News & Discussion: Adelaide Development Plan Amendment 2012

[Howie]

Paul Pruszinski has kindly cleared up a few misconceptions around OLS and Shielding.

Under the aviation act, there is a document called MOS139. Section 7.1 and 7.2 deal specifically with the issue of OLS (obsticle limitation surface) and Shielding. OLS is a concave space over the city determined by a series of different mathematical calculations determined around 1956, and any structure that penetrates it must be referred to Dotars (a division of CASA) for final approval. Buildings are permitted above the OLS where they are "shielded" by an existing building. Shielding is a cone at 10% emulating out and down from that structure. The graphic provided by the governement is showing that 10% cone from the cities tallest building. It isnt totally correct as other buildings already penetrate that cone, so they also form a shield (eg post office on Gouger st). Hence although we have unlimited hieght in a massive portion of the city, the hieght limitation is the higher of OLS or Shielding.

[UrbanSG]

I think Westpac's days as Adelaide's tallest are numbered.

The OLS is almost higher than Westpac in a portion of the NE CBD where there is now unrestricted heights. Part of the document refers to the OLS being tied back to the Adelaide Airport ground level which is between 3m and 17m above sea level not CBD ground level.

The OLS is often breached and I think a breach above Westpac may still be approved by CASA. Not to mention PAN-OPS surface which is higher than OLS and is the real level CASA worries about. However it is amlmost impossible to find this level as it apparently changes often.

Basically a developer needs to test CASA.

[phenom]

Yep and if my memory serves correctly (it might not!) Westpac House (nee State Bank) was obviously built under the auspices of a State Government statutory authority and therefore had the full support and influence of the State Government of the time to get it built despite airport related height limits.

These current reforms suggest a pretty strong likely support from the current State Government for any kind of tower that would exceed the height of OLS/shielding limits particularly where the tower was already located in a 'maximum' height zone and the breach of OLS/shielding was semi-trivial (ie maybe 20m or 30m more) - which I think would hold some sway (whatever it might be) over CASA decision making.

[Waewick]

so any ideas of the announcement due today?

[[Shuz]]

I'm hoping a new tallest, or something pretty bloody darn close to it!

[Waewick]

I'm hoping a new tallest, or something pretty bloody darn close to it!

I doubt it - why would the government announce that?

[Pants]

Let's not get too far ahead of ourselves. Check the Angas St. thread.

[Waewick]

so is that all 4 of the announcements?

[[Shuz]]

I think there's another one tomorrow...

[Howie]

Nope that's it for now. The last announcement is unlikely to be made.

[Waewick]

Nope that's it for now. The last announcement is unlikely to be made.

well I guess we can be happy with that we got

out of interest was it an announcement by a government deaprtment or a private firm?

[[Shuz]]

Nope that's it for now. The last announcement is unlikely to be made.

Why?

[Wayno]

Nope that's it for now. The last announcement is unlikely to be made.

Why?

slated to happen later. patience grasshopper.

[Wayno]

Paul Pruszinski has kindly cleared up a few misconceptions around OLS and Shielding.

Under the aviation act, there is a document called MOS139. Section 7.1 and 7.2 deal specifically with the issue of OLS (obsticle limitation surface) and Shielding. OLS is a concave space over the city determined by a series of different mathematical calculations determined around 1956, and any structure that penetrates it must be referred to Dotars (a division of CASA) for final approval. Buildings are permitted above the OLS where they are "shielded" by an existing building. Shielding is a cone at 10% emulating out and down from that structure. The graphic provided by the governement is showing that 10% cone from the cities tallest building. It isnt totally correct as other buildings already penetrate that cone, so they also form a shield (eg post office on Gouger st). Hence although we have unlimited hieght in a massive portion of the city, the hieght limitation is the higher of OLS or Shielding.

It's EXCELLENT that the developer community now understands & can 'talk the talk'. To date developers only have tested ACC imposed limits. Now they can test aviation act limits!

[UrbanSG]

This is a good article that refers to Brisbane's new tallest proposal and Airport height issues:

http://www.brisbanetimes.com.au/busines ... 1n5hs.html

Apparently Brisbane's OLS is 120-140m, not that different to Adelaide, however Brisbane is at a lower elevation. Yet a 274m high building has been approved by CASA. The article discusses the lack of clear information available from CASA. This must be referring to the PAN OPS level, which is very unknown and seems to change at times?

Surely it's only a matter of time before a developer, especially with experience from interstate, proposes Adelaide's new tallest?