Water Options program were reviewed in The key assumptions reviewed included: Climate variability and climate change. Impacts on inflows to the ACT Reservoirs following the 2003 bushfires. Future population growth from the ACT and Queanbeyan and the possibility to service additional areas. Reduction targets in per capita water use set by the ACT Government. Environmental flow requirements. Acceptable levels for the duration, frequency and severity of water restrictions during drought times. The findings of this investigation showed that there were no major changes to the variables outlined above and no changes to the government recommendations made in April 2005 were required. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 9

18 Report to Government In 2007 ACTEW again reviewed the Future Water Options program (ACTEW, 2007a). The severe impact of the protracted drought was clearly highlighted in the record low inflows recorded during The situation forced ACTEW to review Canberra s water supply and explore alternatives to ensure future water security. In July 2007 ACTEW Corporation submitted to the ACT Government a number of recommendations to further secure the ACT and region s water supply (ACTEW, 2007b). The recommendations were based on extensive analyses including work completed by ACTEW in 2004 and 2005 as well as updates and additional work completed specifically for this review. More than 30 reports supported the recommendations and were made available to the public via the ACTEW website and in hard copy. These reports included investigations into a range of matters including: Main reports Water Security for the ACT and Region: July Community Consultation Report: July Enlarged Cotter Dam: July Water Purification Scheme for the ACT: July Angle Crossing Option: July The Cotter Dam Option: April The Tantangara Dam Option: April Technical studies and supplementary reports Future Water Options Review, Water Security Program: July Economic benefit-cost analysis of new water supply options: April Planning Approvals Water Security Program: July Methodology for evaluating Future Water Options: July Land Status Report on the Proposed Water Security Program: July Cotter Recreation Issues Paper: July Enlarged Cotter Dam Cost Estimates Review: July Enlarged Cotter Dam Review and Update of Cost Estimates and Comparisons: July Preliminary Ecological Review for the Proposed Water Transfer from LMWQCC to Cotter Catchment: July The Tennent Dam Option: April Seawater Desalination Concept Report: July Inputs to the Water Purification Process Preliminary Assessments: July Water Purification Plant Options Assessment Study: July Proposed Water Purification Plant Power Supply Study for LMWQCC: July Preliminary Review of Environmental Factors for Discharge of Recycled Water into Cotter Reservoir: July Technical Feasibility Assessment of a Water Purification Plant at Lower Molonglo Water Quality Control Centre: July WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

19 Pumping Station and Pipeline from LMWQCC to Cotter Preliminary Sizing and Cost Estimates: July Pumping Station and Pipeline from LMWQCC to Cotter Cost Estimates Review: July Water Quality Monitoring Program for Use of Purified Water in the Canberra Water Supply Network: July Salt Management Sub-Report 1 Treatment Options for Dewatering Brine Waste: July Salt Management Sub-Report 2 Review of Offsite Disposal Options Evaporation Ponds: July Salt Management Sub-Report 3 Review of Offsite Brine Disposal Options Pipelines: July Salt Management Sub-Report 4 Review of Offsite Brine Disposal Options Landfill and Other Alternatives: July Salt Management Sub-Report 5 Discharge to Molonglo and Murrumbidgee River System: July Salt Management Sub-Report 6 Social and Human Impacts: July Salt Management Sub-Report 7 Review of Options Multi-Criteria Analysis: July These reports remain available to the public from ACTEW. In making its 2007 recommendations, ACTEW noted that its Future Water Options report (ACTEW, 2005a) to the ACT Government included recommendations that were explicitly based on six key assumptions. ACTEW undertook to monitor those assumptions and report back to the Government if any significantly changed. A major change occurred in relation to climate change and climate variability (ACTEW, 2007b). In earlier reports, based on the most pessimistic approach to analysis by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), ACTEW assumed a 30 per cent reduction in long term average inflows into our dams. In fact, over the period average inflows declined by 63 per cent and in 2006, by nearly 90 per cent. ACTEW advised that the medium to long-term outlook was for a further significant deterioration in the ACT s long-term average inflows from a 30 per cent reduction to almost a 50 per cent reduction. The current situation is described in section 2 of this report: however the 2007 predictions have been borne out and the ACT is still in a situation requiring significant new/expanded water supply infrastructure to ensure the region s future water security. ACTEW indicated to the Government that the key challenge for the medium to long term was to build additional water supply assets that could function with both much reduced long term average inflows into our dams as well as with more frequent and longer drought periods. ACTEW reviewed the 2005 report and recommended a series of new investments including: Immediately increase the storage capacity of the Cotter Reservoir from 4GL to 78GL. In addition to extracting more water from the Murrumbidgee at the Cotter Pump Station, the ACT Government also develop the same capacity from Angle Crossing (2005 recommendation described above). ACTEW also advised that it believed the ACT must have a new source of water that is largely independent of rainfall in our existing catchments and recommended that consideration be given to either the Tantangara Transfer or Water Purification Scheme. ACTEW stated that more analysis and planning were required prior to it being in a position to decide between these options. ACTEW committed to conducting these investigations and advised the ACT Government in late 2008/early 2009 on which should be implemented. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 11

20 1.2 Why the change in recommendations? Six assumptions underpinned the Future Water Options reports of These assumptions were that; The Government s water conservation targets will be met. Environmental flows will be delivered according to ACT Government guidelines. Catchment re-growth will respond to bushfires; The population will continue to grow according to the ACT Government s Spatial Plan; ACTEW will meet its service obligations to customers; and Projections of climate change and climate variability will occur in line with predictions made at that time. In relation to these assumptions, recent information has shown that there has been a deterioration in inflows into our storages as discussed above. In addition to this change it was determined that the future climate outlook has not improved. Population projections have changed, with predictions by the Australian Bureau of Statistics of increases greater than were foreshadowed and used in the Canberra Spatial Plan (ACT Government, 2004b). Using the high growth scenarios from the Australian Bureau of Statistics, the 2032 population of the ACT and Queanbeyan is now predicted to be 562,152 persons, an increase of persons (approximately 9 per cent) over the Spatial plan predictions. If cross border water supply was required, this figure would include outlying areas of the ACT and the 2032 population would increase further to 570,585 persons (in excess of ten per cent increase). The ACT Government s Think water, act water strategy (ACT Government, 2004a) prescribes the use of high population growth projections by stating that work being done to predict when new water supply infrastructure will be needed will therefore be using these higher growth projections for contingency planning to ensure that, if increased water supply is needed, necessary planning and design will be done well in advance of the need to begin construction. This strategy remains to be Government policy, and the further increases in population projections indicate that prudent supply planning continues to be necessary Climate change and climate variability Based on the same cautious approach that ACTEW has previously taken to the analysis conducted by CSIRO, but adjusted with new data from the last nine years, average annual inflows were estimated to be around 105GL a year to the three main ACT dams. In fact the last three years has seen an average inflow into the ACT s water storages of 50GL. This represents a substantial reduction from the long term average inflows (around 200GL a year) and a further reduction from the average annual inflows that was assumed based on CSIRO climate change research from the 2005 Future Water Options report (132GL a year). Figure 1.1 demonstrates long term inflows into ACT storages. Figure 1.2 demonstrates the reduction in inflows to three ACT storages over the last nine years. The continued decline in inflows and the continuing uncertainty of climate change, suggests prudent investment to ensure future water security for the ACT. 12 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

21 Figure 1.1 Inflows to Corin, Bendora and Googong Reservoirs The ACT currently needs to extract 65 to 70GL a year to meet customer demand. Approximately 30GL are lost due to evaporation, spills from reservoirs after major storm events and environmental flows. In light of this the ACT require about 100GL to flow into the storages every year. Water supply planning can not be based on average inflows of 100GL being available each year. This is because both the CSIRO analysis (CSIRO, 2003) and the modelling supporting ACTEW s 2007 report show that within that average, there will be droughts both longer and drier than the current drought. Such droughts are expected to occur with significantly greater frequency than in the past. The inflows into our storages for 2006 were 26GL, in 2007 were 66GL and in 2008 were 59GL. These years remain significantly below our long term average and even lower than the 105GL ACTEW estimated in its 2007 report to the ACT Government. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 13

22 Figure 1.2 Annual inflows into Corin, Bendora and Googong Reservoirs As stated previously, and now further reinforced by the climatic conditions of the past three years, the key challenge for the medium and long term is to build additional water supply assets. Additional assets must have the capacity to store and function with a much reduced long term average inflows, and withstand more frequent drought conditions which are longer and drier than recent/current experience, without the need to impose high level water restrictions for extended periods. ACTEW investigations to date demonstrate that there is a need for additional water supply capacity. The financial cost of this extra capacity is an essential investment that was justified (and accepted by the ACT Government) on the grounds of ensuring the ACT and region s water security. Since ACTEW s 2007 report to Government (ACTEW, 2007b), which noted some fundamental changes to climate predictions, ACTEW has been undertaking an ongoing review of available evidence to more accurately forecast the climate scenario in the short to medium term. Reports from the CSIRO, (CSIRO, 2003, 2004a, 2004b), Bureau of Meteorology (CSIRO & Bureau of Meteorology, 2007), the NSW Government and the Murray Darling Basin Commission (MDBC, 2008) all support a scenario that predict hotter and drier weather for the foreseeable future, with little chance of improvement in rainfall and the likelihood of significantly above average temperatures. These predictions reinforce the need for the ACT Government to have in place a diverse range of measures to ensure that the ACT community is protected from severe water restrictions and has a secure water supply for future generations. 1.3 Criteria for new water supply assets Choosing new water supply assets to meet this challenge is guided by several criteria: Maximising the use of existing service infrastructure, both ACTEW s and others. Increasing the diversity of sources of water (both rainfall and rainfall independent options). Ensuring that adopted choices include at least one source of water which is not dependent on rainfall in ACTEW s water supply catchments. Maximising operational flexibility to provide backup capabilities in the event any part of the system is out of operation for whatever reason. Providing a net economic benefit to the community. 14 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

23 Optimising outcomes from capital and operational costs and minimising the consequent flow-on cost to consumers. Minimising the environmental impact of the water supply solutions. In the planning and selection of new water supply assets for the region, ACTEW assessed all relevant options, to ensure a solution that will deliver water security through a diverse range of measures Economic benefit approach The ACTEW s report to the ACT Government (ACTEW, 2007b) set out a net economic benefit approach which was also applied in the Future Water Options report (ACTEW, 2005a; CIE, 2005, 2007, 2008). The net economic benefit of implementing each scenario is calculated by deducting the capital and operating costs of each supply option from the gross economic benefit to the community arising from any reduced time in drought restrictions. (More detail provided in section 5.11) Gross economic benefits The costs of restrictions have been updated since the 2007 report (CIE, 2008) and are summarised in Table 1.1. Table 1.1 Previous and revised costs of water restrictions ($million per/year) Restriction level Restriction costs used in previous modelling (Stage 4 costs*3.5) Restriction costs used in current modelling Stage 1 $5.6 $7.0 Stage 2 $44.9 $48.8 Stage 3 $62.1 $121.6 Stage 4 $488.5 $324.1 Using these costs, ACTEW has examined three scenarios to assess the benefits associated with the options proposed. It is important to note that with different climate scenarios, different combinations of water supply options provide the optimum solution to achieve the desired level of security. Three scenarios have been chosen as the future climate is more uncertain than any other assumption used in ACTEW s water supply planning to date. 1.4 Water security options under various climate change scenarios Climate scenario climate If the future climate is similar to the predicted 2030 climate change scenario (ie a reduction in annual inflows of around 50 per cent) then the combination of the Enlarged Cotter Dam and the Murrumbidgee to Googong Water Transfer, is predicted to successfully reduce the time the ACT will spend in severe water restrictions (ACTEW, 2007b). The addition of the Tantangara Transfer provides even further reduced time in restrictions Scenario 2: Repetition of the last six years climate The reduced inflows in the past few years have been much worse than that predicted by the 2030 climate change scenario outlined above. In fact since 2001, the decrease in inflow has been about 65 per cent. As ACTEW has previously stated, in addition to the Enlarged Cotter Dam, increased pumping from the Murrumbidgee River speeds drought recovery and keeps storages at a higher level. It also indicates that the Tantangara Transfer, when teamed with increased Murrumbidgee pumping, is the best performing option in the early stages of recovery, assuming it can be implemented in the timeframe required. This analysis reinforces the need to increase pumping from the Murrumbidgee River, with the addition of the Tantangara Transfer to provide additional diversity and security as shown in Figure 1.5. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 15

24 Figure 1.3 Projected storage with climate continually repeating Scenario 3: Repetition of 2006 climate If the climate experienced in 2006 is more typical of the future ACT climate, permanent Stage 4 restrictions are expected unless all feasible options Enlarged Cotter Dam, Murrumbidgee to Googong Water Transfer, Tantangara Transfer and the large Water Purification Scheme are implemented as soon as practical. Even with all these major infrastructure items in place it will take some years before restrictions are no longer required. Figure 1.5 shows that under the repeated 2006 climate scenario, the ACT would be in Stage 4 restrictions and eventually run out of water somewhere between 2016 (Enlarged Cotter Dam + Angle Crossing (Murrumbidgee to Googong Water Transfer)) and 2026 (Enlarged Cotter Dam + Angle Crossing (Murrumbidgee to Googong Water Transfer) + Tantangara). The graph shows the importance of Tantangara Transfer, and the ability to pump this water via the Murrumbidgee to Googong Water Transfer, to the ACT s long term water security. It is important to note the annual cost of remaining in Stage 4 restrictions is $324 million. The consequences of running out of water are difficult to quantify but would be extreme. Figure 1.5 also show that should no action be taken and the 2006 climate become the norm that Canberra is likely to run out of water by 2013, or be faced with more severe water restrictions than what is currently being experienced. 16 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

25 Figure 1.4 Projected storages with repeated 2006 climate To avoid a position where Canberra runs out of water, or experiences substantial times in higher stage of restrictions, it is important to consider the recent climate history as a potential long term future climate situation. In this climate scenario the importance of the Tantangara Transfer becomes apparent. In Figure 1.5 the orange line demonstrates that building the Enlarged Cotter Dam, Murrumbidgee to Googong Water Transfer and Tantangara Water Transfer projects represents a mechanism to delay the ACT running out of water. While there have been some suggestions that this climate scenario is unlikely, the climate of the past three to five years indicates that a trend towards this climate should be considered. Evidence of this change can be seen in the ACT over the past three years: The inflows in 2006 were 26GL. Inflows in 2007 were 66GL. Inflows in 2008 were 59GL. This demonstrates a significant reduction compared to long term average flows. 1.5 Alternatives considered When considering the need for new water sources investigations are commonly based on estimates of population growth, existing water consumption, environmental flows and assuming the worst possible drought (when compared to historic records). Initial consideration of the future water needs of Canberra estimated that new water sources would be required when the population of the ACT and Queanbeyan reached 405,000. The Australian Bureau of Statistics predicts that this level will be reached in In April 2004 ACTEW published a report that was undertaken to identify options for a new water source for the ACT entitled Options for the Next ACT Water Source (ACTEW, 2004a). This report found that it was ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 17

26 necessary to include other important factors such as the effects on the availability of water due to bushfires, impacts of climate change and climate variability, water consumption patterns and the possibility of future requirement to supply water to neighbouring towns and new development estates in surrounding NSW. In conducting and reassessing the ACT future water requirements the report examined a wide range of options for a new source of water. In doing this it also re-assessed previously proposed schemes and investigated new options. The full lists of options were reviewed and grouped into shortlisted and not shortlisted options based on their relative merits. The following is an outline of the options considered Shortlisted options Enlarged Cotter Dam. Tennent Dam. Coree Dam. Tantangara. Supply to Stromlo. Supply to Stromlo. Supply to Tuggeranong. Coree Arch to Bendora Gravity Main. Coree Arch to Coree Gravity Main. Coree Embankment to Bendora Gravity Main. Coree Embankment to Coree Gravity Main. Pump to Cotter River. Tunnel. Yaouk Valley to Porcupine Creek. Yaouk Valley gravity pipeline. Options not shortlisted: Water Farm. Cross Border Supplies. Groundwater. Stormwater reuse. Riverlea Dam. Welcome Reef Dam. Carwoola Dam Molonglo river. Lower Cotter Catchment Dam (below Bendora). Enlarged Corin Dam. Enlarged Bendora Dam. Enlarged Googong Dam. Raising Googong Spillway fuse plug. In response to the recent reduction in inflows, ACTEW s 2007 report to Government (ACTEW, 2007b) undertook another review of water supply options for Canberra. The review assumed that demand management targets were met and considered all the previous water supply options (including those outlined above and the findings of Future Water Options, 2005), including: The do nothing option. Enlarged Cotter Dam. Tennent Dam. Tantangara transfer. Angle Crossing options. Seawater desalination. Groundwater. Water purification scheme. Stormwater. Rainwater Collection (Private Tanks). Greywater use. Other Non-potable reuse options. Accelerated demand management. Cloud seeding. Watermining TM. Evaporation Control on Reservoirs. 18 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

27 1.5.1 Do nothing A key aspect of the Future Water Options Study was an assessment of the need for an additional water supply option. The report An Assessment of the Need to Increase the ACT s Water Storage (ACTEW,2004b) determined that new scientific knowledge of the potential combined effects of climate change and bushfire impacts has meant that additional water storage will be needed sooner than previously expected. The predictions of future conditions using the six planning variables show that reservoir storage levels would become low to very low in periods of drought. The ACT will not run out of water, but only if severe and onerous water restrictions are applied, or unless some unforeseen event occurs. Furthermore, over the coming years water restrictions will be increasingly detrimental to the community and at the same time become less effective. This is because restrictions would come on top of a substantial reduction in per capita water use through meeting the water efficiency targets, which within themselves will require permanent water restrictions. Unless the ACT is willing to accept the regular recurrence of water restrictions of a severity and frequency unprecedented in planning elsewhere in Australia, then additional water storage is required, and the Do Nothing option is not feasible. The Do Nothing option is considered in detail in all analysis as the baseline. Full details of the option assessment are contained in Water security for the ACT and region Recommendations to the ACT Government, (ACTEW, 2007b). A summary of the options considered are provided below. (Detailed description and assessment of these options is available online from New dam in the Cotter Catchment As part of the Future Water Options studies in 2005, four alternatives involving the Cotter Catchment were under consideration (ACTEW, 2005b): Construction of a new 73GL Coree Dam, upstream from the existing Cotter Dam. Retain the existing dam, plus greater use of environmental flow releases from Bendora Dam. Enlargement of the existing dam to a 45GL Cotter Dam. Enlargement of the existing dam to a 78GL Cotter Dam. The Coree Dam option has been found to be more expensive to construct than an Enlarged Cotter Dam as additional concrete is required due to the wider valley. The pump station and pipeline that would be required for this option are also more expensive as a new power supply would need to be provided. If Coree Dam were to be built then an Enlarged Cotter Dam would not also be built, as water captured by Coree would normally flow into the Enlarged Cotter Dam. As an Enlarged Cotter Dam would be downstream of a new Coree Dam, it will enjoy more inflows (larger catchment). The proposed Coree Dam would be higher in elevation and would have slightly less energy costs from pumping. From a water quality perspective, a new Coree Dam would have marginally better quality water, but with the completion and upgrading of the Mount Stromlo Water Treatment Plant, water from lower Cotter can easily and successfully be treated. A new Coree Dam is likely have negative impacts on endangered fish in the existing Cotter Reservoir as it would prevent upstream passage to existing river habitat and breeding grounds. The 2005 studies also recommended that ACTEW include the review of existing infrastructure such as pipelines, pumping stations and water treatment plants associated with these options to determine upgrade needs to convey the water to various locations within the Canberra and Queanbeyan water supply system. In this review the Cotter Dam options were refined and it was determined that the best option would be to construct a separate dam wall downstream of the existing dam wall as opposed to incorporating the existing structure in a new one (Raising the existing dam wall). The primary reasons for this recommendation were: The volume of the existing dam wall was too small to provide any financial benefit or saving in construction cost. Technical and practical difficulty associated with ensuring an adequate bond between the existing dam wall and a new wall. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 19

28 Concerns in relation to the quality of the concrete in the existing dam wall and whether it could withstand the load of a much larger structure on it. Construction issues associated with incorporating the existing intake tower and pipe work would have added a significant degree of complexity which offset any gains from use of the old dam. With the existing Cotter Reservoir back into operation there are no significant benefits through greater use of environmental flow releases from Bendora Dam. The smaller (45GL) Cotter Dam option was primarily discarded on the basis of hydrological assessment (it did not add sufficiently to future water yield) and because of a potential fish passage threat to the existing Macquarie Perch population. Extensive modelling of the 78GL Cotter Reservoir option did not show the same potential fish passage problem as which occurred with the 45GL option. Further studies have been conducted since 2005 to ensure fish passage will not be affected by the enlarged dam. The Future Water Options Review (ACTEW, 2007a) included a detailed review of the Enlarged Cotter Dam proposal which led to the Enlarged Cotter Dam: Update Report (ACTEW,2007c) This report reconfirmed the Enlarged Cotter Dam as a favoured infrastructure option to secure the ACT s water supply. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Enlarged Cotter Dam option. Pros Existing dam site on Territory land. High yield at relatively low cost. Minimal environmental impacts. Cons Requires pumping. No increase in diversification. Management of endangered fish Tennent Dam One of the alternative dam options considered as part of the Future Water Options project was the construction of the Tennent Dam on the Gudgenby River in the Naas Valley (ACTEW, 2005c). The construction of this dam would also require building a new water treatment plant on site or pumping of water to the existing Mount Stromlo Water Treatment Plant. The proposed dam included a number of complexities that would need further assessment and would translate into a long design and planning lead time before implementation including: The Naas Valley has an existing community of rural lessees who would need to be relocated if a dam was built. The site has an existing road linking Tharwa with the Boboyan Road, which would need to be entirely relocated. The site has areas of Yellow Box Grassy Woodlands, which have national significance (EPBC listed communies). The woodlands is also home to several threatened species of birds. The site has a number of European and Aboriginal Heritage sites. Apart from these matters, the key issue against this option is the uncertainty of flows in the Gudgenby river system. This river has long term average flows of about 57GL per year, compared to 138GL per year for the Cotter River. Over the last six years the Tennent catchment inflows have reduced by 70 per cent compared to 40 per cent in the Cotter Reservoir and 35 per cent for Tantangara reservoir. This provides a clear indication that the Gudgenby River flows are much less resilient to drought than the other river systems 20 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

29 considered. To further illustrate this reduction, it is worth considering that had the Tennent Dam been in place in 2006 it would have received inflows of less than 6GL in total. This option is also the most expensive dam option that was considered. In 2005 capital costs for the Tennent proposal were estimated at $292 million (159GL dam), with annual operating costs likely to be similar or slightly lower than the existing water supply system. Preliminary investigations and modelling predict 5 to 10 years to build and fill the reservoir (assuming average annual inflows against predicted climate change reductions). ACTEW recommends retaining the Tennent Dam site as a future water supply option for the ACT. Further reading on the Tennent Dam is provided in ACTEW, 2005c. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Tennent Dam option. Pros Diversification through a new catchment. Larger dam option available. Cons Uncertainty of future inflows. Longer timeframe to build and fill. Endangered yellow box woodlands. Leaseholder relocation. Road relocation. Heritage Tantangara Transfer This option was initially evaluated under the Future Water Options project (ACTEW, 2005d) and has been further developed since then. In light of the recent changes to national water management, this option appears to be more promising than when it was when last considered (by ACTEW) in 2004/2005. The Tantangara water transfer involves the following main actions: Purchasing water from irrigators downstream of the ACT. Storing purchased water in Tantangara Reservoir. Transporting that water from Tantangara to the ACT (Most likely run of river transfer along the Murrumbidgee River). There are some considerable uncertainties with this option that remain unresolved including: Having a Murray-Darling Basin Water Cap agreed for the ACT. Altering the Snowy Hydro s operating licence. Protracted negotiations with other parties (including licence owners, Snowy Hydro and the NSW and Commonwealth Governments). The cost to purchase water was estimated to be approximately $38 million. Operating costs will be a function of negotiations with Snowy Hydro and others. In accordance with the ACT Government directive, work is progressing on this option. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Tantangara Transfer option. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 21

30 Pros Provides added diversification. Improves use of Googong Dam. Quick to implement. Cost effective. Cons Changing Snowy Hydro s operating licence. Protracted negotiations. Losses in run of river delivery Angle Crossing option (Murrumbidgee to Googong) The Angle Crossing option was a primary recommendation of Future Water Options in 2005 (ACTEW, 2005a). The scheme involves the installation of a weir and pumps in the Murrumbidgee River at or near Angle Crossing at the southern border of the ACT. Water would be pumped, via a pipeline, from Angle Crossing, under the Monaro Highway to Burra, before being discharged into Burra Creek. The recent agreement for a regional approach to water management has helped in obtaining better regional support for this option. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Angle Crossing option. Pros Provides additional diversification. Quick to implement. Improved use of Googong Reservoir. Cons Inter-jurisdictional approvals required. Land owner negotiations Seawater source Desalination of seawater to serve Canberra and Queanbeyan was also considered as a potential water source for the ACT as part of the Future Water Options assessment (ACTEW, 2004a). This option would consist of: A seawater reverse osmosis process plant located on approximately 35 hectares on the NSW south coast. The intake and outlet would be located in water depths of approximately 20m offshore to optimise dispersion and intake water quality. The plant would have a capacity of 50ML/day. A one pass reverse osmosis process would be required if the water is to be delivered to the Queanbeyan River. A two pass reverse osmosis process would be required if the water is to be delivered directly to the existing water supply network so as to match existing water quality. The intake would draw approximately 140ML/day to produce 50ML/day of potable water. Reject water would be discharged to the ocean as is the case with similar plants in Sydney and Perth. 22 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

31 A 750mm diameter pipeline approximately 100km long, located within road reserves wherever possible, would connect the plant with the existing supply system. There would be a main pump station at the plant site and three more along the route. Electricity would be sourced from the grid. Without Commonwealth intervention, under NSW planning laws, the proposal would need to be assessed under the NSW Environmental Planning and Assessment Act A 2.5 year to 3 year timeframe would be required to gain approval, construct and commission the plant. For more information see GHD, This option is not considered appropriate at this point in time, mainly with regards to the potential complexity in obtaining approval to construct a project of this scale as well as the estimated cost for construction and operation. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Seawater Source option. Pros Proven technology. Rainfall independent. Cons Higher cost. Higher energy use. Inter-jurisdictional approvals Groundwater Groundwater, in the ACT and surrounding NSW, was examined in the Future Water Options studies and is still not considered a viable option. Groundwater can provide benefits on a small localised scale and is already being extracted and used at various locations in the ACT. More detail on the consideration of the groundwater option is available from the report Options for the Next ACT Water Source (ACTEW, 2004a). Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the groundwater option. Pros Potentially provides diversification. Cons No large aquifers in or near the ACT. Transfer costs to the ACT water network. Sustainability of extraction. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 23

32 1.5.8 Water Purification Scheme ACTEW is investigating adoption of existing (advanced) technology to treat used water (waste water) to a standard that is safe for human consumption. Membrane filtration and reverse osmosis is the preferred combination of treatment processes that provides a multi-barrier approach to water purification. Membrane filtration uses hollow fibre membranes with fine pores to filter particles and micro-organisms. The membrane surface acts like a screen to retain the microorganisms; similar to a screen door that retains insects. This step removes microscopic particles, contaminants and pathogens. Reverse osmosis is the process of pushing water through a membrane or filter that traps almost all suspended and dissolved substances and micro-organisms to one side and allows water to come out the other side. The membranes have very small pores, small enough to trap more than 99 per cent of sodium and chloride ions. This step removes pollutants such as salts, organic compounds and viruses. A further process under consideration (as part of a multi barrier approach) is the inclusion of ultra violet disinfection and advanced oxidation. Ultra violet light is used to disinfect water. UV light is effective at destroying micro-organisms such as Giardia and Cryptosporidium and other pathogens. Oxidation is effective in destroying chemical compounds. Strong oxidation agents such as hydrogen peroxide are commonly used to remove trace organic constituents. The proposal could also take advantage of natural water treatment processes by letting the purified water flow into the natural environment (wetland). Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Water Purification Scheme option. Pros Less directly dependent on rainfall than a dam Proven technology Assist in avoiding restrictions under extremely dry future climate scenarios Cons Higher cost Higher energy use May not be used in wetter periods Stormwater use Stormwater harvesting is promoted in the ACT Government's Think water, act water strategy, as it can assist towards meeting the 25 per cent target reduction of drinking water consumption per person by It is also factored into the ACT Government s Waterways: Water Sensitive Urban Design General Code (2008a) that targets a 40 per cent reduction in drinking water use for all new developments and re-developments. The ACT Government carries out stormwater harvesting from most urban ponds and lakes for use on community parks and ovals. Golf courses, nurseries and other large water users also use stormwater. The ACT Government is currently undertaking the Canberra Integrated Urban Waterways Project with assistance from the Australian Government Water Fund. This project will implement stormwater storage, harvesting and use up to 3GL per year by 2015 as well as providing stormwater improvement benefits. A feasibility study is currently underway to determine what level of use is feasible. The project will cost $17 million (excluding ongoing operations, maintenance and monitoring costs). Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the stormwater option. 24 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

33 Pros Local use of existing storages can be cost effective. Provides some stormwater control. Cons Poor water quality. Highly variable quantities. Large storages required. The most cost effective systems are already implemented Rainwater collection (private tanks) Rainwater tanks can store runoff from the roof for garden watering and other household uses, contributing towards reducing the residential water demand and serving as a water conservation measure. The ACT Government's Rainwater tanks: Guidelines for residential properties in Canberra (2008b) provides information on this subject. Rainwater tanks are promoted in the ACT Government's Think water, act water strategy, as they can assist towards meeting the 25 per cent target reduction of drinking water consumption per person by The strategy recognises the benefits of installing a rainwater tank in terms of water saving and stormwater reduction. The effectiveness of a tank is increased when the water is used for internal purposes such as toilet flushing, clothes washing as well as garden watering effectively providing a way for the tank water to replace drinking water all year round. The ACT Government has provided household rebates for the installation of rainwater tanks to assist the community contribute to water conservation. To be eligible for a rainwater tank rebate, the tank must be plumbed for some internal use, for example to the laundry or toilet. The use of rainwater tanks is also promoted in the ACT Government s Waterways: Water Sensitive Urban Design General Code (2008a). It is estimated that the cost for installing a tank in all households in the ACT would be about $330 million to $550 million and deliver approximately 8GL per year. Rainwater tanks are also dependent on rainfall thereby reducing the benefit of rainwater tanks during drought periods. There is limited opportunity for citywide rainwater tank use at levels above what is already being put in place. Although rainwater tanks are dependent on rainfall and they can be expensive to install they represent a means to reduce dependence on mains water. The assessment found this option to be a costly solution that would not translate into the storage required to secure the ACT s future water needs. At best this could be a supporting solution. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the rainwater collection option. Pros Supplement existing drinking water use Can be used in toilets and laundry Reduce stormwater runoff Cons Higher cost Rainfall dependent Difficult to obtain large enough storage ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 25

34 Greywater use Greywater is wastewater from hand basins, showers, spas, washing machines, laundries, (but not from the toilet or urinal which is blackwater). The use of greywater varies from bucketing or siphoning, connecting the outlet drain to a diversion pipe or installing an appropriate greywater treatment system. Greywater use is promoted in the ACT Government's Think water, act water strategy, which includes a target to increase reclaimed water from 5 per cent to 20 per cent by The strategy is continuing to investigate ways to encourage the take-up of greywater use with consideration being given to incentives and rebate schemes. It is also promoted in the ACT Government s Waterways: water sensitive urban design general code (2008a). Greywater use can replace some drinking water use and contributes to water conservation measures. In addition, it also reduces wastewater flows, which reduces treatment costs and discharge volumes to waterways. Due to poor water quality however, untreated greywater should only be used for irrigation and cannot be stored for more than 24 hours unless an appropriate treatment system is used (ACT Government, 2007a). Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the greywater option. Pros Replaces drinking water use on gardens Reduces sewerage flows (and treatment costs) Cons Higher cost Care needed in handling due to potential health issues Ongoing maintenance Other non potable reuse options large scale irrigation Non-potable reuse options involve the extension of the existing ACT water reuse schemes for irrigation purposes. This provides additional reuse of water for irrigation of open spaces, parks, ovals and golf courses through Central Canberra, Belconnen, Woden and Tuggeranong and effectively reducing the use of potable water for these uses by approximately 3GL/annum. This proposal will require a capital cost of more than $100 million. Additional capacity beyond this extension becomes even more expensive. To implement this proposal, approximately 100km of new pipelines will need to be constructed through largely existing urban areas. It also requires several pumping stations to be constructed and connection to decommissioned reservoirs. The demand for non-potable reuse is mostly limited to seasonal demand during warm and dry periods. It has the advantage of allowing use of sports ovals through periods of drought, but does not reduce the probability that severe restrictions will be required for larger Canberra, particularly in current and future droughts. The scheme could only be implemented in some parts of the city, resulting in a potential inequitable distribution of the resource, with some areas benefitting by having access to playing fields during drought whereas other areas of the city would not. This scheme provides only limited additional flexibility to the water supply system, as it provides non-potable water to limited areas of Canberra only through the summer months. It does not supplement the drinking water supply during years with low inflows to reservoirs (like 2006) and only provides limited offsets to the drinking water supply during periods of water restrictions. ACTEW continues to examine ways to further expand non-potable reuse where it is viable, including assessment of storage options, seeking suitable winter demand and water pricing. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for other non potable reuse options. 26 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

35 Pros Provides irrigation water during droughts. Cons Higher cost. Disturbance during installation of pipes. Seasonal use of water Accelerated demand management This option requires implementing activities to build on the current ACT Government s demand management (water conservation) program and target a 20 per cent per capita water consumption reduction by 2011, rather than the government s proposed target of 25 per cent reduction by This will involve increased technical assistance and financial incentives to: Adopt low-flow showerheads, dual flush toilets, internal water audits, water-efficient gardens and leak minimisation. Ensure commercial and business establishments use water efficiently and minimise leaks. To install rainwater tanks and grey water recycling systems. Some proposed demand management measures of the Government s 25 per cent reduction are planned for new houses yet to be built, or involve new appliances not yet readily available (ISF, 2003). As these features cannot be brought forward to any significant extent, the full 25 per cent demand reduction may not be achievable by 2011; and ACTEW only considered this option able to deliver a 20 per cent reduction. The outcomes of the analysis of this option indicate a short-term advantage with no long-term impact on future demand. The cost of this option is about $150 million. The ranking of this option compared to others indicates this is not a preferred option to provide necessary water security (ActewAGL, 2007). Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for accelerated demand management. Pros More efficient use of water. Fast tracks ACT Government s existing program. Benefits current drought situation. Cons No additional long-term benefit. Requires considerable community support. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 27

36 Cloud seeding Cloud seeding is a form of weather modification which changes the amount or type of precipitation that falls by dispersing substances into clouds to serve as cloud condensation or ice nuclei. The usual intent is to increase precipitation, but hail suppression is also commonly practiced with these methods. Silver Iodide and dry ice are the most commonly used substances in cloud seeding. Seeding requires clouds to contain liquid water colder than zero degrees Celsius. The introduction of a substance such as Silver Iodide, which has a crystalline structure similar to that of ice, then induces freezing and promotes precipitation. Clouds can be seeded from the air or ground level. Snowy Hydro Limited embarked on a six-year research project of winter cloud seeding to assess the feasibility of increasing snow precipitation in the Snowy Mountains. As there have been no cloud seeding studies in the Canberra region, preliminary investigations of seeding types and frequency of suitable atmospheric conditions are required, followed by a four to six year experiment. The correct cloud formations are required for cloud seeding to be successful, therefore research into the types and abundance of clouds over the Canberra water catchment areas needs to be undertaken to determine the usefulness of cloud seeding in the region. ACTEW, ActewAGL and Snowy Hydro Limited are cooperating to understand the potential of cloud seeding for the ACT. A proposal is being developed that builds on the expertise that Snowy Hydro Limited has obtained in the cloud seeding operations to assist with meteorological research into the appropriateness of cloud seeding for the ACT. While cloud seeding has shown to be effective in altering cloud structure and size and converting cloud water to ice particles, it is more controversial whether cloud seeding increases the amount of precipitation at the ground. This is partly problematic given the difficulty associated with discerning how much precipitation would have occurred had cloud seeding not take place. Nevertheless, there is more credible scientific evidence for the effectiveness of winter cloud seeding over mountains (to produce snow) than there is for seeding warm-season cumuliform (convective) clouds. Cloud seeding essentially makes the wet times wetter and has minimal benefits in dry times. Benefits of cloud seeding will generally only become tangible over a long term period, following a trial period to assess effectiveness. On this basis cloud seeding was ruled out as a reliable future water source for the ACT. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the cloud seeding option. Pros May increase rainfall. Ongoing research by ACTEW. Cons May not increase rainfall. Uncertain. Several years to test and prove Watermining TM Watermining TM is a process by which wastewater is taken from a sewer system and treated for reuse in the local vicinity, such as for irrigating ovals, parks and playing fields. ACTEW currently operates a Watermining TM scheme at Southwell Park (Lyneham), supplying irrigation water for the adjacent Southwell Park playing fields. The plant was commissioned in 1995 as a demonstration facility of new technology. In 2005, ACTEW investigated localised Watermining TM opportunities for the ACT including Watermining TM schemes in areas including Kambah, Stirling, Isabella Plains, Condor, Melba and Charnwood. Investigations highlighted that watermining schemes were expensive and even if maximised across the ACT at a localised scale, would provide little benefit to the overall security of the ACT water supply. Although Watermining TM may have opportunities to benefit individual sites in the ACT, it does not have the potential to provide sufficient water at a reasonable cost to meet the security required for current and future droughts 28 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

37 ACTEW continues investigations into the feasibility of watermining opportunities and constraints for individual sites within the ACT. These investigations consider smaller scale plants than previously considered. Based on the existing information, a list of pros and cons were developed in order to decide between the alternatives. Below are the pros and cons for the Watermining TM option. Pros Reduces drinking water demand. Further locations being investigated. Cons Higher cost. Seasonal use. Not a major supply option Evaporation Control on Reservoirs ACTEW also investigated techniques for reducing evaporation from existing water supply reservoirs. None of the options examined provided a cost effective solution. The options were only suitable for the smaller reservoirs, Bendora and Cotter, which have relatively insignificant evaporation losses compared to Googong and Corin reservoirs and will not provide any significant increase to the ACT s water security if implemented. ACTEW will continue to review new products and techniques that become available. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 29

38 1.6 Preferred options Of all the above options, the following are considered as future supply options: Water Transfer scheme from Angle Crossing to Googong Dam. Enlargement of the Cotter Dam. Implementation of a water purification scheme at Lower Molonglo Water Quality Control Centre. Storage and transfer of water from Tantangara Reservoir. Construction of Tennent Dam be retained as a longer term option. Many of the other options have a role to play in either reducing the demand for water or providing some additional supply. After examining these options individually and in varying combinations, ACTEW chose the Enlarged Cotter Dam as a high-priority option for the following reasons: It provides the greatest net economic benefit to the community. It will deliver amounts of water similar to those projected for the large Tennent Dam option, but at half the capital cost and with less risk. It can also be brought into operation more quickly. It was assessed by the fish impact study conducted by Lintermans (2005) as having the lowest environmental impacts of any of the dam options. It will make use of existing infrastructure via the pump station at Lower Cotter and the Mount Stromlo Water Treatment Plant. It will draw water from a catchment that is much more reliable in times of drought than the Tennent catchment or the Googong catchment. It will capture the environmental flows that are released from the Corin and Bendora reservoirs, which often spill over the current Cotter Dam. It will catch much of the overflow from storm events that the current dams in the Cotter system cannot store. 1.7 Government decision major water security projects for the ACT In October 2007, following from the ACTEW Water Security recommendations (ACTEW, 2007b), the ACT Government announced a range of projects that will be implemented to secure Canberra and the region s water supply into the future and unlock the potential to provide water through extended dry (drought) periods. The projects endorsed by the Government include: Enlarging the Cotter Dam from 4GL to 78GL, with planning and design work to begin immediately and work expected to be completed within three to five years. The installation of infrastructure to increase the volume of water transferred from the Murrumbidgee River to the Googong Dam. Design of a demonstration water purification plant, with the water produced during demonstration to be used for purposes other than drinking (Government Press Release (October 2007) included in Appendix C). The Government instructed that the planning and design and construction of the Enlarged Cotter Dam commenced immediately. 30 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

39 1.8 Enlarged Cotter Dam updated report, July 2007 The report was commissioned against the context of the investigations into Canberra with a long-term reliable source of water. These investigations span the ACT Government s Think water, act water strategy, ACTEW s Future Water Options project (as reviewed) and the October 2007 Government decision into this matter (see descriptions above). The water options studied by ACTEW in 2004 recommended an enlargement of the Cotter Dam. The July 2007 Enlarged Cotter Dam update report (Appendix S) builds on the April 2005 report, The Cotter Dam Option, which confirmed the Enlarged Cotter Dam as an important component in securing the ACT s future water supply. Both of these reports are publically available on the ACTEW website at Both reports found that a Roller Compacted Concrete (RCC) gravity dam is the most appropriate for the proposed dam site. The 2007 report states that sites chosen for the main dam and the two saddle dams are suitable for the structures envisaged. The 2007 report included findings on further investigation relating to more detailed site investigations including hydrological and geotechnical investigations into the proposed dam. A number of recommendations documented in the report have been addressed since its publication, mainly through further investigations, design updated and/or the investigations associated with the preparation of this EIS document. The following recommendations as documented in the report are considered important in the context of this EIS and have been addressed as follows: Table 1.2 Recommendations from the Enlarged Cotter Dam Update Report 2007 with EIS responses 2007 report referencer 2007 report recommendation Actions taken to date 3.10 Further Geotechnical investigations to be completed prior to the project proceeding to construction including further drilling, RCC mix designs and onsite material assessment for availability and usefulness Probable Maximum Flood and Return Period flood studies completed to date are to be reviewed. 6.5 In relation to Saddle Dams the dam type, cut off provisions borrow areas for earthfill and material flow analysis should be addressed in design. 7.4 and 7.5 Background studies are required to address/consider a range of technical and environmental issues associated with the proposal. Although no critical constraints in the project were identified the following matters should be considered: Ongoing review of the Planning and Development Bill, Regulations and the implementation thereof. ACTEW continued its investigations into the suitability of the site for the construction of the dam as well as the opportunity to utilise onsite materials in the construction of the dam. This work is ongoing and will be informing detail design as the project progresses. Details are in section 4.3 of this report and Appendix F This recommendation is addressed in the design of the ECD under the ANCOLD guidelines as described in section 5.12 These matters are reliant on a range of issues including availability and suitability of on-site materials, geotechnical investigations and dam design. The saddle dam design and construction are considered as key components of the proposal described in the EIS. ACTEW actively continued its investigations into the environmental suitability of the site for construction and operation of the proposed Enlarged Cotter Dam. With regards to the 2007 report recommendations: ACTEW approached and has been in regular discussions with ACTPLA since November Discussions were held in relation to the appropriate approval requirements under the Planning and ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 31

40 2007 report referencer 2007 report recommendation Actions taken to date Conformation that a Territory Plan Variation are not required to accommodate this infrastructure. Seek early advice from ACTPLA re scoping of the EIS. Undertake analysis of the work required on background work for impacts on fish, heritage and flora. 8.8 No issues in relation to Environmental assessment conducted were considered to having a serious impact on the project (with appropriate mitigating measures). Further work with regards to likely impacts include the effect of the reservoir on: Aquatic ecology; European and indigenous heritage sites; and Terrestrial flora and fauna. 9.9 In relation to recreational development of the Cotter: Prepare a master plan for recreational development of the Cotter; Consider inclusion of relevant aspects into the construction contract of the Enlarged Cotter Dam; Consider the preparation of a publicity program to involve the Canberra Community in the progress of construction of the dam 13.1 General recommendations (not included above): Prepare a comprehensive implementation program to allow detailed program management of the project. Consideration to be given to the type of contract delivery method best suited to the project. Development Act, suitability of the Territory Plan provisions for this proposal, timing and contents of a request for Scoping of an EIS application. These discussions are ongoing and form a cornerstone in seeking planning approval for this project. Further detailed assessment into specialist technical considerations for the Enlarged Cotter Dam project has been completed and the recommendations of these reports are presented in this EIS and/or have been considered in the design of the proposal. Technical Investigations for the EIS for the Enlarged Cotter Dam proposal covered a vast range of topics (tailored to address the 2005 and 2007 Enlarged Cotter Dam reports as well as the matters raised in the 2008 ACTPLA Scoping Document (See Appendix A)). A detailed Aquatic Assessment (Appendix J) and supporting Fish Management Plan (Appendix K) have been developed to support the Enlarged Cotter Dam proposal; A detailed Cultural Impact Assessment (Appendix M) has been developed to support the Enlarged Cotter Dam proposal A detailed Terrestrial Flora and Fauna assessment (Appendix I) has been developed to support the Enlarged Cotter Dam proposal ACTEW commissioned and prepared an assessment of potential for recreational development of the Cotter. The findings of this assessment have been considered in the preparation of the Enlarged Cotter Dam proposal and this EIS. The Enlarged Cotter Dam project includes a broad Community Engagement strategy that spans the entire Enlarged Cotter Dam design and construction time. Details of this strategy are included in the Community Feedback Report included at Appendix N. This has been prepared and a summary has been included at section 2.7 of this EIS; ACTEW has chosen an Alliance Delivery model to manage the design and implementation of the Enlarged Cotter Dam project. 32 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

41 1.9 The proponent ACTEW Corporation Ltd (ACTEW) is the proponent. ACTEW Corporation Limited (ACTEW) is a government owned company with assets and investments in water, wastewater, electricity, gas and telecommunications totalling $1.4 billion. ACTEW owns the water and wastewater assets and business in the ACT, is a 50 per cent owner, with Singapore Power International and AGL Energy Limited, of ActewAGL and holds an 18 per cent investment in TransACT Communications Pty Limited. ACTEW was corporatised on 1 July 1995 and has reporting and compliance obligations under the Corporations Act 2001 and other legislation. It has three wholly owned subsidiary companies: ACTEW Distribution Limited. ACTEW Retail Limited. ACTEW China Pty Limited. ACTEW Distribution and ACTEW Retail are ACTEW s partnership companies in the ActewAGL Distribution and Retail partnerships. ACTEW Distribution Limited is also a joint owner of Ecowise Environmental Pty Limited, Australia s largest single provider of integrated environmental analytical, monitoring and consulting services. ACTEW China holds business investments in the People s Republic of China. ACTEW strives to optimise its water and wastewater utility services, and in doing so maintain a leadership role of a multi-utility operating in the public private partnership model. ACTEW aims to manage its assets and business sustainably to provide quality service to its customers while building value for its owners Structure of this EIS The proposal to enlarge the Cotter Reservoir triggers the requirement to complete an Environmental Impact Statement (EIS) before lodging a development application. The process of preparing an EIS is described in Chapter 3. This EIS is structured to reflect the requirements of the Planning and Development Act 2007 and the Planning and Development Regulation The structure also responds to the requirements of the EIS Scoping Document issued by the ACT Planning and Land Authority (ACTPLA) on 30 June The Scoping Document is presented in Appendix A. The structure of the document is outlined in Table 1.2. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 33

42 Table 1.3 Document structure Chapter Outline 1 Introduction A description of the background conditions, works and decisions that have led to the proposal to enlarge the Cotter Reservoir. 2 Project description A description of the actual project that is being assessed in this EIS. This includes descriptions of the proposed construction methodology and operating conditions for the proposed dam, saddle dams and ancillary works. 3 EIS process and methodology A description of the statutory processes involved in preparing the EIS and the methodology adopted. 4 Existing conditions A description of relevant matters that have been considered to inform discussion about the potential impacts that have been identified and are detailed in Chapters 5 and 6. 5 All potential environmental impacts A brief discussion of all of the potential environmental impacts that have been identified for the project. Where potential environmental impacts are identified as potentially significant, the reader is referred to a detailed discussion in Chapter 6. 6 Potentially significant environmental impacts A detailed discussion of each of the potentially significant environmental impacts that have been identified for the project. The discussion includes proposed management and mitigation techniques to be adopted and a residual risk analysis. 7 Consultation A description of the consultation with stakeholders that has been undertaken and will continue to occur as the project proceeds through detailed design, development approval and construction, to identify important issues, gauge opinion and inform the key stakeholders about the project. 8 Commitments and recommendations Based on the discussions of all of the potential impacts and the proposed design, management and mitigation measures to be adopted, a consolidated list of commitments and recommendations is presented. A table of the content of this document, referenced to the requirements of the Scoping Document and the Regulation, is presented in Appendix A. 34 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

43 2 Project description 2.1 Location, context and tenure The Australian Capital Territory s western boundary was largely chosen to follow the boundary of the Cotter catchment. Most of the catchment has enjoyed a high level of protection since the early 1900 s to support a safe and secure water supply for Canberra. The Lower Cotter Catchment has been subject to a much higher level of disturbance as a result of human activity when compared with the upper sub-catchments. Prior to the establishment of the ACT (and the completion of the Cotter Dam in 1915 which was Canberra s only water storage facility for over 40 years) approximately 3,000ha of the Lower Cotter Catchment were cleared for grazing purposes. Overgrazing resulted in serious soil erosion which was further exacerbated by rabbits, and in order to protect the catchment (and Canberra s water supply) freehold and grazing leases within the catchment were terminated by To stabilise the landscape, a program of tree planting was established with 3,000ha of pines (Pinus radiata) planted by 1931 (ANU, 1973). Over time more Eucalypt forest was cleared for pine plantations (1931 to 1961) however this practice ceased due to community pressure and concerns about the impacts on water quality in the Cotter River and Reservoir. Prior to the 2003 fires, 4,200ha of pine plantations were established in the lower catchment. With the completion of Bendora Dam in 1961 and Corin Dam in 1968 management priorities for water shifted to the middle and upper sub-catchments. Concerns about water quality in the lower Cotter receded when Corin and Bendora dams were completed and water abstraction from Lower Cotter Catchment was suspended for over thirty years (ACT Government, 2007b). The 2003 bushfires destroyed most of the Lower Cotter Catchment, including the pine plantations. Figure 2.1 illustrates the land use patterns adjacent to the Cotter Reservoir in the Lower Cotter Catchment. In recent years there has been various revegetation and rehabilitation activities by the Government, CSIRO and ACTEW to assist in the post fire restoration. Although small pockets of pine plantations remain the majority of the catchment is now managed as native vegetation or revegetation areas, as shown below. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 35

44 Figure 2.1 Lower Cotter Catchment land use map and access trails 36 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

45 The Cotter Dam lies on the Cotter River approximately 18km due west of Canberra City in the ACT. The location in a regional context is shown in Figure 2.2. Figure 2.2 Location of Cotter Dam ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 37

46 The focus of the project is within an area colloquially known as The Cotter. While this area is not formally defined, it generally includes the area around the confluence of the Cotter, Paddys and Murrumbidgee rivers, including Cotter Avenue, Cotter Campground, Casuarina Sands, the existing dam and Cotter Pumping Station. The Enlarged Cotter Dam will be constructed approximately 125m downstream of the existing Cotter Dam. This site will be the focus of the construction activities. However, a considerably larger area will be affected by this project. Construction will have a temporary impact on a specific area. This is indicated in Figures 2.3. and 2.4. The details of the construction site are approximate at this stage and will be refined for the Development Application (DA). The areas shown are the maximum areas anticipated for use. The works within this area will include the quarrying and stockpiling of dam building material, the preparation of concrete for construction of the dam and all of the peripheral works. These areas will further include general construction activities including vehicle parking, site compounds and offices, field storage, set out areas and the like. These areas are approximately 81ha for the main construction area and 11ha for the clay borrowing areas that are currently being investigated (refer to section 2.3 for details). These areas will be temporarily impacted upon during construction and will be rehabilitated upon completion of the construction works. There will also be some impacts on a wider area due to the need to transport materials to site. These impacts will generally be temporary and the affected area will be rehabilitated once the construction phase is completed. These areas include the upgrading of several existing forestry roads to allow general site access and circulation as well as the delivery of plant and materials to the site during the construction time (as shown in Figure 2.3). 38 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

47 Figure 2.3 Main engineering infrastructure and construction area set-out (concept) ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 39

48 Figure 2.4 Indicative construction area at clay borrow sites 40 WATER SECURITY MAJOR PROJECTS FEBRUARY 2009

49 After completion of the Enlarged Cotter Dam the reservoir will inundate approximately 282ha. This is an increase of approximately 232 ha, as shown in Figure 2.5. Figure 2.5 Comparison of Cotter Reservoir and Enlarged Cotter Dam inundation areas ACTEW will seek to obtain leases or easements over the built assets to ensure long-term access for maintenance and operations. A complete description of the land and tenure is presented in section 4.5. ENLARGEMENT OF THE COTTER RESERVOIR AND ASSOCIATED WORKS ENVIRONMENTAL IMPACT STATEMENT 41