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Cotter Dam expansion up to 14 metres, the trickier 65 to go.

By johnboy 27 September 2011 24

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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24 Responses to
Cotter Dam expansion up to 14 metres, the trickier 65 to go.
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milkman 5:02 am 29 Sep 11

welkin31 said :

#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.

Yep – the idea is that the extra storage means the catchments higher up can be used more effectively.

gooterz 12:19 am 29 Sep 11

Which will be finished first?

Glenlock or Cotter?

chewy14 7:37 pm 28 Sep 11

dungfungus said :

I trust Actew are using only Australian concrete and steel in this construction?

Well seeing as all the aggregate has been quarried on site, at least you know that part will be true blue Aussie rock.

dungfungus 7:27 pm 28 Sep 11

I trust Actew are using only Australian concrete and steel in this construction?

braddonboy 2:18 pm 28 Sep 11

Thanks all.

welkin31 1:40 pm 28 Sep 11

#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.

YetAnotherBlowIn 12:34 pm 28 Sep 11

Deref said :

No mention of the problems they’ve been having with scaffolding, though.

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.

chewy14 12:27 pm 28 Sep 11

braddonboy said :

krats said :

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

Thanks krats…so the new dam wall is only good if it rains a lot?

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.

Henry82 11:13 am 28 Sep 11

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 11:02 am 28 Sep 11

krats said :

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

Thanks krats…so the new dam wall is only good if it rains a lot?

Deref 10:16 am 28 Sep 11

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 9:46 am 28 Sep 11

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

johnboy 8:44 am 28 Sep 11

The vid appears to be back now.

braddonboy 8:07 am 28 Sep 11

I’m sure this question has been answered somewhere, but what happens to the old dam wall?

chewy14 5:14 pm 27 Sep 11

Deref said :

YetAnotherBlowIn said :

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?)

Same here. Very odd.

Obviously they can’t let you see the part of construction where they bury Megatron in the bottom gallery of the dam. Oops.

Deref 3:41 pm 27 Sep 11

YetAnotherBlowIn said :

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?)

Same here. Very odd.

johnboy 2:31 pm 27 Sep 11

how curious…

YetAnotherBlowIn 2:27 pm 27 Sep 11

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?)

rohbo 1:07 pm 27 Sep 11

Spectra said :

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.

Yeap looks like typical slip forming to me: http://en.wikipedia.org/wiki/Slip_forming

davo101 12:56 pm 27 Sep 11

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.

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