Milwaukee – Re-routing the Rain

Since the 1990s, Milwaukee has conducted various tree canopy studies, including measuring the benefits provided by the city’s trees. According to one of the most recent analyses, a 2008 assessment using the U.S. Forest Service’s i-Tree and UFORE tools, more than 3.3 million trees are growing in the city, covering 21.6 percent of the city’s land with tree canopy.[1] Approximately 200,000 of these trees are street trees, which are cared for by Environmental Services. According to Milwaukee’s Forestry Services manager, David Sivyer, about 98 percent of all street sites that are able to support trees currently have trees, and these trees help mitigate some of the city’s stormwater issues.

Milwaukee, like many cities, has a combined sewer system in place, meaning that untreated sewage and stormwater all flow into one pipe system for treatment. As a result, when heavy rain hits, the system’s 2,446 miles of sewers[2] can back up and dump untreated water straight into Lake Michigan and nearby rivers and waterways. For example, a torrential downpour in July 2010 resulted in an estimated two billion-plus gallons of untreated sewage and stormwater entering waterways in the Milwaukee area.[3] The city of Milwaukee is turning increasingly to green solutions to help with its stormwater control.

In 2004, Mayor Tom Barrett created Milwaukee’s first Green Team, which has been tasked over the years with creating a sustainability plan for the city. Major components of this plan involve green infrastructure and natural resources management. As the managers of greenspaces across the city, Environmental Services’ projects are key elements in the city’s overall sustainability.

Not long after the formation of the Green Team, Environmental Services began examining the 120 miles (476 acres) of green boulevards that line the city. About 80 to 90 percent of Milwaukee’s 1,400 paved streets are pitched toward the roadway edge or right of way, according to Scott Baran, an Environmental Services landscape designer. The remaining percentage pitch toward the middle of the roadway, and that’s where Environmental Services has been focusing its efforts for more than five years to create bioswales in the roadway medians.

 

Bioswales. Credit: City of Milwaukee

Bioswales. Credit: City of Milwaukee

Bioswales, or landscaped areas with gently sloped sides designed to control water drainage, offer a number of advantages. First, by design, they help control water flow. Instead of running off the street into the city’s pipe system, rainwater instead runs into the soil of the bioswale, where it’s absorbed by the plants and shrubs. Second, bioswales reduce maintenance costs. It’s less time consuming to maintain the bioswale’s native shrubs and perennials than to maintain grass. By focusing on roadways already pitched toward the median, Environmental Services was able to create bioswales at reduced cost, as only excavation and curb cuts around the sewer grates were needed instead of whole-scale repaving and re-pitching efforts.

Environmental Services isn’t the only group, though, looking to reduce and refine maintenance of landscaped areas in Milwaukee — nor are they the only group that has realized the value of cross training.

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References

[1] i-Tree. i-Tree Resources. i-Tree Ecosystem Analysis Milwaukee: Urban Forest Effects and Values September 2008. http://www.itreetools.org/resources/reports/Milwaukee%20Ecosystem%20Analysis.pdf (accessed Aug. 9, 2012).

[2] City of Milwaukee. Department of Public Works. About DPW. http://city.milwaukee.gov/mpw/general/About.htm (accessed Aug. 9, 2012).

[3] Behm, D. 2 Billion Gallons of Sewage, Stormwater Overflowed. Milwaukee Journal Sentinel [Online] 2010. http://www.jsonline.com/news/milwaukee/99365209.html (accessed Aug. 9, 2012).