In this handout provided by the California Department of Water Resources (pixel.water.ca.gov), Water continues to move down the damaged spillway at Oroville Dam with an outflow of 80,000 cubic feet per second (cfs) on on February 17, 2017 in Oroville, California. Last weekend overflow waters from the emergency spillway eroded much of the area below the spillway. (Photo by Brian Baer/ California Department of Water Resources via Getty Images)
The early February images of the crumbling flood-control spillway at Lake Oroville were dramatic and, make no mistake, the danger was real. So real in fact that 180,000 people had to be evacuated from a huge swath of land in several counties near the lake.
As we said at the time, state, federal and water agency officials will have much to answer for once the crisis has passed. But we aren’t there yet, the state is still conducting triage, as it should be.
On Monday water officials slowly began shutting off spillway water flows from the lake so they can finally begin assessing the problem’s full scope. It is the right thing to do, as long as it can be done safely. A more intense visual inspection should give investigators clues as to causes and fixes, both temporary and long term.
After monumental early February rains, the water level in California’s second-largest reservoir lapped near the top of containment. It was a situation that called for relief, which is exactly what the concrete-lined alternate spillway is designed to do.
But soon after the diverted water came roaring down the spillway, disaster struck. Huge chunks of concrete broke loose and were tossed about like pebbles by the raging water. Officials decided to use the emergency spillway, which is an earthen structure designed —as its name would imply — to carry excess water during an emergency. It had never been used in its 46-year history. Unfortunately, the structure didn’t work properly and threatened to give way. That is when officials ordered the mass evacuation.
With the emergency structure teetering and the threat of even more storms coming, officials had no choice but to try to dramatically draw down the lake’s water level as quickly as they could. That meant opening the damaged spillway and hoping that it could stand the pressure.
It did. Now, as the spillway flow is turned off, experts will get a closer look and do their best temporary repairs before either more major storms hit the area or, more likely, this year’s massive Sierra snowfall begins to melt into the lake.
Through coordinated use of barges and heavy equipment, the state hopes to clear away the debris piles that have collected in the spillway and are preventing the restarting of the hydroelectric plant at Lake Oroville.
When it is working, the hydro plant can release water in such a way that theoretically will help the Department of Water Resources better manage reservoir levels throughout the spring runoff.
This is tricky business and the danger should not be minimized, but it is a necessary undertaking that can give state water experts important insights about the viability of the infrastructure at Lake Oroville.