Heavy equipment that was removing debris shut down for the night 15 minutes later, but firefighters and others continued to shine flashlights and probe metal rods into the wreckage throughout the early morning hours. Dogs used in the Mexico City earthquake crawled among the rubble sniffing for survivors before the canine search was called off on Wednesday afternoon.
Cranes, bulldozers and other heavy equipment brought to the site by iron workers, carpenters and construction workers stood idle much of Wednesday as Caltrans officials tried to figure out how to extricate the victims and the cars without sending the freeway section to the ground.
"It is possible that if a piece of concrete is moved, the rest will come down like a domino," said Craig Kocian, Oakland's acting city manager. "Caltrans is making the decision how and when to move the blocks. Right now, it is like a deck of cards."
By late afternoon, workers had begun reinforcing the freeway with steel and wood pipes to prevent another collapse, and a huge Navy helicopter lifted a tractor that could be operated by remote control on top of the upper deck. The tractor was to be used to remove concrete burying the vehicles.
Many of the volunteer rescuers were exasperated by their inability to do more. "Hey, if there are people alive up there, why can't we get them out?" asked Dwain Tolbert, 32, a construction worker. "We are volunteering. If we get killed, it's our own business."
As volunteers grumbled about their uselessness, Caltrans officials expressed similar frustration about their inability to understand why the freeway collapsed. Greg Bayol, a spokesman for the Caltrans San Francisco office, said the freeway might have tumbled either because the sections pulled apart or because the columns holding the upper deck twisted. Twisting might have been prevented by jacketing the concrete columns in steel, a "minimal" project, he said.
"Are we doing soul searching? Of course we are," he said. "The idea that a highway had the potential of killing 300 people--it's horrible."
William Schaefer, Caltrans' chief engineer, disputed Bayol's contention that the collapse could have been prevented. He said researchers at UC San Diego are now trying to devise ways to make multi-columned freeways earthquake-safe but they probably won't have any answers for another year. Although engineers know how to design such safe structures, they do not know how to retrofit existing freeways, he said.
The Nimitz section was retrofitted in 1977 to prevent it from pulling apart latterly in an earthquake under a $54.2-million statewide program. Schaefer said that the retrofitting appears to have prevented the freeway from falling laterally off its support systems but obviously didn't resolve other problems that caused the collapse.
"We don't know why it collapsed," he said. "We're trying to find out."