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Sustainable City Center: Tree Canopy and Permeable Parking Lot
April 2004 - December 2005 (completed project)
The Minneapolis Parks and Recreation Board is using a $100,000 EPA Great Cities grant for two sustainable design projects that will help relieve some common environmental problems found in urban core areas. In one part of the project, 44 locust and elm trees were planted on a downtown city street to demonstrate and measure the benefits of a tree canopy on the so-called urban heat island effect. The other part of the sustainable design project calls for developing guidelines for the construction of permeable surface parking lots to reduce urban stormwater runoff. A media event Sept. 19, 2005, with EPA and city officials publicized the tree and parking lot project.
The EPA grant is being leveraged by $40,000 from a Minneapolis community group to plant additional shrubs and bushes near the new trees. Another $40,000 in funding will be provided by a watershed management organization to help the city build a demonstration parking lot with environmentally friendly permeable surface. The tree canopy and permeable parking lot will modify some of the negative effects of the asphalt jungle such as excessive urban heating and stormwater runoff. On warm sunny days the concrete and asphalt structures in an urban core grow hotter and retain heat longer as compared to more natural areas. This is the urban heat island effect. The higher temperatures increase energy used to cool buildings. The same man-made structures create water runoff problems. Most of the rainfall that occurs in a downtown area runs off impervious surfaces, picking up pollutants along the way and then draining into nearby streams or causing sewer systems to overflow. A typical city block generates more than five times the runoff than a woodland area of the same size.
There are a number of studies which have examined the benefits of urban trees in terms of energy use. Some studies have shown one shade tree can reduce air conditioning needs by up to 30 percent. Trees also dampen noise and absorb air pollution. Minneapolis will use a U.S. Forest Service model to calculate the benefits of its new trees. As an extension of developing a sustainable tree canopy, the city will undertake a study into environmentally friendly parking lots. If the Minneapolis demonstration lot shows promise in reducing rainwater runoff, a model city ordinance will be developed. Both parts of this project will add to the body of knowledge about how to make cities more "green." It is expected the Minneapolis tree canopy and parking lot demonstrations will provide important environmental benefits and add data to the emerging science of sustainability.
Contacts
EPA Minneapolis Great Cities Leader:
- Syed Quadri, 312-886-5736, ( quadri.syed@epa.gov)