Contractors remove sediment and debris below the Oroville Dam flood control spillway. Dale Kolke/DWR

Contractors remove sediment and debris below the Oroville Dam flood control spillway. Dale Kolke/DWR

Things have appeared relatively quiet at Oroville Dam for the past couple of weeks, but a lot has been happening.  DWR has been clearing debris from the diversion pool and has successfully started up releases through the Hyatt Powerplant, but the drawdown had some negative impacts downstream.  Here is our latest update.

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  1. When we last reported, DWR had begun reducing outflow from Oroville in order to facilitate removal of debris from the diversion pool. Outflow reached zero on February 27, and once water had stopped flowing over the principle spillway, the world got a glimpse at the incredible damage that had been done.  See DWR’s amazing footage of the spillway on February 28.  For other videos and drone footage of the dam facilities, see DWR’s Twitter feed.
  2. As reported last week in the San Francisco Chronicle and the Sacramento Bee , it appears that when outflow from the dam was reduce to zero, the resulting “drawdown” of the river downstream led to sloughing of the riverbank in a few areas into the river. This is perhaps an unanticipated impact of the reduced reliability of the spillway – downstream conditions, which for decades have been reliably predictable, changed dramatically at a time when that predictability turns out to be pretty important.
  3. A key reason to remove debris was to allow for the Hyatt power plant, which is located at the base of Oroville Dam, to start releasing water from the lake. This accomplishes two things: (1) it allows for investigation of the principal spillway, which was significantly damaged during February’s high water and outflow events; and (2) it allows for continued releases of water out of the facility, which creates space behind the dam in the event we get surprise storms in March and April.  The Hyatt power plant began releasing water on March 3 at a rate of approximately 2,300 cfs.  As of Monday, March 13, outflow from the plant was up to 12,900 cfs.
  4. DWR intends to resume use of the principal spillway to discharge up to 50,000 cfs by the end of this week, and has advised the public to avoid the river due to this anticipated increase in outflow. DWR has continued to add incredible photos to its photo feed.
  5. While the outflow has been low or nonexistent, crews have removed over one million cubic yards of material from the diversion pool.
  6. A few days before DWR ceased all releases of water over the principal spillway, the National Marine Fisheries Service (NMFS) sent a letter to the Federal Energy Regulatory Commission (FERC) formally expressing concerns about the impacts of reduced flow and dredge-cleaning operations on federally-protected fish in the Feather River, offering “technical assistance” in the form of recommendations to minimize those impacts, and recommending that FERC initiate consultation with NMFS in order to discuss mitigation for any impacts.  While there were efforts by State agencies to rescue impacted fish (see news story about those efforts), the formal reaction to that letter by members of the California Congressional delegation was one of displeasure.  In a letter to President Trump, the members of Congress requested an exemption from the Endangered Species Act and the National Environmental Policy Act for all repair work at the Oroville Dam.
  7. DWR performed its monthly snow survey and reported on March 9 that statewide snow levels were at 168% of the April 1 average, and 179% of normal for this date. This virtually ensures that skiers will enjoy amazing spring conditions for the first time in years.  It also ensures that plenty of water has yet to come down into our reservoirs, including Oroville, through spring.  Whether it comes down quickly due to early warm weather, or at a slower pace, remains to be seen.

We will continue to follow these issues and blog about them over the next few weeks and months.  In particular, we will try to keep readers informed about how and whether the principal spillway might be repaired.