The Target Center recently had a 2.5-acre (1-hectare) green roof installed on it. It includes 900 rolls of pre-grown vegetated mats of sedum and native plants. More than 1,580 cubic feet (413 m 3) of soil was blown on the roof top, to a maximum height of 165 feet (50 m). The roof features a 2 3/4-inch (70-mm) growing zone in the center of the main arena roof structure and a 3 1/2-inch (89-mm) growing zone around the perimeter where the structural capacity is greater to maximize storm-water retention and plant vigor. Additional plantings of species native to Minnesota prairies are planned, in addition to water-efficient irrigation lines and concrete pavers.