Engineering surveys carried out at the Wanapum Dam on the Columbia River this week have shown that a crack found in one of dam’s spillways is stabilizing.

In a statement, Grant County PUD said that surveys carried out on Monday show the crack had closed nearly an inch, with the damaged section of the spillway monolith having moved back upstream by approximately 1 inch. The PUD said this confirms that the section is becoming more stable as a result of lowering the water level behind the dam. Additional alignment measurements were planned.

The water level behind Wanapum currently stands at a historical low of around 543ft asl. The river drawdown is been carried out as a stabilizing measure after divers inspecting the condition of the spillway discovered a 2-inch wide horizontal crack across one of the dam’s 65-foot spillways on February 26.

Grant PUD continues to work in conjunction with the Federal Energy Regulatory Commission as well as upstream dam operators and stakeholders to monitor and evaluate this incident. Public safety and the safe operation of the dam is the utility’s top priority, it said.