Questions are growing faster than answers about Hanford's 618-11 burial site, which is leaking a super-high concentration of radioactive tritium toward the nearby Columbia River.

The biggest questions focus on the small subterranean plume's horizontal and vertical speeds and directions. But right now, there are no answers or even really good guesses.

Eventually, answers or educated guesses will determine:

-- How fast the Department of Energy starts cleaning out the highly radioactive 618-11 site.

-- If neighboring Energy Northwest should worry about highly concentrated tritium seeping into two wells that provide drinking water for 50 employees working at the partly-built Reactor No. 1.

-- The speed and potency in which this underground glob of tritium will reach the river.

On Thursday, DOE and CH2M Hill Hanford Inc. officials updated reporters on the latest findings about the 618-11 burial site, which is 3 1/2 miles from the river.

The officials said Hanford has become more sure that the super-high tritium concentrations just outside of 618-11 actually are from the site's northeastern section and not from a much weaker massive tritium plume flowing through the same area. And experts believe the apparently narrow tritium plume has seeped roughly 260 feet east of 618-11 in an unknown period of time.

In the 1960s, highly radioactive wastes from the 300 Area -- including 11 to 22 pounds of plutonium -- were buried at 618-11 just northwest of Energy Northwest's complex. The wastes are in a variety of large containers, with many bottomless for unknown reasons. Hanford's records are incomplete on the wastes buried there.

In 1999 and early 2000, a monitoring well just east of 618-11 showed a previously unsuspected tritium concentration whose radioactivity was 8 million picocuries per liter. The federal drinking water standard for tritium -- based on cancer risks due to steady ingestion -- is 20,000 picocuries.

DOE and CH2M Hill then collected numerous soil gas samples -- looking for helium created by decaying tritium. Plus two new wells were drilled 60 feet down to the aquifer to collect ground water samples.

In October, these samples showed a short, narrow plume of excessively radioactive tritium oozing east. In October, a tritium concentration of 7 million picocuries was found where the earlier 8-million-picocurie reading was found just east of 618-11. And a reading of 1.5 million picocuries was found in another new well 260 feet further east -- putting it where Hanford's existing maps had shown very low and benign tritium levels.

Now the questions of speed, direction and other unknowns come in.

Tritium is Hanford's fastest-moving subterranean radioactive liquid -- moving at the same speed as ground water. The ground water around 618-11 area takes five to 30 years to reach the Columbia, said Jane Borghese, CH2M Hill's ground water monitoring task leader. Meanwhile, tritium's radioactivity decays by half every 12.3 years.

But this area's geology is tricky. Plus questions exist on how a small, highly concentrated tritium plume from 618-11 interacts with a huge plume of weakly concentrated tritium flowing from the 200 Area. Those factors influence the 618-11 tritium's speed and direction, Hanford officials said.

Energy Northwest is also in path of 618-11's plume, noted Mike Goldstein, a U.S. Environmental Protection Agency official. Most of Energy Northwest's drinking water comes from the Columbia.

But two wells reaching 400 feet deep at the never-finished Reactor No. 1 -- two miles southeast -- provide drinking water to about 50 people working there.

Those two wells are also the backups for about 1,000 Energy Northwest workers if the river supply system fails. There is one other deep backup well near Reactor No. 2 -- unused for many years.

Energy Northwest spokesman John Britton said Reactor No. 1's wells are frequently tested with all tritium samples showing less than 200 picocuries so far.

But the aquifer stretches vertically from 60 feet to 450 feet, which means extra tritium could seep into the 400-foot wells at Reactor No 1.

"We don't see an immediate threat at No. 1. But it is a threat, and we're keeping an eye on it," Britton said.

DOE does not plan to start cleaning out 618-11 until 2010. The site's heavy radioactivity means equipment must be invented to handle the wastes by remote control. And the estimated cost is $330 million.

Meanwhile, DOE wants to start up a plan early next year to clean up most of the riverside areas by 2012.

Many Hanford groups are not happy that 618-11 is not in that planned acceleration, and they are pushing DOE to speed up tackling 618-11 to that plan.

But Hanford's unions have indicated they would oppose adding 618-11 to an accelerated cleanup if it means working within the highly radioactive area before sufficient safety measures can be developed.

Hanford experts expect to know enough in about six months to be able to plan the next move on 618-11.