Niagara Tunnel

The Niagara Tunnel (nt) has created great confusion in the blog writing of geofish (gf), and rightly deserves some clarification.  He actually became involved at the beginning of his career, but doing a micro-gravity survey which accurately laid out the contours of the St. David Gorge.  Once the company (util) split up, he was no longer involved.

His blogs first started to note the tunnel in 2008.  Although many of the news articles can no longer be located, he published some observations on rock squeeze.  and a note on tunneling in these conditions. 

In 2009, bad news continued to flood out about the tunnel.  gf wrote his series about the tunnel - Disaster of the Niagara Tunnel

Part 1  - outlining the reasons for the tunnel
Part 2
Part 3
Part 4
Part 5

Of course, merely criticizing is not satisfying for gf, he has to rub it in, by showing how it could have been done correctly.

Niagara Tunnel - Doing it Right
Part 1
Part 2
Part 3
Part 4

The more radical concept here was the idea to give up on a circular cross-section, which meant not using a conventional tunnel boring machine.

After that, there were numerous posts showing pictures and updates of the tunnel.  During all the 3 m overbreak sections, gf was wondering how they would get back to a standard circular lining, but was shocked to realize that they intended to keep the irregular over-broken shape.  They were just laying in steel sets that conformed to the new shape.  gf began to worry that this was a very dangerous thing they were doing, since nearly-flat steel sets would be prone to explosive buckling failure, with only a little inward displacement.

For a while, the tunnel enjoyed the benefits of a sandstone roof, but became, once again, mired in overbreak, once it broke through at a shallow angle.  The final word was that the dreaded rockbursts had begun, making the tunnel as safe as an afternoon drive in Afghanistan.

The TBM is now entering the final stretch, as it only has a few hundred metres to go.  It will commence a curve upwards which will put some strain on the heavily-patched main beam, but it should hold.  When the machine finally limps through, there will be the classic celebration and photo-op.  Four years late and four billion over, it should be a muted affair.


Now that the tunnel is almost complete, gf won't be commenting on it, since that is boring.  But what is the rationale for his estimate of 4 billion rather than 1.6 billion?  It's just a matter of timing.  The first estimate of $1b assumed it was a cakewalk and would be done in a year.  The second estimate of $1.6b came right after the overbreak was slowing them down, but they assumed it was just a small section, and they would be done in the same time because they were tightening some curves.  The cost of these things is totally in the time of keeping a full crew underground, and interest rate charges.  After that estimate came the tunnel roof failure and the realization that most of the rock was bad.  The tunnel is 4 years late, and has 10 times the rock reinforcing originally envisioned.   A court agreement made the contractor blameless, and he has been running on a gold-plated cost-plus contract.  Industry experience indicates that this is bad.

What is the income?  Much is made of the fact that it will carry enough water for blah-blah thousands of houses.  But is this true?  The Niagara water allowance is very complicated, and only at night do the existing Twin Tunnels suck the falls dry.  Nobody wants the power then so they spill water to power the pumps to the pumped storage.  They could easily use the nearly-free nuclear power, at that time.  The power is only valuable during the peak hours, where they drain the pumped storage.  What will this tunnel do?  When gf worked on this 30 years ago, the tunnel only worked if they could increase the pumped storage, which proved nearly impossible.  We haven't heard of any work to expand this.

What of the 100 year life?  100 years of nothing is still nothing, but will the tunnel last?  gf has said that he could go strolling in  the tunnel and find the first signs of rock squeeze.  If that is true, then in 20 years the cracked and deformed lining will start to interfere with the flow.  Many power stations and tunnel in the region have had this problem, and the tunnel cannot be immune.

In July 2011 there was another major rockfall.  Once again, nobody was looking up at it when it happened.  The rockfalls show that the rock is squeezing, and each rockfall adds somewhat to the total cost.