Installation of the 2.5 acre green roof—the largest green roof in Minnesota—is underway MINNEAPOLIS--(BUSINESS WIRE)--Installation of the 2.5 acre green roof vegetation on the City-owned Target Center begins today. Over the course of two days a 165 ton crane will hoist five truckloads of plant material, which includes 900 rolls of pre-grown vegetated mats of sedum and native plants for installation on top of the arena's main roof. More than 540 cu yards of soil is being blown onto the rooftop between 120'– 165' in the air, using a blower truck. The roof is the largest green roof in Minnesota and, at the time of design, the fifth largest green roof in the United States. The green roof is installed on a state-of-the-art waterproofing membrane which includes a leak detection system called Electro Field Vector Mapping (EFVM). The membrane will help withstand constant dampness, high alkalinity, and exposure to plant roots, fungi, and bacterial organisms as well as varying hydrostatic pressures. The green roof features a 2.75" growing zone in the center of the main arena roof structure and a deeper 3.5" growing zone around the perimeter where the structural capacity is greater to maximize storm water retention and plant vigor. The pre-grown mat of sedum and native plants creates the base of the green roof system and will be complemented by additional plantings of plants native to Minnesota's prairies once the roof is installed to enhance plant diversity and ecological resilience. To complete the roof by Fall 2009, 11 miles of sustainable, water-efficient irrigation lines will be installed and 14,000 concrete pavers for firebreaks and roof protection will be laid. Green roofs provide ecological benefits by reducing the negative effects of hard surfaces like traditional roofs on stormwater quality, volume, rate, and temperature on the receiving waterbody, in this case, the Mississippi River. At 113,000 square feet, almost 3 acres, this green roof has potential for mitigating stormwater runoff from a significant amount of impervious surface in a downtown location where space does not permit use of other Low Impact Development Techniques to mitigate for the negative effects of hard surfaces on receiving waterbodies. Positive impacts on local water bodies are valuable in a City that prides itself on its legendary waterbodies: The City of Lakes in the Land of 10,000 Lakes.
