Boston’s Big Dig Tunnel and Climate Change: Good news and bad news

Those of us who live and work in the post-Sandy Northeastern U. S. are painfully aware of the bad things that happen when salty seawater floods transportation infrastructure.  And unfortunately the future portends both significant sea level rise and an increase in extreme weather events.  Fortunately, lots of clever people are working hard to evaluate the vulnerability of key infrastructure and what to do about it.

So, how bad would it be if Boston’s Big Dig tunnel system (which carries I-93 under downtown) was flooded?  Very bad.  Even if one element of the system were knocked out, it could shut down a lot of central Boston, the Interstate highway system, and possibly some subway lines, making a transportation mess at just the time you would need maximum recovery (and potentially evacuation) capacity.

So a new study led by Ellen Douglas of UMass Boston, assessing the Big Dig’s vulnerability, is very timely.  The study team inventoried assets (tunnels, vents, buildings, etc.), undertook sophisticated hydrodynamic modeling (including both hurricanes and Nor’easters), and developed statistical probabilities for flooding at hundreds of locations.  The verdict?

The good news is that most of the Big Dig’s facilities have only a small chance of being flooded, and that is likely only in the most extreme events.

The bad news is that the most vulnerable facilities are actually the portal ramps that take traffic from surface level to the tunnels and vice versa.  Even so, it appears to be a solvable problem.  The “fix” for portal vulnerability is probably floodgates, which is likely to cost in the tens of millions of dollars rather than hundreds of millions.  And these can probably be designed and built over time.

Congratulations to the study team (the results are in a webinar slide show, which should be available soon on the ICNet website at http://theicnet.org/).  The takeaway for the rest of us, I think, is that key infrastructure elements in exposed locations are all going to need detailed, site-specific analysis.  If these are done right, they can save us from at least some of the ravages of future Sandys.