Hanford workers have retrieved as much waste as possible from the first five single-shell tanks at Hanford until the tanks are ready to be closed, the state of Washington has confirmed.

That clears the way for planning and preliminary efforts to demonstrate some of the work that will be required to close the Hanford tank farms, where 53 million gallons of high-level radioactive waste are stored in underground tanks.

Demonstration work likely will include adding a small amount of grout to one of the tanks and cleaning up some of the highly contaminated equipment around the tanks, such as piping.

"The road to closure is a lengthy road," said Moses Jaraysi, a CH2M Hill Hanford Group vice president.

CH2M Hill, the Department of Energy contractor for the tank farms, believes it has completed work to retrieve waste from seven of Hanford's 149 leak-prone single-shell tanks.

The state so far has finished its assessment on the first group of five, finding that the initial retrieval requirements of the legally binding Tri-Party Agreement have been met. It based its decision on an in-depth review of waste sampling and analysis, chemistry data and measurements to estimate how much waste remained in the tanks.

Estimating the waste left in the enclosed tanks has been done by lowering video cameras inside the tanks to photograph waste on the concave bottom and then transferring information to a computerized drafting program. Estimates also had to be made on how much waste is sticking to the sides of the tanks and resting on ridges that circle the inside.

The final determination is that the largest tank, which is 75 feet in diameter, contains 340 cubic feet of waste on its bottom and sides. That is within the legal limit of 360 cubic feet.

Four smaller tanks have 18 to 20 cubic feet of waste, which is well within the legal limit of 30 cubic feet. Limits were set to ensure at least 99 percent of waste is removed from the tanks.

The state considered the chemical risk, whether the limits of technology had been reached in emptying the tank and the amount of waste remaining in determining that retrieval work had been completed.

However, the public should not consider the work finished, cautioned Jeff Lyon, a nuclear waste program specialist for the state. The tanks still must be closed, which could require them to be removed from the ground or for the tanks with remaining waste to be filled with grout or other material to prevent them from collapsing.

No decision will be made on tank closures until completion and approval of the Hanford Tank Closure and Waste Management environmental impact statement. A draft of that report could be ready in August.

But DOE, Hanford contractors, the Washington State Department of Ecology and the Environmental Protection Agency have discussed what information may be needed to make good decisions on how to close the tanks, Lyon said.

Whatever closure method is picked likely will require grout to be mixed with the remaining waste to stabilize it or protect workers.

A demonstration project would add less than a foot of grout to one of the tanks.

The demonstration project also could test ways to clean up ancillary equipment, such as piping, valve boxes and pits, which are the concrete boxes connected to risers from the underground tanks that allow access into the enclosed tanks.

Although cleanup work has been done elsewhere at Hanford on similar ancillary equipment, it has not been done on equipment contaminated with high-level radioactive waste.