Is Sand Mining Really Being Managed?

Sand Mining

1 October 2021

After 18 months of sand mining, we’re wondering if mining is managed at all at Semaphore? If so it’s not clear how.

A common definition of managing is “to succeed in doing or dealing with something, especially something difficult”. Any but the crudest of mining operation requires much more than moving material from A to B.

Success implies control of removal, deposition, and rehabilitation. In this case it implies an understanding of the beach

How it works?

The Department depends on surveyed lines called profiles to assess the state of the beach. Some local profiles are shown below.

A map of Coast Protection Board profiles near Semaphore
Coast Protection Board profiles in the vicinity of Semaphore. Profiles are placed approximately every 500m along the Metropolitan Coast..Surveys have occurred regularly since 1975

That’s all well and good if these profiles were on a uniform stretch of beach. But looking a little more closely we find the profiles don’t really represent state of the beach between the Semaphore and Largs Bay jetties.

  • The Semaphore jetty profile is just south of the jetty. It’s in an area of generally accumulating sand (although the Phase 1 report did find significant erosion due to over mining Point Malcolm in 2019)
  • Kanowna Rd sits in the middle. The Department decided not to mine the centre of the area between the two jetties, and hasn’t mined there in any of the campaigns to date – obviously different to the rest of the beach.
  • The Largs jetty profile is immediately north of the jetty. The Department itself excavated this section to allow the Department of Transport to inspect the jetty.

So we can’t see how the data in these profiles can reflect the true state of the beach.

What to do?

When challenged the Department responded that they could track relative sand removal by tracking earthmoving equipment using GPS.

To support this, they presented the image below to the Semaphore Working Group in July 2021.

An image of scrreper GPS traacks prented to the Semaphore Working Group in July 2021
GPS tracks of the scraper mining the beach between the Largs Bay and Semaphore Jetties in May 2021

PAREPG pointed out that GPS tracks don’t show the point from which sand is removed.. For example, the scraper must make multiple trips to the sand stockpile immediately north of the Semaphore jetty. Sand mined from the northern section near Largs must be carted to the same point.

So activity here doesn’t mean sand removal – it just doesn’t make sense.

The Department has commissioned two reports to look at the impact of it’s operations on the beach:

both recommend monitoring the beach before and after mining campaigns, but the Department refuses to follow these recommendations.

Better ways exist

In 2020 the Department used a survey method called a Digital Elevation Model (DEM) to look at sand extraction north of the Largs Jetty. The method used a small survey vehicle to collect height over an area of the beach . A digital elevation model (DEM) was built from these points.

Two images of a Digital Elevation Model of the beach between Largs Jetty and Strathfield Tce
Two images of a Digital Elevation Model of the beach between Largs Jetty and Strathfield Tce. The model is built by surveying heights at closely spaced intervals. The image on the left shows the beach height in June 2020, that on the right the difference in height in April (before the mining campaign) and June (after).

In this case, the model shows that contractors did not remove sand uniformly along the beach. Instead they removed sand from closest to the jetty as this represented the shortest carting distance to the stockpile further south. The result is effectively a hole in the beach making this section of the dune more prone to erosion. The erosion in this section was quite visible after mining.

Departmental staff claim that in spite of a $38m budget to build a sand pipeline they are not prepared to commit the resources to follow basic recommendation of their own consultants

The Department has no effective means to evaluate the impact of it’s operations on the beach. By spinning the GPS story they attempted to make out that they did.

Not only poor management but a poor attempt at deception!