MARYSVILLE  (CBS13) — Emergency repairs being made to an unstable trestle in Marysville.

It’s happening along a bridge right above the Yuba River.

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A spokeswoman for Union Pacific tells CBS13 a bridge instructor first noticed a dip in one of the trestles on Thursday.

There’s a pipe below that trestle which contains diesel fuel, prompting a big turnout of emergency crews.

Union Pacific crews are working around the clock to repair the sagging trestle. A crane is now laying down the foundation to secure it.

The trestle is sagging almost three feet below normal.

“This is a very serious concern, you can’t have a train going over that in this condition,” said Russ Brown, a spokesman for Yuba County.

County water officials shut off water flow to the Yuba River, so the piers supporting the trestle don’t sink even lower.

“It’s not uncommon when you have rivers and heavy storms and a lot of flow where the footage can become compromised,” Brown added.

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It’s not the first time the bridge has had failures after a storm. What had the county more worried was a pipe below this trestle which officials say contains diesel fuel.

“If it fell and collapsed it could have flowed down the river and put the traffic bridge in danger,” said County Supervisor Mike Leahy.

Crews were able to vacuum most of the fuel out of that pipe and have booms on standby to capture any residual fuel.

“They have a process to keep the fuel from floating downstream, it’s a big concern for the county and we are keeping a very close eye on that,” Brown added.

“First time I’ve seen it take a dip like this,” said Corey Watson.

Watson is a regular around town, who says it’s time to upgrade the aging trestles.

“It’s been around a long time, my family and I have jumped off that trestle for many years,” said Watson.

It’s a man-heavy operation to get the trestle back up and running, a quick-fix, for now.

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This operation will continue for the next few days. The whole track is shut down to Amtrak and freight trains, which have been rerouted through the Sacramento subdivision.