We know it will cost alot - yes, that's as precise as it gets if you listen to some of the figures floating around in the media. Here's some explanation and comparison pricing on a tunnel for Ottawa:

The Ottawa LRT tunnel proposal requires about 2.5 km of twin tunnels from
Bronson to Campus. The Task Force has estimated $450 million, which has
become a controversial element of the plan. It averages $180 million/km.

It could, however be compared to Toronto's Sheppard Subway, completed in
2002 at $875 million for 5.5 km, including 5 stations, (one of which has a
very large underground bus interchange). This averaged $160 million/km.

The Laval metro extension which opened in 2007 was 5.2 km with three new
stations and cost $745 million. The cost was under $145 million/km

The Ottawa tunnel also replaces 2.5 km of surface-running LRT and the cost
of this, say $150 million, should be subtracted from the $450 million before
considering the amount as as additional cost to the previous plan.

Vancouver's 19.5 km Canada line, will open from downtown to the airport and
Richmond in 2009. More than a third is tunnel and most of the rest elevated,
which is also high cost. Estimated cost of $1.9 billion, (2003 $), INCLUDES
trains, maintenance facility and 16 stations, so about $100 million/km.

Tunnel boring requires one boring machine for 2 tunnels, though some
projects use two, and digs about 10 m per day. This means that for Ottawa,
5 km of single bore tunnels would take about 500 days or just over 16
months. This is quite reasonable and has very little impact on the surface,
utilities, existing transit, or traffic, except at the station sites.

Rick Chiarelli's claim that Ottawa's tunnel would cost $1.4 billion is
completely unsupportable. The Task Force estimate is certainly in the
ballpark.

And how long can we go on expanding our billion dollar Transitway to a
city-wide $3-billion Rapid Transit network, WITHOUT spending more than a
pittance in the downtown core?

David Jeanes