State officials insisted Thursday that hundreds of recently revealed cracks in the new Oroville Dam spillway are normal and don’t threaten the integrity of the recently completed first stage of work.
In a conference call with reporters Thursday, DWR spokeswoman Erin Mellon said the hairline cracks were first noticed in late August. The cracks, which number in the hundreds, were first reveled to the media this week. Mellon downplayed their importance.
“There are lots of what is anticipated and expected in a construction project, that we may not jump into, like the nitty gritty details of,” she said.
Jeff Petersen, project director for Kiewit Construction, said the cracks don't affect the structural integrity of the spillway. Adjusting the concrete mixture could reduce the number of cracks, Petersen said, but experts need to be careful not to reduce the concrete's strength.
But Robert Bea, a distinguished forensic engineering expert who is part of a team studying the February disaster, said that micro-cracking is not "something you expect to see," and can in fact invite erosion and other processes that can weaken the structure when it is under a heavy load — such as if large amounts of water need to be drained from the lake.
Federal regulators told state officials late last month that they share the state's conclusion that "the current condition of the hairline cracking does not warrant repair at this time."
Reconstruction work on the spillway scheduled for next year is supposed to more than double its current capacity by strengthening it with structural concrete.