A large dam in Washington state has a 65-foot-long crack below its waterline, say officials who are planning repairs at the Wanapum Dam, which is owned by a county utility. Divers found the 2-inch-wide crack that runs sideways after an engineer noticed an odd curve in a conduit near the dam's roadway.
Officials have said the public is not at risk.
To assess the damage, the water behind the dam on the Columbia River is being drawn down to the shallowest levels since its reservoir filled some 50 years ago, according to the Grant County Public Utility District. At 7 a.m. PST Tuesday, the National Weather Service reports, the water level stood at 545 feet — more than 24 feet lower than its recent high recorded a week ago.
"At this point we already know there's a serious problem," Thomas Stredwick, spokesman for the Grant County Public Utility District, told The Seattle Times after the crack was found last week. "We want to make sure the spillway is stable enough that inspectors are safe when inspecting it."
The utility says that while "survey readings taken [last week] showed that the area has moved outside of historical norms," other recent surveys didn't show additional movement. A photo posted by the utility shows what the county employee saw last week: a pronounced curve in a conduit and part of the concrete, just below the guardrail where cars drive on the dam's road surface.
The agency has closed the dam's park and announced that boats can't be launched nearby because of the lower water levels. Official say repairs may take up to a month. The problem is being worked on by both local and federal officials, as Northwest Public Radio reports.
The hydroelectric dam near the town of Vantage in central Washington is more than a mile and a half long, according to the Grant County utility. The entire spillway, which includes the damaged area, is 820 feet long.
On the utility's website, Stredwick explains the affected area:
"A spillway is the portion of the dam that allows water to "spill" past the dam as opposed to running through the turbines. 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."
But local residents are concerned.
"It's pretty crazy. It's one of the biggest dams in the state, and it's going to be a catastrophe if something happens," Kyle Rosskelly tells TV station KIMA in Yakima.