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Coxwell Sanitary Trunk Sewer Bypass

That was my first thought ... but I've seen some photos taken from other angles, that look very similar. If it's real, it looks totally unreal.
 
it's real. it think it may be caused by an underground river cave system and could be deeper than 300 feet. how the hell are they going to plug that and how safe is the rest of the neighbourhood? apparently this is no first in guatemala. that is absolutely horrifying.
 
^^ ... no.

Wouldn't it be more logical to integrate a sewer into a bridge crossing the valley instead of buried underneath? If they need to bypass the sewer, why don't they just build an aboveground one. They could probably do it joint planning with the DRL and use the same bridge structure! (pure speculation there.)
 
W. K. Lis said:
Ed Norton? Don't get him angry or he'll turn in Ralf Krandem.

3598.jpg
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Pow! Right in the kisser!
 
Second_in_pie said:
^^ ... no.

Wouldn't it be more logical to integrate a sewer into a bridge crossing the valley instead of buried underneath? If they need to bypass the sewer, why don't they just build an aboveground one. They could probably do it joint planning with the DRL and use the same bridge structure! (pure speculation there.)
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I think your perception of what is flowing where might be off a bit.

The existing arrangement has the trunk sewers arriving together from the east (via the Taylor Creek valley) and the north and west via the West Don Valley and the Central Don Valley.

Those pipes meet at a junction in the base of the valley, where the flow is then directed south under Coxwell Avenue to the Ashbridges Bay Sewage plant.

The pipe is maybe 40 feet down at valley level, and its height (or depth) remains fairly constant all the way to the plant (so its about 160ft below the crest of the valley wall at Coxwell and O'Connor.

What's at issue is a crack in a section of pipe where the depth is in the 150ft range.........and the by-pass is to avoid not so much a giant sinkhole, though I suppose that could happen; but more so that if the pipe failed, the sewage in the valley would have nowhere to go; and so would all be dumped, un-treated, into Taylor Creek and the Don River. Stink and disease aside, this would totally flood the bike path level with sewage.

So the proposed solution is a new pipe, being tunneled under a side ravine to the corner of Coxwell and O'Connor.

Like the existing pipe the depth will be constant; because it has to meet the existing sewer under coxwell, to send the sewage south.

There will only be big shafts at the intersection and at the junction point in the valley for putting in and taking out the tunnel boring machine.

The TBM will do all the piping.

********

As to how the sewers ended up down there in the first place...........

God bless cheap engineers! They figured that water always flows down hill (gravity) so by laying the sewers in the valleys, in-line with existing streams, they avoided any use of electric pumps in our sewers, all flow is by gravity alone.

On the other hand......since the sewers are right there, beside the creek, the engineers also thoughtfully made the sewers too small for a severe rain fall; because they had a handy 'overflow' (the adjacent waterway) to dump sewage if the sewer reached capacity.

Which, btw, it does these days after most rain falls.....
 
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Okay, well then I guess that my plan would be upgraded slightly to putting the entire works that goes through the valley in an aboveground aqueduct. I was assuming that the sewers met near O'Connor, actually outside the valley, but this is not the case, right?

That really seems like the easier solution right now to me. Just dig to shallower parts of the sewer outside the valley on either side and link it across using a bridge. Much better than maintaining the existing structure and digging a new sewer underground. It might be faster too, since time seems like it might be an issue.
 
Liquids generally don't flow up hill. Pumps would be noisy, expensive and unreliable.
 
Second_in_pie said:
Okay, well then I guess that my plan would be upgraded slightly to putting the entire works that goes through the valley in an aboveground aqueduct. I was assuming that the sewers met near O'Connor, actually outside the valley, but this is not the case, right?

That really seems like the easier solution right now to me. Just dig to shallower parts of the sewer outside the valley on either side and link it across using a bridge. Much better than maintaining the existing structure and digging a new sewer underground. It might be faster too, since time seems like it might be an issue.
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1) Yes, the junction of all the sewers is at Valley level (well 40ft below the valley bottom surface that you or I would walk on).

2) Lifting all the existing valley level sewers would be a project of enormous magnitude.......we're talking many Billions of Dollars. While in my opinion it was unfortunate that the routes and depths chose were used; the decision is basically done, because you can't just easily change elevation by several hundred feet or move just 1 sewer, that's the not the way that the system works. in very limited sections, it may be possible to implement (over time, as in decades) more of a grid-based sewer network; with less use of the valley space....but changing all of it......is really out of the question in the next 50-100 years.

3)In terms of an immediate solution, you have to remember that at Coxwell and O'Connor that pipe is 150 ft down or so. There is no shallower spot, until Coxwell starts descending towards the Lake near Upper Gerrard. The By-Pass is not a completely new pipe to the sewage plant, just a work-around of one 200M long section. They are considering building a new tunnel under Coxwell either beside or above the exiting sewer......as part of a separate project.........the budget is in the 500M area...
 
44 North said:
Whoa. I thought it was a minor crack with the potential to worsen, not an averted catastrophe. Thanks for the link.
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So did the City. It looks like it got a lot worse since the primary inspection in 2009. Good thing that it was dealt with.

Now, to work on the rest of the sewer...

Dan
Toronto, Ont.
 
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