No Massey Bridge Rethink say Liberals

So with the present Massey Tunnel at 22 metres below sea level, what you are saying is that the position of any new tunnel would need to be 40-60 metres below the present river bed. This would mean between 51 – 71 metres deep.
The river is said to be 11 metres deep. Any new tunnel would therefore be two to three times deeper than at present. This would necessitate a far longer entry and exit slope at both ends. This would be easier at the south side because there is more land before highway 17 and River Road. The north side would be far more complicated for connecting to Steveston Highway and require a long loop north, cutting across private land and the old Fantasy Gardens site, or a massive loop and bridge back over from the east.
(http://richmondbc.info/__shared/assets/Sch_2_PFM_GP_01181643348.pdf)

Every building above the low-rise level in Richmond, the tanks at the Annacis Island sewage treatment plant and a number of other huge structures built on the delta were designed with concrete raft foundations which spread the load. A box tunnel lays flat and does not create point loads like bridge foundations built on an array of deep piles. It seems reasonable that the bottom slab of the tunnel box could extend outwards to distribute the weight over a larger area, like a spread footing.
The geotechnical conditions would probably preclude deep bored tunnels because the soft soils extend too far downward in this location (in excess of 330 m / 1,100 ft) to gain adequate additional “traction” from more compact or solid soils, though this is not impossible as seen in much larger undersea tunnel projects around the world, though these projects would need to have similarly extremely deep soil conditions for a fair comparison. The key question is cost. A deep bored tunnel will extend several additional kilometres at both ends to maintain a reasonable slope. That will cost about $300M per km, but only for a narrow diameter tunnel. Even a 15 m diameter tunnel may be deemed inadequate. Seattle’s Bertha is 18 m for less than 50,000 vehicles a day, to some critics is THE definition of waste of public money. Increase the diameter to accommodate an adequate number of lanes and the cost escalates dramatically. How would a $5+B large diameter, deep bore tunnel over a longer length be justified for less than 80,000 vehicles and negligible transit? That’s $15+B with a 50-year debt amortization period and P3 profits.
Should a shallow tunnel flood, it can be pumped out a lot easier and quicker than a deep bored tunnel could. Geotech concerns were already expressed about the bridge foundations which, after all, have to support a 10-lane deck and two massive towers on two small points on the earth, but that info seems to have been suppressed, just like the cost of financing over 50 years (which was leaked to the Opposition by MoTI insiders after the Libs refused to release it). With geotech in mind, it is a sign of deep ignorance or possible negligence to portray the gargantuan bridge as a reinforced concrete structure instead of a much lighter (but likely more expensive) steel superstructure. Nonetheless, the thing could sink slowly over the years.
I don’t believe an experienced structural engineer would find it impossible to design fairly flexible waterproof joints between tunnel box segments reinforced with high-strength, non-corrodible steel cable bundles, seismic dampers, double or triple membranes, and other features. The Millennium Line, Evergreen Line and Canada line guideway segments are joined at several points with post-tensioned cable bundles pulled tight by a powerful electric winch then locked in place. The concrete joints are cast with precision and are very tight, giving a strong friction fit. The existing GM tunnel could be retrofitted further with some of these features.
Location is also important. The Alex Fraser bridge was built closer to the North Delta rise where the alluvial soils are shallower. Should the engineering challenges and expense of GM prove to be excessive, then twinning the AF may be a second choice while upgrading the existing GM tunnel. In my view the twin should be a two-lane rail transit-only bridge, or a four-lane rail + bus transit structure. The AF location is closer to the centres of population than GM, both north and south of the Fraser. The bridge deck is a bit more than 3 km to the 22nd Street Station, less than 5 km from Edmonds Station, and about 8 km to King George Station. It’s possible to conceive a large-scale SoF light rail network connecting to SkyTrain through several points on the south Burrard Peninsula rise (some tunnelling required) and extending southward with branches in all directions to Richmond, Tsawwassen, South Surrey / White Rock, North Delta and Surrey Centre. This would also be a great opportunity for North Delta to become a real city instead of remaining a mere bedroom community, and start generating its own town centres and concentrated employment corridors along new transit lines while gently infilling its land-hungry detached home subdivisions to do its share to accommodate the million+ people expected to arrive by mid-century.
This last concept illustrates how a relatively modest new bridge needn’t be considered only as a conduit for traffic and a generator of myths by being defined as a device to “relieve congestion.” These are not worthy city-building concepts because they are inhuman. However, as a more affordable piece of people-moving transit infrastructure, this alternative bridge idea will help to build a far more sustainable and humane Metro.