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Connected residents will be supplied primarily from North Pine Water Treatment Plant which draws water from North Pine Dam's storage 2.JPG

North Pine Dam Upgrade

Planning for the dam upgrade is underway.

The upgrade will increase North Pine Dam's capacity to withstand extreme floods.

The required upgrades reflect advances in dam design, as well as updated safety guidelines and engineering standards since the dam was built in 1976.

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Home What We're Doing North Pine Dam Upgrade

Like all major infrastructure, dams are regularly assessed and upgraded to comply with improving engineering standards and the latest guidelines.

North Pine Dam can withstand rare and extreme floods including possible inflows much greater than the January 2011 flood. However, the largest possible flood we can estimate would exceed the capacity of the dam.

With a large population living downstream of the dam, the risk to downstream communities means the dam needs greater capacity to withstand the Probable Maximum Flood (PMF).

Reduced Full Supply Level

Lowering dam water storage levels is an accepted and long-established way of reducing the safety risks associated with rare and large flood events. Dams which have previously been lowered as part of our Dam Improvement Program include Sideling Creek, Cooloolabin and Leslie Harrison dams.

The reduced Full Supply (FSL) Level for North Pine Dam is 36.0 metres Australian Height Datum (AHD). This level is equivalent to about 68% of its original water storage capacity or Full Supply Volume (FSV).

With the reduced FSL, it is possible releases from the dam may occur more frequently in minor flow events (much smaller than those that flood houses). This may result in temporary closures to roads in low-lying areas downstream.

 

When inflows from rainfall occur in the future, there will be flood releases if the lake level is expected to exceed 36.0 metres AHD (68% of its original water storage capacity).

Any future flood releases will continue to be managed in accordance with the 2019 Flood Mitigation Manual for North Pine Dam.

The reduced FSL is not expected to impact the long-term water supply security for South East Queensland.

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  • Downstream view of North Pine Dam. Photo credit Peter Hansler

    Investigative work

    Geotechnical drilling work is being undertaken downstream of the North Pine Dam spillway.

    Seqwater is conducting geotechnical investigations downstream of the main dam spillway at North Pine Dam. 

    This work is part of Seqwater's Dam Improvement Program to help to assess what upgrade work North Pine Dam may require in the future. 

    Seqwater contractors will be undertaking this investigation work from Monday 10 February 2020 for approximately five weeks, subject to any wet weather or unforseen project delays. 

    What to expect:

    • Work hours are from 6.30am-6.30pm Monday to Saturday
    • Work may be required on Sunday, from 9am-5pm
    • Equipment will include a drilling rig, trucks and utility vehicles
    • There may be a minor increase in noise and traffic during this work. 

    Access to the lake and recreation areas will not be affected during this work.

  • Why was the Full Supply Level reduced at North Pine Dam?

    Seqwater reduced the Full Supply Level for North Pine Dam following further assessments of the potential safety risks associated with rare and extreme flood events.

    Lowering the full supply level for the dam until an upgrade is completed is a precautionary measure, which will help reduce the safety risks associated with rare and extreme flood events, beyond which the dam has experienced to date.

    North Pine Dam is in good structural condition and continues to safely operate.

    How much water has been released to reduce the Full Supply Level?

    Due to the dry conditions and low lake level at the time the reduced Full Supply Level was enacted in December 2019, there was no requirement to release any water that was stored in the dam.

    What does lowering the Full Supply Level achieve?

    Lowering the Full Supply Level of dams is an accepted and long-established way of reducing the safety risks associated with rare and extreme flood events. The reduced Full Supply Level assists to reduce the peak lake level in the dam for potential flood events in the future.

    Dams which have previously been lowered as part of our Dam Improvement Program include Sideling Creek, Cooloolabin and Leslie Harrison dams.

    If the dam is safe, why do improvements need to be made?

    North Pine Dam is in good structural condition and continues to safely operate. The existing dam can withstand rare and extreme floods including possible inflows much greater than the January 2011 flood. However, the largest possible flood we can estimate would exceed the capacity of the dam.

    With a large population living downstream of North Pine Dam, the risk to downstream communities means the dam needs greater capacity to withstand the Probable Maximum Flood (PMF).

    The planned upgrade will enable the dam to continue to operate safely and improve the capacity of the dam to withstand rare and extreme floods in the future.

    North Pine Dam is one of a number of dams across South East Queensland identified for upgrade as part of Seqwater’s Dam Improvement Program.  Other dams across currently scheduled for future upgrades include Lake Macdonald and Ewen Maddock dams on the Sunshine Coast and Wivenhoe and Somerset dams.

    Why are upgrades needed?

    The upgrade of the dam will increase the dam's capacity to withstand rare and extreme floods.

    With a large population living downstream of North Pine Dam, the risk to downstream communities means the dam needs greater capacity to withstand the Probable Maximum Flood (PMF). The potential options to increase the capacity of the dam for extreme floods may require a selection or combination of spillway modification, dam raising and strengthening. 

    We are in the early planning stages and no options have been finalised or decided at this time. Seqwater will continue to conduct assessments and investigations to develop and review feasible options.

    What is the likelihood of the dam failing?

    North Pine Dam is in good structural condition and continues to safely operate. With the reduced Full Supply Level, it is estimated that North Pine Dam can withstand a flood about two times larger than the rare extreme flood that occurred in January 2011.

    Data collected from significant rainfall and flood events since the dam was designed and constructed, and the developments in flood estimation methods, have improved the ability to estimate the magnitude of potential rare and extreme flood events.

    The probability of a flood sufficient to cause dam failure is low. The planned upgrade will aim to provide capacity for extreme floods up to three times larger than the January 2011 flood.

    How much was the water level reduced by?

    The reduced Full Supply Level (FSL) for North Pine Dam is 36.0 metres Australian Height Datum (AHD). This level is equivalent to about 68% of the dam's original water storage capacity or Full Supply Volume (FSV). The dam was below 60% in December 2019 when the reduced FSL was enacted so there was no need to release water at the time.

    How will the reduced level impact water supply?

    The reduced Full Supply Level for North Pine Dam is not expected to impact the long-term water supply security for South East Queensland. This will be reviewed periodically until the dam is upgraded to make sure there are no negative impacts to water supply and long-term water security.

    Are homes more at risk of flooding now that Full Supply Level has been reduced?

    Reducing the Full Supply Level for the dam until an upgrade is completed will help reduce the safety risks associated with rare and extreme flood events, beyond which the dam has experienced to date (i.e. floods considerably larger than the 2011 flood).

    The flood operations for North Pine Dam with the reduced Full Supply Level are not expected to impact downstream flood levels for large and rare floods that can flood houses. It is possible releases may occur more frequently in minor flow events (much smaller than those that flood houses), which may result in temporary closures to roads in low-lying areas downstream.

    Any future flood releases will continue to be managed in accordance with the 2019 Flood Mitigation Manual for North Pine Dam.

    When will the dam be upgraded?

    Planning for the North Pine Dam upgrade is underway. Seqwater will provide further information about the timing and impacts as planning progresses.

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