The water level is being lowered at Wanapum Dam on the Columbia River in the US as engineers work towards stabilizing a crack found on the dam’s spillway.

The precautionary drawdown will see the river at its lowest level since completion of the reservoir in 1964.

Dam operator Grant Country Public Utility District is working in conjunction with the Federal Energy Regulatory Commission as well as upstream dam operators and stakeholders to monitor and evaluate the 65ft long, 2-inch wide horizontal crack which was discovered by divers inspecting the dam’s spillways on 26 February. A Grant County PUD employee noticed a slight bend in the conduit below a guardrail at the dam, which led to the spillway inspections.

The crack is at the bottom of the fourth spillway pier from the left in the photo below. A slight bend is noticable in the conduit below the guardrail. This anomaly spotted by a Grant PUD employee resulted in discovery of the crack.
The crack at Wanapum Dam is at the bottom of the fourth spillway pier (left in this photo) Wanapuma Dam deck
(Photos Courtesy GrantCounty PUD)  

The dam is continuing to produce electricity, but is closed to the public for recreational use. Grant PUD said the dam is not at risk of causing downstream flooding, with a spokesman confirming that even 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. Under current conditions, the amount of water that would flow through this section of the dam would be within the range of normal river conditions.