Cleaning out some old computer files, I came across this blast from the past: a 2001 Seattle Times article on Seattle’s seismically-vulnerable Alaskan Way Viaduct, which contained this little gem…
A 1996 study by engineers at the University of Washington found that the viaduct was built on soil that could liquefy in an earthquake. Engineers also found problems in the way the columns were connected to the foundation.
The UW study concluded that retrofitting would cost $340 million, tearing it down about $120 million and replacing it $530 million.
OK, picking apart old cost estimates is like shooting fish in a barrel. Still, the UW estimates from 1996 now seem somewhere between quaint and comical, considering that the current cost estimate for replacing the Viaduct with a deep-bore tunnel is $3.1 billion—or $4.2 billion, if you also include related improvements to streets, transit and the waterfront.
It’s not just inflation that’s driven up the cost. The real problem is that these sorts of mega-projects tend to be financially risky: cost estimates rise the harder you look at the project, and the projects themselves rarely go according to plan. Bent Flyvberg, a world expert on megaprojects, finds that…
…real cost overruns of between 50 and 100 per cent are common, and overruns above 100 per cent are not uncommon, while demand is typically overestimated, with typical overestimates between 20 and 70 per cent.
(Sadly—and to be fair to the substance of Flyvberg’s research—these sorts of problems are particularly prevalent in urban rail.)