For decades, underground highways in Southern California were a frustrated commuter's fantasy -- too costly, too hard to build and, given the wealth of land, not necessary.
But Los Angeles is in its 18th year as the nation's most congested metropolis, freeways have little or no space for new lanes and traffic experts are running out of time-shaving options.
For The Record
Los Angeles Times Tuesday September 20, 2005 Home Edition Main News Part A Page 2 National Desk 1 inches; 45 words Type of Material: Correction
Tunnel map -- A map with a story in Sunday's Section A about proposed tunnel projects in Southern California showed California Highway 39 connecting with California 2, the Angeles Crest Highway. California 39 is closed about three miles short of California 2 because of landslides.
So civic leaders are joining engineers to consider burrowing the longest highway tunnels in America.
"Tunnels," said Wolfgang Roth, a geotechnical engineer working on one possible project in the Antelope Valley, "may finally have their day."
Three massive projects are under study in Southern California, each dwarfing any of the nation's 337 underground roadways, including the 2.6-mile tunnel in Boston's infamous "Big Dig," the most costly public works project in U.S. history:
* Congress recently approved $2.4 million to study a five-mile, $2-billion tunnel that would help link the Long Beach and Foothill freeways in Pasadena and South Pasadena, and keep 100,000 cars a day off city streets.
* For Orange and Riverside counties, Congress set aside $16 million to study a 12-mile tunnel that would connect fast-growing commuter towns in the Inland Empire to jobs on the coastal plain. Buried beneath Cleveland National Forest and projected to cost from $3.5 billion to $5 billion, it would be the second-longest in the world -- after a 15.2-mile project in Norway.
* A complex of tunnels and surface highways under study by the city of Palmdale would slice 23 miles directly though the San Gabriel Mountains from the Antelope Valley to Glendale, cutting the commute in half. It could cost $3.1 billion or more.
While some policy makers remain skeptical, others say engineering breakthroughs in Europe and Japan have made tunnels faster to build and more affordable -- especially where real estate prices have pushed the cost of new freeways skyward.
"The technology has evolved, so tunnels are becoming truly competitive alternatives," said Mark Pisano, executive director of the Southern California Assn. of Governments.
Giant tunnel-boring machines can drill quickly through the earth, cutting holes 45 feet in diameter. "If the hard rock stands up nice, the boring machine eats right through," said Roth. "Even with the fractured hard rock, as the machine advances, you stabilize the tunnel walls with rock bolts or 'shotcrete,' " he said, using the futuristic term for sprayed concrete.
Another benefit of tunnels is that they seem to generate less political dust than surface roads.
"There's a new interest in the invisible highway -- getting them out of sight," said engineer Harry Capers, tunnels committee chairman for the American Assn. of State Highway and Transportation Officials, citing projects in New Jersey, Maryland and New England. "It's been catching on."
Nothing makes tunnels more attractive, however, than dire traffic projections.
With Southern California's population projected to grow from 18 million to 23 million by 2030 -- and with three of four motorists still traveling alone -- the average speed on most area freeways during the peak morning commute is expected to drop from 34 mph to 20 mph or less.
Long tunnels, however, are not simple to build. Even the 31-mile English Channel train tunnel, an engineering wonder, took much longer than anticipated and cost double the original estimate.
Southern California, with its mountainous terrain, underground aquifers and seismic vulnerabilities, may prove the ultimate testing ground for subterranean highways.
The San Gabriel Mountains, through which the Antelope Valley connector would run, are "fault-infested," said Leon Silver, a retired Caltech professor, citing two known faults the proposed tunnels would cross.
"One has to be extraordinarily careful," he said. "There are more faults in the San Gabriels that we don't know about than we do."
Another consideration is groundwater, which can make tunnels cumbersome to construct and vulnerable to damage. Dig too deep in Cleveland National Forest, for instance, and pressure from groundwater could crack the tunnel lining. Planners say they can go no farther down than 750 feet, and may need to place some of the roadway above ground.
Roadway tunnels carry their own dangers as well. With narrow confines and limited ability to vent smoke, they've seen serious accidents.
In one 1999 crash, oil from a damaged truck caught fire inside the seven-mile Mont Blanc tunnel between France and Italy. Nearly 40 people died.
Perhaps the greatest obstacle to highway tunnels is cost, especially given the fierce competition for funds to expand rail, bus and highway systems across the state. An underground passageway can easily cost two to three times as much per mile as a freeway. The most obvious funding solutions are onerous: steep gas taxes or tolls.
