The Lake Oroville saga continues, yesterday we wondered if the collapse of the spillway might have been due to missing or substandard REBAR, and many experts weighed it on that topic. It now appears that there was REBAR there, and the failure was likely of a nature of lack of maintenance and age combined. It appears the earth underneath the spillway was compromised, and that led to the collapse of the structure without anything to support it.
Today, it is a race against time and water, as DWR has ramped up outflow to 65,000 cubic feet per second, and in doing so, is sacrificing the damaged spillway in hopes that there will not be an uncontrolled release from the emergency spillway, something that has never happened in the history of the dam. During the super El Niño of 1997-1998, it came within 1 foot of the emergence spillway. Now, given the fact that inflow is still exceeding outflow, and emergency release looks very likely.
Here’s video from yesterday showing the damage and concrete blowing out:
Unfortunately, the last update of data at 11:00AM PST today shows a water surface elevation value of 895.84 feet, or 4.16 feet to the top at the 900 foot mark where the emergency spillway starts to kick in.
The rate of rise has slowed from yesterday, and no new additional rain is expected today, but with afternoon temperatures expected to be above freezing well above 4000 feet, we are going to see snow-meltwater continue to flow in. As of 11 AM, they were letting out 65,029 CFS, but have a staggering inflow of 132,107 CFS, more than double the release rate:
What’s more worrying is this graph comparing the 1997/98 super El Niño year to this year:
They’ve got a hockey-stick of storage going on, and much earlier in the water year than 1997/98…and they have a busted spillway.
We’ll update this story as more is known.
Here is a historical video for perspective:
UPDATE1: about an hour ago, officals say they “think” they can avoid the emergency spillway:
With a break in the weather and increased outflow from Oroville Dam’s heavily damaged spillway, state officials said Friday morning they no longer believe the swollen reservoir will breach the dam’s emergency spillway.
After a grim assessment late Thursday, officials announced Friday morning they think they can avoid using the dam’s emergency spillway, which they’ve been working feverishly to avoid. The emergency structure feeds into an unlined ravine, and the water would propel soil, trees and other debris into the Feather River.
The announcement came after William Croyle, director of the state Department of Water Resources, told reporters Thursday evening that water levels in Lake Oroville could reach the brim sometime Saturday, forcing activation of the emergency spillway. The emergency system, which has never been used, would dump water onto an exposed hillside, dislodging trees and earthen debris into the Feather River and potentially affect communities downstream.
As of 11PM on 2/10/17, Lake Oroville is now less than a foot from the top and overflow on to the emergency spillway.