Campus Stormwater Discharge Reduced Due to Green Landscaping

Project Summary: The University of Wisconsin at Milwaukee has installed green rooftops, bioswales, and other natural landscaping projects that have lead to a dramatic decrease in the water the campus discharges into the Milwaukee sewer system.

Project Name: University Decreases Runoff

Location: Milwaukee, Wisconsin

Description: The University of Wisconsin at Milwaukee has been reworking their campus to reduce stormwater discharge. Seven

The native prairie green roof on top of the Sandburg Commons. Green rooftops can absorb rainwater, slowing the time it takes for the water to reach the sewer system and helping the sewer cope with heavy rain events. Photo courtesy of Jim Wasley.

The native prairie green roof on top of the Sandburg Commons. Green rooftops can absorb rainwater, slowing the time it takes for the water to reach the sewer system and helping the sewer cope with heavy rain events. Photo courtesy of Jim Wasley.

buildings on campus have green roofs incorporated into their design, including a Wisconsin native dry-prairie, one with solar panels in the landscape, and a vegetable garden used by a campus café. These green roofs will absorb water and heat more effectively than traditional roofs ever could, while benefitting wildlife by providing habitat. A 5,000 square foot spiral garden on campus catches rainwater drainage from some of the green roofs and other traditional rooftops to decrease runoff into Lake Michigan. The garden and two cisterns that double as fountains at the end of it slow the flow of water, allowing it more time to seep into the ground. The presence of native plants also slows the progress of the water, increases absorption in the landscape, and filters nonpoint source pollution that collects on the rooftops and in the nearby parking lot.

Three students determine the volume and contours of a swale in the spiral garden. Understanding the volume and other aspects of a swale allows engineers and landscape architects to calculate the positive impact the bioswale can have during a heavy rain event—helping to slow and absorb water as it flows through the depression. Photo courtesy of Jim Wasley.

Three students determine the volume and contours of a swale in the spiral garden. Understanding the volume and other aspects of a swale allows engineers and landscape architects to calculate the positive impact the bioswale can have during a heavy rain event—helping to slow and absorb water as it flows through the depression. Photo courtesy of Jim Wasley.

 

Approximate Cost of the Project: Between $2,000,000 and $2,500,000, with some funding from the Great Lakes Restoration Initiative

Resource Challenges Addressed: Excess runoff and erosion, nonpoint source pollution, energy use and maintenance costs, lack of wildlife habitat in urban spaces

Key Partners (Public and Private): Great Lakes Restoration Initiative, Milwaukee Metropolitan Sewerage District, University of Wisconsin at Milwaukee, and WE Energies

Types of Jobs Created: Landscape designers, biologists, university research assistants, construction workers, truck drivers, and general laborers

Results and Accomplishments: The spiral rain garden in combination with the green rooftops are estimated to reduce average stormwater runoff into the city’s sewerage system by 97 percent. This impact is in part due to a large area of impervious surface whose runoff was diverted into the spiral rain garden, providing the space and time for water to absorb into the landscape instead of running off into Lake Michigan.

Website: http://www4.uwm.edu/pps/Sustainability/CampusInit/green-roofs.cfm

Originally Published: August 30, 2013

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