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.
HydroWorld.com 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:
- Seismic activity
- Foundation settlement or uplift
- Activities at the U.S. Army's Yakima Training Center
- 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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