FLORISTON (CBS13) — An out-of-control, out-of-nowhere river of mud was lodged free by thunderstorms in the Sierra, closing a portion of Interstate 80 about a mile and a half from the state border.

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Interstate 80 is now open in both directions, with westbound lanes slowly reopening with CHP escort.

Drivers reported seeing the rush coming toward them.

“From here, probably 150 yards, you’ve got the whole hillside that just came down,” said Preet Dosanjh. “As we pulled over, we saw the water was just gushing.”

“And there was this little VW trying to get through it, and it pushed up against the median,” said Gustavo Diaz.

30 seconds of sheer panic.

“All of a sudden, you saw halves of trees sliding down against the thing,” said Frankie Cisneros.

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A hillside that gave way sent mud and pieces of trees and rocks rushing into the roadway, powerful enough to push a car up against the center divider. Mud was several inches deep across the lanes and deeper on the shoulder.

Mud on the road was at least half-a-foot deep, and in some spots it was waist-deep.

“I was walking and had to change my pants, because I got up there and went to walk and I sank,” says Cisneros.

The debris field was the size of a football field, and, unlike the slide’s sudden arrival, the mud was going nowhere fast.

Caltans closed Interstate 80 in both directions near the state line. Traffic was snarled for miles. A painfully slow start to Zach’s cross-country move to Boston.

“You just couldn’t get through.”

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Hours later, cars stuck in the mud were finally free. For everybody else stuck in traffic while cleanup continued, it shaped up to be a very long night.