Oroville >> Although stabilizing the emergency spillway at Oroville Dam has been the first priority of the Department of Water Resources, several other initiatives are underway.

DWR is actively removing a debris bar that built up at the base of the main spillway in an effort to get the Hyatt Powerhouse under the dam back in operation. That will allow release of another 13,000 cubic-feet of water per second from the lake.

The debris forms something of a dam that has raised the water in the Diversion Pool to a level where the powerhouse can’t be operated. The deposit consists of chunks of concrete, rocks, dirt and vegetation that eroded from around the main spillway after its concrete floor breached on Feb. 7.

With a rising lake level, DWR had no option but to keep running the damaged spillway even though it knew it would “tear the thing up,” acting DWR Director Bill Croyle told a press conference Sunday.

The department had hoped to run the main spillway at 55,000 cfs, a level where erosion had stabilized, officials said at that time. The water was running clear in the main spillway at that level early on Sunday, suggesting it had washed down to clean, solid rock.

But when the hole appeared in the hillside below the concrete lip of the emergency spillway later that afternoon, releases were increased to 100,000 cfs to stop the flow over the emergency spillway and drop the water level to relieve pressure on the concrete structure where the lake overflows.

A comparison of pictures taken before and after the releases were increased shows that there has been considerable additional erosion on the south side of the main spillway. But again, the water was running clear Tuesday morning, indicating the water has scoured down to solid rock again.

Sunday, heavy equipment cut a road to the water level on the south side of the Diversion Pool to make way from a giant excavator that was unloaded on the closed stretch of Oro Dam Boulevard above. A steady stream of gravel trucks moved in and out from the construction site.

Croyle said Sunday the plan was to put barges in the pool near the dam and scoop the debris into the barges. He said the spillway flow would not have to be cut off to do the work. Monday he said the work was underway.

Power lines

Croyle also said on Sunday that PG&E would be moving transmission towers for a DWR power line from the Hyatt Powerplant that crosses the spillways. The flow in the main spillway was reduced at one point last week when it appeared erosion was threatening the base of the towers.

Croyle said the plan was to move the towers higher up toward the gates of the spillway, an area that was more stable.

PG&E also plans to move a couple of transmission towers from a line it operates that crosses the Diversion Pool. The towers are located in a potential runoff zone from the emergency spillway, and moving them would eliminate the potential they might wash into the river.

The utility removed the wires from the poles last week, and planned to remove the towers by helicopter Saturday. That date was bumped back to early this week, but PG&E spokesman Paul Moreno said Monday the project has been delayed until DWR says it’s safe.

Reach City Editor Steve Schoonover at 896-7750.