A Calgary man is facing numerous charges after police discovered large-scale marijuana grow-ops in two industrial parks.

The 53-year-old man was arrested earlier this month after a five-month investigation by the Alberta Law Enforcement Response Teams (ALERT).

Last August, police found evidence that a grow-op had previously been set up in a rented space in the Airways industrial area in northeast Calgary.

A fully-operational 814-plant set-up, worth more than $1 million, was found in the southeast Foothills Industrial Park in December.

The inside of both units had been set up to be used exclusively to produce marijuana, resulting in significant damage.

Both premises were declared unfit for human habitation by city building inspectors and Alberta Health Services.

The 400-member ALERT team is made up of municipal police, RCMP and provincial sheriffs.