The Wanapum Dam is downstream from the Vantage Bridge, which is the Interstate 90 crossing over the Columbia River in Washington state. (Grant County Public Utility District photo)

Engineers Monitoring Crack in Columbia River Dam

Water levels above the Wanapum Dam are being reduced to 20 feet lower than the normal high operating level to reduce pressure on the spillway after divers found a 2-inch-wide crack that was 65 feet long in the base of one of the spillway piers.

The Grant County Public Utility District is reducing the water level below its hydroelectric Wapanum Dam on the Columbia River because a major crack has opened along the base of one of its spillway piers. Divers confirmed Feb. 27 that the 2-inch-wide crack is 65 feet long, and the district is lowering the water level in the reservoir above the dam to reduce pressure on the spillway. As of March 3, the level will be 20 feet lower than the normal high operating level, according to a district news release that said district officials and independents engineers are monitoring the dam in conjunction with the Federal Energy Regulatory Commission.

Boat ramps in the reservoir can't be used for the time being because of the lowered water level.

The dam is downstream from the Vantage Bridge, which is the Interstate 90 crossing over the Columbia River in Washington state.

"The spillway consists of multiple, independent structural sections that support the spillway gates. Each of Wanapum Dam's 12 spillway gates are capable of passing roughly 80,000 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. 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," the district's release states. "The team of engineers and regulatory agency personnel are working through the weekend to provide constant monitoring and on-going evaluation of the area. Public safety is the utility's paramount concern. The dam continues to generate electricity without any additional constraints on electric generation except for reduced water levels behind the dam. All boat launches on the Priest Rapids and Wanapum reservoirs are currently unavailable because of the low river elevation."

The district also operates the Priest Rapids Dam on the river.

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