Repair work started at Wanapum Dam

EPHRATA - Repair work began earlier this month on a damaged spillway pillar at Wanapum Dam, and has started on the rest of the dam.

Grant County PUD officials discovered a crack at the foot of one of the spillway pillars on Feb. 27. Hydro Director Dawn Woodward reported at the May 13 PUD commissioners meeting that the cause of the crack was a math error in the calculations during the design phase.

The same error affected the construction of the entire dam, she said, and the repair plan included reinforcing all the spillway pillars. At Monday's commission meeting, Woodward said those repairs are underway also.

The pillars will be reinforced with cables inserted into holes drilled through the pillars into the bedrock, stretched tight and the holes filled with concrete. The holes already have been drilled, Woodward said, and the cables will be made to order, depending on their position.

The cracked spillway will get additional anchors to close the fracture, she said. The principle is the same as the pillar reinforcement, a cable stretched and cemented in place. Woodward said that might require more anchors than first estimated, because officials discovered the cracked pillar could have the potential to slide forward without sufficient reinforcement.

The repair plan has been submitted to the Federal Energy Regulatory Commission and a board of consultants overseeing the project, Woodward said. The plan hasn't been approved by the regulators, and board member Terry Brewer asked if the PUD was taking a chance by proceeding with repairs before FERC signed off.

Woodward said the PUD is taking a risk, but FERC officials have talked about the plan with PUD officials, and she thought there was little risk the plan would be rejected.

The water levels behind Wanapum Dam had to be dropped in order to keep the crack from widening. They're still at the Feb. 27 level. Woodward said she anticipated that the utility will need to complete the repairs on the cracked pillar and reinforce the remaining pillars before it will be allowed to raise the water level.

The lower water levels have exposed large sections of land that are usually underwater, and for environmental and cultural reasons PUD officials have closed the shore. Memorial Day was the first holiday weekend of the summer, and law enforcement and dam security talked with plenty of people from Friday through Monday, said Jeff Grizzel of the PUD. They made about 900 contacts in all, Grizzel said, but there were no citations or arrests.

The lower water levels required remodeling the fish ladder at Wanapum, and so far it's working, Grizzel said. Additional remodeling may be required to accommodate the upcoming sockeye salmon runs, he said.