Project Overview

The NSW Government proposal to raise the Warragamba Dam aims to provide capacity to facilitate flood mitigation by increasing the crest levels of the central spillway by approximately 12 metres and the auxiliary spillway crest by around 14 metres above the existing full supply level for temporary storage of inflows.

WaterNSW as the owner and operator of Warragamba Dam has been tasked by the NSW Government to undertake the detailed concept design and Environmental Impact Statement (EIS) for the Warragamba Dam Raising project.

Project timeline

About the project

The large Warragamba Catchment is the major source of inflows for the most dangerous and damaging floods in the Hawkesbury-Nepean Valley.

Warragamba Dam is not currently designed or operated to mitigate floods.  

The project would reduce flood risk by creating a dedicated flood mitigation zone above the current full water supply level of the dam. Capturing and gradually releasing inflows would delay and lower the peak of floodwaters downstream. This would substantially reduce the risk to the lives, homes and communities of many thousands of people living and working in the floodplain.

The water supply storage level of the dam would not change. The proposed flood mitigation zone would only be used and operated to temporarily store inflows during floods.

Detailed investigations have been carried out to determine the downstream benefits and upstream impacts of the project. A final decision on the project will only be made after all environmental, cultural and economic assessments are complete.

EIS now on public exhibition

The Warragamba Dam Raising Environmental Impact Statement is on public exhibition from the 29th of September to the 19th of December 2021. This display is an opportunity for the community to make comment on the environmental assessments for the project.

Information on how to make a submission can be found here.

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Frequently asked questions


In June 2016, the NSW Premier announced the proposed Project to raise Warragamba Dam to significantly reduce risk to life and damages from flooding in the Hawkesbury-Nepean Valley. The Project is a key element of the Government’s ‘Resilient Valley, Resilient Communities – the Hawkesbury-Nepean Valley Flood Risk Management Strategy’ (Flood Strategy) which, after extensive review of alternate options, identified raising Warragamba Dam as the most effective infrastructure response to reducing risk to life and damages.

For more information, please refer to Chapters 1, 3, 4 and 5 of the Environmental Impact Statement.

The Project is being overseen by Infrastructure NSW (INSW) on behalf of the NSW Government as a component of the broader Hawkesbury-Nepean Valley Flood Risk Management Strategy (Flood Strategy).

WaterNSW, as the dam owner and operator, is leading the environmental assessment and detailed concept design for the proposed Project to raise Warragamba Dam Raising for flood mitigation (the Project).

For more information, please refer to Chapters 1 and 2 of the Environmental Impact Statement.

The Warragamba Dam Raising Project requires an environmental impact statement as it is considered to be State Significant Infrastructure (SSI).

All SSI applications have to go through a comprehensive assessment process with extensive community participation and are evaluated against social, environmental and financial aspects. The main steps in this process include Early Consultation, Preparation of the draft EIS, Review of the draft EIS, Exhibition of the finalised EIS, Responding to Submissions on the EIS, Assessment of SSI and Determination of SSI. To find out more about each of these steps, visit the NSW Government Major Projects page for an explanation of each step of the SSI process.

The assessment of the merits of the SSI project is determined by the NSW Minister for Planning and Public Spaces.

As the Project will also impact on matters of national environmental significance, it also requires Australian Government approval under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The Australian Government will review the NSW determination and make the final decision on whether or not to approve the Project or to approve with conditions.

For more information, please refer to Chapter 2 of the Environmental Impact Statement.

The Secretary’s Environmental Assessment Requirements (SEARs) issued by the NSW Department of Planning, Industry and Environment (DPIE) define the key issues and desired performance outcomes of the Project. The Environmental Impact Statement has been prepared in line with the SEARs using the current guidelines to ensure impacts are assessed objectively and thoroughly.

Section 5.12(2) of the NSW Environmental Planning and Assessment Act 1979 (EP&A Act) provides that a State Environmental Planning Policy (SEPP) may declare any development or class of development to be State Significant Infrastructure (SSI), which requires approval from the NSW Minister for Planning and Public Spaces under section 5.14 of the EP&A Act. The Project is SSI and accordingly requires approval from the Minister under Part 5, Division 5.2 of the EP&A Act for the reasons set out below.

  • State Environmental Planning Policy (Infrastructure) 2007 (Infrastructure SEPP) provides that works for the purpose of water storage facilities (clause 125(2)) and flood mitigation (clause 50(1)) could be undertaken by WaterNSW without obtaining development consent under Part 4 of the EP&A Act
  • clause 14(1) of State Environmental Planning Policy (State and Regional Development) 2011 declares development to be SSI if the development is permissible without consent under Part 4 of the EP&A Act and is a type of development specified in Schedule 3 of the State and Regional Development SEPP. Schedule 3 includes:
    • clause 1(1) Infrastructure or other development that…would be an activity for which the proponent is also the determining authority and would, in the opinion of the proponent, require an environmental impact statement to be obtained under Part 5 of the Act
    • clause 4(1) development for the purposes of water storage…carried out by or on behalf of a public authority that has a capital investment value of more than $30 million

Accordingly, the Project is subject to assessment and approvals process under Part 5, Division 5.2 of the EP&A Act.

For more information, please refer to Chapter 2 of the Environmental Impact Statement.

An Environmental Impact Assessment (EIA) is the process of undertaking surveys, studies and gathering data to enable an analysis of potential environmental impacts from a development proposal.

These studies and data are compiled, assessed and included into an Environmental Impact Statement (EIS) that is then considered and determined by the NSW Minister for Planning and Public Spaces.

For the Warragamba Dam Raising Project, following the state approval, the EIS is provided to the Commonwealth for a decision on matters within the Environment Protection and Biodiversity Conservation Act 1999.

For more information, please refer to Chapter 2 of the Environmental Impact Statement.

The concept design has been undertaken at the same time as the environmental assessment to ensure that both the construction and operational impacts and benefits of the dam raising can be identified and assessed comprehensively in the Environmental Impact Statement. An advantage of undertaking the two in parallel is the ability to feedback findings in the field and, where possible, adjust the design to avoid the potential environmental impacts.

As part of the Hawkesbury-Nepean Valley Flood Risk Management Strategy, feasible alternatives to the Project were considered prior to its eventual selection as the preferred option.

This consideration of alternative options is consistent with the Secretary’s Environmental Assessment Requirements (SEARs), which require analysis of any feasible alternatives.

The merits of the Project and concept design options were considered in the context of a range of alternatives based on how well they performed in reducing risk to life and damages from flooding, as well as environmental, engineering, social and economic factors. This is detailed in Chapter 4 of the Environmental Impact Statement (Project alternatives and options). Raising Warragamba Dam was found to have the highest net benefit compared with alternatives assessed.

Detailed discussion of the methodology, evaluation and selection of options, including consideration of levees, dredging, river diversions and other infrastructure options, can also be found in the Taskforce Options Assessment Report which is available in an accessible version on the Infrastructure NSW website at https://www.insw.com/media/1976/taskforce-options-assessment- report-2019-v2.pdf.

Historically, the large Warragamba catchment has contributed up to 70% of floodwaters during major floods. Modelling done for the Flood Strategy shows the Warragamba catchment can contribute up to 75% of flows during floods in the valley.

Raising Warragamba Dam for flood mitigation is the most effective option as it provides a single point of mitigation for the catchment that has the largest contribution to regional floods.

Creating the proposed flood mitigation zone at Warragamba Dam would have significant benefits in reducing flood risk in the most dangerous and damaging floods – those with a 1 in 50 to a 1 in 1,000 chance per year. Around 65% of the average annual damages occur with flood events that are between the 1 in 50 and the 1 in 500 chance per year flood.

For more information, please refer to Chapters 3 and 4 of the Environmental Impact Statement.

No, the Warragamba Dam Raising Project does not provide for more water supply storage.

The currently proposed dam raising will provide an airspace above the existing full supply level that allows for temporary storage of large inflows (for around 50% more water than the current dam storage volume). This airspace is not for the use of further permanent water storage.

The purpose of raising the dam wall is to create airspace above the full supply level which provides a flood mitigation zone (FMZ) to temporarily hold back large inflows and delay releases downstream.

The Project would delay the spilling from the dam by using the FMZ to temporarily store inflows. This would reduce the peak of the flood and provide more certainty of time for evacuation. After the flood peak, the inflows captured within the flood mitigation zone would be released in a controlled way.

For more information, please refer to Chapter 5 of the Environmental Impact Statement.

Warragamba Dam is operated as a water storage facility. In developing the Hawkesbury-Nepean Valley Flood Risk Management Strategy, INSW investigated the following options for flood mitigation:

  • pre-releasing water ahead of a predicted flood inflow
  • changing its operation to temporarily hold back flood water (known as surcharging)
  • permanently lowering the full supply level to provide a flood mitigation zone (FMZ)

Pre-releasing and surcharging have limited effectiveness with minor benefits for small floods, and negligible benefits for larger floods. Pre-releasing could also contribute to downstream flooding, impacting evacuation routes and resulting in the loss of drinking water from the storage should a forecasted event not occur.

As part of the alternatives examined, the Hawkesbury-Nepean Valley Flood Mitigation Taskforce considered two options to create an FMZ by reducing the dam’s existing full supply level - lower the full storage by 5 metres and 12 metres.

The 5-metre lowering was found to have limited benefits for the larger floods, which pose the most risk to lives and property.

The 12-metre lowering would only provide around 45% of the flood mitigation benefits, in terms of peak flood levels downstream for the key floods, compared to raising Warragamba Dam. It would also provide less evacuation warning time.

The 12-metre lowering would also reduce the dam’s drinking water storage by around 40 percent, significantly impacting water security for greater Sydney and the capacity to cater for prolonged drought conditions. Under the 12-metre lowering option, major new sources of water would need to be built at significant costs.

If the project is approved the delivery phase of the Project is expected to take around five years.

The final cost for the Project will be influenced by the completed detailed design, conditions of planning approval, competitively priced proposals from construction contractors for the Project and contemporary market conditions.

For more information on costings please refer to chapter 4 of the Environmental Impact Statement.

There is no plan to reduce the existing planning controls in place in the Hawkesbury-Nepean Valley. There is a real and substantial existing risk to life, property and community from rapid and deep flooding in the Hawkesbury-Nepean Valley. The dam raising proposal, would significantly reduce this risk to people’s lives and livelihoods downstream, provide more time for evacuation and reduce flood damages by over 70% on average over the long-term.

For more information please see the ‘Land Use in the floodplain’ FAQ on the Hawkesbury-Nepean Valley Flood Risk Management Strategy page on the Infrastructure NSW website.

The dam raising design will follow dam safety criteria in accordance with the Dams Safety NSW regulations.

When dams are modified, the structural integrity and safety of the dam, both during and after the upgrade, is the first and fundamental priority. There are stringent guidelines for building or modifying any large dam.

For more information, please refer to Chapter 5 of the Environmental Impact Statement.

Warragamba Dam Raising is a project to provide flood mitigation capacity to reduce the significant existing risk to life and property in the Hawkesbury-Nepean Valley downstream of the dam. This is achieved through raising the level of the central spillway crest by around 12 metres and the auxiliary spillway crest by around 14 metres above the existing full supply level for temporary storage of inflows. The spillway crest levels and outlets control the extent and duration of the temporary upstream inundation. There would be no change to the existing maximum volume of water permanently stored for water supply.

The current design includes raising the dam side walls (abutments) and roadway by 17 metres now to enable a future adaptation to projected climate change later this century.

For more information, please refer to Chapter 5 of the Environmental Impact Statement.

In terms of volume, the raised dam wall will temporarily capture around an additional 1,000 gigalitres (GL) of water in the flood mitigation zone before slowly releasing the water after the peak of the flood. One GL is equal to 1 billion litres.

The existing maximum volume of water stored in the dam is around 2,000 GL.

There are no low-cost options for providing flood mitigation to reduce the significant existing flood risk to communities in the Hawkesbury-Nepean floodplain.

The costs of the proposed raising of Warragamba Dam largely relate to construction and provision of environmental offsets for potential upstream impacts. Warragamba Dam currently stores around 80% of Greater Sydney’s supply. With the dam raising there would be no change to the dam’s full supply level or any associated costs to the city’s water supply system.

The key costs associated with options that lower Warragamba Dam’s full supply level relate the need to replace the water supply lost to Greater Sydney’s system. Projected population growth means the city’s water supply is now at its sustainable limits. Any reduction in supply from Warragamba Dam would trigger high-cost investment in alternative supplies such as desalination. These alternative water supplies would need to be in place before the dam supply level could be lowered.

Further, due to the deep ‘V’ shape of the valley behind Warragamba Dam wall, a disproportionate volume is held towards the top of the water storage. To achieve the same flood risk reduction benefits as raising the dam by 14 metres, the full supply level would need to be lowered by around 25 metres, more than halving Greater Sydney’s available water supply.

In 2017, the Project team contacted known groups and advertised in local papers, inviting any Aboriginal people who hold cultural knowledge relevant to, or who have a right or interest in determining the cultural heritage significance of Aboriginal object(s) and/or place(s) in the area surrounding Lake Burragorang and/or along the Hawkesbury-Nepean between Warragamba Dam to the confluence of the Colo River.

There were 22 Aboriginal representatives who became the Registered Aboriginal Parties (RAPs) for the Project.

The consultation process undertaken for the Project followed the current NSW framework, being the Aboriginal Cultural Heritage Consultation requirements for proponents (April 2010).

RAPs have been:

  • provided with the project assessment methodology to comment and provide input
  • involved in Aboriginal Cultural field surveys
  • in attendance at consultation workshops
  • provided copies of drafts of the Aboriginal Cultural Heritage Assessment Report for review and comment
  • consulted on mitigations and recommendations

For more information, please refer to Chapter 18 of the Environmental Impact Statement.

There were two key elements to the Aboriginal Cultural heritage assessment that informed the Environmental Impact Statement (EIS) for the proposed dam raising project:

  • archaeological assessment
  • cultural values assessment.

The archaeological assessment was supported by field surveys which focused on areas of spiritual and historical importance as identified by the Registered Aboriginal Parties (RAPs.) The field surveys were carried out in areas that would be disturbed by construction works and areas potentially affected by upstream inundation such as rivers, creek lines and large sandstone rock platforms, boulders and ridge lines.

Each of the field surveys teams comprised two archaeologists and between 1 and 3 representatives from the RAPs. Important features were noted and archaeological sites’ GPS positions recorded. Field surveys were undertaken over more than 70 days between May 2018 and June 2019.

The cultural values assessment was undertaken to assess the potential impacts of the Project on intangible values that contribute to the Aboriginal cultural heritage of the landscape. The assessment focused on known cultural value stories and places identified in the study area.

For more information, please refer to Chapter 18 of the Environmental Impact Statement.

WaterNSW (independent of the Warragamba Dam Raising Project) manages a consent application program for individuals and communities with significant cultural or historic connections to places in the Special or Controlled Areas. This includes entry to sites of Aboriginal significance by Aboriginal groups or individuals with cultural links to the sites. It also includes visits to sites by non- indigenous former owners, residents, or their descendants and families who can show a direct clear historical or cultural link to the sites.

Access to the Special and Controlled Areas is restricted to the public to protect water quality. This helps create a buffer of land around water storages and infrastructure which act as a filter for water quality, restricts harmful activities and helps manage the resources.

For more information, please refer to Chapter 18 of the Environmental Impact Statement.

A total of 2,655 hectares (including 464 hectares of the project upstream impact area) were surveyed upstream to provide a representative sample. The data collected from the survey enabled the development of a predictive model. The predictive model was used to extrapolate the survey findings across the unsurveyed portion of the 1,400-hectare project upstream impact area.

For more information, please refer to Chapter 18 of the Environmental Impact Statement.

Consultation has taken place during different stages, including to inform the design process and the preparation of a socio-economic assessment as part of the Environmental Impact Statement (EIS). The public exhibition stage of the EIS provides further opportunity for additional consultation and commentary.

WaterNSW has been conducting ongoing stakeholder consultation and broader community engagement on the Warragamba Dam Raising Project since 2017, including:

  • briefings for special interest groups and other stakeholders
  • consultation with Warragamba, Silverdale and Warragamba residents, business owners, local councils, sporting group, emergency services and other representatives
  • briefings, consultation and involvement in survey work for Registered Aboriginal Parties (RAPs)
  • site visits with interested parties into the upstream catchment area
  • engaging with property owners in the upstream study area to enable the collection of data to inform the EIS

For more information, please refer to Chapter 6 of the Environmental Impact Statement.

WaterNSW conducted a series of phone and web surveys with groups and agencies that interact with community members. In addition, face-to-face surveys were conducted with a variety of businesses about the potential effects and benefits of the Project. The responses were used to inform the Socio-Economic Impact Assessment (SEIA) of the EIS.

The SEIA methodology was developed in accordance with local and international social impact assessment standards. WaterNSW undertook early consultation with councils and emergency services, and scoping of potential Project effects, to identify groups to participate in the surveys who are representative of the community.

In addition, the Hawkesbury-Nepean Valley Flood Management Taskforce and Hawkesbury- Nepean Valley Flood Risk Management Directorate have ongoing engagement activities with key stakeholders and the community on the Hawkesbury-Nepean Flood Risk Management Strategy, including an overview of the Warragamba Dam Raising Project as a key element of the strategy. More information around the Flood Strategy is available online at: www.insw.com/flood-strategy.

For more information, please refer to Chapter 21 of the Environmental Impact Statement.

There are a number of ways the community has had, and will continue to have, opportunities to provide input into the Environmental Impact Statement (EIS) including through:

  • directly contacting the Project team by email, phone or letter to provide feedback
  • talking to the Project team at information sessions, community workshops, briefings or community forums
  • participating in online engagement activities
  • submissions from the Registered Aboriginal Parties for the Project during consultation on the Draft Aboriginal Cultural Heritage Assessment
  • making a formal submission to Department of Planning and Environment during the public exhibition of the EIS

Community members are invited to view the EIS during the public exhibition period and make submissions about EIS matters that interest them. All submissions will be addressed as part of the subsequent Submissions Report. More information about how to view and make a submission are available via www.waternsw.com.au/WDR.

There are two non-Aboriginal Heritage registers that each contain one item located in the Project construction zone:

  • The State Heritage Register (SHR) – Haviland Park (SHR 01375)
  • Section 170 Heritage and Conservation Register – The Warragamba Supply Scheme (#4580161), that partially overlaps

An exclusion zone will be established around specific items within the curtilage to protect them from any potential impacts.

For more information, please refer to Chapter 17 of the Environmental Impact Statement.

For the environmental impact assessment, three study areas were defined based on geographical location and potential impact:

  • upstream study area - located within the catchment area of the dam and up to the level defined by the probable maximum flood with the raised dam
  • downstream study area - located in the rivers and flood plains of the valley up to the level of the probable maximum flood of the raised dam
  • construction zone study area - the construction footprint within the dam precinct

A risk assessment framework was developed to identify and assess biodiversity features that are most likely to be sensitive to hydrological changes from flood mitigation operations.

It is predicted that the 1 in 10 chance in a year event would likely have the greatest change in extent due to differences between the existing flood operations and those with the raised dam. Potential biodiversity impacts assessments are therefore focused on the 1 in 10 chance in a year event area.

Potential biodiversity impacts are principally related to:

  • A reduction in flood frequency contribution from Warragamba resulting in reduced water availability to plants and wetland replenishment. However, any flood-dependent vegetation would be largely reliant on local catchment flows, rather than overbank flooding from the Hawkesbury-Nepean River
  • Increase in low level inundation durations during the discharge of the FMZ for five to eight days longer than existing discharge. Vegetation in these areas that is not tolerant of additional inundation may be adversely impacted.

For more information, please refer to Chapter 9 of the Environmental Impact Statement.

To assess the potential change in upstream inundation associated with the Project, flood modelling was undertaken. The full range of flood events and lake variables were modelled to determine what the likely inundation level would be.

Building on previous hydrological modelling carried out for the Project, further modelling was undertaken (using the Monte Carlo technique) to generate around 20,000 flood events. These events represent around a 200,000 year period of time. This was then analysed by selecting the peak inundation level for each 20-year period to determine the ‘average’ or likely inundation.

This approach was used for determining an area of likely inundation for both the existing dam and the raised dam. The area of project impact will be between 2.8 metres and 10.3 metres above the full supply level and is around 1,400 hectares.

The Environmental Impact Statement assessment has assumed a precautionary approach of complete loss of biodiversity and other environmental values in this area even if not identified by survey. It is a precautionary approach as it is unlikely to occur as sensitive areas/sites would have differing risks of impact depending on their respective locations in terms of elevation and tolerance to inundation.

For more information, please refer to Chapter 8 of the Environmental Impact Statement.

The Warragamba Offset Strategy (Strategy) incorporates all offset requirements for unavoidable upstream, downstream and construction area impacts. The Strategy will meet the biodiversity offset requirements of NSW and Commonwealth Offset Policies and would source appropriate compensation for impacts through:

  • the purchase of suitable land and retirement of biodiversity credits
  • other supplementary measures (e.g. actions within specific threatened species recovery plans targeted at potentially impacted species)

For more information, please refer to Chapter 13 of the Environmental Impact Statement.

The Project would not change the management of the water quality controls for drinking water or supply capacity from the dam. For more information, please refer to Chapter 27 of the Environmental Impact Statement.

Part of the Kowmung River has been declared a wild river under the National Parks and Wildlife Act 1974. GIS analysis using spatial data sourced from NSW Spatial Services identified a small section of the Kowmung River (about 1,250 metres) within the Project study area but well above the project upstream impact area. The Project would not impact on the declared wild river section of the Kowmung River.

The EIS analysis of depth-duration curves for the closest cross section downstream of the declared wild river section of the Kowmung showed no material difference between the existing situation and that with the Project for all flood events up to the 1 in 100 chance in a year event and a very small difference (less than 0.3 metres) up to the 1 in 1,000 chance in a year event.

The declared wild river sections for the Grose River and Colo River are located outside of the Project downstream study area and would not be affected by the Project.

For more information, please refer to Chapter 20 and Appendix J of the Environmental Impact Statement.

One of the key justifications and objectives of the Project is to reduce flooding risk from large rainfall events which are predicted to increase in intensity with climate change.

Drawing on contemporary climate change research, the Project has been designed to be resilient to the future impacts of climate change with the height of the abutments (side walls including roadway) of the dam wall being constructed to enable future adaptation to the projected climate change later this century if needed.

For more information, please refer to Chapter 14 of the Environmental Impact Statement.

As part of the Environmental Impact Statement (EIS), a Biodiversity Assessment Report has been prepared for upstream and downstream impacts of the Project. This assessment identifies threatened and endangered species that may be impacted because of the Project.

Flooding of areas upstream of Warragamba Dam happens now when the lake rises above the full supply level and spills. The Project would only influence the level of the lake - it will not have any effect on the rate of rainfall or impacts caused by rainfall, run-off and erosion. While this increase in temporary inundation may impact certain aspects of ecosystem health the extent to which this may occur is substantially dependent on a large range of independent variables such as topography, frequency, depth and duration of inundation, geographic setting, ecosystem characteristics, land use, germination from flood-borne seeds, edge effects and similar matters.

There would be an increased extent and duration of temporary inundation of three threatened ecological communities in the catchment when the flood mitigation zone is operational.

For more information, please refer to Chapters 8 and 13 of the EIS.

The Regent Honeyeater (Anthochaera Phrygia) has a broad breeding and foraging habitat extending from south-east Queensland, along the east coast of NSW and into southern Victoria and was recorded in the study area.

There are three large key breeding areas within NSW including Bundarra-Barraba, Capertee Valley and Hunter Valley areas (other breeding areas are Pilliga Woodlands and Mudgee-Wollar).

The Burragorang River Valleys are a subsidiary area of the Capertee Valley with potential breeding and foraging habitat occurring within the upstream impact area. The Regent Honeyeater is not limited to the 1,400 hectare Project upstream impact area.

The Environmental Impact Statement (EIS) has taken a precautionary approach by assuming a complete loss of all environmental values in the Project upstream impact area, despite the potential that the temporary inundation could result in minimal impact where the breeding and foraging habitat may remain largely intact.

For more information, please refer to Chapter 8 and Appendix F1 of the EIS.

WaterNSW engaged the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to undertake a controlled experiment to study the tolerance of the Camden White Gum due to flooding and soil saturation. The study concluded that the trees responded well to inundation and there was no evidence of negative impact on the growth of existing trees.

The Environmental Impact Statement (EIS) has taken a precautionary approach by assuming a complete loss of all environmental values in the Project upstream impact area, despite the evidence suggesting flood tolerance in this species.

For more information, please refer to Chapters 8 and 13 of the EIS.

The Environmental Impact Statement (EIS) concludes that the Project impacts to the Greater Blue Mountains World Heritage Area (GBMWHA) would not result in a loss in values that would lead to change in listing status.

The EIS includes a consistency report with Australia’s obligations under the World Heritage Convention; the Australian World Heritage management principle; and the GBMWHA Strategic Plan.

Under Section 137 of the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), an approval decision must comply with Australia's obligations under the World Heritage Convention; the Australian World Heritage management principle; and a plan that has been prepared for the management of a declared World Heritage property under section 316 or as described in section 321 of the EPBC Act.

For more information, please refer to Chapter 20 of the Environmental Impact Statement.

Temporary inundation of the Greater Blue Mountains World Heritage Area (GBMWHA) and National Parks in the upstream catchment already occurs now during flood events as the lake rises.

There are about 300 hectares within the project upstream impact area listed as GBMWHA. This represents about 0.03 percent of the total GBMWHA. To compensate for and offset the assessed impact of GBMWHA, the Warragamba Offset Strategy focuses on purchasing and managing additional and appropriate land containing the values of the Greater Blue Mountains World Heritage Area to achieve no net loss. The Warragamba Dam Offset Strategy would ensure the integrity of the GBMWHA is maintained.

For more information, please refer to Chapter 20 of the Environmental Impact Statement.

The Project would have no long-term impacts on surface water and groundwater hydrology.

Any impacts would be flood-related and short-term. The Project would have minimal impacts on downstream flood-dependent ecosystems as these are reliant upon water sourced from other tributaries and not often from Warragamba Dam, unless there is a spill.

For more information, please refer to Chapter 15 of the Environmental Impact Statement.

A Construction Flood Management Plan will be developed to minimise any changes in hydrology up and downstream of the dam and minimise risks to the construction site. For more information, please refer to Chapter 15 of the Environmental Impact Statement.

The dam operator WaterNSW will supplement the existing flood operating protocols with new rules that account for the new flood mitigation zone function in consultation with relevant regulatory authorities.

The current primary function of the auxiliary spillway is dam safety - to protect the structural integrity of the dam in an extreme flood. In such an event, it allows excess floodwaters to bypass the central spillway, preventing the dam from overtopping. It does not mitigate floods and it is not possible to use it for flood mitigation without raising the dam and modifying the spillways.

The dam raising Project and involves major modifications to the auxiliary spillway in conjunction with raising the height of the dam to provide a flood mitigation zone. These modifications would enable the auxiliary spillway to be used for flood mitigation.

Although flooding can also be generated by the other tributaries in the Hawkesbury-Nepean Valley, flows from the large Warragamba Catchment are the major contributor to the most damaging and dangerous floods.

While the dam raising will not completely eliminate flood risk in the valley, it will significantly reduce it. It is not possible to build a dam high enough to capture the most extreme, rare floods possible in the valley.

By temporarily storing and controlling the release of floodwater, the proposed dam raising would: protect homes and communities by reducing the depth and area of inundation; keep evacuation routes open for longer. It will also help minimise the velocity of floodwaters, reducing damage, debris and erosion downstream.

For more information, please refer to Chapter 5 of the Environmental Impact Statement.

With a raised dam, floods would be reduced in severity and depth. For example, the 1 in 100 chance per year flood level would drop by around 4 metres from 17.3 metres to around 13.2 metres at Windsor. However, to ensure the benefits of the dam raising would be maintained over time, the current 1 in 100 chance per year flood levels across the floodplain would be maintained and not lowered to the new level.

The Department of Planning, Industry and Environment has recently released its Flood Prone Land Package, which enables councils to have more flexibility to make informed decisions on land planning and development controls in flood-prone areas, giving them greater ability to manage the risk of flooding in their local government area. The Department is also developing a new Regional Land Use Planning Framework for the Hawkesbury-Nepean floodplain.

By limiting new growth to those areas where people can be safely evacuated in a severe flood, the framework will ensure the cumulative impacts of planning decisions are considered, and flood risk to life and property is not increased. Consistent with other natural hazards, flood resilient building controls are being developed for residential development, and land use planning controls being implemented in relation to flood risk.

During major rainfall events, access to National Parks and any campsites, walking routes and river crossings in the National Parks is already restricted. National Parks and associated facilities are closed to public access during and after major rainfall events for safety reasons and to minimise any damage to unpaved roads and fire trails.

During a flood event with an FMZ operation there may be minor increased impacts and lengths of closures, these would only occur infrequently during and after major rainfall events. No known public campsites would be affected by the Project.

Should the Project be approved, an Employment Strategy will be developed which will:

  • offer a clear and efficient process for people to access information about employment and provide an opportunity to register interest in the Project
  • establish liaison with local job network providers to provide information on employment opportunities for local job seekers
  • develop a framework to increase the representation of young people, Aboriginal and Torres Strait Islander people and women in the construction industry by providing employment pathways, training and skills development

For more information, please refer to Chapter 21 of the Environmental Impact Statement.

Should the Project be approved, a Local Industry Participation Plan would be developed with the aim of:

  • encouraging the Project’s contractors, where possible, to locally source their workforce and their suppliers for goods and services
  • providing a process for local businesses to register interest in project-related supplier and service-provider opportunities
  • working with the local networks and local businesses to plan for how to benefit from the incoming workforce
  • working with government stakeholders to build businesses’ capacity through business development and mentoring

Should the Project be approved, a Construction Community and Stakeholder Engagement Plan would be developed including a range of measures to identify and manage impacts and opportunities associated with Project construction.

Work will also be undertaken with the Warragamba DamFest Committee to support its ongoing success during the estimated five-year construction phase.

There is currently no evidence to suggest that oyster farmers almost 50 kilometres from the dam in the river’s tidal estuary would be significantly impacted by the change in water flow if the dam is raised.

However, businesses are included in the impact assessment reporting under the scope of the Environmental Impact Statement (EIS). The EIS includes a Social and Economic Impact Assessment report. This report assesses likely changes to population size or characteristics; housing; way of life; amenity; sense of place; health and wellbeing; recreational access and business activity.

Business owners, including oyster farmers, have been consulted with in relation to any potential impacts under different flooding scenarios and the controlled release of floodwaters from the flood mitigation zone if the dam is raised.

For more information, please refer to Chapter 21 of the Environmental Impact Statement.

The Local Government Areas of Penrith, Hawkesbury and the Hills produce a range of agricultural produce including turf, fodder, citrus, poultry, mushrooms, dairy and grapes.

The Project would provide a delay to the flood peak to enable producers more time to arrange for evacuation of stock and equipment than the current situation.

For more information, please refer to Chapter 15 and 21 of the Environmental Impact Statement.

The modified dam would have a similar visual appearance to the existing dam. The visual amenity in and around the dam would be the same or improved.

For more information, please refer to Chapter 25 of the Environmental Impact Statement.

Local communities were consulted through stakeholder workshops on a number of topics including managing construction impacts. Local communities will be notified in advance about construction activities, the temporary closure of recreation venues, changes in traffic arrangements and heavy vehicle routes during the construction period.

The construction site will allow for consideration of maintaining the function of the Visitor and Education Centre at the dam as far as is practical depending on activities and secured access to ensure public safety as a priority.

Ongoing consultation with relevant State agencies and local government will be undertaken to identify and implement appropriate solutions to minimise disruption of areas surrounding the Project site.

An Emergency Response Plan would be developed which will include:

  • engagement with medical and emergency service providers as part of ongoing planning and Project development
  • provision of appropriate onsite medical response facilities and personnel
  • response and evacuation procedures

The EIS assessment found that it is unlikely that there will be impacts on air quality in breach of ambient air quality criteria.

Procedures for construction activities with the potential to have air quality impacts will be controlled by dust suppression features such as water spraying to avoid, minimise or mitigate these impacts.

The measures include to:

  • minimise Project and cumulative dust generation from stockpiles, haulage routes, work activities, exposed ground surfaces and materials handling/storage
  • minimise generator and vehicle emissions during construction
  • modify or cease dust generating works during unfavourable weather conditions

For more information, please refer to Chapter 7 of the EIS.

The EIS assessment identifies construction activities that may be impacted by construction noise and outlines how exceedances will be managed in accordance with construction noise guidelines.

Procedures for construction activities would include processes and controls to assess, monitor, minimise and mitigate noise and vibration impacts during the activity.

The use of temporary noise walls and other appropriate noise management measures will be utilised for activities that have the potential to cause noise or vibration impacts.

All residents potentially affected by excessive noise or vibration from the construction of the Project would be consulted in advance of the activity.

For more information, please refer to Chapter 19 of the EIS.

Impacts from works or activities that are required to be undertaken outside of normal working hours will mainly relate to noise. The activity, and equipment, where applicable would be fitted with appropriate noise mitigation features to ensure that noise levels generated would comply with assessed allowable noise levels for the area. Noise levels will be monitored from receivers fitted near closest residential areas. Noise tests would be undertaken prior to an activity to confirm compliance as part of the construction procedure for that activity.

For more information, please refer to Chapter 19 of the Environmental Impact Statement.

Some minor low-level blasting may be required to supplement activities where conventional excavation equipment may not be able to access work areas. Should this be required a blasting design and monitoring of controlled trial blasts would be undertaken to confirm site specific conditions and validate the blast design to meet vibration and overpressure limits.

For more information, please refer to Chapter 19 of the Environmental Impact Statement.

It is currently proposed that spoil unable to be reused onsite would be sent off-site for reuse or disposal. Another option that would be investigated during construction planning is placing excess material on site and revegetating of area – as was undertaken for the auxiliary spillway construction Project.

Off-site waste re-use would be managed in accordance with relevant NSW EPA resource recovery exemptions. Waste would be disposed of at appropriately licensed facilities.

For more information, please refer to Chapter 26 of the Environmental Impact Statement.

A hazardous materials assessment would be carried out prior to and during the demolition of sections of the dam. Demolition works would be undertaken in accordance with the relevant Australian Standards and relevant NSW WorkCover Codes of Practice, including the Work Health and Safety Regulation 2011 (NSW).

Potentially contaminated areas directly affected by the Project would be investigated and managed in accordance with Section 105 of the Contaminated Land Management Act 1997. Asbestos handling and management will be undertaken in accordance with an Asbestos Management Plan.

All dangerous goods and materials would be stored and handled on site in accordance with relevant Australian Standards. Materials would be transported in accordance with the Storage and Handling of Dangerous Goods Code of Practice (WorkCover NSW 2005), Dangerous Goods (Road and Rail Transport) Act 2008 (NSW), Dangerous Goods (Road and Rail Transport) Regulation 2014 (NSW) and relevant Australian Standards.

For more information, please refer to Chapter 26 of the Environmental Impact Statement.

The Environmental Impact Statement assessment of traffic impacts found that the road routes both north and south of Warragamba Dam will provide a good level of service for local traffic with the additional construction traffic.

The following measures would also be implemented:

  • queueing of heavy vehicles would be permitted only within the dam precinct perimeter
  • all construction traffic from the north would use Production Avenue through the industrial area of Warragamba to access the site with traffic lights installed at Warradale intersection
  • heavy vehicle site access would be restricted to the standard working hours only. No heavy vehicle access would be permitted for periods outside standard working hours unless required for an emergency, consideration would be given to ensure that the operation of general construction traffic would be minimised during periods of school bus operations.

For more information, please refer to Chapter 24 of the Environmental Impact Statement.

The Warragamba Special Areas were extensively impacted by the Green Wattle Creek, Ruined Castle and Erskine Creek fires during the 2019-2020 bushfire season.

This particular fire affected parts of the Project study area where it burnt out of control for at least nine weeks. A total of 278,700 hectares in the Wollondilly area were affected by this fire until it was officially declared as ‘contained’ on 30 January 2020. The fire was declared as ‘extinguished’ by the NSW Rural Fire Service on 10 February 2020 following a torrential rain event.

The section of the Greater Blue Mountains World Heritage Area within the Project upstream study area (the area closest to the water of Lake Burrogorang) was relatively unaffected by the 2019- 2020 bushfire event, with 70% of the area mapped being classified as “low” or unburnt.

In order to prepare the Warragamba Dam Raising Environmental Impact Statement (EIS), comprehensive environmental field surveys of the Project areas were completed over a number of years before the 2019-2020 bushfires in the catchment.

Following the bushfires, the NSW Department of Planning, Industry and Environment issued a ‘Guideline for applying the Biodiversity Assessment Method’ at severely burnt sites. The guideline provides fire mapping and aerial imagery resources along with instructions for applying the biodiversity assessment method depending on the severity of the burnt vegetation and the assessment stage of the Project.

The guideline outlines the approach to identifying the biodiversity values that existed on, and prior to, severe bushfire for the purpose of preparing or finalising a Biodiversity Development Assessment Report or a Biodiversity Certification Assessment Report.

As per the guideline, WaterNSW consulted with the Department of Planning, Industry and Environment regarding any additional considerations that may be required. As a result, the assessment includes consideration of the unburnt area as refuge for species displaced.

For more information, refer to Chapter 8 of the Environmental Impact Statement.