By this time next month, the steam plant for Hanford's 300 Area just north of Richland should be gone.

The seven-story 384 Power House is one of the largest buildings remaining at Hanford's 300 Area and the last to come down in the north half of the area.

On Wednesday two excavators were tearing it down, including the portion of the building covered with asbestos siding. That's a change for Department of Energy contractor Washington Closure Hanford.

In the past, buildings with midcentury Transite paneling containing asbestos had the panels individually removed and lowered to the ground.

But at the steam plant, Washington Closure is using an excavator equipped with a bucket and a "thumb" to grab each panel, pull it from the building and lower it to the ground.

"It's pulling it down as gently as it can and in as big pieces as possible," said Rudy Guercia, the Department of Energy project director for Hanford's river corridor.

The panels weigh 138 pounds each and Washington Closure concluded it would be safer to do a mechanical demolition than to raise crews in baskets up to seven stories high to remove the paneling, said Mike Swartz, project manager for Washington Closure.

The 5-by-10-foot panels, which are more than double the size commonly used at other Hanford buildings, were bolted onto the building, then caulked at the seams.

"It makes it very hard to get out," Guercia said.

Washington Closure borrowed technology from another profession to help with the project. The panels are soaked with firefighting foam before they are removed as a precaution to reduce any airborne materials.

However, Washington Closure said the asbestos in the panels is nonfriable - it doesn't easily crumble into a powder that could be breathed in. The corrugated siding is thicker but similar in composition to siding used on many Richland homes built during World War II and the early years of the Cold War.

Before work to remove the panels began, one of the steam plant's panels was accidentally knocked to the ground during demolition of an adjoining portion of the building. Work was briefly stopped and the Environmental Protection Agency confirmed that asbestos had not become airborne at detectable levels.

Sampling is being done in nine locations to check for airborne contamination. None has been recorded, according to DOE. The EPA will get its first daily monitoring report today.

The contractor's work plan requires it to comply with the National Emission Standard for Asbestos, said Alicia Boyd, EPA environmental engineer.

While siding is being removed, a second excavator equipped with shears is tearing through the metal and cinderblock portions of the 60,000-square-foot building. Both excavator operators are wearing respirators and water is sprayed onto the demolition site to keep down dust.

Before demolition began, workers spent seven months inside the building preparing it, including draining equipment oil and removing friable asbestos from 10,000 feet of piping, Swartz said.

Moving from manual removal of the siding to mechanical removal will speed up the demolition. The work that the excavator can do in 10 minutes would take workers several days, Guercia said.

The building, which supplied heat and steam power for operating heavy equipment from World War II until the mid '90s, should be gone in about three weeks. If the demolition method proves successful, it could be used at other Hanford facilities along the Columbia River, including the K Reactors.