Confederation Line (Stage 1) | In Service 1.0

[Uhuniau]

Originally Posted by lrt's friend

All that water and washed out earth had to go somewhere. We are very lucky this wasn't a tragedy.

"Flooded" is a rather imprecise term. How "flooded" are we talking? A foot of water? Three feet? Five feet? To the ceiling?

[Richard Eade]

From the Ottawa Citizen:

The water in the tunnel isn’t deep — maybe enough to slosh around. The Rideau Transit Group, which is the city’s LRT contractor, doesn’t think it’ll hamper the construction schedule for the $2.1-billion transit project. RTG is also taking the lead on fixing the road, but the city doesn’t know yet if the sinkhole was caused by LRT work.

http://ottawacitizen.com/news/local-news...e-stabilized-after-weekend-concrete-work

So, the ‘flood’ level is about what would have been there while the road headers were grinding, and spraying water on, the rock portions of the tunnel.

Remember, the face of the tunnel was being dug into the till, so they were past the ‘protection’ of the rock wall of the valley. Water that filled the basin of the sink hole eventually drained through the loose fill in the valley and found its way to the face of the tunnel. There was obviously no water proofing at the tunnel face and the tunnel itself offered zero water back-pressure - so part of the basin’s water naturally drained into the tunnel. Since, I believe, the lowest point of the tunnel is west of the canal, the water flowed back along the tunnel, settling in its gentle curve. This is why we got the report that 300 metres of the tunnel were ‘flooded’.

Despite the sensational headlines, it is really a ‘Move along; nothing to see here’ situation. Yes the tunnel needs to be pumped out, but there should be no long-term implications from the ‘flooding’.

Assuming, of course, that there is not rampant, uncontrolled, growth of mold in the damp tunnel. (There, I just introduced a new concern that the media can run with.)

[rocketphish]

Ottawa Sinkhole, Day 6: LRT tunnel water as high as 2.5 metres deep under sinkhole

Jon Willing, Ottawa Citizen
Published on: June 13, 2016 | Last Updated: June 13, 2016 6:43 PM EDT

The LRT tunnel is half-filled with water directly under the Rideau Street sinkhole and the city doesn’t know yet if a “roadheader” machine is submerged.

Steve Cripps, the city’s director of the rail implementation office, said the water is about 2.5 metres high at the deepest part. The tunnel is about five metres in diameter.

The water level decreases moving westward toward Elgin Street, around which the water is a couple of inches deep, Cripps said Monday.

The water probably started entering the tunnel directly below where the sinkhole swallowed a massive chunk of Rideau last Wednesday, he said.

“Once you get farther to the west from where they were excavating, there is concrete-type material that lines the cavern,” Cripps said. “Any seepage would have likely come in at the face where they’re excavating.”

Workers have been tunnelling from west to east and have made it just past Sussex Drive.

The city’s LRT builder, Rideau Transit Group, is also working on all the fixes. RTG is pumping the water out of the 200-metre section of tunnel through pipes to a water treatment facility at LeBreton Flats, purpose-built for the LRT project. The water is then poured into the city’s sanitary sewer.

Workers will be pumping water for at least a week and it won’t be until then that they can access the face of the tunnel where they stopped digging, Cripps said.

Cripps noted that pumping water is a regular chore during construction since there’s always water seeping into the tunnel as workers dig. Any water that comes out of the tunnel must be treated before being dumped into the sewer.

There could be LRT construction equipment impacted by the flooding in the tunnel, including one of the three 135-tonne roadheader machines.

“The roadheader would be in the tunnel in the area that has water, so we don’t know what that really means because it’s probably a bit farther in than crews have gone to date,” Cripps said. “It is possible that it’s partially submerged in water. We don’t know what that really means at this time.”

The city isn’t concerned about other parts of the tunnel already excavated.

Cripps said the section of tunnel up by Elgin is sound because there has been temporary lining installed before the concrete liner goes in. Plus, the ground to the west is largely solid bedrock, compared to the softer ground around Rideau.

“The part we haven’t been to yet, because they’re still pumping water out, is right at the face where the excavation was happening,” Cripps said. “It’s too deep to get in there and have a look right now, but the part we have been in there’s been no evidence of damage.”

Workers have only 50 metres left under Rideau until the entire 2.5-kilometre length of tunnel is excavated. Cripps said RTG will likely start tunnelling westward from the Rideau station cavern, but first it needs to gauge the flooding in the tunnel on the other side of the non-excavated portion.

The big breakthrough moment was expected to happen in late June or early July, but Cripps said that will probably be pushed back. However, the full transit project is still on schedule. A two-week tunnelling setback in a multi-year construction project isn’t “substantive,” Cripps said.

It appears three vehicles actually fell into the sinkhole from the surface.

There was the van parked on the north side of the street, and there were two construction vehicles that dropped into the cavity. A lift, like the van, was later encased in concrete, but RTG managed to rescue a crane, Cripps said.

On the surface, RTG has finished the first phase of concrete work and “stabilized” the sinkhole.

There was no update Monday on the cost implications of the road collapse and infrastructure repairs.

Cripps said the city has assembled a team of staff and consultants to investigate.

“In terms of what’s caused this and where responsibility lies, we haven’t got that yet and it will be a little while before we do,” Cripps said.

The city has a precautionary boil water advisory for six addresses on Rideau Street: 107, 109, 111, 111A, 113 and 115.

Cripps said the major focus has been on restoring services to businesses in the area.

[email protected]
twitter.com/JonathanWilling

http://ottawacitizen.com/news/local-news...e-stabilized-after-weekend-concrete-work

[rocketphish]

How could the roadheader not be at least partially underwater, if a 5m diameter tunnel is half-filled up? That's a big piece of equipment to possibly be safe and dry up on a bench.

[Uhuniau]

Originally Posted by Richard Eade

Assuming, of course, that there is not rampant, uncontrolled, growth of mold in the damp tunnel. (There, I just introduced a new concern that the media can run with.)

I'm more concerned about the C.H.U.D.s myself.

[zzptichka]

Originally Posted by rocketphish

How could the roadheader not be at least partially underwater, if a 5m diameter tunnel is half-filled up? That's a big piece of equipment to possibly be safe and dry up on a bench.

Oh they know for a fact it's submerged. Just like they knew from the beginning that the tunnel is collapsed and flooded. They are just choosing not to tell it to the public.

[swimmer_spe]

Why not take a canoe and see?

[Richard Eade]

There seem to be very different, and conflicting, stories being fed from RTG to the City and the media, and only when they have no other choice does RTG expand on their explanation.

The last (June 6 update – which was quickly removed from the Ottawa Confederation Line Website) said the following about the running tunnel east of Parliament Station:

Tunnel Excavation and Support

Running tunnel east of Parliament Station: Jawbreaker and Chewrocka excavate the running tunnel bench moving east toward Rideau Station. Crews install the umbrella and arch lining pours are ongoing, part of final concrete works.

So there should be two road headers in the ‘flooded’ section. The third, Crocodile Rouge, was in the Rideau Station cavern. Why are they talking about “the road header” as if there would only be one in there?

The more I keep hearing that things are worse than originally portrayed, the less I trust RTG. I think that, as zzptichka implies, RTG is in full ‘Cover Butt’ mode.

[Buggys]

I think the City is being very cautious about what they say as well, because anything they publically that's not provable to a court could negatively affect negotiations with RTG for assigning blame & cost.

[Catenary]

Originally Posted by Richard Eade

There seem to be very different, and conflicting, stories being fed from RTG to the City and the media, and only when they have no other choice does RTG expand on their explanation.

The last (June 6 update – which was quickly removed from the Ottawa Confederation Line Website) said the following about the running tunnel east of Parliament Station:

So there should be two road headers in the ‘flooded’ section. The third, Crocodile Rouge, was in the Rideau Station cavern. Why are they talking about “the road header” as if there would only be one in there?

The more I keep hearing that things are worse than originally portrayed, the less I trust RTG. I think that, as zzptichka implies, RTG is in full ‘Cover Butt’ mode.

Has the tunnel broken though? The fact that they are pumping water to LeBreton implies that they have, but I don't recall reading about it and it seems that a tunnel breakthrough would almost certainly be covered in the media. There must have been some method to pump water to the east portal.

If the tunnel hasn't broken through, then we know that the two roadheaders are on the west portion of the tunnel away from the hole.

[1overcosc]

Originally Posted by Catenary

Has the tunnel broken though? The fact that they are pumping water to LeBreton implies that they have, but I don't recall reading about it and it seems that a tunnel breakthrough would almost certainly be covered in the media. There must have been some method to pump water to the east portal.

If the tunnel hasn't broken through, then we know that the two roadheaders are on the west portion of the tunnel away from the hole.

From what I've heard:
1) the tunnel west of Rideau station had not yet been broken through; there remained a 50 metre gap between Rideau Station and the running tunnel which had been fully excavated from Lebreton all the way to Sussex
2) it was the tunnel west of Rideau station that had flooded; the Rideau station cavern itself was completely unaffected (which makes sense given the location of the sinkhole)

[1overcosc]

Also, why are all three roadheaders underground? At this point, with the entire tunnel west of the canal fully excavated including the stations, and work on Rideau station being either complete or near-complete, you'd think they would have removed a machine or two.

[rocketphish]

Ottawa sinkhole repair on the right track, says forensic structural engineer

Evelyn Harford, Ottawa Citizen
Published on: June 13, 2016 | Last Updated: June 13, 2016 5:08 PM EDT

Ottawa’s sinkhole repair is on the right track, said Yasser Korany, a forensic structural engineer at Canadian engineering firm Origin and Cause.

Ottawa “stabilized” the Rideau Street sinkhole over the weekend with hundreds of truckloads of concrete in the city’s first phase of repairs.

Pouring concrete into the sinkhole is the most “sensible” way to stabilize the surrounding buildings and ensure the safety of the workers, said Korany, who has performed more than 500 investigations into structural failures in his 25-year engineering career.

He estimates, from an independent analysis of Ottawa’s sinkhole, that two to three weeks is a “realistic and pragmatic” timeline to ensure the sinkhole’s walls are stable.

Though he doesn’t have access to the information available to the Ottawa sinkhole investigation team, his extensive career, including his experience assessing sinkholes in the United States, provides him with the expertise to conclude that investigators can’t rule out the LRT-sinkhole connection.

“Having a sinkhole form where construction is taking place would make any investigator curious,” he said. “It’s a factor that can’t be ignored.”

However, he said people who point the finger too early at a single cause are often proven wrong after further investigation.

“It’s usually multiple factors that’ll cause this type of thing,” he said. “It might be a simple situation of unfortunate circumstances joining forces to cause this sinkhole.”

Korany said LRT construction, a water main break and natural causes are all possible factors that could’ve contributed to the massive sinkhole. He said he’s confident investigators are looking at all possible causes.

Going forward, he said, the $2.1-billion LRT project will have to reassess tunnel integrity and soil conditions where the sinkhole occurred. The buildings that surround the sinkhole will also have to be reassessed for structural integrity.

Geological assessments done prior to LRT construction revealed the existence of sandy soil in the area where the sinkhole occurred, but Korany said the full extent of excavation risk might not have been known.

“We need to remember that there can be significant soil variations very close together,” said Korany, who knows that sandy soil can be a difficult geological hurdle for developers to overcome. He has worked on least a dozen cases related to soil-foundation failures.

http://ottawacitizen.com/news/local-news...n-the-right-track-says-forensic-engineer

[Melgibson1972]

They're obviously trying to cover their bums. I heard 5-8 weeks for cleanup in the flooded tunnel, the water is almost as high as the Sea-Can crews use for lunch and tool storage I have heard (5-7 feet) and yes as I stated earlier, one of the 8 million dollar roadheaders that was at the face is buried and submerged in water. Clear cut attempt to mislead the public taxpayers to avoid outrage. This won't be a 2 week fix as they are stating. As someone else stated, all that earth had to go somewhere. Wondering now how they will proceed without creating more sinkholes after they do proceed excavation of the rest of the soft ground with the weight of 3000 supposed meters of concrete on top and now that all that soft till has been saturated with water and compromised. I hope somehow this gets accomplished safely but as a concerned citizen and taxpayer I'm starting to have my doubts with RTG in charge of this, hope nobody gets hurt

[Norman Bates]

As I recall cement requires 24 days to dry to its rated strength.

Plus there's several different types and strengths of concrete. At such short notice, and such large volume, what decisions were being made about what type was being poured down the sinkhole?

I'm guessing that it was 'give us any kind that you've got from as far away as you can'.

[ortelius]

From where to where does the softer area go? (ah geology, fascinating, something that happened a long time ago is causing this).

I'm concerned with this. I wonder if there are similar examples worldwide out of the dozens of subways system, where they had to build in softer areas.
Maybe a civil engineer here could comment on what's the solution in these cases.

[Uhuniau]

Originally Posted by Melgibson1972

I hope somehow this gets accomplished safely but as a concerned citizen and taxpayer I'm starting to have my doubts with RTG in charge of this, hope nobody gets hurt

What's the issue with RTG? I thought they have been doing pretty good work on such a large and complicated project.

Their comms since the collapse could have been better, but is there a pattern of behaviour otherwise, going back further in time, that causes concern about RTG?

[lrt's friend]

I have to admit that I am shocked that we have now had two cave ins with this project that have put the citizens of Ottawa at terrible risk. We should not be minimizing concerns about it. It is a serious engineering failure.

It does point to the issue of the safety of boring a tunnel through soft material. Let's face it, this was being done in order to minimize disruption on city streets but should have another approach to tunneling been taken at this location even if it meant the closure of Rideau Street for a year. Can you imagine if the Rideau Canal had been compromised?

In my opinion, our safety should have come first.

[AndyMEng]

Clearly what we should have done from the start is call Kit Latura...

[roger1818]

Originally Posted by Melgibson1972

They're obviously trying to cover their bums. I heard 5-8 weeks for cleanup in the flooded tunnel, the water is almost as high as the Sea-Can crews use for lunch and tool storage I have heard (5-7 feet) and yes as I stated earlier, one of the 8 million dollar roadheaders that was at the face is buried and submerged in water. Clear cut attempt to mislead the public taxpayers to avoid outrage. This won't be a 2 week fix as they are stating.

Even if they know that the roadheader, they don't know if it has been damaged. From a PR perspective, it sounds a lot better if they provide an operational update with the status update.

As someone else stated, all that earth had to go somewhere. Wondering now how they will proceed without creating more sinkholes after they do proceed excavation of the rest of the soft ground with the weight of 3000 supposed meters of concrete on top and now that all that soft till has been saturated with water and compromised.

The thing about sand is it won't absorb water (though the water will fill in the gaps between the grains of sand), but will let it drain through very effectively. While digging, it would be normal for them to have water come out, which is why they had pumps to drain it away. After the leak developed, there may have been an increase in water, but the large depth of sand would have acted as a flow control, limiting the increase in flow, making it difficult to notice.

As the water drained, it would drag some of the sand with it. The only clue would be that even though they are digging out material, they aren't advancing, but it is probably normal for this to happen from time to time, so they probably didn't think much of it.

Once the water has drained out of the sand, it will be wet, but that is actually a good thing as the surface tension of the water will help the sand to stick together (if you have ever made a sand castle, you will know that wet sand will hold its shape much better than dry sand). The worst thing would be to hit a patch of dry sand, as it would freely pour from above, making it difficult to hold in place until they can encase the tunnel. It is actually quite possible that they did hit a patch of dry sand, causing everything to shift a bit, including the water pipe, creating a crack. Just a theory though.