Rain runoff may have undermined Oroville Dam’s concrete spillway, report says - LA Times
▻http://www.latimes.com/local/lanow/la-me-oroville-dam-cause-spillway-20170216-story.html
▻http://www.trbimg.com/img-58a67289/turbine/la-me-oroville-dam-cause-spillway-20170216
Officials have estimated that fixing the spillway could cost $200 million or more. Because the spillway has been used to reduce the water levels at the reservoir, officials said they still need to assess the level of damage.
Records show the same section of spillway was repaired in 2013 but do not provide details.
Large swaths of Northern California are on track to experience their wettest winter on record, with many areas having already surpassed their average precipitation for an entire year. A new series of storms is set to hit the Oroville area over the next few days. But officials are confident they’ve drained the reservoir enough that the rains won’t overwhelm it a second time.
With the reservoir’s water level down more than 30 feet since Sunday and getting lower, Croyle said at a news conference Thursday that engineers will slow releases down the Oroville Dam’s damaged main spillway from 100,000 cubic feet of water per second to 80,000 cubic feet per second over a period of several hours.
The reduction will allow crews to move into the concrete channel to clear out trees, branches and other debris that has clogged the spillway and forced the downstream hydroelectric plant to go offline, Croyle said.
There was no estimate on when the power plant would be back up and running, but it will probably not be before Monday, he said.
Meanwhile, the herculean effort to reinforce the emergency spillway before more rain arrives used a caravan of helicopters and trucks to fill three deep fissures in the dirt hillside with rocks and cement.
Les menaces intermédiaires ne sont jamais prises suffisamment en compte. La culture de sécurité est en perdition.
#environnement #barrage