Wanapum Reservoir full
Workers prepare to replace concrete on the downstream side of Wanapum Dam.
BEVERLY - More than a year after a crack was discovered in a spillway pillar, Wanapum Dam is back at normal operating levels, and the reservoir behind the dam is full.
As of March 25, the water was at 570 feet above sea level, which is considered in the normal range of operations, said Chuck Allen, PUD public affairs officer.
All boat launches are operational, except for those closed due to construction. Boat launches operated by Washington Fish and Wildlife Department were expected to open about last week, Allen said.
Current estimated cost of the repairs is $69 million, Allen said.
The crack was discovered in a spillway pillar in late February 2014 and required an immediate drawdown of the reservoir. Water levels dropped as much as 26 to 30 feet, according to the PUD. Rock Island Dam operator Chelan County PUD was required to drop the water levels behind Rock Island.
When Grant PUD employees looked for the cause of the crack, they found a calculation error in the original design. That meant repairs were required for the entire dam.
The repairs required reinforcing all spillway pillars, starting with holes drilled through the dam and into the bedrock. Cables were cemented into place and stretched out before being tied off.
The cracked pillar supports the fourth spillway gate, and required additional reinforcement. The crack caused damage to the pillars on either side also, and they too required extra repairs.
A concrete structure at the bottom of the third spillway pillar had to be replaced, and the fourth pillar received additional reinforcement with metal cables and bars. Work on that is continuing, since it could be completed after the reservoir was raised back to operating levels.
The left riverbank has settled in some spots in the half-century since the dam was built, and some reinforcement was required there also.
After the cables are tied off, they're capped and cement will be poured over the caps. That work, and the final repairs, are continuing, and should be completed by June.
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