2 March 2012

Thar she blows! New Cotter Dam overspilled

| johnboy
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The Cotter Dam Expansion Dam Cam is showing the worst case scenario of flood waters rising over the under-construction wall as the capacity of the river diversion is comprehensively overwhelmed.

Let’s hope the raging torrent doesn’t undermine the wall or this will become a disaster of 2003 bushfires proportion.

We certainly hope that doesn’t happen, but it’s not like this was meant to happen either.

UPDATE 01/03/12 09:10: Thanks to dpm for pointing us at the above video compression of the overspill

cotter dam overspill

[Photo by Androo]

UPDATE 02/03/12 8:18: And she’s still going very strong this morning:

cotter dam

UPDATE 02/03/12 09:31: This in from ACTEW supremo Mark Sullivan:

MarkS
2012/03/02 at 8:21 am

This morning observations are that the dam structure is sound. Heavy machinery has remained safe and cranes are fine. Have lost some forms and scaffolding and some light equipment. Biggest concern is the washing out of earthwork on the downstream side (looking at damcam it is on the left abutment or the right hand side looking at the dam). Possibly be a week before we get back on the dam and looks like a three week clean up. Flood is a one in one hunred year event so top marks to the engineers. Now we wait till tomorrows renewed assault.

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dungfungus said :

HenryBG said :

shauno said :

I blame Tim Flannery for saying never again would we have our dams filled.

Tim Flannery said no such thing.

Please take care you don’t fall for fossil-fuel-industry-funded propaganda which is intended to “prevent science from being taught in the classrooms”, as recently leaked documents have revealed.

Depends what you mean by “science”

Suddenly the interests of academia and industry lobbyists collide ans post-modernist thinking gets a new lease of life.

Science is science. And liars hate science, because science proves them wrong, hence the big anti-science PR-campaign that’s on at the moment.

HenryBG said :

shauno said :

I blame Tim Flannery for saying never again would we have our dams filled.

Tim Flannery said no such thing.

Please take care you don’t fall for fossil-fuel-industry-funded propaganda which is intended to “prevent science from being taught in the classrooms”, as recently leaked documents have revealed.

Depends what you mean by “science”

Deref said :

Does anyone know what Lake George is looking like?

It looks wet, like any other lake.
When Lake George is empty, why isn’t it just called “George”?

shauno said :

I blame Tim Flannery for saying never again would we have our dams filled.

Tim Flannery said no such thing.

Please take care you don’t fall for fossil-fuel-industry-funded propaganda which is intended to “prevent science from being taught in the classrooms”, as recently leaked documents have revealed.

Does anyone know what Lake George is looking like?

Peekz said :

Surely this rain was factored in the to project schedule?

I am positive that rain was factored into the project schedule as is with most major construction schedules – but I dont believe the data was there to be able to throw this amount of rainfall on BOM’s crystal ball…

IYou would reasonably expect a reduction in our water prices now, since we have had so much of it lately? I mean it was put up becuase we had so little of it before (and our water quality is so good). Fat chance I guess.

I suppose we have to boost ACTEWS profits back somehow somehow for being so responsible when there was a shortage of water (and I do think Canberrans in particular have done a great job in being responsible, with the odd exception – and have had restrictions longer than most other states)

I blame Tim Flannery for saying never again would we have our dams filled.

Skidbladnir said :

MarkS said :

Flood is a one in one hunred year event so top marks to the engineers.

*grumblegrumblegurmble*

Annual 1% non-dependant probability.
There is a sixty something percent chance of a 1% annual flood risk being realised once or more in a 100 year period.

The water table around my place has risen above ground level, so I have some minor flooding under my house. The same thing happened about 18 months ago, when we had a very wet weekend that was also a once in (some number of years) weather event.

Seems like these once in 40/80/100/whatever year rain events are becoming quite frequent. 🙁

YetAnotherBlowIn8:39 pm 02 Mar 12

Mark Sullivan has tweeted this photo taken from the abutment above the new dam. You can’t see the tracks on the excavator in the bottom of the photo which makes the water, what, 1 metre deep?

If the dam was built already this would have filled it?

Funky Claude5:29 pm 02 Mar 12

Peekz said :

thatsnotme said :

Hmmm, interesting. So Mr Evil = Funky Claude’s troll account??

No, Funky Claude just can’t quote properly.

Defiantly not a troll account. I thought I would be smart and delete the bulk of the post and somehow ended up integrating the two. I will go back to watching from the sidelines.

I think we should leave it like this and just build a few more viewing platforms. We could be Australia’s version of Niagra Falls – we’ll make a motza from the honeymooners!

dpm said :

We’re not very good at making things here in the ACT, are we…

Not sure what you mean exactly? 1) You can’t control the weather and 2) for something that was/is half-built when this rain ‘event’ hit (I love it how the media have embraced the new ‘event’ terminology!), there don’t seem to be any issues that have been caused by human error in the building process. Not sure what more they could have done here…..? 🙂

Surely this rain was factored in the to project schedule?

We’re not very good at making things here in the ACT, are we…

Not sure what you mean exactly? 1) You can’t control the weather and 2) for something that was/is half-built when this rain ‘event’ hit (I love it how the media have embraced the new ‘event’ terminology!), there don’t seem to be any issues that have been caused by human error in the building process. Not sure what more they could have done here…..? 🙂

Skidbladnir said :

MarkS said :

Flood is a one in one hunred year event so top marks to the engineers.

*grumblegrumblegurmble*

Annual 1% non-dependant probability.
There is a sixty something percent chance of a 1% annual flood risk being realised once or more in a 100 year period.

You’re right of course Skid, but the “One in X years flood” is understood by most people; incorrectly, but nevertheless understood.

Thoroughly Smashed11:08 am 02 Mar 12

We’re not very good at making things here in the ACT, are we…

It seems to be holding up…

As long as we don’t try to implode the dam in 50 years we should be fine 😉

However, top marks for communication go to ACTEW on this one.

MarkS said :

Flood is a one in one hunred year event so top marks to the engineers.

*grumblegrumblegurmble*

Annual 1% non-dependant probability.
There is a sixty something percent chance of a 1% annual flood risk being realised once or more in a 100 year period.

thatsnotme said :

Hmmm, interesting. So Mr Evil = Funky Claude’s troll account??

No, Funky Claude just can’t quote properly.

caf said :

Interestingly the same thing happened during the construction of Googong Dam – http://www.engineer.org.au/images/4-11.jpg – and that’s a rock-fill dam.

I prefer this picture of Googong spilling. I like to wonder what was going through the minds of the engineers watching.

EvanJames said :

OpenYourMind said :

Let me just say how cool it is to have the local expert tell us how it is on RiotACT. Thanks MarkS

Seconded. Excellent work, great to see.

Thirded – thanks, Mark.

It must be disheartening to everyone working on dam. I bet it’s going to take a lot of work before they can get started again.

Great work, guys, thanks for your efforts.

This morning observations are that the dam structure is sound. Heavy machinery has remained safe and cranes are fine. Have lost some forms and scaffolding and some light equipment. Biggest concern is the washing out of earthwork on the downstream side (looking at damcam it is on the left abutment or the right hand side looking at the dam). Possibly be a week before we get back on the dam and looks like a three week clean up. Flood is a one in one hunred year event so top marks to the engineers. Now we wait till tomorrows renewed assault.

Hmmm, interesting. So Mr Evil = Funky Claude’s troll account??

Mr Evil said :

rohbo said :

Mr Evil said :

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

If you know how to get some very heavy machinery off a 40m high wall i’m sure ACTEW would love to hear from you. Mark S from ACTEW said they got off everything they could with the cranes and the rest was too heavy so had to stay.

Umm, maybe the same way they got them up there in the first place?

Anyway, maybe I should have expressed myself better – the really heavy stuff isn’t the problem, as obviously if a 40 or 60 tonne object is going to be swept off the wall by the overflow, then I would suggest that there’d be bigger issues to worry about with the dam itself at that point. It’s some of the other smaller vehicles that appeared to be still on the dam in the photo that Mark submitted earlier this morning.

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

I love arm chair critics, while you are sitting at your computer sipping your latte, photocopying stuff that no one really cares about, these guys are out slugging their guts putting together a remarkable structure that is built to contain 78 gigalitres of water, I can’t even fathom how much that is.

They have successfully built it in such away that the integrity is holding after a heavy onslaught of rain, no one is injured, they have done everything they can to make it safe – there and down stream and you think you could have done it better.

Good work Mr Evil. *sarcasm*

This time, good work to the construction workers up on the dam. *sincere*

Funky Claude6:23 am 02 Mar 12

Funky Claude said :

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

I would dear say that they had better access to forecasts and warnings than what you and I are privy to, and and as the equipment involved in the construction is worth thousands I doubt that they have adopt a reckless attitude to “add to the debris pile unnecessarily” as you suggest.

Not sure what has happened here, only the last sentence is mine. First two are quotes from Mr Evil

Devil_n_Disquiz5:19 am 02 Mar 12

androo said :

I grabbed a short video of the overtopping shortly after it began. Sorry for the quality, using a flipcam but the audio gives you an idea of how loud it was.

You weren’t standing on a rock were you ? I came down and stood beside a couple who were filming. I was wearing bright yellow flouro shirt taking a few pics.

Thanks for posting the time lapse videos. Amazing.

Do they always keep the lights on at night at this site?

Funky Claude said :

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

I would dear say that they had better access to forecasts and warnings than what you and I are privy to, and and as the equipment involved in the construction is worth thousands I doubt that they have adopt a reckless attitude to “add to the debris pile unnecessarily” as you suggest.

I think in fairness Actew have been preparing for a rain event for the last month or so, as they have been dropping the level in the dam considerably. You may or may not have noticed also the campgrounds on cotter rd have been shut for a while and i think this your answer why they do that. As much as you might like to think otherwise its a weather event its out of anyone’s hands really. Bulk water would of moved what ever machines they could, but its a wall so the access is restricted, and cranes have limitations too.

Funky Claude11:04 pm 01 Mar 12

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

I would dear say that they had better access to forecasts and warnings than what you and I are privy to, and and as the equipment involved in the construction is worth thousands I doubt that they have adopt a reckless attitude to “add to the debris pile unnecessarily” as you suggest.

BerraBoy68 said :

It may be nothing or just something on top of the Dam wall effecting the water flow, but the smooth flat lines that were at the top of the wall up till now don’t look all that smooth anymore, (ref: ACTEW Dam Cam 10:12:57) particularly toward the right hand side as you look at it. It almost looks like something’s given way. I hope not. Ever been so riveted watching a live cam before.

Looks like the forms starting to detach you can see them more clearly on the most recent shots. The forms being the black pieces of ply that hold in the most recent layers of concrete. Still they are pinned into the concrete with steel rods maybe 1.5 metres long so must take a far bit of force to bust them off.

Another timelapse from the DamCam: http://www.youtube.com/watch?v=cvZwferhuTo

This one was started at 11:30am and covers footage up until about 10:10pm. You get to watch the last minute preparations, and the rain!

Mr Evil said :

rohbo said :

Mr Evil said :

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

If you know how to get some very heavy machinery off a 40m high wall i’m sure ACTEW would love to hear from you. Mark S from ACTEW said they got off everything they could with the cranes and the rest was too heavy so had to stay.

Umm, maybe the same way they got them up there in the first place?

Anyway, maybe I should have expressed myself better – the really heavy stuff isn’t the problem, as obviously if a 40 or 60 tonne object is going to be swept off the wall by the overflow, then I would suggest that there’d be bigger issues to worry about with the dam itself at that point. It’s some of the other smaller vehicles that appeared to be still on the dam in the photo that Mark submitted earlier this morning.

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

I could crap on about the capacity of those tower cranes, the likely weight of the equipment left on top and the likely difficulty in getting a big mobile crane anywhere near enough to be of any use, but with the know it all layman such as yourself it will never be of any use.

Suffice it to say, don’t give up your day job. Or if your day job is construction related, consider giving up.

On topic, damn that is some serious water. It’ll be interesting afterwards to see if any of the gear on top has moved. In any case, there’s going to be some damage to clean up and repair. Poor bastards. I saw photos from the first time they got flooded out and the place was a serious mess.

Thank you MarkS, what an absolute treat to be given on-site updates.

I grabbed a short video of the overtopping shortly after it began. Sorry for the quality, using a flipcam but the audio gives you an idea of how loud it was.

It may be nothing or just something on top of the Dam wall effecting the water flow, but the smooth flat lines that were at the top of the wall up till now don’t look all that smooth anymore, (ref: ACTEW Dam Cam 10:12:57) particularly toward the right hand side as you look at it. It almost looks like something’s given way. I hope not. Ever been so riveted watching a live cam before.

way cool video! and thanks to JB for pointing us to the damcam, it has entertained me all night!

I am leaving reception area and then heading home. Will update early tomorrow as we understand extent of damage. Right now it is not good but not as bad as it could be. Structure secure. Lots of water and debris. Please can the rain stop

OpenYourMind said :

Let me just say how cool it is to have the local expert tell us how it is on RiotACT. Thanks MarkS

Seconded. Excellent work, great to see.

Interestingly the same thing happened during the construction of Googong Dam – http://www.engineer.org.au/images/4-11.jpg – and that’s a rock-fill dam.

Mr Evil said :

Umm, maybe the same way they got them up there in the first place?

The machinery including vehicles rise with the dam wall. They were put there when it was at the valley floor and they go up with it. I assume the only way they come off is when the wall peaks and they can be driven off the top onto the neighbouring hillside.

Mr Evil said :

Umm, maybe the same way they got them up there in the first place?

They got them up there by building a dam underneath them. Unbuilding the dam to get them down seems a little drastic.

Hmmm… In the video at 0:38 it looks like something big and round wasn’t “tied down” that well.

Bananabanana9:18 pm 01 Mar 12

Oooo, I wish that video had sound

rohbo said :

Mr Evil said :

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

If you know how to get some very heavy machinery off a 40m high wall i’m sure ACTEW would love to hear from you. Mark S from ACTEW said they got off everything they could with the cranes and the rest was too heavy so had to stay.

Umm, maybe the same way they got them up there in the first place?

Anyway, maybe I should have expressed myself better – the really heavy stuff isn’t the problem, as obviously if a 40 or 60 tonne object is going to be swept off the wall by the overflow, then I would suggest that there’d be bigger issues to worry about with the dam itself at that point. It’s some of the other smaller vehicles that appeared to be still on the dam in the photo that Mark submitted earlier this morning.

The point I was making is that we have had several days warning that the rainfall was going to be high, but some people seem to have been caught slightly ill-prepared by it all.

And as to my comments about objects seen floating down the river; yes, I understand that there will always be plenty of stuff that is washed down a river in flood, as witnessed on LBG last time we had a flood like this – but isn’t it a good idea to try and ensure that if at all possible that we don’t add to the debris pile unnecessarily?

While dam cam stays up lets stay away. Some of the time lapse stuff is incredible.A slight abatement in flow last hour brings some hope. AS for I-filed my stake in this thing is not insignificant and I remain positive. No pumping going on. Bendorra over by a metre or so so and adds to woe. To my spys on the left abutment stay warm and dry

All I can say is “holy crap!”

And thanks to MarkS (Sullivan?) for keeping us up to date.

How exciting

Camelicious said :

I guess ACTEW is pumping as hard as they can out of Corin and Bendora, since I believe the pipes out of Cotter aren’t connected.

There is no pipeline to Corin – water released from it just flows down the river to Bendora.

…almost tempted to pop out and have a look how Cotter Bridge is holding up (the one next to the pumping station)… but then again, that could be a really dumb idea… hopefully the bridge will still be there once all this is over…

OpenYourMind8:56 pm 01 Mar 12

Let me just say how cool it is to have the local expert tell us how it is on RiotACT. Thanks MarkS

MarkS said :

Already seeing upstream debris and this will increase and may cause some problem.

If anything really bad is going to happen, I suspect a log-jam of debris caught at the top of the dam that breaks away suddenly will be what causes it.

johnboy said :

And if any of the avid Dam Cam watchers see something dramatic be sure to get a screenshot at send it in to images@the-riotact.com

Been grabbing shots every 30s since shortly after it started to overflow (took a few moments to write a script). Might compile a time-lapse video when it’s all over.

Cheers Russ, be sure to share!

Mr Evil said :

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

Was any attempt made to secure loose material on the worksite before it became apparent that the waters were going to breach the top of the current wall? Whilst watching some of the webcam footage an amount of timber and what appeared to be an upturned watertank could be seen floating down the river in front of the dam – what measures are taken to prevent this material flowing down the river to become a problem further downstream?

So just where were the vehicles supposed to go? There’s no road leading off the top of the dam – if it was as easy as just driving off the top, do you not think they would have done that? So the alternative is craning the vehicles off of the dam. I don’t profess to know anything about crane operations, but I’d imagine that lifting something like the vehicles that have been left up there wouldn’t be easy, or necessarily safe.

And honestly…timber floating down the river? Maybe a water tank? If you can manage to differentiate between what naturally flows over the dam in an event like this, and what may be construction material, based only on the dam cam images, then you’re obviously watching a different dam cam to me.

With no connection to this project at all, I think I can safely say that yes, there would have been significant efforts made to secure as much as possible on the site. Everything that’s lost down the river costs money, and I have enough faith in the people in charge of this project to believe that they’re not going to deliberately throw money away if it can be easily avoided. I’m sure this site has been a hive of activity over the last few days, preparing for the worst. Time will tell whether those preparations were good enough.

Cranes are very solid. Currently pinned more than forty metres into ground. At the bottom of my list for now

Don’t worry! CEO Mark Sullivan said on 666 earlier that the workers had “tied everything down” … I’m sure on the basis of this competent chap’s assurance that everything we (not Mr Sullivan) have paid for will be safe ………….

I guess ACTEW is pumping as hard as they can out of Corin and Bendora, since I believe the pipes out of Cotter aren’t connected. Will be interesting to have a look at the Dam Cam in the morning to see what’s left there because there’s a lot of water coming over the wall right now.

I wonder how long the ungrouted abutments will remain firm before hydrostatic pressure works its magic.

Some good comments. The dam will have a constructed spillway but steps are designed to dissipate energy. Heavy machinery cannot be lifted of the dam or driven off. Most lighter material was moved. Tanks difficult to lift so tied down. Already seeing upstream debris and this will increase and may cause some problem. While dam is keyed into the abutment it is gravity that holds the 185,000 cm of concrete in place. Scaffolding and formwork the big issue as flow increases. Will try and contribute but things getting busy. Bloody rain

And if any of the avid Dam Cam watchers see something dramatic be sure to get a screenshot at send it in to images@the-riotact.com

No concerns about the cranes Mark?

Mr Evil said :

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

If you know how to get some very heavy machinery off a 40m high wall i’m sure ACTEW would love to hear from you. Mark S from ACTEW said they got off everything they could with the cranes and the rest was too heavy so had to stay.

A couple of questions.

Why were vehicles left parked on the topside of the dam when there had been pretty ample warning that NSW/ACT was going to receive a lot of rain in the next few days, and numerous flood warnings had been publicly issued?

Was any attempt made to secure loose material on the worksite before it became apparent that the waters were going to breach the top of the current wall? Whilst watching some of the webcam footage an amount of timber and what appeared to be an upturned watertank could be seen floating down the river in front of the dam – what measures are taken to prevent this material flowing down the river to become a problem further downstream?

johnboy said :

Thanks for the clarification Mark.

So even with no spillway you’re not worried about the flow undermining the dam wall? (what spillways were invented to prevent)

The water coming down the sides doesn’t look great from here either.

I think it is safe to assume that the dam is sitting up against fairly solid rock (at least I certainly hope it is) so a one off event like this is unlikely to undermine it.

If it was an earthen dam, then the lack of a spillway would be tremendously concerning, but that concrete isn’t going anywhere in a hurry.

johnboy said :

Thanks for the clarification Mark.

So even with no spillway you’re not worried about the flow undermining the dam wall? (what spillways were invented to prevent)

The water coming down the sides doesn’t look great from here either.

I didn’t think the dam was going to have a constructed spillway?

The stepped face is designed to dissapate the energy as it overflows.

johnboy said :

Thanks for the clarification Mark.

So even with no spillway you’re not worried about the flow undermining the dam wall? (what spillways were invented to prevent)

Is that not the point of the stepped wall? To break up the water and take away most of it energy before it hits the bottom?

I’m wondering if any of that scaffolding will till be there in the morning? Looks like a fair bit of water coming over.

Devil_n_Disquiz7:56 pm 01 Mar 12

The sound of the water flowing over the wall is quite something else. Impressive to say the least.

It would appear (from DamCam) that water is flowing over the entire structure now.

Lets keep this right. A 3metre diversion tunnel is going thru the dam on the left hand abutment. This was built in 2011 and is performing well. You cannot fully divert a river. The threat to the dam is neglible. It is a very stable mass concrete mass. What is at risk is the dam construction infrastructure.

Thanks for the clarification Mark.

So even with no spillway you’re not worried about the flow undermining the dam wall? (what spillways were invented to prevent)

The water coming down the sides doesn’t look great from here either.

Uh oh spaghettios.

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