The CHP on Monday morning closed the Highway 101 north-Third Street offramp into downtown Santa Rosa for the cleanup and removal of a wrecked big rig and a diesel spill.
Officers closed the offramp at about 10 a.m. It was expected to remain closed for about 12 hours, said CHP Officer Kerri Post.
"It's a hefty cleanup," she said.
The rig's driver lost control as he headed north on Highway 101 at about 5:55 a.m.
It was raining heavily and he said at the scene that he'd begun hydroplaning and the tractor-trailer rig began to jacknife.
The 48-foot empty trailer and engine rig ran off of the highway and down the steep embankment. It stopped on its side at the edge of the offramp traffic lanes.
Injuries to the driver apparently were minor. There were no other vehicles involved, said the CHP.
The wreck caused about 40 gallons of diesel fuel to spill into the embankment.