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Milwaukee, WI


MMSD Testing Unique Way to Manage Water Where it Falls

(Milwaukee, WI) – An experiment is underway to determine whether the marriage of blue roofs and green roofs can create a smarter way to manage rainfall on rooftops and reduce water pollution.  It’s taking place atop the Milwaukee Metropolitan Sewerage District’s (MMSD) headquarters building.

Green roofs capture and store water with vegetation and a planting medium, such as soil.  The traditional green roof that has been on MMSD’s headquarters building for 10 years can hold up to 1,500 gallons of water.  Blue roofs can store several inches of rain on a roof, depending on structural support, by enlisting low cost inlet restrictors on roof drains to prevent water from getting into the drain until it reaches a level higher than the inlet restrictor.

Combining the two styles involves placing a traditional green roof planter box on top of a tray that will hold water like a blue roof.  The green roof tray will capture rainfall, storing some water, while allowing excess water to fill the blue roof style boxes below.  The blue roof boxes can be equipped to empty right before another storm or hold the water so plants in the green roof boxes above have access to moisture during dry periods. 

Learn more about green roofs, managing water where it falls and MMSD's Fresh Coast 740 program @

MMSD's blue and green roof experiment sits higher on the rooftop surrounded by its traditional green roof.


News Release from Vegetal i.D.:

Green Roof Company Partners with Local Organizations to Pilot New Stormwater Management Solution

Milwaukee, Wisconsin – July 7, 2014 – Vegetal i.D. has announced a collaboration between the Milwaukee Metropolitan Sewerage District (MMSD), Fund For Lake Michigan, The Water Council, UW-Milwaukee, and UW-Whitewater to closely monitor the performance of a new stormwater management solution.  The technology being tested is an advanced system combining a blue roof with a green roof that is poised to bring green roof based stormwater management performance to a whole new level.

Green and blue roofs are a component of a new form of low-cost high-impact stormwater management known as green infrastructure. The goal of green infrastructure programs is to mimic natural systems in order to manage stormwater on-site and minimize problems such as polluted runoff and basement backups.

The alternative solution involves the expansion and maintenance of traditional grey infrastructure systems, which can be extremely expensive and often does not completely solve the problem. This is why cities are turning to green infrastructure systems such as green roofs to deal with rainwater at the source, and minimize taxpayer expenses.  

In Greater Milwaukee Area of Wisconsin, the Milwaukee Metropolitan Sewerage District has spearheaded the green infrastructure movement for over 10 years.  The goal, known as Fresh Coast 740 is to capture 740 million gallons of water every time it rains.  To achieve this goal the program invests in high impact green infrastructure such as rainwater harvesting, porous pavement, and bio-swales and by obtaining key pieces of land to remediate into greenways and wetlands that manage great amounts of stormwater naturally and increases resistance to flooding.

Green roofs are a part of the green infrastructure solution.  They absorb and retain water on the roof and use it to grow plants that cool cities, clean water, add biodiversity to urban areas, and improve property values. “Green roofs are like sponges and absorb lots of water, but when the soil is fully saturated from previous rainfall, it doesn’t have much effect,” according to Gaëlle Bergès, of Vegetal i.D.  This is why Vegetal i.D. is launching a new stormwater management compliment to green roof systems known as STOCK & FLOW®.

STOCK & FLOW® is a reservoir below the green roof that adds 2 inches of rainwater capacity to a traditional green roof, passively irrigates the plants, and controls the way in which water is released from the roof. Imagine decentralized living systems with the reliability of a machine.  The system irrigates itself with the water it captures during rainfall while the excess water retained in the reservoir of STOCK & FLOW® is released to the sewer system at a slow and constant rate to make it easier for the city to manage while it is simultaneously preparing it for the next rain event.

This month Vegetal i.D. is launching a pilot project to demonstrate the performance of STOCK & FLOW®. The project will compare stormwater management performance of 2 versions of STOCK & FLOW®, a typical extensive green roof, and a standard roof. They will also measure performance metrics such as the productivity of the plants and their ability to cool the roof.

This study will also assess the costs and benefits associated with these systems.  This will enable policy makers and sewer system managers like MMSD to better understand the costs and benefits associated with these systems.  The information can be used to better incentivize and regulate stormwater management which helps to drive the use of green infrastructure solutions.

Vegetal i.D. is a branch of Le Prieuré, a French company that installed its first green roof in 1989 and has focused on innovation ever since.  In 2000 Vegetal i.D. patented HYDROPACK®, the first modular green roof system in Europe.  HYDROPACK® is a tray system that is sold fully vegetated with water reservoirs packed into stackable trays that can be easily transported and installed on rooftops of nearly any pitch.  

Since its inception, HYDROPACK® has been installed on over 2,000 rooftops and has become one of the most trusted modular green roof systems. The North American branch of Vegetal i.D. launched in 2011 with a plant nursery located in Batavia, NY and has since focused on growing and developing the green roof industry in the U.S. and Canada.  More information on STOCK & FLOW and other Vegetal i.D. solutions can be found at