The Stanley Park Storm Water Treatment Wetland was developed in conjunction with the expansion of the Lions Gate Bridge and Stanley Park Causeway. Prior to expansion, run-off from the causeway flowed uncontrolled and untreated into the forest and streams of Stanley Park, as well as into Lost Lagoon, Beaver Lake and, eventually, Coal Harbour. Since plans to expand the causeway – which already averaged 65,000 cars a day – would increase the volume of polluted storm water being discharged, the Vancouver Board of Parks and Recreation insisted on a management system that would divert and treat this run-off.

The newly constructed wetland acts as a settling pond and natural treatment and filtration system for storm water run-off. First, oil and grit are captured before the run-off enters the system. Next, storm water enters a large pond where silt, sand and gravel settle out. In this pond micro-organisms and sunlight work to break down contaminants. Over time, run-off flows through a series of marsh terraces and deep pools where further contaminants are filtered and absorbed by native wetland vegetation and settled out in sediment before the treated water is released into Lost Lagoon. The new system diverts causeway contaminants from the vulnerable Beaver Lake ecosystem and significantly reduces pollutants entering Lost Lagoon and Coal Harbour.

The long-term aim of this facility is to retain storm water contaminants in a controlled area so as to protect the surrounding environment. The system is currently being supervised and maintained by the Vancouver Board of Parks and Recreation.