Work underway to stabilize Wanapum Dam

Workers have installed the first of 35 giant anchors intended to stabilize the broken Wanapum Dam.

The Grant County Public Utility District said Tuesday the anchors begin at the top of the spillway and run deep into the bedrock below the dam, ensuring the long-term stability of the spillway on the Columbia River near Vantage. The 200-foot-long anchors will be installed throughout the spillway.

Work is also underway to use 50 steel bars to repair a portion of the spillway where a crack appeared earlier this year. That work has been likened to driving screws into a block of wood.

The cost of the repair work is estimated at $69 million and will continue into next year, said utility officials who believe that with federal approval they can begin raising the water level in the reservoir behind the dam by the end of the year.

The reservoir was lowered 26 feet after the 65-foot crack in the spillway was discovered in February at the dam.

Once the water level is raised, the utility can restore public access to the shoreline, generate more electricity, address public safety concerns and protect culturally sensitive sites that were exposed by the low water level.

Until then, the shoreline and access points will remain closed to the public, the utility said.

The utility will pay for the repairs with cash reserves and bond sales. It is not expecting any rate increases for customers beyond the previously planned 2 percent included in the current forecast.

Wanapum Dam continues to generate electricity at a reduced level, the utility said.

Modifications of Wanapum Dam’s two fish ladders proved successful during this year’s record-breaking adult salmon migration. Over 700,000 salmon and steelhead have already passed the dam on their journey to upstream spawning habitat, the utility said.

The drawdown of water also allowed the utility to accelerate plans for improvements to three boat launches on the reservoir.

In May, the utility determined the crack stemmed from a math error during construction in the early 1960s. It said more concrete and reinforced steel should have been used in all 13 of the spillway’s supporting blocks.

Investigators believe the crack may have originated a number of years ago and spread gradually, ultimately allowing enough water into the fracture to push the upper portion of the spillway pier out of place, revealing the problem.