The CHP was notified at about 8:05 p.m. of the crash, which did not block traffic or cause other accidents, Caggiano said.
Two eastbound lanes were closed until about 1:20 a.m. as Caltrans crews cleared the big-rig and cleaned up more than 60 gallons of diesel fuel that spilled during the crash.
The white 2000 Peterbilt tractor, which was hauling a load of rubbish in an open-top trailer, had been navigating an on-ramp that leads from West Grand Avenue to the MacArthur Maze, CHP Officer Ralph Caggiano said.
"Somehow he lost control of his truck, and on that transition ramp, instead of turning right with the curve, he lost control and went left over the side," Caggiano said.
The truck landed in the grassy shoulder that borders eastbound I-80 before the split with Interstate Highway 580.
The driver sustained a broken arm from the crash and the trailer spilled some of its load onto the grassy patch, he said.