Nine tractor-trailer rigs hauling 130 tons of steel plate from Pennsylvania and Texas rolled into the night Wednesday, each "double-teamed" with two drivers so they wouldn't have to stop until they arrived in Coolidge, Ariz., today.

Their urgent mission: Provide Stinger Welding Co. with enough material to fashion steel girders to replace the steel that melted like plastic in an inferno of burning gasoline April 29.

Stinger stands to earn 25 percent of the $200,000-a-day bonus promised by Caltrans to Rancho Cordova contractor C.C. Myers if it beats the June 27 deadline for rebuilding the Interstate 580 connector ramp that collapsed in the heat of the tanker-truck accident and fire.

Last week transportation officials expressed concern that steel might be difficult to come by in a hurry, but plans laid quickly by C.C. Myers and Stinger seem to have put those fears to rest.

"I don't see it being a huge thing," said Stinger's president, Carl Douglas. "It was not difficult to find it. We are heavily involved in the steel market."

On the other hand, the 2-inch steel plate needed for the top of the I-beams that will hold the concrete decking was only available from one supplier in the entire country, he explained.

Four truckloads of the thicker plate left the A588 & A572 Steel Company in Sewickley, Pa., on Tuesday morning and is due to arrive at Stinger tonight, Douglas said.

Five truckloads of the other steel, in half-inch plate for the "web" that connects the top and bottom of each I-beam, and 1-inch plate for the tops, left Ranger Steel in Houston on Tuesday and should arrive today.

"We'll get to work," he said, of his 60 workers, on two extended shifts, "as soon as the material comes through the door."

Meanwhile, the driver of the tanker, James Mosqueda, was discharged Tuesday from St. Francis Memorial Hospital in San Francisco, said hospital spokeswoman Linda Gillespie. He crashed a tanker carrying 8,600 gallons of gasoline in the early morning hours April 29.

Mosqueda was treated for second-degree burns on his hands, arms and face at St. Francis over the previous nine days, after being transferred to the hospital's specialized burn center from Kaiser Permanente Oakland.

After surviving the crash on the ramp from westbound

I-80 to southbound I-880, Mosqueda escaped the truck with second-degree burns on his face, hands and arms. Fleeing the fire that would defy firefighters' efforts and melt massive steel beams, Mosqueda walked nearly a mile and found a cab driver to take him to Kaiser.

As work moved along quickly, large numbers of commuters continued to ride public transit, keeping traffic lighter than usual and making the maze detours through Oakland manageable.

The Bay Area Rapid Transit system announced Tuesday that last week was the busiest in the system's nearly 35-year history.

BART trains, which were longer and more frequent to handle the extra load, carried passengers on 2.13 million trips, beating the previous record of 2.11 million trips set during Fleet Week in October.

"Clearly, people turned to transit after the meltdown at the maze," said BART spokesman Linton Johnson, explaining that the system added 22 cars to its normal 515 operational cars last week. There are 669 BART cars, but many are normally sidetracked for maintenance or on standby.

Even with the excess riders, Johnson added, the system has not suffered unusual complications and has maintained its goal of running 94 percent on-time.