A tank leaking plutonium at a contaminated nuclear waste site in Washington has prompted the state's governor to sound the alarm over the threat it poses.

"The lack of an immediate threat does not in any way shape or form should be allowed to reduce the recognition of the long-term threat of this material reaching the ground water or the Columbia River," Governor Jay Inslee said Saturday.

The U.S. Department of Energy has confirmed liquid levels are dropping in one of nearly 200 underground tanks at the Hanford Nuclear Reservation, about 400 kilometres southeast of Vancouver.

While there's no immediate risk to human health, critics worry it's only a matter of time until the toxic sludge finds its way into regional food systems.

Tom Carpenter, executive director of Hanford Challenge, a non-profit that monitors the nuclear reservation said state officials are now waiting for the federal government to patch the leak.

Carpenter said a plan is in place to drain the tanks and solidify the waste into glass, but the treatment plant meant to do the work has been plagued with problems.

"Mismanagement, short-range-thinking, profiteering by contractors and incompetence by the government agency that's supposed to be running this plant," said Carpenter.

Over the years, more than a million gallons of radioactive waste have already leaked into the ground at Hanford.

Carpenter said plutonium has already been detected in local fish stocks and worries that if changes don't come soon, wild salmon stocks could be next.

He said his organization is now asking the U.S. Congress for help.

With files from the CBC's Luke Brocki