Minneapolis shows "green" leadership

A 2.5 acre green roof—the largest green roof in Minnesota—will reduce the heat island effect downtown and prevent one million gallons of storm water drainage into the Mississippi

Target Center's green roof. Source, and more photos.

September 15, 2009 (MINNEAPOLIS)—

The City of Minneapolis celebrated the greening of the Target Center roof at a completion celebration today on top of the arena. 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 Target Center is also the first arena in North America to install a green roof.

“We lead best by example,” said Council Member Lisa Goodman, “and building one of the nation’s largest green roofs will allow us to ask others to do the same.”

“With the redesign of the Target Center roof, Minneapolis has again proven that sustainability and economic progress can go hand in hand,” said Minneapolis Mayor R.T. Rybak. “Green initiatives such as this will not only improve the environment for city residents, but continue to cast Minneapolis as a leader when it comes to green industry.”

Benefits of the Green Roof reen roofs provide ecological benefits by reducing the negative effects of hard sufaces, like traditional roofs, on stormwater quality, volume, rate, and temperature on the receiving waterbody, in this case, the Mississippi River. It is estimated the green roof will capture one million gallons of stormwater annually, preventing drainage into the Mississippi River.

The green roof will also help in mitigating the heat island effect in downtown Minneapolis by reducing the roof’s temperature by as much as 80 degrees Fahrenheit.

There are opportunities, under public contract, to provide jobs for Minneapolis residents; 75% of the workers who worked on the installation of the roof were Minneapolis residents. Twenty of the workers were graduates of training programs at Summit Academy OIC.

Construction of the Vegetated Roof

Pre-grown mats of sedum plants create the base of the green roof system. Mats were laid 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 1.75” growing zone in the center of the main arena roof structure and a deeper 2.5” growing zone around the perimeter where the structural capacity is greater to maximize storm water retention and plant vigor. The roof uses the pre-grown mats as the base of the green roof system and contains a variety of Sedums and Minnesota prairie plants, including Columbine, Lanceleaf Coreopsis, Wild Strawberry, Dotted Blazing-Star, and Lupine. It includes lupines to target the Karner Blue Butterfly, a federally listed endangered butterfly that needs lupines to survive.

Prairie seed was also used to increase long-term resilience of the green roof. More than 11 miles of sustainable, water-efficient irrigation lines were installed and 14,000 cement  pavers for firebreaks and roof protection laid.

Minneapolis as an Environmentally-Friendly City

Minneapolis is recognized as one of the most environmentally friendly cities in the country. Target Center’s green roof is just one of many examples of how City government has led by example and taken advantage of the benefits of being green.

City Hall is also home to a green roof, and several Public Works and Fire Department facilities use solar arrays to help generate power. The City has also adopted a Leadership in Energy and Environmental Design (LEED) Silver standards, which require new or significantly renovated City facilities to meet some of the highest standards for sustainability in their planning, design, construction and commissioning.

A new ordinance limits vehicle idling in the city to reduce emissions, and Minneapolis is the first U.S. city to require higher fuel efficiency for taxis. The City’s innovative stormwater utility program has dramatically increased the use of rain gardens and other effective practices to protect our lakes from stormwater runoff. 

Minneapolis has also created a unique program to provide microgrants to community organizations to  upport their efforts to fight climate change.

Since Minneapolis’ sustainability initiative was launched in 2003, City leaders have developed a series of 25 indicators, including things like air quality, bike paths, green jobs, and tree cover. Each indicator includes specific numeric targets, which serve as goals for Minneapolis to reach in the coming years. To learn more about Minneapolis’ sustainability efforts, visit www.ci.minneapolis.mn.us/sustainability.

Reprinted from a press release.

Click here to see how other cities are going green.
Click here for an informative slide show on green roofs.
Little did I know, there's a whole green roof industry.

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