If approval to clear the smelter site is granted by the NSW Government, carefully designed explosive charges will topple the 198m tall stack like a giant falling pencil.

Yesterday Port Kembla Copper general manager and director Ian Wilson confirmed a major project application had been lodged with the Department of Planning to clear the controversial site of all buildings and structures in preparation for sale.

The copper smelter was closed on July 28, 2003, after a Japanese consortium spent more than $600 million on new technology that ultimately did not live up to environmental and operating claims made by the company and an enthusiastic Premier Bob Carr.

"This decision by the company and its Japanese partner effectively ends more than a century of smelting on the site," Mr Wilson said.

He said because the stack did not conform with existing standards for earthquake, wind loading and strength, the company had little choice but to demolish it.

Its fate was finally sealed after an engineering inspection uncovered carbonisation, colloquially known as concrete cancer, throughout the stack's outer layer.

Large chunks of concrete have begun falling from the very top sections of the stack, posing a potential safety risk.

"We are now patrolling the area around the stack every day to keep an eye on things until we get the go-ahead to demolish the site," Mr Wilson said.

The stack's end would be a low-key affair in the wake of the tragedy surrounding the demolition of the Royal Canberra Hospital 10 years ago.

The ACT Government urged tens of thousands of citizens to show up for the Canberra Day demolition, but it ended in disaster with 12-year-old Katie Bender killed by flying debris.

"I've read the coroner's report and such a thing will not be promoted on this occasion," Mr Wilson said.

Soon after the smelter's shutdown in 2003, the area was declared a risk site and the company capped large areas of contaminated land using concrete or asphalt, and extracted contaminated groundwater.

That work was completed to the satisfaction of the Department of Environment and Climate Change, but monitoring of the site will continue for at least another five years.

Once approval for demolition is received, it will take between 12 and 15 months to clear the site.

The only two things expected to be left standing are a small brick chimney and the assay office fronting Military Rd - both are heritage listed.