Oroville Dam – Recent developments
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 : 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.