THIS JUST IN … Oroville Dam, Friday noon: Water to flow down damaged spillway today; Spill event to last five to six days

Erosion control measures and dredging continues along the diversion pool below the Lake Oroville flood control spillway on March 15, 2017.
Kelly M. Grow/ DWR

The Department of Water Resources held a media call this morning to give an update on the situation at Oroville Dam.  Here’s what they had to say:

Acting Director Bill Croyle began with the numbers.  The lake elevation is 864’; the lake has risen about one foot in the last 24 hours.  The pleasant weather in Butte County and up canyon last week has really allowed the work to continue on the emergency spillway and removal of debris from the diversion pool.  Inflows to the lake are at about 16,000 cfs; tail race elevation at the power house is 225.6’.  To date, 1.25 million of the 1.7 million cubic yards of debris has been removed.  Flows out of the Hyatt Power Plant are at 12,900 cfs.

Today at 11am, we’re going to reactivate the flood control spillway,” he said.  “We’re going to open the gates and progress over a number of hours up to 50,000 cfs.  Over the past couple of weeks, we’ve been evaluating what that level of release should be, whether that’s 40,000 cfs or 50,000; so we’re going to start at 50,000 cfs.  Towards the end of this run which will be five to six days depending on the inflow into the reservoir, we’ll ramp down to 40,000; continuously evaluate the condition of the flood control spillway to see how its performing, and then we’ll make decisions here during the week on how we will step down out of 50,000 to 40,000 and ultimately back down to zero.”

“We do have some incoming weather.  It is weather so the forecasts keep changing every day.  We’re modeling and forecasting that twice a day, rerunning our reservoir models and looking at what that might do to reservoir elevations, and that will impact when we start stepping down the reservoir from 50,000 to 40,000 and if there’s some other steps as we go down to ultimately zero about a week from now.”

“The Hyatt Power Plant is running right now at 12,900, so as we step up our flows on the spillway today, we’ll start backing off on the Hyatt Power Plant.  Ultimately, today that will be zero coming out of Hyatt.  The reason for that is we want to make sure we understand the backwater effect on the power house.  We want to protect that power house so if we start moving that water and we have a backwater effect, again raising the elevation against the Hyatt Power Plant, we want to understand how high it might get, again as we reach full capacity on the spillway.  Our desire of course is to reoperate that Hyatt Power Plant as soon as we can.  We might wait for the duration of this event and restart that plant later in the week, but if we feel like it’s safe to run both the spillway and the power house at the same time, we’re obviously going to do that because it helps us move water out of the reservoir.”

“With the incoming weather, it does look like this morning.  It is forecasted to be a little cooler than it was forecast a couple days ago which is in some ways good.  I would like to see some additional snowmelt when the rain comes so we can move some water during this spill event out of the reservoir, so again that would be one of the factors that might extend the duration of this spill.”

“We do need to spill the reservoir and get down to an elevation that we’re targeting of 835’, 838’, that would be right where we’ll need to stop, unless our spillway acts the way we hope it does with all the mitigation measures that we’ve put in place.  Again, that decision on where we do and how we step will be made later in the week as we assess the function of the spillway.”

“We’ve gone in with our multiagency teams with a lot of independent consultants and our regulatory agencies, and we’ve all been working hard together over the past number of weeks to look at what mitigation measures we might take to ensure that we can continue operation of this flood control spillway.  This includes grouting the face underneath the spillway where we had the damage occur; some rock bolting where we’ve gone into the spillway and rock bolted, or basically reconnected or reinforced the concrete spillway back to Mother Earth.  The idea is to make sure nothing moves around while we go through this spill event.  We’ve also gone to extreme efforts to basically clean out and caulk every crack that we can find on the deck.  The idea there is to ensure that we don’t have any additional water moving down through that deck that might further compromise the system.”

“I want to remind people that what you see today you might now see tomorrow.  I want to set that expectation because this is an impaired system.  What we’re doing in mitigation measures, continuous monitoring throughout not just this spill event, but every day we’re continuing to assess the condition and what things are moving around, and that’s why it so important to better understand the mitigation measures that we were fortunately able to put in.  When we come back off of this spill event, we’ll go back in, reassess, see what’s moved around or not moved around and if there’s additional measures that we can take, we will take them.”

“Our project operations center back in Sacramento is part of the modeling every day.  They are working very closely with the California Nevada River Forecast Center, and taking those models and taking those forecasts and rerunning them to see what it looks like.  They are also looking at history; how often did we spill over the spillway during wet years and dry years.  We’re obviously on the wet side of things right now with our snowpack pushing over 168% in this watershed, so the idea is what is our prediction for future use of this spillway.  The sooner we can get water out of this reservoir down to a level that is safe for us to get out on that spillway, and start the reconstruction process, the better.  That will help us meet our objective of having a spillway we can use by the beginning of flood season next year.”

“At the moment, with the snowpack we have, we’re looking at 3 spills, like that we will do today between now and June 1st.  We obviously don’t want to use this spillway if we don’t have to, but today will be the first of those potentially three spills.  If we have a mild cool spring, early summer, then our models suggest we can get away two spills, including this spill today, so the operation of the Hyatt Power Plant is very helpful, to not only get water out of the reservoir, but help balance downstream water conditions within the flood control system.”

“In other words, with Hyatt operating, we’ll have about 13,000 cfs, any water that we can spill out of the spillway or come out of the Thermalito afterbay will help minimize these large elevation changes within the river system all the way down the system.”

“We do have flood operations. John Patch is here today.  He and his staff are completely connected up with this incident command post to make sure we are communicating not only between each other but within the flood control partners.  This is part of what we do on a daily basis during our normal flood operations.  So we expect that with the 50,000 cfs, again we’ll be balancing those flows today between Hyatt Power House going to 0, discharges from the Thermalito Afterbay, and then ultimately the spill off the spillway all through the number of hours midday today.”

“We expect water levels within the Feather River to move up between 10 and 15 feet depending upon the geometry within that flood control system, so an important message today is please stay out of the flood control system.  It’s a dangerous place to be during flood season, so as we make these water level changes and increase flows, so I’d encourage the public and our other agency partners to be very careful and if possible, stay out of the flood control system.”

“The Hyatt Power Plant is still operating 5 of its turbines today.  It will go to 0.  They’ve been working since March 2.  The Hyatt Power Plant is important because it’s how we maintain our water supply and managing our reservoir elevations through the coming spring.  At some point, we won’t be able to get additional water over the spillway, so again that water has to come through that Hyatt Power Plant.”

“The work on the emergency spillway is almost done.  That spillway has been reinforced and armored up into the areas that were affected by the erosion, at least in the upper part.  The armoring has been done, so to the extent, if we had to use it, that we’ve mitigated the major concerns that we’ve have there.  That doesn’t mean that we’re done there but with regards to our emergency response actions based on what happened a couple weeks ago, that work should be done here in the next couple of days; then as part of the recovery process, we’ll go back in and reassess that area.”

“In closing, I want to talk about the recovery activity.  So as soon as you start an emergency response incident, you start recovery.  Our advance teams have been brought together.  It’s a multi-agency team with our third party consultants and now we have the independent board that is overlooking all of the work that is being done by this process.  They are based out of Sacramento, but the advance teams have been in and out of the incident command post and crawling all over both the emergency spillway and the spillway itself.  So this week, a number of drill rigs have been mobilized to the site to start collecting the geotechnical information that they need to start vetting out all the information they need to kind of fine tune the corrective actions or the mitigation actions that are needed to reinforce and repair the flood control spillway and the emergency spillway.”

“There are some no regrets projects that we’re moving fast on.  Those no regrets projects include improving our haul roads going into the base of that area, primarily from the north.  It includes the mobilization of a rock crushing plant; rocks have been removed from this area, taking off, crushed and analyzed to see if we can use some of this rock in the reconstruction of the spillway.  We also plan within the next couple weeks to mobilize a concrete batch plant.  We know we’re going to need some concrete onsite, so securing those resources, putting them onsite, developing those staging areas and processing areas are critical to how we step through this as fast as we can.”

“The drilling for the geotechnical information has been started.  They wanted to jump into the spillway, but we didn’t want them to do that until after this spill event.  As soon as we can dry up that spillway, then you’ll see their drill rigs dropped into the spillway so that they can go and poke those holes and assess that geology underneath that spillway while we have a dry environment in that spillway before we do the next spill.  Most of those activities will actually start within the next couple of weeks, and then they’ll be complete fairly shortly after that.”

Then Tracy McReynolds from Department of Fish and Wildlife spoke about the Feather River fishery resources.  She began with praising the effort between DWR and DFW in the mitigation actions taken after the spillway incident.

We have successfully tagged our first million spring-run chinook salmon and we plan to release the first million of spring run chinook salmon on Monday, March 20 in river,” Ms. McReynolds said.  “Then we will continue tagging the second million, which will bring our total to 2 million successfully tagged spring run chinook salmon.  After the spring run chinook salmon are tagged, we will move into the fall run chinook salmon that are at the Thermalito annex and the Feather River hatchery.  After the fall run are tagged, we will then move to the steelhead.”

There have not been any major losses due to the incident that has occurred,” Ms. McReynolds said.  “It has been successful; we have had our department pathologist out on a bi-weekly basis to assess the health of the fish populations.  They are looking good and healthy, so we haven’t had any major losses.  We will continue to monitor the health of the steelhead and fall run that remain in the facilities, and we will continue to work with the Department of Water Resources to mitigate any future incidents and be prepared to get through a successful collection, rearing, tagging, and release season.”

During the question and answer phase, Acting Director Bill Croyle was asked about the design of the new replacement spillway.

I think we’re about two weeks from actually seeing what some of those graphics look like,” said Mr. Croyle.  “They are looking at what both permanent and temporary options might be.  We’re running this together, not only with the various design teams but with the regulatory agencies and the independent board that is overlooking everyone’s shoulder.  They are vetting those alternatives; we expect to have our top two within the next two weeks.  Then they’ll go through an assessment of constructability, schedule, and resources.  We need to make sure the resources are available to do one or more options.  We’re doing two because if there’s a critical flaw in any of that – schedule, resource needs, or just the design, then we can off that and choose the other option.”

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