The stunning destruction at Oroville Dam and the work ahead

Posted February 17, 2017

180,000 people evacuated from area around a huge United States dam have been told they can go back to their homes.

The erosion damage below the Oroville Lake emergency spillway is seen from the air on February 13, 2017, in Oroville, California.

The Butte County Sheriff's Department cited "lower lake levels, further inspections, ongoing work to shore-up the Oroville Dam emergency spillway and updated weather forecasts" to announce the change at 1pm local time on Tuesday.

In a press conference on Tuesday, authorities announced that all evacuations have been reduced to evacuation warnings, allowing residents to return to their homes. He said it has been stable for days and is handling those 100,000 cubic feet per second releases, which means they've been able to make a lot of room in the lake.

Aerial footage shows water gushing down the spillway of Oroville Dam during the same week the spillway collapsed because of damage, causing at least 188,000 people to evacuate the area.

Experts said problems like the cracks in the concrete spillway and spots in nearby areas where water seeped from the reservoir through a hillside were common issues with dams. They say they have drained enough water that the emergency spillway will not be needed to handle runoff from the approaching storm.

As a result, levees were built along South Chickamauga Creek, but they would not be sufficient in the event of an extreme storm, said Tom Barnett, senior manager of TVA's river forecast center.

Mr Croyle said work crews had made "great progress" cementing thousands of tonnes of rocks into holes in the spillways.

Gov. Jerry Brown asked for roughly $162 million for cleanup from flooding, and cost estimates to fix the Oroville Dam's emergency spillway could run as high as $200 million. The emergency spillway was used for the first time in the dam's 48 year history last Saturday, when the lake reached capacity.

A spillway is a structure that allows a controlled release of water from a dam.

In fact, the department said it hasn't received any reports about boils on any part of the Oroville Dam structure.

"I would think they could probably sustain a couple of inches of overflow on that but I don't know how much more", Bingham said.

The crisis prompted the evacuation and forced operators to resume using the damaged main spillway to lower the lake below the emergency spillway level.

But Oroville is bracing for rain on Wednesday that could add a strain to the spillway, and an additional problem looms.

And then, barely a day after the lake started to flow over the emergency spillway wall, the evacuation was ordered.

"People know the dam survived the quake", said Mackay Mayor Wayne Olson.

"We have a pretty rigorous dam safety review", Coffey said.

"I'm safe where I'm at", Azevedo said.