The federal government is officially ramping up its plans to clean up contaminated sites across Canada, promising to create 7,300 jobs in the process.

Environment Minister Peter Kent launched the next phase of the government's long-term plan on Thursday, targeting the remediation of 1,100 high-priority sites over the next three years.

High-priority sites are places officials believe are having the biggest impact on human health and the environment.

Experts will also be assessing about 1,650 additional sites to see how toxic they are and how much they will cost to clean up.

"Our past has made us what we are today, but some of those past practices have had harmful effects on the environment," Kent told a news conference at Ottawa's National War Museum, which sits on remediated land.

"Our government is committed to addressing those effects and ensuring our government is protected for all future generations."

$1B to be spent over 3 years

About $1 billion has been set aside for the three-year exercise — money that Kent said will create 7,300 jobs in waste management and remediation, or about 1,500 full-time jobs per year.

It's the second part of a 15-year program that was created in 2005, backed by $3.5 billion in funding.

The federal environmental auditor recently pointed out that Ottawa's contaminated site funding falls $500 million short of meeting outstanding liabilities. And there's little information about how much the thousands of unassessed sites will cost to clean up.

There are more than 21,000 probable sites in the federal government's inventory — so many that the environmental auditor says Ottawa can't possibly assess the full extent of the risks to human health and the environment.

"In our view, given the number of sites that remain to be assessed, the government cannot know the full extent of potential risks to human health and the environment that federal contaminated sites pose," Environment Commissioner Scott Vaughan wrote in his spring 2012 report.

Most sites in Ottawa, Montreal

Hundreds of the sites are in cities, he said, pointing in particular to Ottawa and Montreal. Often, the sites are near aquifers that are tapped for drinking water, he added.

"The government has not created a consolidated strategy for ensuring that all federal contaminated sites are adequately addressed. There is a need to assess the risk that financial resources may not be sufficient to achieve planned results."

The auditor's examination of the sites that have been remediated so far suggest that most of them have soil contamination as a result of fuelling activities, spilling, leakage from storage tanks or dumping of contaminants.

Groundwater and surface water are also often at stake. And air quality is at risk if fumes or dust emanate from the sites.

The contaminants are usually toxic so that even small amounts can have nasty effects. Often lead, arsenic or radioactive substances have been identified.