Anybody Seen Tony & Doug Around Here?

Part of the nearly $1 billion upgrade to the Silicon Valley Clean Water system — the joint powers authority that accepts, treats and cleans all the sewage from Belmont down to the northern parts of Menlo Park — involves upgrading the main pipelines that feed into the facility at the eastern edge of Redwood Shores.

The existing pipelines are large — about 4.5 feet in diameter — but the new pipelines are huge: 10 feet in diameter! And they are contained within a 16 foot wide tunnel 40 feet or more underground. Extending from just south of San Carlos Airport, under the airport and then out to the shore.

Naturally such a large pipeline couldn’t be laid by the simple expedient of digging a ditch, laying the pipe, and burying it. That would involve moving staggering amounts of dirt and muck and, more importantly, would drastically impact the airport and a lot of businesses, homes, roads, etc. Upgrading infrastructure that serves a large and growing community — and must exist inside the community — is a challenge.

So instead the engineers went a different route: they ordered a custom-built tunnel boring machine and dug out a tunnel under the ground, lining it with concrete walls, all without disturbing anyone living or working above them.

Today I got to walk through part of the first completed section, which basically runs underneath the airport for about a mile. Here’s the north end where we started, just south of the San Carlos Transfer Station (aka “the dump”):

Tunnel North End (click to enlarge)

Things get surreal pretty fast walking through the tunnel. Pretty soon you’re lost in the darkness except for the light cast by the work lights:

We stopped about a thousand feet in, after the last turn1. From that point it’s straight shot for almost a mile to the south end:

Anybody seen a couple of well-dressed nerds down here?
(click to enlarge)

Which makes it look suspiciously like a rumored secret government installation built in the 1960s… 🙂


  1. The boring machine has a 650 turning radius…which doesn’t sound like much, but when you remember it’s a 600+ foot long machine — made of multiple connected cars, each of which performs a function necessary to cutting and building the tunnel — it’s actually pretty impressive. 

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