Crack in Wanapum Dam closing

BEVERLY — A crack discovered in a spillway at Wanapum Dam has closed by almost an inch, the result of lowering the level of the Columbia River behind the dam, according to Grant County PUD officials.

Engineers surveyed the spillway Tuesday and found the damaged portion of the spillway had moved back upstream by about 1 inch, according to a PUD press release.

The horizontal crack was discovered Feb. 26, after engineers doing a routine inspection found a slight bend in the upper level of the spillway the previous day. Divers did a follow-up inspection and found the horizontal crack, about 2 inches wide, which spans the entire width of the spillway, about 65 feet. The crack was about 70 feet below the surface.

Grant County PUD officials lowered the river level behind the dam in response. Currently the pool behind the dam is about 543 to 545 feet above sea level. Normally the water level is about 570 feet, the press release said.

"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 press release said.

The drawdown put the river at historically low levels, exposing new sections of shoreline. "We remind those that visit the shoreline during this time not to damage or disturb the shoreline area. Recreational vehicle activity along the shoreline is prohibited," the release said. State and federal laws prohibit removal or alteration of any archeological object along the shoreline.

The spillway allows water to spill past the dam instead of being diverted to the turbines. It is built from "multiple, independent structural sections that support the spillway gates," the press release said.

More information on the incident and the steps being taken to fix it will be available in Wednesday's Columbia Basin Herald.