(Newswire.net -- February 13, 2017) -- Sudden orders for evacuations ensued after officials found that the emergency spillway at the dam at Lake Oroville was eroding Sunday. The dam remained intact, but in the worst-case scenario, an uncontrolled release from the dam could send a 30-foot wall of water downstream into the Feather River, and cause flooding of the communities living near Lake Oroville.
The dam has two spillways - the primary and the emergency spillway, and now both have major problems. First problem happened last week, when according to the California Department of Water Resources, the primary spillway was damaged by erosion.
California Department of Water Resources announced on Twitter at 4:30 PM local time on Sunday, that the dam’s spillway is predicted to collapse within the next hour, and that they will use helicopters to fill the holes by dropping rocks in an effort to stop the erosion and stabilize the auxilliary spillway.
Authorities are also making efforts to make the water level of the lake to drop 50 feet by reducing the amount of water travelling down the emergency spillway as the main spillway is releasing water at 100,000 cubic feet per second instead of the usual 55,000.
Butte County Sheriff, Kory Honea, said at the press conference late Sunday night that he is not going to lift the evacuation order until he has a better idea of what this means and what risks this damage can pose for more than 16,000 people who reside in the city of Oroville.
Also, California Governor, Jerry Brown, issued a state emergency order to help local authorities with the situation and evacuations, reports the CNN.
Lake Oroville gets water from the northern Sierra Nevada mountain range which is experiencing one of its wettest seasons. Also, this winter’s heavy rainfall in Northern California has filled Lake Oroville to the verge of overflow.
The emergency spillway is only used if water levels reach 901 feet in elevation. It hasn't needed to be used in its 48-year history, until this weekend.
According to California Fire, about 35,000 people from Butte County, 65,000 from Yuba County, 76,000 from Yuba City and 12,000 from Marysville City have been evacuated.
Butte County Sheriff used the most urgent of language when he ordered the emergency evacuations. "This is an evacuation order. Immediate evacuation from the low levels of Oroville and areas downstream is ordered. A hazardous situation is developing with the Oroville Dam auxiliary spillway. Operation of the auxiliary spillway has led to severe erosion that could lead to a failure of the structure. Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville. In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second. Immediate evacuation from the low levels of Oroville and areas downstream is ordered. This in NOT A Drill. This in NOT A Drill. This in NOT A Drill."
Built by the California Department of Water Resources in 1968, Oroville Dam is an earth fill embankment dam on the Feather River east of the city of Oroville, California.
At 770 feet high, it is the tallest dam in the U.S. The dam impounds 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) and is located in the Sierra Nevada foothills east of the Sacramento Valley.
Los Angeles Times wrote that more than ten years ago, authorities had discussions about how to strengthen the dam and to prevent a situation like this from occurring. Many groups for environmental protection then warned of the problem, but the authorities have refused them.
In 1997, Oroville county was also evacuated due to the fear of flooding. However, the situation was not even close to today’s dramatic circumstances.