Grant PUD narrows causes of Wanapum Dam fracture

The foundation below Wanapum Dam was not a factor in creating the fracture on the structure’s pier monolith No. 4, Grant County Public Utilities District has determined. reported Grant PUD divers discovered a 65-foot-long by 2-inch-wide horizontal crack in the pier monolith in February, leading the company to hire Kuney-Goebel JV and subcontractors to perform the drilling as part of a forensic investigation in March.

Preliminary drilling was completed earlier this month, providing data Grant PUD used to determine the fracture was not caused by:

  1. Seismic activity
  2. Foundation settlement or uplift
  3. Activities at the U.S. Army’s Yakima Training Center
  4. Operation of the spillway gates

The utility said it anticipates drilling and the root cause analysis to be completed by June — both of which must be completed before repairs are made to stabilize the spillway.

Grant PUD is also working on modifications to Wanapum Dam’s fish ladders that were necessitated following a drawdown of the reservoir. The work should be completed by April 15.

The dam is also home to a 1,038-MW Wanapum hydroelectric plant. Grant PUD previously said the plant is only producing about half the electricity it would under normal river conditions.

The facility is a sister plant to the Priest Rapids project. Combined, the two have an output capacity of nearly 2,000 MW.

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Michael Harris formerly was Editor for

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