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Flooding on the Enlarged Cotter Dam. Actew video

By 30 March 2012 13

Actew’s movie makers have been busy with the footage from the flood event and now there’s five minutes of aquatic goodness which the ACT’s paying for one way or another.

They posted it with this note:

The extraordinary rainfall and flooding at the beginning of March 2012 has had a signifcant impact at the Enlarged Cotter Dam construction site. However the team is well underway assessing the situation and getting started on the clean up.

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13 Responses to Flooding on the Enlarged Cotter Dam. Actew video
#1
nobody3:48 pm, 30 Mar 12

Damn, if only our Damn Government had approved the Cotter Dam expansion Damn-well earlier the new Dam would be finished and Damn-well full by now. Where’re probably Damned to another drought now, and the new Dam will take Damn years to fill. Now the Dam is just a Damn mess.

#2
Deref4:14 pm, 30 Mar 12

What a mess.

Kudos to ACTEW for producing and publishing this series of videos documenting the construction.

#3
goggles135:49 pm, 30 Mar 12

the power of nature never fails to impress me

#4
dungfungus6:10 pm, 30 Mar 12

Not much water coming through the “diversion” tunnel. Looks more like a suburban size stormwater drain. Appears totally inadequate.

#5
chewy1410:49 pm, 30 Mar 12

dungfungus said :

Not much water coming through the “diversion” tunnel. Looks more like a suburban size stormwater drain. Appears totally inadequate.

Yeah, only capable of 2GL/day. Totally inadequate for an ARI 100 yr flood. They should have totally predicted that.

#6
pandaman11:29 pm, 30 Mar 12

dungfungus said :

Not much water coming through the “diversion” tunnel. Looks more like a suburban size stormwater drain. Appears totally inadequate.

If memory serves, that tunnel is 3m in diameter which makes it 2.5 time bigger in area than the biggest stormwater trunk main I have ever seen. While you are correct in that it was totally inadequate for the flows they copped due to that rain, I believe that the designers could not have readily predicted that a larger tunnel would be required. Additionally, the concept of simply “building a bigger tunnel” as seems to be the tone of your post, is not neccesarily so simple. I won’t go into details, but given that the taxpayer has been complaining about cost blowouts since day one, I don’t think a bigger diversion tunnel would have gone down any better with them.

#7
welkin318:08 am, 31 Mar 12

IMHO ACTEW are straining at the facts if they said – “The extraordinary rainfall…”
In the seven days 28 Feb to 5 March Mount Ginnini got 360.8mm – Mount Ginnini has only been operational for a decade or so and has its unreliable periods.
Daily data available here;
http://www.australianweathernews.com/recent_AWN_daydataCurrentMonth_element.html
Of course there are few reliable long term rain stations in places as remote as the Cotter catchment – so to understand rain history you have to check places as nearby as possible. In this case data from Brindabella Station show that in March 1950 – for a 7 day period from 18th to 24th – 492.7mm fell.
This is backed up by big falls at Wee Jasper State Forest – recorded over 4 days 20th to 23rd March 1950 – 380.8mm.
Brindabella Station is so near the Cotter catchment that there is every likelihood that in March 1950 the Cotter river was hit by a similar rain event compared to our recent one-hell-of-a-wet-week.

#8
chewy148:58 am, 31 Mar 12

welkin31 said :

IMHO ACTEW are straining at the facts if they said – “The extraordinary rainfall…”
In the seven days 28 Feb to 5 March Mount Ginnini got 360.8mm – Mount Ginnini has only been operational for a decade or so and has its unreliable periods.
Daily data available here;
http://www.australianweathernews.com/recent_AWN_daydataCurrentMonth_element.html
Of course there are few reliable long term rain stations in places as remote as the Cotter catchment – so to understand rain history you have to check places as nearby as possible.

In this case data from Brindabella Station show that in March 1950 – for a 7 day period from 18th to 24th – 492.7mm fell.
This is backed up by big falls at Wee Jasper State Forest – recorded over 4 days 20th to 23rd March 1950 – 380.8mm.
Brindabella Station is so near the Cotter catchment that there is every likelihood that in March 1950 the Cotter river was hit by a similar rain event compared to our recent one-hell-of-a-wet-week.

And? You do know what extraordinary means right?

#9
dungfungus11:36 am, 31 Mar 12

pandaman said :

dungfungus said :

Not much water coming through the “diversion” tunnel. Looks more like a suburban size stormwater drain. Appears totally inadequate.

If memory serves, that tunnel is 3m in diameter which makes it 2.5 time bigger in area than the biggest stormwater trunk main I have ever seen. While you are correct in that it was totally inadequate for the flows they copped due to that rain, I believe that the designers could not have readily predicted that a larger tunnel would be required. Additionally, the concept of simply “building a bigger tunnel” as seems to be the tone of your post, is not neccesarily so simple. I won’t go into details, but given that the taxpayer has been complaining about cost blowouts since day one, I don’t think a bigger diversion tunnel would have gone down any better with them.

When you say “a bigger diversion tunnel would not have gone down any better with them” you are applying the same sort of mentality that was prevalent when the GDE was planned as a two lane road when it was obvious to everyone else that a four lane road was necessary (and a cheaper option at the time).
Today we read in the CT that the arboretum mob are going to build something like the “world’s best children’s playground” when something much less would suffice.
Apparently money does grow on trees.

#10
pandaman1:46 pm, 31 Mar 12

dungfungus said :

pandaman said :

dungfungus said :

Not much water coming through the “diversion” tunnel. Looks more like a suburban size stormwater drain. Appears totally inadequate.

If memory serves, that tunnel is 3m in diameter which makes it 2.5 time bigger in area than the biggest stormwater trunk main I have ever seen. While you are correct in that it was totally inadequate for the flows they copped due to that rain, I believe that the designers could not have readily predicted that a larger tunnel would be required. Additionally, the concept of simply “building a bigger tunnel” as seems to be the tone of your post, is not neccesarily so simple. I won’t go into details, but given that the taxpayer has been complaining about cost blowouts since day one, I don’t think a bigger diversion tunnel would have gone down any better with them.

When you say “a bigger diversion tunnel would not have gone down any better with them” you are applying the same sort of mentality that was prevalent when the GDE was planned as a two lane road when it was obvious to everyone else that a four lane road was necessary (and a cheaper option at the time).
Today we read in the CT that the arboretum mob are going to build something like the “world’s best children’s playground” when something much less would suffice.
Apparently money does grow on trees.

So you’re claiming that it was entirely obvious to you from day one of the dam construction, that a bypass capacity of greater than 2 Gigalitres per day would be required? If so, on what data had you based your analysis? That a 3m wide tunnel doesn’t look much bigger than the stormwater drain down the road from your house?

Fact is, we had several periods of rainfall that amounted to the heaviest falls this region has experienced in at least 30 years. The designers were not expecting it, therefore the bypass tunnel was too small.

I don’t know why I’m bothering to argue. You strike me as the sort who would’ve complained till you were blue in the face if they’d splashed out and spent 20 million or so on a 4.5m diameter tunnel which then ended up being too big if we got bugger all rain. Anyway, do you have any idea how wrong you have to be in order for me to take the side of BWA and Actew? Very wrong indeed. As a fellow taxpayer\constituent\generally exploited working stiff, I suggest you look further back than the inclement weather claims to see where the costing for this thing all went horribly wrong.

#11
Golden-Alpine1:55 pm, 31 Mar 12

I wonder what the downstream effect would have been if the current dam under construction wasn’t there.

#12
welkin315:39 pm, 31 Mar 12

Just remember fellow ACT taxpayers – this RiotACT article 7 Jan 2011.
“Wet 2010 just a blip according to ACTEW ”
http://the-riotact.com/wet-2010-just-a-blip-according-to-actew/35157
The ACTEW quote;
“Actew managing director Mark Sullivan said once the rains stopped predicted to be in February or March the territory would again have to face at least 20 years of low rainfall.

Although the rains offered breathing space, Actew says there is no reason to doubt scientific predictions of another two dry decades.”
no reason to doubt -

true believers -
and we will all pay.

#13
OpenYourMind10:49 pm, 31 Mar 12

Everyone says the GDE was such a dreadful project because only one lane each way was originally built. The first thing that jumps out to me is that it’s not like the engineers didn’t know it needed to be four lanes. Hell, they even planned for that with 2nd bridges etc. To me, it seems more like a financial decision. Maybe I’ve worked in Govt too long, but the reality is that you only have a certain amount each FY to spend. Maybe it wasn’t that bad a decision to start off with a lane each way and then at least we had a GDE that was built ready for the four lanes in the future. We did the same with the southern part of Drakeford Drive. I remember seeing the columns for the 2nd bridge down toward the Hyperdome and thought that the planning wasn’t too bad. Just a thought.

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