I posted Nick's letter below because it was rational, thoughtful, and practical. However, I don't necessarily buy all of his premises (that the state would usurp all viaduct money if the replacement weren't a tunnel, thereby leaving zero money for traffic throughput that the state is adamant we need; that the mayor and mayor alone is responsible for posing a tunnel alternative, when it was Licata and the council who were around when the impractical decisions were being made; that a three-way vote in 2007 would have settled this dispute). But again, Nick's letter was great so I ran it.
But it doesn't touch on this sort thing, a problem with roadway megaprojects and tunnels that are oversold, overpriced, and underused:
ONE of Queensland's largest initial public offerings, Rivercity Motorway, has collapsed, owing $1.3 billion. ... Rivercity's initial traffic forecasts predicted the road would carry 60,000 vehicles a day and that this could increase to 100,000 within 18 months. But traffic volumes are closer to 20,000 vehicles, despite initial moves to discount the toll by as much as 50 per cent to encourage motorists. [...]
Rivercity was forced to write down the value of its assets by $1.56bn to $258 million last year, based on revised traffic forecasts for the $3bn tollroad. Actual traffic on the road in the first year of operation was less than a third of the originally forecast 60,000.
Megaproject proponents who ballyhoo them as less risky and more useful than they really are account for the number-one reason projects like these don't meet their budget. For the deep-bore tunnel, we're relying on $400 million in tolling bonds and assuming that 40,000 vehicles a day will pay $3.50-$4.00 tolls in each direction at peak hours. Will people pay that much (when I-5 and surface streets have no tolls) and will 40,000 drivers a day use it? The people behind this tunnel say yes, don't worry.