A World War II-style grenade was exposed in the Columbia River by the drawdown of water behind the cracked Wanapum Dam.
The Grant County sheriff's office says it was found Thursday evening by security for the Grant County Public Utility District.
It was detonated by a Washington State Patrol bomb squad in a blast that may have been heard in Vantage. No one was hurt.
The sheriff's office says the grenade was rusty and had apparently been in the water a long time.