DWR: cracks on spillway are normal, expected

The brand new, never-before used Oroville Dam Spillway is once again making headlines after workers have noticed cracks running up and down the main chute.

Posted: Nov. 30, 2017 5:36 PM

The brand new, never-before used Oroville Dam Spillway is once again making headlines after workers have noticed cracks running up and down the main chute.

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But, Department of Water Resources officials are saying it's not a problem; these cracks have been there for months.

There are hundreds of cracks running along the about half-mile long chute.

“These hairline cracks do not in any way affect the structural integrity of the spillway,” said Kiewit project director Jeff Petersen.

He and the DWR stand by that statement, saying it's a normal occurrence and there's nothing to worry about.

“It is physical property of the concrete during the curing process to shrink slightly, which leads to internal stresses, and therefore normal for concrete to crack during the stress,” he said.

DWR Spokesperson Erin Mellon said some cracks were discovered in late August after the first slabs were poured.

The DWR has not released any pictures of the cracks, partly because you can barely see them. All in all, there are hundreds of cracks along the main chute, each one being about as thick as an average finger nail, which is less than half of a millimeter.

“In mapping, in some cases they actually have to spray water on it to allow the crack to actually be seen visually,” said the project incident commander Jeanne Kuttel.

Right now, there is still concrete dry finishing work happening on the main chute, which should be done by mid-December, but most of the attention has shifted to the emergency spillway.

They expect that to be even more challenging than the first phase, and it will require even more roller compacted concrete. Currently, the main focus is to finish the secant pile wall for the emergency spillway.

“This is an underground wall that will prevent the kind of uphill erosion that occurred below the emergency spillway back in February,” Petersen said.

He said that wall is now about 60% complete.

Prep work has also begun for the other parts of the emergency spillway. Earlier this month crews started control blasting downstream of that spillway, and the blasting will likely continue every other day through the end of the year.

The DWR has two community meetings coming up next week to update the public.

The first will be held on December 6th at the Memorial Auditorium in Oroville, and the second at the Yuba-Sutter fairgrounds on December 7th. Both meetings will be from 6-8pm.

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