henderson dam upgrade - flinders council

Henderson Dam Upgrade

Temporary Water Supply Options and Approval Pathway

CDO file ref. 004-PRE-EN-0001 Revision no. A Date 3 September, 2019

Annexure 18.4.1 - September 2019

Introductions

• Nick Wallis – CDO Alliance Project Supervisor - Henderson Dam

• Eve Lancaster – CDO Alliance Environment Lead

• Jay Knight – CDO Alliance Environmental Consultant

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Purpose

1. Provide an overview of water supply security options investigated to facilitate the upgrade of Henderson Dam.

2. Detail the preferred option.

3. Understand approvals process for the preferred option.

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Whitemark Water Supply

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• Henderson Dam – 40ML

• Cannes Hill – 24ML

Henderson Dam

Pats Weir

Cannes Hill Dam 1 & 2

Cannes Hill WTP


Henderson Dam Upgrade - Purpose

Current Capacity – 40ML Designed Capacity - 85ML

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Improved drinking water security


Works Required

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• Raise the height of the dam (~2m).

• Install a clay liner to make the dam watertight.

• Replace the spillway to accommodate future floods events.

• Modifying outlet works to suit.

• Manage water levels to facilitate and assure water security during construction (CWMP) including:

• Water storage;

• Flood mitigation measures and

• Temporary water supply.


Anticipated Construction Period

Preparations Construction Post-construction

1 October 2019 - 21 December 2019

1 January 2020 – 31 March 2020

1 April 2020 - 30 June 2020

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Whitemark Water Supply Security During Construction

Options considered:

1. Creating extra storages near Pats Weir.

2. Water storage bladders.

3. Bore water.

4. Containerised Temporary Reverse Osmosis (“RO”) Desalination Plant.

5. Applying Stage 2 water restrictions.

Assessed on:

Feasibility, cost, schedule, environmental and stakeholder impacts.

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Options Assessment

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Whitemark Water Supply Security During Construction

Preferred Option 1:

A. Temporary RO Desalination Plant; and

B. Implement Stage 2 Water Restrictions.

Least Preferred Option 2:

1. Bore water from the Willis Road Bore.

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Option 2 - Bore Water (Willis Road)

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• Bore water chemically different to typical surface water feed characteristics may alter quality of water discharged into Pats River at current discharge location below Pats Weir resulting in need to:

• High salinity waste stream requiring relocation of discharge point to the tidal zone (not Pats Weir);

• Require running the WTP at a lower efficiency; and

• Diminishing returns on water cartage.


Option 1a – Temporary RO Desalinisation Plant

The proposed Temporary RO Desalination Plant can produce approx. 100kL of treated water per day.

How?

• An intake pipe draws seawater into the plant.

• Seawater is treated to meet Australian Drinking Water Guidelines (ADWG).

• Reject brine is returned back to the marine environment.

• Treated water stored on site for transfer to Whitemark

• 250kL seawater will produce approximately 150kL of reject brine.

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A similar RO plant


Option 1a – Temporary RO Desalinisation Plant

Requirements:

• Suitable location to cater for the plant, water tanks and trucks to collect and cart treated water to Whitemark.

• Suitable power supply.

• Pumps and piping – pumps to fill tanks and piping for inlet and discharge lines.

• Environment and stakeholder considerations.

• Planning and Approvals?

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Option 1b - Stage 2 Water Restrictions

• Stage 2 restrictions are designed to reduce non-essential use of water by approximately 25% of average consumption.

• Non-essential residential and commercial use is limited to alternate days and watering of lawns is banned.

• Full details available online: https://www.taswater.com.au/News/Outages---Alerts/Water-Restrictions

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https://www.taswater.com.au/News/Outages---Alerts/Water-Restrictions






Option 1a – Temporary RO Desalinisation Plant Site Selection

• Three (3) locations around Whitemark

• Three (3) locations around Lady Barron

Site Selection by Marine Solutions based on:

• Capacity to provide consistent volume of high quality water intake;

• Environmental impact of discharging the reject brine; and

• Stakeholder impact.

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Site Selection - Whitemark

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Site Selection – Pats River Mouth / Airport

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Site Selection - Lady Barron (TasPorts)

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Site Selection - Lady Barron

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Preferred Locations- Lady Barron Slipway

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Crown Land & Tidal Crown Land


Preferred Location - Lady Barron Slipway

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Site Selection - Lady Barron Slipway

We conducted:

• Desktop-based natural values research and field assessment

• Tidally and barometrically corrected bathymetric mapping

• Hydrodynamic assessment, including current profiling and wave characteristics

• Water quality monitoring

• Underwater video transects

• Marine threatened, protected and sensitive species survey

• Introduced marine pests survey

• Noise assessment and baseline noise monitoring

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Option 1a – RO Intake and Discharge

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Preferred Location - Lady Barron Slipway

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Traffic Management

• Approx. 5-10 trucks movements per day.

• Anticipate day light carting.

• Public Access?

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Planning & Approvals Requirements?

• What further information do Flinders Island Council require to progress this option?

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Questions?

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henderson dam upgrade - flinders council

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