Crews at California Dam Dealing With Natural Asbestos

Oroville Dam's damaged spillway is expected to be back in use today.

The floodgates were opened at 11 a.m., after the spillway was dry for almost three weeks, and within an hour the flow had reached a brisk 50,000 cubic feet per second. The facility can release water at up to 15,000 cubic feet per second through its power turbines, but water from past storms and melting snow are flowing into the lake at a faster clip.

In the interim, Croyle said, DWR must use the spillway to keep the reservoir from reaching capacity. The lake elevation is 860 feet, about 41 feet below the emergency spillway.

These flow levels will be achieved by reducing releases from the Hyatt Powerplant and then adding releases through the regular Oroville Dam gated flood control spillway.

"We're going to be watching to see what happens, and we believe the measures we've taken have really been proactive to try to mitigate the concerns of losing additional concrete off the spillway", Croyle told reporters at a morning briefing.

The spillway will release water at 50,000 cfs by the end of Friday, Croyle said. Nearly 200,000 people were ordered to evacuate the northern California town after a hole in the emergency spillway in the Oroville Dam threatened to flood the surrounding area.

Anglers, boaters, and other river users are advised to be aware of the increase in flows, as the river will become deeper and swifter, it says.

One complication is that some of the serpentine rock scoured clean by previous flows contains asbestos. The dirt hillside and eroded earth beneath the main spillway are now caked in layers of gray concrete.

Repairs cost $100 million through February, or about $4.7 million a day, according to the state.

Workers have cleared out 1.25 million cubic yards of the broken-off concrete and debris that earlier washed from the main chute into the Feather River below.

  • Joanne Flowers