Drawdown eases pressure on Wanapum dam crack

Drawdown eases pressure on Wanapum dam crack

Wanapum Dam's 12 spillways - the impacted spillway is the 4th pier from the left

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by KREM.com

KREM.com

Posted on March 4, 2014 at 11:10 AM

Updated Tuesday, Mar 4 at 11:51 AM

BEVERLY, Wash. – Engineering surveys taken at Wanapum Dam showed that the cracked area found on one the dam’s spillways was stabilizing, officials said Tuesday.

WATCH: Crack in Wanapum Dam triggers Flash Flood Watch

As of Monday, the crack had closed by nearly an inch, and the damaged section of the spillway monolith moved back upstream by approximately 1 inch. Officials said the measurements confirmed that the section was becoming more stable as a result of lowering the water level behind the dam.  Additional alignment measurements were planned Tuesday.

WATCH: Diver finds crack in Wanapum Dam spillway

The drawdown of the Columbia River was a stabilizing measure taken after divers inspecting the condition of Wanapum Dam discovered a 2-inch wide horizontal crack across one of the dam’s 65-foot spillways on Feb. 26.  Grant County PUD then decided to drop the reservoir by about 25 feet.

A spillway is the portion of the dam that allows water to “spill” past the dam as opposed to running through the turbines.  Each of Wanapum Dam’s 12 spillway gates are capable of passing roughly 63,000 cubic feet of water per second based on current river conditions. In a worst case scenario, if one of the spillway sections failed, the remainder of the spillways and the main dam structure would remain intact.

Wanapum Dam continued to generate electricity Tuesday. With the reservoir at historic lows, boat launches were closed and people along the shoreline were reminded not to dig for archaeological objects in the newly exposed areas.
 
Grant County PUD planned to continue to work in conjunction with the Federal Energy Regulatory Commission and other officials to monitor and evaluate the situation.






 

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