Down the Tube: Part 1

The other day I needed to bicycle to a part of Alameda that I never visit, so I did the natural thing and used an on-line map to investigate. The route looked predictable until I got to step 24: "Turn left on Posey Tube Trail - Take the stairs." That's when it dawned on me that while I knew one could theoretically walk or cycle on the sidewalk through the Posey Tube, I'd never actually tried to do so. In fact, I'd never personally met anyone who had attempted this passage.

Posey Tube Portal

Each day, about 50,000 drivers in the San Francisco Bay Area use the Webster and Posey Tubes, tunnels that allow vehicles to pass under the estuary separating Alameda and Oakland, California. Only a few dozen intrepid pedestrians and bicyclists brave the Posey Tube on any given day, at least according to a City of Alameda Estuary Crossing Study from 2009. Seems to me there are four basic reasons for the imbalance between motorized and non-motorized use: Only the Posey Tube is accessible for pedestrians and bicyclists, that access is a single four-foot wide sidewalk, the air quality inside the tube is awful, and the noise is deafening. In short, when non-motorized commuters succeed in finding their way to the Posey Tube, they may wish they hadn't.

The Posey tube (named after George Posey, Chief Engineer and County Supervisor) was the first tube constructed at a cost of about $4.5 million.  Completed in 1928, it replaced the problematic Webster Street swing bridge that hampered ship access to the inner bay. The old swing bridge was disabled at least once when it was struck by a ship and the bridge was scrapped after the Posey Tube opened. The Posey Tube originally featured one lane leading to Alameda and the other leading to Oakland. When the Webster Tube was completed some 35 years later in 1963, it became a oneway route to Alameda and the Posey Tube became a oneway route to Oakland. Both tubes were constructed by sinking pre-cast concrete sections and then connecting them once they were underwater.

I have no real need to use the Posey Tube as part of my regular bicycle commute, but nevertheless there's an odd attraction to trying my hand at it, at least once. Maybe it's the fact that part of the futuristic getaway chase scene in George Lucas' directorial debut, THX 1138, was filmed in the Posey Tube. Or maybe it's the deco-inspired structure that houses the fans that remove (most of) the vehicle exhaust from the Posey Tube. Or maybe it's that so few people attempt to travel through the Posy Tube in anything but a motor vehicle. Whatever the reason, I hereby vow to traverse the Posey Tube. At least once.

Rather than just showing up on my bike and taking the plunge, I wanted to conduct some reconnaissance and clear up some confusion about these structures. Why can non-motorized users only access the Posey Tube and not the Webster Tube? Why is only one sidewalk open to pedestrians and cyclists?

Finding the pedestrian/bicycle access to the Posey Tube involves navigating a maze of oneway and dead end streets in the Forth Street neighborhood, almost beneath interstate 880. It's fairly easy if you use an on-line map. Once you get to 4th Street, locate the intersection with Harrison Street and you'll be at the foot of the Posey Tube's deco-inspired ventilation structure.

A quick drive in my car provided more answers. The Posey Tube was constructed with sidewalks on both sides, but only the right (southeast) side is open to pedestrian and bike traffic. The lefthand (northwest) sidewalk has emergency call boxes and what appears to be a fire sprinkler system. The pipe and sprinkler heads anchored to the sidewalk surface would certainly present a hazard to any bike or pedestrian who might try to use that sidewalk, but the point is moot: Access to that sidewalk is blocked by a locked gate on the Oakland side.

Wrong side. No Entry. Or Exit for that matter.

The newer Webster Tube was constructed with only one sidewalk on the right (or northwest) side. Emergency call boxes are stationed along this walk, every few hundred yards, leading one to conclude the Webster Tube's only sidewalk is intended for emergency use by a driver of a disabled vehicle or fire crews.

Make your way to the southeast side of the Posey ventilation structure and you'll encounter a weight-lifting gym, occasional piles of rubbish and, quite possibly, the strong smell of urine. Eventually you'll find a stairway that leads down to the Posey Tube Trail. If the stairway is blocked by a locked gate, you're on the wrong side.

Southeast entry. All hope abandon ye who enter here...

Walk down the stairs of the southeast side (carrying your bike, if necessary) and you will have entered the Oakland pedestrian portal to the Posey Tube.

What comes down, must go up ...

During the short period I stood photographing at the portal (at 3:30pm on a Monday), three cyclists came through to the Oakland side. Since the path is too narrow for bikes to pass in opposite directions, the common procedure is for one cyclist to pick up their bike and dangle it over the railing to allow the other cyclist to pass. I will probably try to transit the Posey Tube during non-peak hours for both motorized and non-motorized vehicles. And I'll probably take my BikeFriday since it is lightweight and has fairly narrow handlebars. I intend to video my transiting the Posey Tube, so stay tuned.