Sponsored by Ontario Ministry of Environment, Ontario Great Lakes Foundation, Great Lakes Sustainability Fund and the City of Sarnia, Ryerson University has installed two 5m³ Atlantis exfiltration tanks in the lowest part of a parking lot area in Sarnia, ON. Sizing of the exfiltration volume was based on the 2003 MOE Stormwater Guidelines. The parking area is about 1000 m². The tanks are intended to test two retention volumes: 5 m³ (1st yr) and 10 m³ (2nd yr). A complete monitoring program using on-site monitoring instrumentation is in place. The Atlantis tanks have been performing as expected since they were installed.