Wet Feet in the LRT tunnel?

Rumours can be fun to hear. Even when they are highly unlikely. Sometimes the most improbable ones become accepted wisdom or folklore, especially when they tap into partisan or subliminal emotions or confirm existing biases.

When I first went to work at Tower C, Place de Ville, newbies were educated as to why there was one more elevator on one side of the lobby than the other. The building is structurally unsound, so the story goes, and the “missing” elevator shaft was filled with concrete to stabilize the building. This got more credibility since so many of the occupants of the tower were engineers.

New high school students are usually told of the secret swimming pool on the roof level. I try this on the seniors at my father’s retirement residence. I can assure you that the near demented are less credulous than the 14 year olds who are victims of an age when nothing is improbable. Granny still has common sense.

Claridge’s ICON tower at the corner of Preston & Carling has a nine storey deep basement. This will drain Dows Lake for sure. Never mind that even a one storey basement in that neighbourhood is lower than Dows Lake, which is in fact at the highest point, being held back behind a dam, along the top of which runs Queen Elizabeth Driveway. If the lake is going to leak away, it would have done so years ago into the rubble stone foundations of the adjacent homes, or even into the existing Trillium Line Otrain tunnel that runs right under Dows Lake.

Mind, consistency and logic aren’t always obvious. How else do we explain all the engineering reports for the proposed high rises at Preston/Carling intoning seriously about mitigating the adverse affects of run off from the construction sites into the lake … when the lake is uphill from the condos, and water tends to run downhill. It’s OK, city staff didn’t notice the error either.

Back in the days when large neighbourhood fires were common, the dam at Dows Lake was deliberately breached to permit the lake to flood into the neighbourhood, with the headwaters rushing down Preston Street, to extinguish the fire.

Another recurring rumour in this west side neighbourhood comes around every election, when campaigners  hint darkly to residents of co-ops and Ottawa Community Housing that their units are going to be turned into “luxury condos” if certain other guys win, but if their candidate wins, then much-needed repairs will come. The apparent contradiction between dilapidation and luxury seems to escape at least some people.

So what is the current rumour about LRT??  One making the circuits over the last month is that the new Confederation Line LRT would not open in November. The hand over couldn’t occur, the story goes, because the tunnel keeps flooding. Sometimes this is because of a leak in the bottom of the Rideau Canal. Other times, it is a leak from the Ottawa River. As evidence, note the every-week mention in the city’s updates to “hydro-vacing” (hydro means water, vacing means vacuuming, so they are constantly pumping water out of the tunnel / Rideau Station. And remember the Sinkhole ! [look triumphant at this point !]

That the tunnel is under  — very far under — the Rideau Canal is not widely understood. And it could leak, couldn’t it? Yup, just like the current Otrain tunnel under Dows Lake, there are pumps to keep the water removed, rather like a sump pump in a basement. And the transitway at Lees Station is also well below Rideau River level, and yes, there are pumps there too. And I don’t recall it ever flooding.

So lets look at just how deep the Confederation tunnel is. First, refresh your memory as to the route:

Here’s a profile of the length of the tunnel. Up/down has been exaggerated compared to the left/right length of the tunnel. Like the map above, the tunnel begins at the west portal (near Pimisi Station / Booth Street) descends, travels under the downtown, then sinks lower to go mostly under the fault line at the Rideau canal, rising slightly to reach Rideau Station * :

Note that where the west tunnel portal is on the left, is just a few feet above the water level of the open aqueduct that cuts through the Flats. And the water in that aqueduct flows in at river height, at the western end of the Flats. So right at the start, the tunnel looks like it goes below the level of the Ottawa River.

After passing through the two downtown stations (shown as white squares of excavation) the tunnel descends again far under the Canal (any clues here as to why the Confederation Square station was eliminated??) and into the Rideau Centre Station. Certainly looks below the level of the Ottawa River to me.

Here’s a drawing of the uptown stations, nestled between the building foundations and parking garages:

here is a comparison of our downtown portion to other subway systems:

Now at the Rideau Station, the tunnel is considerably deeper, 26m below the surface, or 85 feet, or 8 1/2 stories down. Rideau Street only appears to run downhill from the canal, it really runs downhill from a bridge over the canal, so in actuality Rideau Street in front of the Rideau Centre is still one metre above canal surface level.

The Rideau Canal surface is at 64m elevation, the Ottawa River at 43m, so its 21m down to the Ottawa River.  The station platforms are  26m down from street level, or 25m below canal level, or 4m below Ottawa River surface level. All elevations taken from Google Earth.

So yeah, in theory you could have wet feet in the LRT station, it being well below the Canal and a bit below the River. But don’t say I started the rumour that your feet will get wet. I’m just spreading the story for your entertainment.



* my PDF won’t enlarge enough to make the data on the tunnel profile diagram legible. Sorry.

2 thoughts on “Wet Feet in the LRT tunnel?

  1. i would not get on that train. ottawa city planners and engineers don’t inspire confidence with all the f#$k up’s they’ve done in the past.

  2. Very interesting plan of the profile of the LRT tunnel. Can you confirm that the blue is bed rock and greenish is the sedimentary ground, glacial deposits and fines. If so I noticed that the only part of the tunnel that passes through this layer is where the sinkhole happened.

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