|Sepulveda Pass in 1962, courtesy of the Dick Whittington Collection at USC|
Hunter Communications Original News Source:
Link to Article:
How Sepulveda Canyon Became the 405
Excerpt: "Eventually, booming development in the San Fernando Valley during the 1920s persuaded the city and county to rebuild the road for automobiles. Traffic was overwhelming the two established routes between the Valley and the Basin, Cahuenga Pass and San Fernando Road, both of which were out of the way for residents of faraway Van Nuys and Owensmouth. New Sepulveda Boulevard – a 50-mile highway stretching between San Fernando and Long Beach – would provide the Valley with a more direct link to the Basin and harbor beyond at San Pedro Bay.
Construction lasted several years and culminated with the opening of a 650-foot tunnel beneath the summit at Mulholland Drive, an event the city celebrated with a grand Spanish-style fiesta. Despite the festivities, by the time traffic started flowing in September 1930, the new Sepulveda Canyon Road was already inadequate. Five years later the state spent $275,000 to pave it, and by the late 1950s traffic engineers had envisioned an audacious construction project that just might keep traffic flowing freely over Sepulveda Pass forever.
The engineers’ plan? Tear Sepulveda Canyon apart and then rebuild it to allow a superhighway to pass through. Beginning in August 1960, earthmovers carved a gorge 1,800 feet wide and 260 feet deep through the mountains, accomplishing in two years what might take natural erosional forces two million. The bulldozers' total haul: 13 million cubic yards of slate, shale, and dirt. Workers then built massive retaining walls to keep the unnaturally steep slopes from slipping and reconfigured the area's natural drainage through a series of culverts. By 1962, an eight-lane concrete freeway with a maximum grade of 5½% sliced through the mountains.
Though traffic did flow freely at first, the San Diego Freeway (originally signed as California 7 and later redesignated Intestate 405) eventually became one of the Southland’s most hated stretches of pavement. And so the work Lankershim and Van Nuys began in 1875 to improve an ancient trail continues to this day. Regional planners are now considering a menu of options – including an underground toll road, a subway, even a monorail – to relieve congestion, and in 2015 Metro completed a five-year, $1.1 billion project to widen the canyon’s concrete river and its artificial gorge."