Ottawa taxpayers are on the hook for $3.5 million to clean-up the site of a former high school that's about to be transformed into a shopping centre.

The money will be paid out to Clydesdale Shopping Centres over a period of 10 years. The company plans to build a retail and commercial centre at the corner of Baseline Road and Clyde Avenue, which was previously home to Laurentian High School.

It's believed Wal-Mart will be the anchor store at the site.

Clydesdale applied for the grant under the city's Brownfields Redevelopment Program, which helps defray the costs of cleaning up contaminated sites.

According to the city, the soil and groundwater at the location is currently contaminated by underground fuel tanks that were previously located at the site.