CommunityUpdate SUMMER 2018/2019

Warragamba Dam Raising Proposal

The NSW Government proposal to raise the Warragamba Dam wall to create a fl ood mitigation zone of around 14 metres is a key element of an integrated strategy to reduce the signifi cant existing fl ood risk in the Hawkesbury-Nepean Valley. This Community Update shares information on how the proposed project will better protect downstream communities from the threat to life, safeguard property and maintain essential infrastructure.

Warragamba Dam is not designed or operated to manage fl oods.

Uncontrolled spilling during an extreme fl ood would have catastrophic consequences downstream.

Investigations are now underway for the proposal to raise Warragamba Dam so that it can be used to capture the peak of a fl ood and release it gradually and to better understand the upstream impacts of the proposal.

Free call: 1800 932 066 | wdr@waternsw.com.au | waternsw.com.au/wdr

Hawkesbury-Nepean Valley Flood Risk Management Strategy: www.insw.com/fl ood-strategy and fl oodstrategy@insw.com

We are continuing the conversation with communities upstream, downstream and those who are neighboring Warragamba Dam. Your views matter and we value your input to the EIS. If you would like to register for further updates, make a comment or monitor our website please contact us:

Contact us

Ensuring dam safetyStrict regulations control construction and modifi cation of large dams. Safety and structural soundness is the fi rst priority.

All upgrades of Warragamba Dam have complied with state, national and international guidelines and these are being applied to the wall raising proposal.

Raising the Warragamba Dam wall in the way proposed has been completed successfully and safely for other large concrete gravity dams overseas.

An independent panel, experienced in the investigation and design of large dams, is providing technical reviews to ensure the design meets international best practice.

The project team is using advanced fl ood estimation techniques using real fl ood behaviours to produce thousands of possible events. The results will be used to consider how mitigation measures will affect evacuation.

Extensive investigation of existing structural concrete and testing of new concrete mixes will be undertaken.

Although extreme fl oods and earthquakes are rare, the dam wall will be designed to remain stable under all conditions.

The design work also includes construction of a scale model of the dam and its spillways which will help the design team’s understanding of water movement.

What are we doing?

Working to international and national standards

Engaging an independent expert panel to review our design

Testing concrete to fi nd the best formula for safety and strength

Ensuring we pass safety standards for possible earthquakes and fl oods

Drilling core samples to ensure we have accurate geological information for our design

Running the design andenvironmental studies in parallel to inform the process

In this Community Update you will fi nd information about:

The current operation of Warragamba Dam and its auxiliary spillway

The consultation effort and next steps in engaging with the community

The existing impacts major fl oods would have on downstream communities

The science and engineering effort underway to test the impact of the proposal

Auxiliary spillway fuse plugs front right Community engagement at Yandhai Nepean Crossing opening

Scale hydraulic model of the upstream topography Scale hydraulic model under construction

Community consultationStakeholder consultation and broader community engagement has been ongoing since 2017, including to date:

• briefi ngs to 10 councils in the region

• formal briefi ngs for the Greater Blue Mountains World Heritage Area Advisory Committee

• briefi ngs for special interest groups

• presentations at meetings of the Gundungurra Indigenous Land Use Agreement (ILUA) Consultation Committee

• briefi ngs and involvement in survey work for Registered Aboriginal Parties

• coordination of catchment special area site visits for the Colong Foundation for Wilderness and Aboriginal stakeholders

• briefi ngs for Yerranderie Management Committee

• doorknocking of more than 220 properties in the survey area to enable collection of survey data for noise, geomorphology, Aboriginal Heritage and biodiversity studies

• pop up stalls at shopping centres and events throughout the region

• ongoing displays at 10 locations which help to keep local communities informed as the proposal progresses.

These activities have shown that there is a high level of community interest in the proposal. Some people have raised concerns about potential environmental impacts. Others strongly supporting the proposal are concerned it is not progressing quickly enough to reduce the risks to people and their homes downstream if it fl oods.

A history of dam upgrades Warragamba Dam, which has a 142-metre-high wall, took 12 years to build from 1948 to 1960.

In the late 1980s, the dam wall was strengthened and raised by fi ve metres to meet contemporary dam safety standards.

In 2002, a 700-metre-long auxiliary spillway was completed to ensure dam safety in extreme and rare fl ood events and to bring the dam up to NSW Dams Safety Committee standards.

Dam operationsThe dam is designed to provide water supply for greater Sydney, not for fl ood mitigation.

Currently, when the dam reaches capacity, water is automatically released via its central drum gate and radial gates.

The auxiliary spillway embankment is divided into fi ve sections called fuse plugs. These have been constructed at different levels across the auxiliary spillway to protect the dam.

In an extreme fl ood, these would wash away progressively to maintain dam safety, allowing the spillway to release water as the fl ood level rises.

2018

2019

2016

2002

Environmental Impact Statement on display for public comment

Auxiliary spillway built to protect dam

Business Case put to NSW Government

Dam wall raised and strengthened for safety

Weare

here

20201980s

Warragamba Dam timeline

NSW Government announces proposal to raise Warragamba Dam for fl ood mitigation

For more information on the science of the dam raising proposal from the design team, visit waternsw.com.au/wdr

m m30 30

28 28

26 26

24 24

22 22

20 20

18 18

16 16

14 14

12 12

10 10

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Existing inundation with current dam 1 in 100 (1%) chance per year fl oodInundation with 14 metre raising 1 in 100 (1%) chance per year fl ood

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Downstream of Warragamba Dam

Penrith fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Penrith properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include maintaining operations of Emu Plains Commercial Centre and community facilities. The Great Western Highway, Western Railway Line and Nepean High School would also remain open.

Windsor/Richmond fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Windsor properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include keeping the railway line operational, reducing potential damage to water, sewer and power infrastructure.

Upstream of Warragamba DamCurrently, when the dam spills, there is inundation upstream of the Warragamba Dam above the full supply level. In raising the dam to create a fl ood mitigation zone of around 14 metres to reduce the risk to life and property downstream, some additional temporary fl ooding upstream would occur.

If the dam wall is raised, preliminary modelling indicates a

temporary inundation increase in the Greater Blue Mountains World Heritage Area of 0.04-0.05% of the total area. This

equates to an area of 400-550 hectares for a 1 in 100 (1%) chance per year fl ood and

the maximum fl ood respectively.

There is only one declared

wild river located in the Warragamba Dam

Catchment – the Kowmung River. Based on preliminary

modelling, there would be no change to the level or extent of

inundation for the Kowmung River, its streams or tributaries, with the proposed wall raising. As part of the environmental assessment,

the impact of temporary inundation on other rivers

and streams is being analysed.

Aboriginal Cultural Heritage fi eld

surveys are ongoing and will continue for the time it takes to satisfy the methods agreed by Aboriginal Parties that have registered with

the project.

With Warragamba Dam raised

Normal river height

With Warragamba Dam raised

Normal river height

Without Warragamba Dam raised

Without Warragamba Dam raisedWarragamba Dam

Lake Burragorang

Greater Blue Mountains World Heritage Area

Kowmung River

Raising the dam mitigates nearly 100% of the risk to homes for fl oods up to the 1 in 200 chance per year at Penrith (similar to the worst fl ood on record in 1867). This would reduce the number of homes impacted by fl ood water from around 2,000 to less than 20 in the Penrith fl oodplain.

With the dam raising, 4,500 homes would no longer be impacted in Windsor/Richmond by a fl ood similar to the worst on record.

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of

the 1867 fl ood as experienced in Windsor - around a 1 in 500 (0.2%) chance per year

fl ood

A fl ood the size of the 1867

fl ood- greater than a 1 in 200

(0.5%) chance per year fl ood

m m30 30

28 28

26 26

24 24

22 22

20 20

18 18

16 16

14 14

12 12

10 10

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Existing inundation with current dam 1 in 100 (1%) chance per year fl oodInundation with 14 metre raising 1 in 100 (1%) chance per year fl ood

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Downstream of Warragamba Dam

Penrith fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Penrith properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include maintaining operations of Emu Plains Commercial Centre and community facilities. The Great Western Highway, Western Railway Line and Nepean High School would also remain open.

Windsor/Richmond fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Windsor properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include keeping the railway line operational, reducing potential damage to water, sewer and power infrastructure.

Upstream of Warragamba DamCurrently, when the dam spills, there is inundation upstream of the Warragamba Dam above the full supply level. In raising the dam to create a fl ood mitigation zone of around 14 metres to reduce the risk to life and property downstream, some additional temporary fl ooding upstream would occur.

If the dam wall is raised, preliminary modelling indicates a

temporary inundation increase in the Greater Blue Mountains World Heritage Area of 0.04-0.05% of the total area. This

equates to an area of 400-550 hectares for a 1 in 100 (1%) chance per year fl ood and

the maximum fl ood respectively.

There is only one declared

wild river located in the Warragamba Dam

Catchment – the Kowmung River. Based on preliminary

modelling, there would be no change to the level or extent of

inundation for the Kowmung River, its streams or tributaries, with the proposed wall raising. As part of the environmental assessment,

the impact of temporary inundation on other rivers

and streams is being analysed.

Aboriginal Cultural Heritage fi eld

surveys are ongoing and will continue for the time it takes to satisfy the methods agreed by Aboriginal Parties that have registered with

the project.

With Warragamba Dam raised

Normal river height

With Warragamba Dam raised

Normal river height

Without Warragamba Dam raised

Without Warragamba Dam raisedWarragamba Dam

Lake Burragorang

Greater Blue Mountains World Heritage Area

Kowmung River

Raising the dam mitigates nearly 100% of the risk to homes for fl oods up to the 1 in 200 chance per year at Penrith (similar to the worst fl ood on record in 1867). This would reduce the number of homes impacted by fl ood water from around 2,000 to less than 20 in the Penrith fl oodplain.

With the dam raising, 4,500 homes would no longer be impacted in Windsor/Richmond by a fl ood similar to the worst on record.

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of

the 1867 fl ood as experienced in Windsor - around a 1 in 500 (0.2%) chance per year

fl ood

A fl ood the size of the 1867

fl ood- greater than a 1 in 200

(0.5%) chance per year fl ood

m m30 30

28 28

26 26

24 24

22 22

20 20

18 18

16 16

14 14

12 12

10 10

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Existing inundation with current dam 1 in 100 (1%) chance per year fl oodInundation with 14 metre raising 1 in 100 (1%) chance per year fl ood

LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹LEGEND

Existing

1% AEP - 1 in 100

14meters

1% AEP - 1 in 100

¹

Downstream of Warragamba Dam

Penrith fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Penrith properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include maintaining operations of Emu Plains Commercial Centre and community facilities. The Great Western Highway, Western Railway Line and Nepean High School would also remain open.

Windsor/Richmond fl oodplainThis image shows potential effects of different fl ood levels (shown in metres) on Windsor properties with and without the raising of Warragamba Dam by around 14 metres.

Wall raising benefi ts for key community services and employment centres include keeping the railway line operational, reducing potential damage to water, sewer and power infrastructure.

Upstream of Warragamba DamCurrently, when the dam spills, there is inundation upstream of the Warragamba Dam above the full supply level. In raising the dam to create a fl ood mitigation zone of around 14 metres to reduce the risk to life and property downstream, some additional temporary fl ooding upstream would occur.

If the dam wall is raised, preliminary modelling indicates a

temporary inundation increase in the Greater Blue Mountains World Heritage Area of 0.04-0.05% of the total area. This

equates to an area of 400-550 hectares for a 1 in 100 (1%) chance per year fl ood and

the maximum fl ood respectively.

There is only one declared

wild river located in the Warragamba Dam

Catchment – the Kowmung River. Based on preliminary

modelling, there would be no change to the level or extent of

inundation for the Kowmung River, its streams or tributaries, with the proposed wall raising. As part of the environmental assessment,

the impact of temporary inundation on other rivers

and streams is being analysed.

Aboriginal Cultural Heritage fi eld

surveys are ongoing and will continue for the time it takes to satisfy the methods agreed by Aboriginal Parties that have registered with

the project.

With Warragamba Dam raised

Normal river height

With Warragamba Dam raised

Normal river height

Without Warragamba Dam raised

Without Warragamba Dam raisedWarragamba Dam

Lake Burragorang

Greater Blue Mountains World Heritage Area

Kowmung River

Raising the dam mitigates nearly 100% of the risk to homes for fl oods up to the 1 in 200 chance per year at Penrith (similar to the worst fl ood on record in 1867). This would reduce the number of homes impacted by fl ood water from around 2,000 to less than 20 in the Penrith fl oodplain.

With the dam raising, 4,500 homes would no longer be impacted in Windsor/Richmond by a fl ood similar to the worst on record.

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the

size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of the 1961 fl ood - around a

1 in 50 (2%) chance per

year fl ood

A fl ood the

size of the 2011 Brisbane fl ood -

around a 1 in 100 (1%) chance per

year fl ood

A fl ood the size of

the 1867 fl ood as experienced in Windsor - around a 1 in 500 (0.2%) chance per year

fl ood

A fl ood the size of the 1867

fl ood- greater than a 1 in 200

(0.5%) chance per year fl ood

CommunityUpdate SUMMER 2018/2019

Warragamba Dam Raising Proposal

The NSW Government proposal to raise the Warragamba Dam wall to create a fl ood mitigation zone of around 14 metres is a key element of an integrated strategy to reduce the signifi cant existing fl ood risk in the Hawkesbury-Nepean Valley. This Community Update shares information on how the proposed project will better protect downstream communities from the threat to life, safeguard property and maintain essential infrastructure.

Warragamba Dam is not designed or operated to manage fl oods.

Uncontrolled spilling during an extreme fl ood would have catastrophic consequences downstream.

Investigations are now underway for the proposal to raise Warragamba Dam so that it can be used to capture the peak of a fl ood and release it gradually and to better understand the upstream impacts of the proposal.

Free call: 1800 932 066 | wdr@waternsw.com.au | waternsw.com.au/wdr

Hawkesbury-Nepean Valley Flood Risk Management Strategy: www.insw.com/fl ood-strategy and fl oodstrategy@insw.com

We are continuing the conversation with communities upstream, downstream and those who are neighboring Warragamba Dam. Your views matter and we value your input to the EIS. If you would like to register for further updates, make a comment or monitor our website please contact us:

Contact us

Ensuring dam safetyStrict regulations control construction and modifi cation of large dams. Safety and structural soundness is the fi rst priority.

All upgrades of Warragamba Dam have complied with state, national and international guidelines and these are being applied to the wall raising proposal.

Raising the Warragamba Dam wall in the way proposed has been completed successfully and safely for other large concrete gravity dams overseas.

An independent panel, experienced in the investigation and design of large dams, is providing technical reviews to ensure the design meets international best practice.

The project team is using advanced fl ood estimation techniques using real fl ood behaviours to produce thousands of possible events. The results will be used to consider how mitigation measures will affect evacuation.

Extensive investigation of existing structural concrete and testing of new concrete mixes will be undertaken.

Although extreme fl oods and earthquakes are rare, the dam wall will be designed to remain stable under all conditions.

The design work also includes construction of a scale model of the dam and its spillways which will help the design team’s understanding of water movement.

What are we doing?

Working to international and national standards

Engaging an independent expert panel to review our design

Testing concrete to fi nd the best formula for safety and strength

Ensuring we pass safety standards for possible earthquakes and fl oods

Drilling core samples to ensure we have accurate geological information for our design

Running the design andenvironmental studies in parallel to inform the process

In this Community Update you will fi nd information about:

The current operation of Warragamba Dam and its auxiliary spillway

The consultation effort and next steps in engaging with the community

The existing impacts major fl oods would have on downstream communities

The science and engineering effort underway to test the impact of the proposal

Auxiliary spillway fuse plugs front right Community engagement at Yandhai Nepean Crossing opening

Scale hydraulic model of the upstream topography Scale hydraulic model under construction

Community consultationStakeholder consultation and broader community engagement has been ongoing since 2017, including to date:

• briefi ngs to 10 councils in the region

• formal briefi ngs for the Greater Blue Mountains World Heritage Area Advisory Committee

• briefi ngs for special interest groups

• presentations at meetings of the Gundungurra Indigenous Land Use Agreement (ILUA) Consultation Committee

• briefi ngs and involvement in survey work for Registered Aboriginal Parties

• coordination of catchment special area site visits for the Colong Foundation for Wilderness and Aboriginal stakeholders

• briefi ngs for Yerranderie Management Committee

• doorknocking of more than 220 properties in the survey area to enable collection of survey data for noise, geomorphology, Aboriginal Heritage and biodiversity studies

• pop up stalls at shopping centres and events throughout the region

• ongoing displays at 10 locations which help to keep local communities informed as the proposal progresses.

These activities have shown that there is a high level of community interest in the proposal. Some people have raised concerns about potential environmental impacts. Others strongly supporting the proposal are concerned it is not progressing quickly enough to reduce the risks to people and their homes downstream if it fl oods.

A history of dam upgrades Warragamba Dam, which has a 142-metre-high wall, took 12 years to build from 1948 to 1960.

In the late 1980s, the dam wall was strengthened and raised by fi ve metres to meet contemporary dam safety standards.

In 2002, a 700-metre-long auxiliary spillway was completed to ensure dam safety in extreme and rare fl ood events and to bring the dam up to NSW Dams Safety Committee standards.

Dam operationsThe dam is designed to provide water supply for greater Sydney, not for fl ood mitigation.

Currently, when the dam reaches capacity, water is automatically released via its central drum gate and radial gates.

The auxiliary spillway embankment is divided into fi ve sections called fuse plugs. These have been constructed at different levels across the auxiliary spillway to protect the dam.

In an extreme fl ood, these would wash away progressively to maintain dam safety, allowing the spillway to release water as the fl ood level rises.

2018

2019

2016

2002

Environmental Impact Statement on display for public comment

Auxiliary spillway built to protect dam

Business Case put to NSW Government

Dam wall raised and strengthened for safety

Weare

here

20201980s

Warragamba Dam timeline

NSW Government announces proposal to raise Warragamba Dam for fl ood mitigation

For more information on the science of the dam raising proposal from the design team, visit waternsw.com.au/wdr

CommunityUpdate SUMMER 2018/2019

Warragamba Dam Raising Proposal

The NSW Government proposal to raise the Warragamba Dam wall to create a fl ood mitigation zone of around 14 metres is a key element of an integrated strategy to reduce the signifi cant existing fl ood risk in the Hawkesbury-Nepean Valley. This Community Update shares information on how the proposed project will better protect downstream communities from the threat to life, safeguard property and maintain essential infrastructure.

Warragamba Dam is not designed or operated to manage fl oods.

Uncontrolled spilling during an extreme fl ood would have catastrophic consequences downstream.

Investigations are now underway for the proposal to raise Warragamba Dam so that it can be used to capture the peak of a fl ood and release it gradually and to better understand the upstream impacts of the proposal.

Free call: 1800 932 066 | wdr@waternsw.com.au | waternsw.com.au/wdr

Hawkesbury-Nepean Valley Flood Risk Management Strategy: www.insw.com/fl ood-strategy and fl oodstrategy@insw.com

We are continuing the conversation with communities upstream, downstream and those who are neighboring Warragamba Dam. Your views matter and we value your input to the EIS. If you would like to register for further updates, make a comment or monitor our website please contact us:

Contact us

Ensuring dam safetyStrict regulations control construction and modifi cation of large dams. Safety and structural soundness is the fi rst priority.

All upgrades of Warragamba Dam have complied with state, national and international guidelines and these are being applied to the wall raising proposal.

Raising the Warragamba Dam wall in the way proposed has been completed successfully and safely for other large concrete gravity dams overseas.

An independent panel, experienced in the investigation and design of large dams, is providing technical reviews to ensure the design meets international best practice.

The project team is using advanced fl ood estimation techniques using real fl ood behaviours to produce thousands of possible events. The results will be used to consider how mitigation measures will affect evacuation.

Extensive investigation of existing structural concrete and testing of new concrete mixes will be undertaken.

Although extreme fl oods and earthquakes are rare, the dam wall will be designed to remain stable under all conditions.

The design work also includes construction of a scale model of the dam and its spillways which will help the design team’s understanding of water movement.

What are we doing?

Working to international and national standards

Engaging an independent expert panel to review our design

Testing concrete to fi nd the best formula for safety and strength

Ensuring we pass safety standards for possible earthquakes and fl oods

Drilling core samples to ensure we have accurate geological information for our design

Running the design andenvironmental studies in parallel to inform the process

In this Community Update you will fi nd information about:

The current operation of Warragamba Dam and its auxiliary spillway

The consultation effort and next steps in engaging with the community

The existing impacts major fl oods would have on downstream communities

The science and engineering effort underway to test the impact of the proposal

Auxiliary spillway fuse plugs front right Community engagement at Yandhai Nepean Crossing opening

Scale hydraulic model of the upstream topography Scale hydraulic model under construction

Community consultationStakeholder consultation and broader community engagement has been ongoing since 2017, including to date:

• briefi ngs to 10 councils in the region

• formal briefi ngs for the Greater Blue Mountains World Heritage Area Advisory Committee

• briefi ngs for special interest groups

• presentations at meetings of the Gundungurra Indigenous Land Use Agreement (ILUA) Consultation Committee

• briefi ngs and involvement in survey work for Registered Aboriginal Parties

• coordination of catchment special area site visits for the Colong Foundation for Wilderness and Aboriginal stakeholders

• briefi ngs for Yerranderie Management Committee

• doorknocking of more than 220 properties in the survey area to enable collection of survey data for noise, geomorphology, Aboriginal Heritage and biodiversity studies

• pop up stalls at shopping centres and events throughout the region

• ongoing displays at 10 locations which help to keep local communities informed as the proposal progresses.

These activities have shown that there is a high level of community interest in the proposal. Some people have raised concerns about potential environmental impacts. Others strongly supporting the proposal are concerned it is not progressing quickly enough to reduce the risks to people and their homes downstream if it fl oods.

A history of dam upgrades Warragamba Dam, which has a 142-metre-high wall, took 12 years to build from 1948 to 1960.

In the late 1980s, the dam wall was strengthened and raised by fi ve metres to meet contemporary dam safety standards.

In 2002, a 700-metre-long auxiliary spillway was completed to ensure dam safety in extreme and rare fl ood events and to bring the dam up to NSW Dams Safety Committee standards.

Dam operationsThe dam is designed to provide water supply for greater Sydney, not for fl ood mitigation.

Currently, when the dam reaches capacity, water is automatically released via its central drum gate and radial gates.

The auxiliary spillway embankment is divided into fi ve sections called fuse plugs. These have been constructed at different levels across the auxiliary spillway to protect the dam.

In an extreme fl ood, these would wash away progressively to maintain dam safety, allowing the spillway to release water as the fl ood level rises.

2018

2019

2016

2002

Environmental Impact Statement on display for public comment

Auxiliary spillway built to protect dam

Business Case put to NSW Government

Dam wall raised and strengthened for safety

Weare

here

20201980s

Warragamba Dam timeline

NSW Government announces proposal to raise Warragamba Dam for fl ood mitigation

For more information on the science of the dam raising proposal from the design team, visit waternsw.com.au/wdr