|The Caldecott Tunnel, western end|
|Location||Oakland / Contra Costa County, California|
|Route||SR 24 (William Byron Rumford Freeway)|
|Opened||Bores 1 and 2: 1937
Bore 3: 1964
Bore 4 Est. Completion: 2013
|Length||Bores 1 and 2: 3,610 feet (1,100 m)
Bore 3: 3,771 feet (1,149 m)
|Number of lanes||2 per each bore|
The east-west tunnel is signed as a part of State Route 24, which is also known as the William Byron Rumford Freeway from Interstate 580 to Walnut Creek, and connects Oakland to central Contra Costa County. (The name of the freeway was the Grove-Shafter Freeway until 1980, when it was named after Rumford.) The tunnel is named after Thomas E. Caldecott (1878–1951), mayor of Berkeley from 1930–1932, member of the Alameda County Board of Supervisors 1933-1945, and president of Joint Highway District 13, which built the first two bores.
Bore 1 (the southernmost bore) and Bore 2 were completed in 1937 and are each 3,610 feet (1,100 m) long and carry two lanes of traffic. Bore 3 (the northernmost bore), built in 1964, is 3,771 feet (1,149 m) in length, and also carries two traffic lanes.The middle bore (Bore 2) can be reversed to accommodate heavy traffic. Generally, it carries westbound traffic from about midnight to noon and eastbound traffic from about noon to midnight.
Construction and expansion 
In the 19th century, traffic over the Berkeley Hills in this area went up Harwood Canyon, now known as Claremont Canyon (behind the Claremont Hotel). The road leading up the canyon from the west was initially called Harwood's Road, later changed to Telegraph Road, and finally, Claremont. The road on the other side of the hills was, and remains, Fish Ranch Road. An inn and stage coach stop called the Summit House once existed at the summit.
The idea of a tunnel through the hills began as early as 1860. In that year, the idea was proposed and rejected by the citizens of Alameda and Contra Costa Counties. It was revived in 1871 with a proposal which described a route running from the end of Broadway, similar to the actual routing of today's Caldecott Tunnel although it is not clear from the description exactly which canyon was being referred to. The proposed tunnel would be only some 500 feet long and would have its outlet in the San Pablo Creek watershed with a road leading into Lafayette. A franchise was granted to a group of developers who passed the franchise onto another group. The proposal languished until the turn of the century.
In 1903 a tunnel was finally built above the present location of the Caldecott Tunnel, in the next canyon south of Claremont Canyon. This tunnel was approached by a new road dubbed "Tunnel Road" which started at the top of Ashby Avenue in Berkeley. The west end of the tunnel was at about while the east end of the tunnel is now in private property owned by the East Bay Regional Park District, on the former site of the Canary Cafe. This tunnel was known as the Kennedy Tunnel, the Inter-County Tunnel or the Broadway tunnel. "Local Intelligence: Kennedy Tunnel". The tunnel was very narrow and arched, such that two tall buggies could not pass each other. A system of lighting a small fire with a newspaper was used to control this one-way traffic. The tunnel height was increased in 1915 by 3 feet to accommodate larger vehicles. When the new Caldecott tunnel was completed, the Kennedy tunnel remained as a pedestrian tunnel, until it was sealed in 1947. "Lafayette: A Pictorial History".
In 1929 construction of the first two bores of the Caldecott Tunnel began. They were completed in 1937, and were originally known as the Broadway Low Level Tunnel as the approach was from the top of Broadway in Oakland, and was below the portal of the old tunnel. However, access from Ashby Avenue was retained as it was designated the connecting thoroughfare from the Eastshore Highway (now Freeway) and the San Francisco – Oakland Bay Bridge, and dubbed State Highway 24. The approach to the east portal on the other side of the Berkeley Hills was via Mount Diablo Blvd., also at that time part of State Highway 24.
The third bore opened in 1964. In the late 1960s the Grove-Shafter Freeway was completed and replaced Broadway as the main route to the Caldecott Tunnel from Oakland as well as replacing Ashby for traffic coming from San Francisco. Ashby Avenue and Tunnel Road were redesignated State Highway 13 and aligned with the new Warren Freeway through the Montclair District of Oakland. The Grove-Shafter Freeway was then designated State Highway 24.
The Caldecott Tunnel was designated a City of Oakland Landmark in 1980, and later received a Preservation Award from the Art Deco Society of California in 1993.
In 2000 the California Department of Transportation began planning for a fourth bore. On February 28, 2007, the California Transportation Commission approved the final funding needed to build the fourth bore. On February 14, 2010 construction of the fourth bore began with the removal of trees at the sites of the future east and west portals. Tunnel breakthrough in the construction of the fourth bore occurred on November 29, 2011. Excavation was completed on August 8, 2012.  Construction is scheduled to be completed by late 2013, with final landscaping completed in 2014.
Incidents and accidents 
On April 7, 1982, an accident involving a gasoline tanker truck in the north bore set off the Caldecott Tunnel fire. The accident caused major damage, and the bore was closed to traffic for several months while repairs were made. During the fire, the tunnel acted as a natural chimney venting the smoke, flames and heat uphill towards the east side entrance to the tunnel. The accident and fire killed seven people, most of whom were overcome by toxic smoke. The fire occurred shortly after midnight when there were few cars in the tunnel; had it occurred during normal commute hours, hundreds could have died. As a result of the fire, it is now illegal to transport hazardous material in a tanker truck through the tunnel except between the light traffic hours of 3:00 a.m. and 5:00 a.m.
In October 1991 the catastrophic Oakland firestorm started on the ridge north of the Caldecott Tunnel. The fire spread quickly west down both sides of the west portal of the tunnel on its way to killing 25 and destroying over three thousand homes, apartments and condominiums.
On July 26, 2007 a car broke out into flames and 2 of the 3 bores were closed down.
Weather phenomena 
Weather conditions can vary greatly from one end of the tunnel to the other. In summer, for example, motorists may enter the tunnel from the east where it is sunny and warm, and emerge on the west end into fog and cold. In winter, during spells of inland tule fog, the reverse can occur.
On a sunny day, it may be well over 90 °F (32 °C) at the east portal, due to the inland nature, while a more coastal-like 70 °F (21 °C) on the Oakland side.
See also 
- Berkeley Hills Tunnel — BART rail transit tunnel, running approximately parallel to the Caldecott Tunnel
||This article uses bare URLs for citations. (April 2013)|
- Carolyn Lochhead, Chronicle Washington Bureau (2009-07-12). "Impatience builds over slow-moving stimulus". Sfgate.com. Retrieved 2010-01-23.
- Cabanatuan, Michael (2010-01-23). "Work begins on Caldecott Tunnel's 4th bore". Sfgate.com. Retrieved 2010-01-23.
- History of Contra Costa County ... - Google Books. Retrieved 2010-01-23.
- Caldecott tunnel excavation completed, San Francisco Chronicle, August 12, 2012
- "http://www.caldecott-tunnel.org/index.php/overview/schedule". Caldecott Tunnel Fourth Bore Project Schedule.
- – Murilee Martin (2007-04-16). "25 Years Since The Great Caldecott Tunnel Fire - News". Jalopnik. Retrieved 2010-01-23.
- "V.C. Section 31301 - Caldecott Tunnel Restriction". Dmv.ca.gov. 1982-09-20. Retrieved 2010-01-23.
- California Department of Transportation website on the Caldecott Improvement Project
- Construction Photo (1936) of the West Portal, Contra Costa Historical Society
- Aerial View (1936) Showing Old and New Tunnels, Contra Costa Historical Society