Here is Tuesday morning’s installment of our update on the Oroville Dam spillway incident. For background, please see our earlier blog posts, starting last Thursday, February 9, and most recently our update of February 13 which sets the stage and provides context. In sum, the evacuation continues; the emergency or auxiliary spillway is stable; workers are adding rock to address the erosion that caused the evacuation; the primary or service spillway is also stable, and is currently evacuating 100,000 cfs from the reservoir; but new storms are forecasted to roll in starting Wednesday, and many people are still worried about how the reservoir and its spillways will handle the water.
Once again we have tried to share the important facts and the context, without hype, sensationalism, or blame. If you find this helpful, please feel free to share it with others who may be interested. And if you would like to be updated when we post a new entry, please add your email on the right where it says “stay connected.”
1. Folks who were evacuated Sunday afternoon and evening in Butte, Yuba, and Sutter Counties have not yet been told they can return to their homes, and rumors about such a plan were denied by Butte County officials on Monday afternoon. Officials indicated midday Monday that they were working on a plan to allow residents back to their homes, but that the situation remains “dynamic.” They also kept using the unfortunate term of “repopulate” to describe the effort. As of Tuesday morning, DWR was stating that the evacuation order would end when “we can be 100 percent assured that they can stay back in their homes.”
2. Water in Oroville Lake continued to drop throughout Tuesday morning, and was down to below 890 feet by 7:00 am (remember that the lip of the emergency spillway is at 901 feet). Outflow from the primary spillway remained near 100,000 cfs throughout the day Monday; the lake had fallen about five (5) feet over the first 24 hours since Sunday afternoon and was down approximately 13 feet since the evacuation started. DWR is aiming to reduce the lake by another fifty (50) feet to prepare for storms scheduled to arrive on Wednesday but at the current rate won’t be able to hit that goal. Bill Croyle, DWR’s acting director, indicated it could take 10 to 15 days to get down to that level.
3. We have now seen some pretty clear pictures that show a large crater at the toe of the emergency spillway, and it was that crater that worried DWR enough try to quickly lower the lake on Sunday night and that led to the Butte, Sutter, and Yuba County Sheriffs calling for evacuations. DWR does not know the reasons for the erosion that led to the crater and resulting evacuation order, but Croyle surmised during a press conference that sometimes slower flows (such as those that occurred Saturday into Sunday) can sometimes cause more erosion than faster flows. Here is a gallery of a few photos; note the crater very close to the toe of the spillway.
4. Importantly, however, Croyle indicated that while there were concerns about the auxiliary spillway, the primary spillway had not suffered additional damage despite the increased 100,000 cfs flows since Sunday afternoon. DWR can tell that little additional damage has occurred in part because the water at the bottom of the primary spillway is coming out clean, rather than being full of soil being picked up at the erosion site. This is good news considering the department’s intention to continue to release water at this level for the next couple of weeks.
5. More rain is headed to Northern California starting Wednesday. DWR indicates that anticipated flows into Oroville from this set of storms should be lower than the flows from last week’s storms – but those flows were significant. This is a topic we expect to cover in detail in future posts.
6. Throughout Monday there were multiple media reports that the State was “warned” twelve years ago regarding safety issues associated with the emergency spillway. These reports specifically reference a motion by Friends of the River, Sierra Club and South Yuba River Citizens League filed to intervene in the Federal Energy Regulatory Commission’s (FERC) relicensing proceeding for Oroville Dam. To be clear, we were not involved in that proceeding and do not have all of the relevant information in front of us. Based on the groups’ motion to intervene (which can be accessed HERE), it appears the groups argued that the emergency spillway needed to be “armored,” as opposed to being left as an exposed hillside, in order for the facility to conform with FERC’s guidelines. The groups cited the damages that could occur to the hillside and downstream to support their argument, including extensive erosion; impacts to the spillway road and transmission towers; and soil, rock and debris in the Feather River that could damage downstream structures. While the motion itself does not appear to articulate concerns about structural damage to the emergency spillway itself resulting from a lack of armoring, it is at least fair to conclude based on the motion alone that they were interested in armoring the emergency spillway for that reason as well. We have not yet located all of the documents associated with the hearing, but it appears relevant to note that the groups brought this issue before FERC, which can mandate conditions upon relicensing, and FERC appears to have not agreed with the groups’ arguments. We have also talked with engineers who have argued that an emergency or auxiliary spillway over bedrock meets all appropriate safety standards. Unfortunately, the unearthing of this document will likely lead to much finger-pointing over the coming weeks and months.
7. Finally, DWR has mobilized trucks, front-end loaders, and helicopters, and is rumored to be filling 
the crater below the emergency or auxiliary spillway with boulders and crushed rock. We haven’t yet seen pictures to confirm that activity, although there are photos of trucks arriving on site with rock and others of helicopters moving large bags of rock. And the Sacramento Bee reported that crews worked through the night to add rock to the crater.
8. As reported by Capital Public Radio, Governor Brown has requested that the President declare an emergency for the Oroville Dam.
For more detailed information about current storage, inflow, and outflow from Oroville Dam, we still recommend the California Data Exchange Center. National Public Radio covered the story on Monday and that story can be heard here. We also found KPAY 1290 News-Talk out of Chico to be a reliable source for listening to DWR’s press briefings. You can access it here, and then click the “listen live” link. Additional sources of information on this incident can be found on the DWR website and DWR has shared this phone number for public updates: 530-872-5951. Look for further updates as we continue to monitor the situation, and consider the consequences of future storm events until the primary and emergency spillways can be repaired.
WE ALSO wanted to acknowledge that the Oroville spillway is not the only challenge being faced by the Central Valley of California. Very high river flows in this very wet year have strained many of the rural levees in the valley. We are aware of a number of stressed levees in the Sacramento-San Joaquin Delta, including at least one district that had to make a relief cut and another district engaged in a serious flood fight after a significant levee slump. Elsewhere in the valley, and downstream of Oroville, other districts are fighting seeps and boils and are on 24-hour patrols. While this news is not as sensational, our hearts go out to our friends who are fighting high water and reminding us of the importance of solid O&M and new capital projects, and the risks that we all face by living, working, or farming behind levees.