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SCIENCE
 

Spillway damage at huge Northern California dam has thousands on edge

Water flows down Oroville Dam's main spillway near Oroville, Northern California. Officials have ordered residents near the dam to evacuate the area.
Water flows down Oroville Dam's main spillway near Oroville, Northern California. Officials have ordered residents near the dam to evacuate the area. Photo by: AP

OROVILLE, Calif. — Nearly 200,000 people remained under evacuation orders Monday as California authorities try to fix erosion of the emergency spillway at the nation's tallest dam. Failure of the spillway could release uncontrolled flood waters.

People were ordered to leave for their own safety.

About 150 miles from San Francisco, Lake Oroville had water levels so high that an emergency spillway was used Saturday for the first time in almost 50 years. The lake is one of California's largest man-made lakes.

Hole In Secondary Spillway Prompts Evacuation Orders

The evacuation was ordered Sunday afternoon after engineers spotted a hole in part of the secondary spillway for the 770-foot-tall Oroville Dam. They told authorities that it could fail within the hour.

"I'm just shocked," said Greg Levias, who was leaving with his wife, Kaysi, two boys and a dog.

What they couldn't fit in their trunk they piled as high as they could in their Yuba City apartment. Then they joined the line of traffic attempting to leave the city where they had moved just three weeks ago.

Panicked and angry residents sat in bumper-to-bumper traffic hours after the evacuation order was given.

Raj Gill was managing a gas station where anxious drivers bought gas and snacks while waiting for traffic to clear. His boss told him to close the station and flee, but he stayed open to feed a steady line of customers.

"You can't even move," he said. "I'm trying to get out of here too. I'm worried about the flooding. I've seen the pictures — that's a lot of water."

Not Enough Blankets At Shelter

A Red Cross spokeswoman said more than 500 people were at an evacuation center in Chico, California. The shelter had run out of blankets and cots for people to sleep on. A truck with 1,000 more cots was stuck in the evacuation traffic, said Red Cross shelter manager Pam Deditch.

A California Highway Patrol spokesman said they would have two planes out Monday to help with traffic control as well as search and rescue.

Kim Zagaris is the state Fire and Rescue Chief. He said at least 250 law enforcement officers from throughout the state are in the area or on their way to help with the evacuation.

Late Sunday, officials said the evacuation orders remained in place although water was no longer spilling over the eroded area.

Butte County Sheriff Kory Honea said at a news conference that many things were still unknown. "We need to continue to lower the lake levels," he said. They need to give the Department of Water Resources time to examine the situation, he said. Then, he added, they can make the decision as to whether it is safe.

Almost 200,000 Ordered To Evacuate

About 188,000 residents of three counties were ordered to evacuate.

Bill Croyle is acting director of the Department of Water Resources. He said officials will be able to check the damage to the emergency spillway now that the lake levels have been lowered.

The erosion of the emergency spillway threatens to undermine the concrete structure and allow large releases of water from Lake Oroville. Those possible flows could overrun the Feather River and other downstream waterways, channels and levees. Towns in three counties could be at risk of flooding.

Oroville Lake levels had decreased by Sunday night as they let water flow from its damaged main spillway.

Plan Is To Lower Lake Level By 50 Feet

Croyle said the department will continue releasing water from the main spillway. The goal is to try to reduce the dam's level by 50 feet ahead of storms forecast to reach the area Wednesday.

Department engineer and spokesman Kevin Dossey spoke to The Sacramento Bee. He said the emergency spillway was rated to handle 250,000 cubic feet per second, but it began to show weakness Sunday at a much lower level.

Honea said there was a plan to plug the hole by using helicopters to drop rocks into the space. But Croyle said that no repair work was done after officials looked at the flow and available supplies.

Jerry Brown is the governor of California. On Sunday, he issued an emergency order to strengthen authorities' response to the problem at the dam and help with evacuations.

David S. Baldwin is Adjutant General of the California National Guard. He said at a news conference Sunday that eight helicopters would be available Monday to assist with spillway reconstruction.

State National Guard Alerted

The California National Guard put out a notification to all 23,000 soldiers and airmen to be ready to deploy if needed, he said. Baldwin says an alert for the entire California National Guard hadn't been issued since the 1992 riots.

Earlier Sunday, officials stressed the Oroville Dam itself was structurally safe.

Unexpected erosion chewed through the main spillway during heavy rain earlier this week. It sent chunks of concrete flying and created a 200-foot-long, 30-foot-deep hole that continues growing. Engineers don't know what caused the cave-in. However, Chris Orrock, a Department of Water Resources spokesman, said it appears the dam's main spillway has stopped crumbling even though it's being used for water releases.

The lake is a central piece of California's government-run water delivery network. It supplies water for agriculture in the Central Valley and residents and businesses in Southern California.

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1
Anchor 5: Text Structure

How does the section "Hole In Secondary Spillway Prompts Evacuation Orders" relate to the section "Not Enough Blankets At Shelter"?

A

Both discuss how the evacuation has changed over time.

B

Both explain reactions to the evacuation and possible flooding.

C

The first section describes a problem and the next section explains how it was solved.

D

The first section lists effects and the next section describes what caused them to happen.

2
Anchor 5: Text Structure

Why does the author include the section "Plan Is To Lower Lake Level By 50 Feet"?

A

to describe the effects of the decisions being made by several state leaders

B

to provide a chronological list of events to which state leaders have had to respond

C

to show how different leaders throughout the state are working to help with the problem

D

to contrast the solutions to the problem that have been posed by different state leaders

3
Anchor 1: What the Text Says

Which piece of evidence BEST explains the need for an evacuation?

A

About 150 miles from San Francisco, Lake Oroville had water levels so high that an emergency spillway was used Saturday for the first time in almost 50 years. The lake is one of California's largest man-made lakes.

B

The erosion of the emergency spillway threatens to undermine the concrete structure and allow large releases of water from Lake Oroville. Those possible flows could overrun the Feather River and other downstream waterways, channels and levees. Towns in three counties could be at risk of flooding.

C

Department engineer and spokesman Kevin Dossey spoke to The Sacramento Bee. He said the emergency spillway was rated to handle 250,000 cubic feet per second, but it began to show weakness Sunday at a much lower level.

D

Unexpected erosion chewed through the main spillway during heavy rain earlier this week. It sent chunks of concrete flying and created a 200-foot-long, 30-foot-deep hole that continues growing. Engineers don't know what caused the cave-in.

4
Anchor 1: What the Text Says

Which paragraph in the section "State National Guard Alerted" suggests this is the most serious crisis California has faced in many years?

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