Battle of the Engineering Consultants On Tysons Tunnel

Proponents of a an underground rail line through Tysons Corner have produced reports from their consulting engineers predicting that a tunnel will cost no more than an above-ground line and take no more time.

Governor Kaine, who so far opposes a tunnel (but who we believe is probably open-minded), has now released a report from his consulting engineers stating that a Tysons tunnel will cost more and take longer to build than an above-ground rail line. (See Washington Post story here.)

As anyone who lives inside the Beltway is well aware, you can always find a consultant to say whatever you want. You could even still find a couple people with scientific degrees who would dispute that smoking is harmful to health.

So, who to believe?

Let's start with the Tunnel's proponents. Clearly, they want a tunnel and they're going to hire consultants who'll come up with figures to support their plan. That's not to say they're dishonest. Rather, they suffer from a significant optimism bias. You can see that in the report of the Governor's consultants, who note that it's not practical to run a tunnel boring machine (like the one pictured here)24-hours a day without some maintenance delays.
They also note that the advanced tunnel boring technology advocated by the Tyson Tunnel proponents has not been used on tunnels as large as those for Metrorail. So, let's just say that the Tunnel proponents are presenting, at best, a very rosy view. Experience shows that with complex high tech construction projects, such rosy views almost never prevail.

That said--and before you tunnel proponents hit the comment button to skewer us--the Governor's report doesn't make a terrific case for the above-ground version. The Governor's engineers say it will cost roughly $160 million more (at a minimum) for the tunnel, and add six months to the project's construction timetable (they add more time for non-construction delays). IF a tunnel would cost only $160 million more on a $4 billion project, and IF it would delay things only another six months, then WE think the tunnel is a viable option.

The biggest variable is whether going for a tunnel would also jeopardize $900 million in federal funding, without which nothing will be built. We don't think folks should sit around and speculate about this--instead, there should be a sit-down with the right people. If the feds are open to a tunnel--and we think they may be--then the tunnel option should be back on the table. (Yes, we know, this is a reversal of our position a few weeks ago; we've been trying to read up since then.)

That said, we also don't buy the doom and gloom predictions about the consequences of having an above-ground rail line through Tysons. Arlington County Board member Chris Zimmerman, who also sits on Metro's board, is correct that this is "once-in-a-generation" issue, i.e., one with major consequences for Northern Virginia over the next 30-50 years.

All things being equal, a tunnel through Tysons would probably be better than an above-ground line. But the above-ground line is hardly a disaster. Tysons would do just fine with such a rail line--it would prosper and grow and incorporate the design into its future.

Our bottom line: the burden is on Tunnel proponents to establish that a Tunnel will not endanger federal funding, nor will it unduly delay the entire process. If they can get by those hurdles, then the Tunnel is the way to go.