"History will be kind to us, because we will write it"
ACTEW have posted more glorious video of their work to build the new Cotter Dam.
Intriguing that they’re building the intake tower with jump form construction which they claim is unique.
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Intriguing that they’re building the intake tower by jacking up the base and shoving the next tier in at the bottom.
I’m not quite sure where you got that idea – it looks like (and was described as) a standard jump-form system. The formwork is in that white bit at the top, the concrete is poured into it (you can see the concrete pump arm on the left) and when that’s set the formwork is “jumped” up to the next level and the process repeated. It’s exactly the same system you’ll see used in building elevator shafts for most buildings.
well they’re the ones claiming it’s unique!
johnboy said :
It might well be a unique way of building intake towers; I really wouldn’t know. The basic principle, however, is extremely well established for building tall, narrow, hollow things. Nice video on it here.
Well it is the only jump-form being used for dam construction, in the ACT, at the present. If you add enough qualifiers to anything it becomes unique.
there we go guys.
Spectra said :
Yeap looks like typical slip forming to me: http://en.wikipedia.org/wiki/Slip_forming
The embedded video is currently reporting “This video is private” when I try to play it and I can’t find the video up on the ACTEW YouTube channel. Has it been taken down for some reason? (Or am I just special?)
how curious…
YetAnotherBlowIn said :
Same here. Very odd.
Deref said :
Obviously they can’t let you see the part of construction where they bury Megatron in the bottom gallery of the dam. Oops.
I’m sure this question has been answered somewhere, but what happens to the old dam wall?
The vid appears to be back now.
The old dam wall will remain and be inundated during extended periods of average to above average rainfall.
http://en.wikipedia.org/wiki/Cotter_River
Congratulations to ACTEWAGL for posting these video reports. I don’t know whether anyone else does it, but it’s a brilliant way of keeping people informed.
No mention of the problems they’ve been having with scaffolding, though.
krats said :
Thanks krats…so the new dam wall is only good if it rains a lot?
When i was there they said the old dam wall would have everything removed, and would only hold water when the total supply was less than 15% (i’m going from 3 month old memory here, so i could be wrong)
braddonboy said :
The old dam wall will be 50m below the new dam wall.
If the water level ever gets down to below the old dam level, I don’t think they can effectively take water anyway.
Deref said :
Well they’re hardly likely to advertise…. or want it recorded for posterity.
My understanding was that once the new wall is finished water will be released from the old dam until the water is level on both sides (of the old dam). From that point on, the equal water level will be maintained as the new reservoir fills naturally until the old wall becomes fully submerged. The old wall will also act as a silt trap, keeping silt away from the intake tower of the new dam. (I also like to picture it acting as a speed bump for any unsuspecting leisure craft as well.)
In regard to removing ‘everything’ from the old dam, my guess would be monitoring and maintenance equipment, maybe the railings and other access stuff.
As for the “unique jump form,” the shape of the form would be unique. As Spectra said, jump forming is mostly used for elevator shafts and this one has curves (there’s a video on the intake tower on the YouTube channel).
And a final pedantic note: slip forms are in constant movement while concrete is being poured, jump forms remain stationary during concrete pours before moving up large sections at a time once the concrete is sufficiently set.
#15 braddonboy 11:02 am, 28 Sep 11 said “…so the new dam wall is only good if it rains a lot? ”
Not quite braddonboy – in the July 2007 ACTEW report, “Water Purification Scheme for the ACT”, in para 1.1.7 it says – “On average some 29 GL of water spills from Bendora and Cotter Reservoirs each year.” Google will find the report for you.
So at that rate – assuming no drawdown at Cotter, it would only take 2.7 years to fill the new Cotter dam – under “average” conditions – whatever ACTEW means by that.
Note the 29GL PA is over half our typical consumption.
I think the huge spillages make the new Cotter a no-brainer. Even a new Cotter half the size would have had big advantages.
Interesting that the Wikipedia entry is a bit misleading – maybe one part of ACTEW not knowing what some other part has already said.
And we have not even mentioned 2010.
Thanks all.
I trust Actew are using only Australian concrete and steel in this construction?
dungfungus said :
Well seeing as all the aggregate has been quarried on site, at least you know that part will be true blue Aussie rock.
Which will be finished first?
Glenlock or Cotter?
welkin31 said :
Yep – the idea is that the extra storage means the catchments higher up can be used more effectively.