The radioactive wastes in Hanford's Tank SX-104 dipped two inches a week ago.

Two Hanford watchdog groups say that's because it's leaking.

The Department of Energy says that's because the barometric pressure increased.

And the Washington Department of Ecology accepts the barometric pressure theory, but is keeping an eye on the situation.

The two-inch drop was recorded Dec. 10 - and rechecked Thursday. Then the waste level crept back up to normal levels by Tuesday. Lockheed Martin Hanford Co. reported the fluctuation to DOE Monday.

The Government Accountability Project and Heart of America Northwest criticized DOE on Tuesday for allowing a tank to leak and for delaying several days to make the suspected leak public.

Tank SX-104 is one Hanford's 177 underground radioactive waste tanks, and is one of 67 on the "suspected leaker" list.

In 1988, it leaked 6,000 gallons. Then DOE pumped out 113,000 gallons, halting when signs of leaking disappeared. That left about 200,000 gallons in the tank.

DOE officials were not sure why the 200,000 gallons were left in 1998 but speculated tank space might not have been available to receive the remaining waste as it would have been pumped.

Meanwhile, liquid wastes in 63 of the 67 suspected leaking tanks have been pumped out to safer double-shell tanks - leaving the four remaining suspected leakers to be pumped by the end of September next year.

Hanford began pumping out Tank SX-104 last September, but a line clogged in three places after 500 gallons were pumped. The last clog was cleared Monday.

Meanwhile, the surface of the liquid wastes inside Tank SX-104 normally fluctuates about three inches. But on Dec. 10, the level was measured at two inches below its normal range.

A rule of thumb is that one vertical inch in a tank equals about 1,000 gallons, DOE officials said.

GAP and Heart of America issued a press release Tuesday charging that:

4,000 gallons had leaked from the tank since Dec. 3, the time of the last normal reading.

Hanford recently cut tank-pumping funds, boosting risks of wastes leaking into the ground.

DOE and Lockheed did not immediately - meaning by Thursday - notify the public of the suspected leak as required by a 1994 settlement of a tank-related lawsuit the two groups pursued against DOE.

Jackson Kinzer, DOE's assistant manager for the tank farms, said heavy atmospheric pressures occurred Dec. 10 and Thursday, entering the tank through its vents to increase the internal barometric pressures to push the liquids down.

Mike Wilson, the Ecology Department's nuclear program manager said: "Based on the information we've seen, that seems to bear out." He added that the state will monitor the tank to see if the theory holds up.

But Tom Carpenter, an attorney for GAP, said, "I don't buy that." The two-inch drop was too great not to be a leak, he said.

Meanwhile, Kinzer said budget crunches forced DOE to shift some tank pumping money to build infrastructure to move and prepare wastes to eventually convert into glass - Hanford's ultimate goal for the wastes. The four suspected leaking tanks are scheduled to be pumped in fiscal 1998, he said.

Kinzer and Wilson said their agencies were told of the abnormal fluctuation Monday. Kinzer said Lockheed needed to first study and verify what happened.

Kinzer criticized Heart of America's and GAP's press release. "It was unprofessional for them to put it out. They did not have the data verified," he said.

However, Carpenter contended it is better to publicly voice suspicions about leaks as they materialize, criticizing the five-day delay in notifying DOE. "They need to tell the public and DOE a lot sooner," Carpenter said.

Wilson believed the notification issue is moot - as long as barometric pressure is the cause for the fluctuation.