Oroville Dam – Explained

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Oroville Dam – Recent developments 

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Oroville Dam: Background

  • Oroville Dam is a tallest dam with a height of 770 feet (235 m) in the USA, on the Feather River east of the city of Oroville, California.
  • The dam fully covers Lake Oroville, the second largest man-made lake in the state of California, capable of storing more than 3.5 million acre-feet (4.4 km3).
  • Oroville Dam is located in the Sierra Nevada foothills east of the Sacramento Valley.
  • Construction begins in 1961 and completed and opened on 1968.

Oroville Dam

Oroville Dam : Bio diversity

  • The dam has confined fish migration up the Feather River and the controlled flow of the river as a result of the Oroville Dam has affected riparian habitat.
  • Multiple aims at trying to counter the dam’s impacts on anadromous fish have included the construction of a salmon/steelhead incubator on the river which began shortly after the dam was completed.

Oroville Dam : 2017 Spillway

  • Recently, at the end of January and February first week, winter storms drenched the northern California and reservoir filled to its high level.
  • Usually Dams are engineered to handle the overflow via “spillway”. When the water reaches a certain level at the Oroville Reservoir, operators can release the excess in a controlled fashion through a giant concrete chute next to the dam, sending the water into the Feather River below.
  • The problem is that Oroville Dam’s main spillway has become severely damaged.
  • On February 7, a giant hole suddenly opened up in the chute, with concrete crumbling and water flying everywhere.
  • High inflows to Lake Oroville forced dam operators to continue using the damaged spillway, causing additional damage.
  • By February 10, the spillway hole had grown to 300 feet (91 m) wide, 500 feet (152 m) long and 45 feet (14 m) deep.
  • Meanwhile, debris from the crater in the main spillway was carried downstream, and caused damage to the Feather River Fish Hatchery due to high turbidity.
  • State workers began evacuating fish and eggs from the hatchery in an attempt to mitigate the damage.
  • But the water levels in the Oroville Reservoir kept rising and rising, and it had to go somewhere. So, on February 11, for the first time in the dam’s 50-year history, water began pouring over the top of the auxiliary or “emergency” spillway to the left of the main concrete chute.
  • The water began eroding the ground beneath the top of the auxiliary spillway, carving deep gullies into the earth.

Oroville Dam : Evacuation

  • On February 12, 2017, an evacuation was ordered for those in low-lying areas along the Feather River Basin in Butte, Yuba and Sutter counties, due to an anticipated failure of the auxiliary spillway.
  • The thousands of evacuees are staying in hotels, with friends, some are sleeping in their cars.
  • The Federal Emergency Management Agency is scrambling to provide cots, blankets, and water.

Oroville Dam : Control measures

  • A swarm of trucks and helicopters dumped 1,200 tons of rock per hour onto the eroded hillside that formed the Oroville dam’s emergency spillway.
  • One quarry worked around the clock to mine boulders as heavy as 6 tons.
  • An army of workers mixed concrete slurry to help seal the rocks in place.

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