Math error likely cause of Wanapum Dam crack

EPHRATA - The root cause of a crack in the base of a spillway pillar at Wanapum Dam was an error in the math calculations during the design phase. The work necessary to fix the crack, and the whole dam, could mean the reservoir won't be partially refilled until October or later, according to information provided during the regular Board of Commissioners meeting Tuesday.

The crack was discovered in one of the spillways Feb. 27, and Grant County PUD officials immediately dropped the water level. Hydro Director Dawn Woodward said PUD officials went all the way back to the beginning, and found a mathematical error in the design calculations.

The error affected all the pillars, Woodward said, and as a result repairs may need to be made to the entire structure. Because of that, Woodward estimated the water levels probably will have to stay low until sometime in the last three months of 2014.

The crack probably developed a few years before it was discovered, she said, and grew over time. The PUD analysis team drilled holes to determine the extent of the fracture, she said, but have experienced trouble drilling on the front face, called the tail race. As a result, PUD officials don't know how far the crack extends, but are prepared to make repairs all the way to the front face, she said.

The PUD's conclusions, and details of proposed repairs, will be submitted to a board of consultants and the Federal Energy Regulatory Commission, Woodward said. The board of consultants is finishing a review of the proposal Wednesday, she said, and may add more conditions before approval.

Woodward said there's no time estimate for raising the pool to its normal operating level.