Oroville – The emergency is over, the construction now begins.
Demolitions are going to increase, the bottom of the broken spillway will be taken out, two concrete-creating factories are being built and new concrete will be laid beginning in mid-June.
The Department of Water Resources gave an update Wednesday in a media conference call on the construction phase at the spillway that began May 13 when the emergency officially ended.
BLOWING UP THE BOTTOM
The contractor Kiewit began demolishing the lower portion of the broken main spillway and building additional roads Saturday after flows were stopped for the season, said DWR’s chief engineer Jeanne Kuttel.
“Controlled blasting is expected to take place more frequently,” she said.
The explosions will mostly take place between 6 p.m. and 7 p.m. and will be “louder than it has been, but not terribly significant,” Kuttel said.
WATER COMES, WATER GOES
The lake elevation was at 827.76 feet at 11 a.m. Wednesday. With the spillway gates shut, the water agency is only using the Hyatt Powerplant to release water from the lake.
With five of six turbines working, the power plant has been releasing as much as it can, with releases this week above 13,000 cfs, according to numbers from the California Data Exchange.
Inflows from the Feather River upstream of the reservoir have fluctuated, at times briefly surpassing the water released, but mostly the water coming into Lake Oroville has been less than what is being released through the power plant. Inflows were at 9,158 cfs at 11 a.m. Wednesday with outflow at 13,491 cfs.
Since the spillway gates closed Friday with Lake Oroville’s elevation at about 829.5 feet, DWR has sold water to contractors, DWR’s acting director Bill Croyle said.
CLOSING DOORS
The emergency might be over, but Croyle wants to increase security at the Oroville Dam.
He said there is sensitivity in “specific areas” and increasing security “may enhance access to other areas.”
California State Parks recently installed a webcam that shows the main spillway. Croyle called it an “important communications resource that we’ve made available.”
Showing the overall work via webcam doesn’t jeopardize security because it doesn’t show the more sensitive areas, he said.
TWO TYPES OF MATERIAL
There’s a difference between roller-compacted concrete that DWR calls RCC and the higher-quality material it calls construction or structural concrete.
“(Roller-compacted concrete) is faster production and serves as a foundation for permanent structural concrete,” said Kiewit’s project director Jeff Petersen.
The plan at the moment is to fill the bottom part of the spillway with the roller-compacted stuff and then cover it with the construction version.
Two concrete plants are planned with the roller-compacted concrete plant at the east side of the spillway and the construction concrete being made at the Spillway Launch Ramp parking lot.
Photos from DWR show that Kiewit was building a “concrete batch plant” in the Spillway Launch Ramp parking lot Friday.
The contractor will try to use the concrete pulled from the Diversion Pool for at least some of the roller-compacted concrete, Petersen said, but he did not know if that would be possible.
“The actual structural concrete will be supplemented with locally-purchased aggregates,” he said.
About half of the 500 workers that Kiewit projects it will have by August will be from local unions, Kuttel said.
There are currently about 200 Kiewit employees at the spillway.
WHAT’S THE SCHEDULE?
The plan before Nov. 1 this year has three main parts. California Natural Resources communications advisor Erin Mellon explained.
1. Repair the part of the main spillway that eroded in February.
2. Remove the concrete at the bottom of the main spillway and rebuild the roughly 600-foot span with roller-compacted concrete.
3. Build the cutoff wall for the emergency spillway.
The roller-compacted concrete in the spillway will have a “test placement” in mid June with full production by July 1, Kuttel said. The structural concrete construction is scheduled to begin in early August.
That will allow DWR to manage outflows from the main spillway up to 100,000 cfs and it has a contingency plan if the bottom part isn’t completed by Nov. 1 to be able to release 50,000 cfs, DWR’s acting director Croyle said.
But the construction isn’t over at the end of October.
In 2018, a concrete “splash pad” will be built between the emergency spillway weir and the cutoff wall. The upper part of the main spillway will be fully replaced and the entire spillway will be covered with the high-quality structural concrete.
Kiewit is contracted through January 2019.
THE COST
The Department of Water resources said Wednesday it expects the entire Oroville Dam spillway drama to cost more than half a billion dollars. About $130 million has been spent so far. Here’s how it breaks down.
Emergency response (projected): $274 million
Recovery (construction contract): $275 million
Total: $549 million
