Below is the Falk Recreation Center at Einstein Medical College in the Bronx. This building's green roof was financed by the NYC Department of Environmental Protection's Green Infrastructure Grant Program.
The tour given by Paul Mankiewicz, who designed this green roof explained that it sits above a swimming pool, so he wanted to pump its "back-flow" water up onto the roof for irrigation, rather than waste it down the drain. Won't the chlorine kill the plants? No, because Paul designed a system where the pool water is sprayed out over the plants to allow the chlorine to off-gas quickly. (Chlorine evaporates from tap water as a gas.) Further treatment of the water can be accomplished easily by applying wood ash to the soil where the water is delivered, he explained.
The plants are thriving quite nicely, in a very lightweight soil that Paul invented, called "Gaia Soil," which incorporates up-cycled polystyrene into its mixture. Like most of his green roof designs, this one contains only local, native perennials so that the earth displaced by the building below can still provide habitat for the many birds and butterflies which depend on these plants for their survival. These plants also do an excellent job of cleaning the air, cooling the building below, and providing a beautiful, brightly colored natural view from the many surrounding buildings. We loved it too!