Caltrans workers and engineers assessed the damage to the Hartnell overpass in Redding Friday.
On Thursday night around 5:30 p.m. a big rig carrying a car crusher on I-5 smashed into the overpass.
Caltrans officials said repairs could cost up to $1 million to replace and repair parts of the overpass that were damaged.
A little after 10 a.m. I-5 was reduced to a single lane as more than two dozen Caltrans workers, engineers and specialists analyzed the bridge.
The semi-truck was traveling from the Willow Creek area and made it under the overpass before the impact with the Hartnell bridge.
Caltrans engineer Lance Brown said the bridge is approximately 17 feet tall and there are no vertical clearances posted on it but it is not considered low because it is above the standard safety height.
Brown was among the many inspecting the bridge along the noisy I-5 corridor.
"Somewhere along the line, along his course of travel he should've said 'whoa he is really high' and taken a look at that. It's basically a small explosion as that thing hit the concrete and blew it out the way it did. All the form work that's up inside the bridge it was exploded out, it's almost vaporized inside," explained Brown.
The City of Redding said the Hartnell overpass will remain closed overnight with a detour at Loma Vista Drive.
They hope to have it reopened by tomorrow but it will be limited to two lanes, one westbound and one eastbound.
The two other lanes will remain closed during repairs which could take up to two months to complete.
Caltrans officials said this will be a lengthy fix.
Beginning next week I-5 southbound will be limited to a single lane in the area as crews begin repairs.
That will take place from 8 p.m. to 6 a.m. and will happen seven days a week.
CHP Information Officer Mark Redding said it's unknown if the driver of the big rig will face any charges and the case is under investigation.