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Alto Tunnel bike, pedestrian plan is a costly pipe dream

The Marin County Bicycle Coalition’s periodic campaigns to reconstruct the half-mile-long Alto Tunnel make the proposal sound deceptively simple by using the misnomer “reopen,” whereas the project’s realities are much more complex.

I prefer the term “reconstruct,” because the proposal is effectively a new bore. The tunnel was partially filled with concrete to stabilize it after the collapse of its southern section in 1982 and, according to the most recent study in 2017 (which involved lowering cameras into its midsection), the entire center section has also collapsed, compromising its structural integrity.

In all discussions about the tunnel, the biggest obstacle has been the cost, not only of the reconstruction itself, but also of acquiring and developing the various segments of rights of way needed to perfect access to its portals. Advocates have consistently underestimated those costs and played down the impacts of such a massive project on the neighborhoods that have been built up around the route since the tunnel was abandoned.

There are two homes above the tunnel’s portals. In my educated opinion (and of several other experts I have consulted), both would have to be vacated in order to stabilize them prior to completing the bore. One of those properties is a true blocking parcel, with an expensive home under which the county has no access rights whatsoever; acquiring those rights would require a taking.

Additionally, there are several parcels on the Corte Madera side under which the county does not own or control the right of way, and two parcels in the middle of the tunnel, still owned by the Union Pacific Railroad, which won’t release them without full indemnification.

There are two alternatives available to cyclists who want to travel between Mill Valley and Corte Madera — the bike lane on Camino Alto, which could be widened, and the Horse Hill multi-use path, which could be regraded. County consultants have estimated the cost of optimizing those routes to be a small fraction of the cost of reconstructing the tunnel.

As far as I can tell, the tunnel proposal has tepid political support. It certainly has strong neighborhood opposition on both the Mill Valley and the Corte Madera sides. Improving the Horse Hill route seems to have political support and no neighborhood opposition.

In 2009, county consultants estimated the all-in cost to reconstruct the tunnel at approximately $60 million. In 2017, after the referenced study of the tunnel’s collapsed interior was completed, they estimated approximately the same cost. However, in order to do so, they devised a new plan, shrinking the width of the bore from the tunnel’s original 16-foot width to 11.5 feet. I suspect that is simply too narrow to accommodate safe two-way traffic for bicycles and pedestrians.

Since 2009, construction, labor and materials costs have increased dramatically. The cost of a proper, 16-foot-wide re-bore of the tunnel today — after acquiring the expired easements and blocking parcels, as well as stabilizing or acquiring the homes above the portals — could easily cost more than $125 million.

Then there is the matter of cost overruns. Referring to the $300 million cost overrun of San Francisco’s Transbay Terminal, then Mayor Willie Brown famously wrote,

“We always knew that the initial estimate was way under the real cost. Just like we never had a real cost for … the Bay Bridge or any other massive construction project. In the world of civic projects, the first budget is really just a down payment.”

The world’s foremost expert on infrastructure cost overruns, Danish professor Bent Flyvbjerg, author of the book, “Megaprojects and Risk,” studied hundreds of transportation projects around the world; he found that 90% exceeded their budgets, and concluded “it seems unlikely that a whole profession of forecasting experts would continue to make the same mistakes decade after decade.”

In other words, project promoters pressure planners to low-ball their initial cost estimates, a problem Flyvbjerg calls the “strategic misrepresentation” of project costs. Flyvbjerg divided projects into categories and regions, noting that tunnels in North America average 33.8% in cost overruns.

The true cost of this proposal is enormous — that much money could go a long way toward solving actual transportation problems.

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