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Adelaide Beach Management Review - Shortlisted options

Options have been shortlisted for the future management of Adelaide’s metropolitan coastline. The methods for doing this include dredging, a pipeline, and/or trucking. All options would require an Environmental Impact Assessment as part of future design development and approval processes.

Dredging

What is it?

Dredging would involve sand being collected from the seabed using a dredging vessel and being delivered to West Beach or other beaches in need of sand. This could include taking sand from deposits offshore of Largs Bay, Outer Harbor and/or Port Stanvac.

Dredging would involve the vessel operating within 2km from shore depending on the location of the sand source, for weeks or months at a time, possibly overnight and at weekends.

Adelaide Beach Management Review - Shortlisted options

Option 1.1 - Dredge existing sand near the shore

Where would the dredge be located?

About 2km offshore of North Haven when collecting sand from the seabed and would move to 100-150m offshore of West Beach when placing the sand.

How would the sand be relocated?

Sand would be collected from the seabed using a small dredge, which would sail south and pump the sand into West Beach using a floating pipeline that runs from the vessel to the shore, to deposit sand near the shoreline. Sand could also be delivered to other beaches as required.

How regularly would dredging occur?

This option would involve an initial large quantity of sand being collected from offshore of North Haven and then delivered to West Beach in the first year of operation and ongoing sand top-ups every 4 years

How long would the dredge be in place?

The initial collection and delivery of a large volume of sand would be expected to take about 3-4 months. Ongoing top-ups would be delivered every 4 years and would be expected take about 2 months to complete.

What would it cost?

The estimated total 20-year cost for this method is $45-50 million subject to the availability of a suitable dredge.

Adelaide Beach Management Review - Shortlisted options

Option 1.2 - Dredge using large offshore sand deposits

Where would the dredge be located?

About 2km offshore at the chosen collection site(s) and then 100-150m offshore of West Beach when delivering the sand.

Where would sand be sourced?

External sand could be sourced from the seabed at larger offshore deposits, including Largs Bay, Outer Harbor, and/or Port Stanvac (subject to further investigations and approvals).

How would the sand be relocated?

Sand would be collected from the seabed using a medium-sized dredge, which would pump the sand into West Beach using a floating pipeline that runs from the vessel to the shore, to deposit sand near the shoreline. Sand could also be delivered to other beaches as required.

How long would the dredge be in place?

Delivery of a very large quantity of sand from nearby sources would be expected to take 3-4 months.

What would it cost?

The estimated total 20-year cost for this method is $55-60 million if using nearby sand sources subject to availability of a suitable dredge.

Adelaide Beach Management Review - Shortlisted options

Option 1.3 - Combination of dredging offshore deposits and trucking quarry sand

This option would be implemented by using a combination of a small amount of quarry sand combined with larger quantities of sand dredged from offshore deposits.

Where would the dredge be located?

The dredge would be located offshore at the collection site and about 100-150m offshore of West Beach when distributing the sand.

Where would sand be sourced?

External sand could be sourced from the seabed at offshore deposits, including Largs Bay, Outer Harbor and/or Port Stanvac (subject to further investigations and approvals). In addition, dredged sand would be complemented by sand sourced from land-based quarries.

How would the sand be relocated?

Sand collected by the dredge would be pumped as a slurry into West Beach using a floating pipeline that runs from the vessel to deposit sand near the shoreline. Quarry sand would be delivered on to the beach using trucks.

How long would the delivery take?

Delivery of a smaller annual quantity of quarry sand would be expected to take about 3 months each year for the first 5 years. Delivery of the medium quantity would be expected to take about 3-4 months every 4 years commencing from the second year.

What would it cost?

The estimated total 20-year cost for this method is $60-100 million subject to the availability of a suitable dredge and sand deposits.

Pipeline

What is it?

Sand pumping uses underground pipelines to transfer sand and seawater from beaches where sand is building up to beaches in need of sand. Operating the pipeline would involve collecting sand from the beach or nearshore for 4 months at a time. Quarry sand would also be delivered annually over the first 5-year period to restore West Beach.

See the below map for an overview of the proposed pipeline system.

Where would the sand be sourced?

A combination of quarry sand and sand collected from dedicated sand harvesting areas between Semaphore Park and Largs Bay would be used. For the pipeline component, sand intake points could be located at Largs Bay, Semaphore and Semaphore South.

Where would the sand be discharged?

The bulk of the pipeline sand would be discharged at West Beach but additional discharge points located along the coastline, including West Beach (Rockingham St), Grange (The Esplanade), Tennyson (Moredun St) and West Lakes Shore (Mirani Ct), would allow sand to be delivered elsewhere as required. Quarry sand would be sourced from land-based quarries and delivered to West Beach using trucks accessing the beach via the Adelaide Sailing Club.

In addition to the delivery of quarry sand, three options have been identified for how sand could be collected and put into the pipeline system.

Adelaide Beach Management Review - Shortlisted options

Option 2.1 Pipeline using tractors/trucks on beaches

How would it work?

Sand would be collected onshore using machinery (trucks and scrapers) and fed into the pipeline through sand collection units. The sand would be pumped south through an underground pipeline and released at West Beach or other locations as required. Permanent booster pump stations would be located along the pipeline route.

Where would the sand be sourced?

Delivery of a small annual quantity of quarry sand would take about 3 months each year for the first 5 years. Sand collection units would be located at Semaphore South, Semaphore and Largs Bay. Sand would be collected from the beach by tractor and sand scraper around the Semaphore and Largs jetties, and the Semaphore South breakwater.

How long would it be in place?

Work would be undertaken annually over about 4 months.

What would it cost?

The estimated 20-year cost for this method is $140-155 million.

Adelaide Beach Management Review - Shortlisted options

Option 2.2 Pipeline using dredge pump systems on jetties

How would it work?

This option involves a pump operating from a crane on the Semaphore or Largs jetties and submerged under the water. The dredge pump would mobilise surrounding seabed sand, which is then pumped into the pipeline system through a pipe under the beach. (See above illustration).

Where would the sand be sourced?

Delivery of a small annual quantity of quarry sand would be expected to take about 3 months each year for the first 5 years. Sand would be collected adjacent to or below the Semaphore and Largs Bay jetties.

How long would it be in place?

Work would be undertaken annually over about 3-4 months. Jetties would likely be closed to the public during collection.

What would it cost?

The estimated 20-year cost for this method is $140-150 million.

Adelaide Beach Management Review - Shortlisted options

Option 2.3 Pipeline using a temporary dredge

How would it work?

A small sized dredge would collect sand from the near shore seabed and pumped directly into the pipeline through the nearest collection station. A mobile collection method using a dredge provides flexibility on where sand can be sourced.

Where would the sand be sourced?

Delivery of a small annual quantity of quarry sand would be expected to take about 3 months each year for the first 5 years. Sand would be collected from the seabed using a small dredge between Semaphore South and Largs Bay jetty.

Where would the dredge be located?

The dredge would collect sand from the seabed offshore near Largs Bay and Semaphore and pump it into the pipeline.

How long would it be in place?

Work would be undertaken annually over about 4 months.

What would it cost?

The estimated 20-year cost for this method is $140-155 million.

Adelaide Beach Management Review - Shortlisted options

Option 3 – Carting: Moving beach sand and quarry sand using trucks and machinery

How would it work?

Sand would be collected from the beach using an excavator and front-end loader and trucked to areas where sand is required. External quarry sand would be delivered using trucks on public roads. Excavators would be used to move the deposited sand to achieve the desired beach profile.

Where would the sand be sourced?

Sand would be collected onshore from Semaphore South and north of the Semaphore jetty and delivered using trucks on public roads to West Beach or other beaches in need of sand. Sand sourced from land-based quarries would be delivered to West Beach using trucks accessing the beach via the Adelaide Sailing Club.

How long would the process take?

Sand delivery would happen twice a year over 2-3 months.

What would it cost?

The estimated 20-year cost for this method is $100-110 million.

Technical detail on shortlisted options

For each shortlisted management option, the following draft technical information has been produced: a description, conceptual layout and a life-cycle cost estimate over a 20-year period. The technical information is available here.

Why weren't some options shortlisted?

Bluecoast Consulting Engineers undertook a high-level technical assessment of a long list of coastal management options. The long list of options was informed by research of interstate and international coastal management techniques alongside input from community members and stakeholders.

The assessment of the long list of options used an evidence-based approach drawing on information and data from previous coastal monitoring, studies and research on Adelaide’s beaches, and the impacts of climate change, as well as results of the first phase of community engagement about what matters to community members. The assessment evaluated the effectiveness, practicality and acceptability of the longlisted options to filter out the least feasible options.

Bluecoast’s assessment included consideration of each option’s:
• Effectiveness in providing coastal protection and amenity, its adaptability to climate change, and confidence in it as a solution
• Practicality in terms of engineering feasibility, strategic alignment with the objectives of the review, and the financial implications
• Acceptability in relation to its potential environmental impacts, future approval pathways, and the likely impact on beach users.

The following options were not shortlisted for further analysis:
• Long-term ongoing delivery of quarry sand
• Removal or bypassing of existing (harbour) structures that impede sand movement
• Construction of artificial headlands, reefs or breakwaters, or other methods that would potentially reduce wave energy such as seagrass restoration
• Installation of groynes and groyne fields to raise beach heights, or construction of seawalls to provide coastal protection
• Planned relocation of properties and infrastructure
• No longer actively managing the coastline.

Have your say!

It is very important to the success of the review that it is informed by an understanding of what matters most to the community so we want your views on the different sand management approaches.

We encourage you to submit your feedback on the shortlisted options by using the state government’s YourSAy portal at: www.yourSAy.sa.gov.au/abmr-shortlist. Submissions close Sunday, 15 October at 5:00pm.

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