Keep Oakland Beautiful Point Of Interest: Caldecott Tunnel.

Keep Oakland Beautiful Points of Interest remind us of how interesting and beautiful Oakland is and why we should care about protecting it. Please click on the photos to enlarge and clarify them.

One of the most well-known features in Oakland is the Caldecott Tunnel (now four tunnels). But, even though many of us pass through these tunnels on a frequent basis, we don’t know much about them.

A century or so ago, a tunnel through the Oakland Hills, connecting Oakland and Orinda, was needed as a speedy alternative to going over the hills. The first tunnel (known as the Kennedy Tunnel, as well as the Broadway High-Level Tunnel and the Inter-County Tunnel) was opened in 1903, but it was small and narrow, only allowing one horse-drawn buggy at a time to pass through (please see a prior blog, Keep Oakland Beautiful Point Of Interest: Kennedy Tunnel). It was an improvement, but it wasn’t an adequate solution as the area’s population and use of automobiles increased. A more comprehensive tunnel was in order.

Digging on the first two bores of the Caldecott Tunnel began in 1929. It took eight years to dig a pair of 3,610-foot tunnels and prepare them to receive traffic. They opened in 1937, one bore allowing traffic to go through the hills in an easterly direction, the other serving westbound traffic.

As the area’s population and automobile use continued to expand, a third tunnel bore was opened in 1964. The addition of this third tunnel allowed the central bore to be used in either direction, via a pop-up lane control system. Thus, two bores were open to westbound traffic during morning rush hour and two were open to eastbound traffic in the afternoon and evenings.

Tunnel 1
Using federal economic stimulus funds, a fourth, state-of-the-art bore was started in 2009. The bore was excavated simultaneously from both sides of the hill, using large machines called ‘roadheaders,’ that grind the rock. Once an opening was made in the rock, it was shored up with steel rods and concrete shot from a high-pressure hose.

tunnel 2

The new Caldecott bore was opened in 2013. It includes 19 jet fans that can quickly remove smoke and other pollutants in case of emergency and it contains sensors that detect levels of carbon monoxide and nitrous oxide in the tunnel.tunnel 3

Today, traffic in bores one and two (the southernmost two bores) flows to the east while bores three and four support westbound traffic.

Here are a few other factoids, associated with the Caldecott Tunnel:

  • The tunnel was named for Thomas Caldecott who was a member of the Alameda County Board of Supervisors and president of Joint Highway District 13 which built the original two bores. Mr. Caldecott was also mayor of Berkeley from 1930 to 1932.
  • During construction of the bores, diggers found fossils of an ancient rhinoceros, a whale, a young mastodon, a camel, a three-toed, dwarf horse, and various plants.
  • The tunnel crosses over the Hayward Fault, a major earthquake zone.
  • Weather conditions between the two ends of the 0.7 mile tunnel can be strikingly different, especially in the summer. Temperature differences at the two tunnel mouths can exceed 20 degrees Fahrenheit and you can enter the eastern mouth of the tunnel in bright sunshine and exit a minute later in cool, Oakland fog.
  • The Oakland Hills Firestorm of 1991 started just north of the tunnel. The fire encompassed both western portals.
  • Today, the Caldecott Tunnel serves about 160,000 commuters daily.
  • The tunnel is a City of Oakland landmark.
  • Six art-deco medallions designed by area elementary school students adorn the fourth bore, three over each tunnel mouth. The designs celebrate the Caldecott Tunnel and its natural setting between Alameda and Contra Costa counties, using the recurring imagery of the sun.

tunnel 4

The six art-deco medallions on the fourth bore portals. The three larger ones are located on the Oakland portal.

Keeping Oakland Beautiful is everybody’s business.

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