Earlier this morning, the Department of Water Resources held a press conference.  Here's what Acting Director Bill Croyle had to say …

The feed for the press conference kicked in just after the start; Mr. Croyle was talking about how the flows on the Feather River are going to be ramped down as they prepare to bring the flows down the spillway to zero.

“ … The flows at the diversion dam of about 620 cfs, maintain the water supply, ensure the water supply going into the fish hatchery to make sure that we protect that resource, and then it will continue to use the afterbay to keep the river moving down from 30,000 down to 10, to 5, and ultimately, this afternoon on the Feather River, we’ll be at 2500 cfs.”

“With the amount of water we have stored in the various pools and dams – the Thermalito Afterbay, the power pool, the diversion pool, the water up there by the Hyatt Power Plant, we have we believe about 7 days worth of storage to be able to work through this period to maintain those minimum fish flows.” 

“We’re planning on a five day construction period, and we’ll reassess our water supply conditions throughout this period every day, in the morning and the evening, to make sure that we don’t have any surprises as we move through this period.”

“At some point, we either open up the pool and making sure we can get the Power Plant up and running.  If we can fire one unit up, that’s about 1500 – 1700 cfs, again that would give us our fish bypass flows and enable us to recharge some of our other storage.”

“At some point, we might have to go back to using the spillway.  One of the challenges that we have during this event is really better understanding the existing flood control spillway.  We want to better understand if we can operate it at a level lower than 50,000 cfs, so if we can get into a range of 20,000-25,000 cfs without further damaging the spillway, that will allow us to really make much better progress or manage our reservoir elevations.  Hopefully the construction and the debris removal crews can stay a little closer to the toe of that and continue to remove that material, thereby allowing us to better operate the Hyatt Power Plant and ultimately prepare for the recovery of the spillway itself.”

“We’re attaching the debris pile by three different angles: from upstream, downstream, and from the west side of the pile.  The hope is that we can get out on the pile as soon as the water comes down with some Cats, move some material around to set up some channels and better access roads and to make that area safe.  Again, we’re going to focus on removing the debris.  At the same time, during this zero flow environment, we have a number of geotechs, geologists, and engineers trying to get access to this area to really look at the geology.  If there are things we can do to better protect the channels that are there in short-term, but really start collecting the information that we need to develop our various alternatives to rebuild and recover the spillways.   We’re going to start off a lot of drone work this morning, so the drones will be flying multiple missions at the same time.  That’s why it’s so important that we don’t have any other resources in the air that are not part of the air operations and controlled by our air command.”

“We’re also going to have a helicopter stationed over the spillway that will photo-document the change in flow conditions throughout this event.  That’s important for our engineers and geotechs to better understand the spillway itself, and again that helps us better answer, do we have to maintain a 50,000 cfs or we could do something a little lower, but that means that we’ll have helicopters above, drones underneath.  We have safety people monitoring all over the place, we have our barges, our excavators down on the dirt pile, we have a lot of resources moving around, monitoring the situation, so our safety people are on high alert to making sure we don’t have any third-party interference because we have too many safety issues here with regard to helicopters, as well as our own drone work.  If we have to shut down because of a third-party drone that’s in our air space, that affects our public safety and that of our first responders, as well as the community of Oroville.  If we have to delay what we’re doing here today, that increases the risk to public safety.”

“This is a big day.  There’s going to be a lot of changes.  Safety is our number one concern today.  We’ve been very lucky with all the equipment.  Our water conditions, the long hours, a little bit of a lack of sleep on many people, so our goal here to make sure that we move through this environment while being safe and making sure we don’t hurt anyone.”

“This is a changed condition.  The environmental resources and fish are high on our screen.  There is a lot of effort going into planning this so the various regulatory agencies and the resource management agencies are tuned up on what we might expect.  A lot of work has been done yesterday.  They flew the Feather River; they will fly the Feather River again today to make sure we understand where those pools might be that might strand fish, so there is a fish rescue plan in place.  Today we’ll do a lot of monitoring as the water level comes down, there may be an opportunity for fish rescues today, but if not, it will be tomorrow and that will continue as we are in this low-flow environment.”

“Again, as we move through this next five to seven days, our goal is to aggressively attack this debris pile.  The more we can dig this channel and open up the Hyatt Power Plant, that allows us another dial that allows us to manage those inflows into the reservoir and ultimately stay more on a drier environment at the bottom of that spillway, and again we can start completing our response phase of this and getting set up for a recovery.”

“We will have a series of technical teams that are moving into the spillway chute if it’s deemed safe here in the next couple days, and that data is needed to better understand that spillway, and then of course to provide that foundation for the geotechnical and geology information that we can to make our selection for what the recovery solution might be in the future.”

“There’s a lot of monitoring going on, today and tomorrow, because of our safety concerns.  We’ll have a lot of runners moving data and people back and forth throughout their project area which goes from the stop of the spillway, the emergency spillway, to the bottom in and around all the heavy equipment that’s working on the debris pile as well as the Hyatt Power Plant as well as the diversion dam and the forebay dam, so we have a lot of people moving around, a lot of communication going on.”

Question: If the spillway can handle 50,000 or 100,000 cfs, why would lowering the flows be a cause for concern?

Answer: “What happens is under certain flow regimes, the water will shoot off the end of the spillway a certain distance, and it falls into a plunge pool.  So if the water doesn’t hit the plunge pool but hits the base of the mountain and erodes the mountain before it hits the plunge pool, then the fear is that erosion would continue up and then cause more concrete to be eroded off the end of the spillway and eating the spillway back towards the dam.  It’s been very stable for about a week and a half now, for which we’re really pleased with.  It’s taken a lot of water over the top of that spillway but the goal is to better understand where that trajectory lands.  Is it in the plunge pool or does it land on the solid metamorphic rock, or does it land on something that can erode.  That’s what we’re going to learn later today and tomorrow.”