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The landscaped area in the Brisbane City Hall parking lot is actually an engineered system for treating stormwater runoff. This area, called a rain garden or bioretention area, collects stormwater runoff from both the parking lot and building roof. Runoff is treated as it filters through the specially-selected vegetation and soaks into the ground. Drain lines buried in the rain garden (the underdrain system) collect the treated water and send it through the City’s stormdrain system to Brisbane Lagoon and out into the Bay.
Another stormwater treatment system, called a bioswale, is located on the opposite side of City Hall along Valley Drive. In this system, parking lot and roof runoff is treated as it gradually flows along the length of the bioswale, being filtered by the grass and soaking into the ground before reaching the City’s storm drain system and flowing to Brisbane Lagoon and out into the Bay. These treatment systems help keep pollutants from our cars out of the Bay.
