The Priest Rapids dam which is up river from the Hanford Reservation is leaking approximately 4 gallons per hour however authorities say there is no immediate threat to the public or property...

According to a post from KNDU News:

Grant County, WA- Officials investigating leaking at the Priest Rapids Dam on the Columbia River say the source is likely the layers between large sections of concrete.
Right now, the dam is leaking up to four gallons of water a minute at four lift joints, the area between concrete blocks poured at different times.
But so far, the Grant County PUD says the dam continues to operate as usual and there's no threat to people or property.
The utility declared a "non-failure emergency" in late March after inspection drilling found leaking in the spillway monoliths. Dam operators lowered the reservoir behind the dam to lessen pressure.

The utility says that inspection drilling has been completed on about half of the spillway and will continue into May.