The Department’s pipeline to pump sand from Point Malcolm to West Beach is gaining pace
It’s difficult to write on this from a local perspective as the Department keeps changing it’s approach.
Initially we were told the purpose was to mine sand between Semaphore and Taperoo.
Next we were told the pipeline would only extend to Point Malcolm. Nevertheless the Department found it necessary to include Semaphore (and beyond?) in engineering surveys to determine the location of intake points. It was made quite clear that the earthmoving machinery would be on the beach for at least 5 months of the year.
Then at a workshop on Tuesday 19th October Port Adelaide- Enfield members were told that sand from the pipeline would be sourced from Point Malcolm ( 50,000 m3 ) and Grange ( 30-40,000 m3) . Sand would still be mined north of the Largs Bay jetty to replace that scoured from Semaphore South by the action of the Point Malcolm breakwater. At this stage the quantity is unknown. Sand will be mined from Semaphore ” should the need arise”.
Early cracks in the solution
This is unlikely to be the final solution as :
- 50,000 m3 is likely to be the upper limit of the breakwater capacity. Recent history has demonstrated that excess will result in increased downstream scouring at Semaphore South and decrease in volumes at the jetty..
- The capacity of Grange to sustainably supply 30-40,000 m3 annually has yet to be demonstrated.
We asked if any substantial substantial studies have been done on Grange at the last Coastal Reference Group meeting on 26 October, but didn’t receive a positive response.
A previous post, Semaphore Stuff Up illustrated that the bulk of sand mined at Semaphore was due to erosion at Semaphore South. We wouldn’t be surprised if a cycle of
- Cart sand mined north of Largs to Semaphore South
- Where it will be eroded and distributed along the beach to Semaphore-Largs.
- Make a big deal over how the beach has recovered as expected and mine Semaphore-Largs to supply the pipeline.
- Cart sand mined north of Largs to Semaphore South etc etc
It is difficult to comment on the pipeline itself as the detail will not be revealed until the development application is available. The application is due to be released on 8 November, which will trigger a 4 week public comment period. However the real impact not be known until it has been operating.
Of the three options to route the pipeline – along or in combination with existing infrastructure, on the beach or through the dunes, the dunes route is the least cost. As our previous suggestion for pipeline access from the existing entry point at the Surf Life Saving Club has been rejected , we expect the rear of the dunes in front of Fort Glanville to be trashed.
What has been demonstrated is that external sand can be supplied at commercial rates to fix the West Beach catastrophe.
What’s needed now is a mechanism to slow the rate of transport along the beaches to keep management to reasonable levels.
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