Almost 200,000 people, who evacuated Sunday over fears that a damaged spillway at Lake Oroville could fail and unleash a wall of water, have to stay away indefinitely while officials race to fix it before more rains arrive Thursday.

KCRA reports water levels at the lake dropped Monday morning, stopping water from spilling over the auxiliary spillway.

More storms are expected to batter Northern California later this week, heightening the sense of urgency for the workers who are attempting to stabilize the area surrounding the Oroville Dam. In the worst case scenario, one official said, an uncontrolled release from the dam could send a 30-foot wall of water downstream.

Butte County Sheriff Kory Honea announced Tuesday evening he was lifting an evacuation order issued on Sunday, Dan Brekke of member station KQED reported. The precariousness of the situation led authorities to evacuate almost 200,000 people downstream.

Southern California dams and reservoirs are not in danger of overflowing.

The earth-filled dam is just upstream and east of Oroville, a town of about 16,000 people.

Helicopters add boulders to the Emergency Spillway to prevent further erosion on February 12. And right now, both have problems. The main spillway is holding, but the release of such high volumes of water has flooded parts of the area - though not even close to the catastrophic inundation that could happen if the emergency spillway collapsed.

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That hole can't be fixed at the moment. By Wednesday night the lake level fell an additional 5 feet and is now 26 feet below the emergency spillway.

"You don't throw a little bit of rock in it", he said.

An engineer with the Federal Energy Regulation Commission responded to the concerns in 2006, saying the emergency spillway's design complied with the commission's engineering guidelines.

Meanwhile, federal regulators have told the dam's managers at the state water resources department they must enlist a group of "independent consultants" to assess what went wrong and how to make long-term repairs. It hasn't needed to be used in its 48-year history - until this weekend. At 8 a.m., water began an uncontrolled flow over the Emergency Spillway, washing debris into the Feather River.

A California sheriff has acknowledged that the evacuation below a California dam's damaged spillway was "chaotic".

"It starts to undermine itself. When water comes down, it will hit that patch and roll off", he said.

Oroville police said their department had a plan in place after the evacuation was ordered to facilitate the potential of a high volume of vehicles on the roadways.