Sunday, November 28, 2021

Repair work at Oroville dam, storms could keep 200,000 evacuated

A team from the Department of Water Resource, monitors the section of damaged main spillway at Oroville dam in Oroville, California, USA, 13 February 2017. Authorities ordered mandatory evacuations of communities below the Oroville Dam, where a hole was found in its emergency spillway, threatening a possible breach and flooding of low lying areas below the dam. Some 170,000 people were ordered to leave their home for high or safer ground. EPA/PETER DASILVA

Los Angeles, Feb 13 (EFE).- Emergency repair work on the damage to the Oroville dam in Northern California, and the storms that in the coming days could aggravate the situation are keeping the roughly 200,000 people who have been evacuated due to flooding danger on tenterhooks.

Authorities on Monday held a press conference in Oroville, located about 250 kilometers (155 miles) northeast of San Francisco, to provide details about the situation after on Monday the evacuation of local residents was ordered due to the severe damage detected in the 235-meter-high (770 feet) dam’s main spillway.

Butte County Sheriff Kory Honea said Monday that the evacuation order remains in place for the towns of Oroville, Palermo, Gridley, Thermalito, South Oroville, Oroville Dam, Oroville East and Wyandotte.

He said that only when the situation is deemed safe, based on the evaluations of California’s Department of Water Resources, federal and state authorities, will they be in a position to determine whether to lift the evacuation order, emphasizing that the main purpose of the measure is to safeguard the public.

A day after the mass evacuation of some 175,000 people from the area below Oroville dam, a few locals stayed behind to look at the Feather River from the Table Mountain Bridge in Oroville, California, USA, 13 February 2017. Authorities ordered mandatory evacuations of communities below the Oroville Dam, where a hole was found in its emergency spillway, threatening a possible breach and flooding of low lying areas below the dam. Some 170,000 people were ordered to leave their home for high or safer ground. EPA/PETER DASILVA

The situation improved slightly in recent hours after the DWR reported late Sunday night that the water level behind the dam had fallen to 275 meters (about 902 feet), thus easing pressure on the structure.

Specifically, authorities said Monday that more than 3,100 cubic meters (109,000 cubic feet) of water per second is moving through the main spillway, despite the 200-foot-long, 30-foot-deep hole that continues to enlarge.

Lake Oroville is California’s second-largest reservoir and the dam is the tallest such structure in the US.
The problems at the dam began last week when a large portion of the main spillway eroded and broke apart, whereupon authorities closed that spillway and opened the emergency spillway for the first time in the dam’s history.

However, on Sunday a crack was found in the emergency spillway and, given the imminent possibility that the dam could overflow – or even burst – the Butte County Sheriff’s Office ordered the evaculation.

The National Weather Service said that the emergency spillway could potentially collapse due to an uncontrolled release of water from Lake Oroville.

A helicopter over flies over the main spillway of Oroville dam with bags of rocks to shore up the emergency spillway of the dam, after overflow from Lake Oroville crested it’s maximum capacity and started to erode the spillway, in Oroville, California, USA, 13 February 2017. Authorities ordered mandatory evacuations of communities below the Oroville Dam, where a hole was found in its emergency spillway, threatening a possible breach and flooding of low lining areas below the dam. Some 180,000 people were ordered to leave their homes for high or safer ground. EPA/PETER DASILVA

According to local media, the emergency has affected between 180,000 and 200,000 people.

The problems at the dam have been aggravated by a very wet winter in California, a state that has been suffering from a drought in recent years but which in the past few weeks has registered exceptionally heavy rains.

Now, emergency services are working around the clock to reduce the water pressure on the spillways and sluices and create space in the reservoir for new rainfall water inflow, given that weather forecasts are for more storms at midweek.

DWR officials said they were intending to use helicopters to drop bags of boulders to fill in the eroded section of the spillway.

California Gov. Jerry Brown on Sunday declared a state of emergency in Oroville, while the state’s 23,000-man National Guard was placed on alert, a measure not taken since the 1992 Los Angeles riots.