After commissioning, "Corner Brook" was deployed on the east coast of Canada, based out of Halifax, Nova Scotia. During a refit in 2006, elevated levels of lead were detected aboard the submarine; they were believed to come from the lead-brick ballast blocks used aboard "Corner Brook". Between October 2006 and January 2008, "Corner Brook" was active for only 81 days. The submarine participated in NATO exercise 'Noble Mariner' during May 2007. During the exercise, which occurred in the Baltic region, "Corner Brook" successfully closed with the aircraft carrier without being detected. The submarine returned to Canada, and in August, she participated in Operation Nanook, a sovereignty exercise held in and around Iqaluit and the Baffin Island coastal and Hudson Strait areas. That year, "Corner Brook" participated in the NATO exercise "Noble Warrior", marking the first time in 15 years that a Canadian submarine had been present in European waters.