Landscape & Irrigation

October 2017

Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.

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INDUSTRY RESEARCH www.landscapeirrigation.com Landscape and Irrigation October 2017 21 that enables field scale research that's subject to highly variable natural conditions, but gives us scientifically valid results because we've built the statistics behind it in the experimental design." Finding the right bioretention system When dealing with stormwater runoff, a bioretention system needs to be able to manage the quantity of water, the speed of the water and the contaminants polluting it. The cornerstone of that system is figuring out the right mix of materials to control the volume of water. "From an engineering standpoint, the most important design element is how you make the growing media," said Fassman- Beck. "We don't use top soil. We use very specific mixes of different materials in what's called an 'engineered media'. What that mix is, is what this research is about." In order to do that, there are 20 duplicated green roof setups in the Living Laboratory. They are all designed to prevent runoff from a rooftop, and to do that they combine different recipes for lightweight growing media. The growing media weighs as little as possible to allow for as much water retention as possible. The researchers are also very interested in the quality of the water that discharges from these different mixes. Some of the basic components of the media include pumice, expanded clay and compost, while various other materials are added to see how they influence water quality. The right mix of growing medium "is the key to controlling stormwater," Fassman-Beck explained. "We're able to test lots of blends." The front of the building houses the rain garden. The rain garden treats ground-level runoff from a nearby parking lot and lawn. A similar rain garden setup is duplicated at the ABS Engineering Center, and will be duplicated at another location on campus later this fall to determine statistical validity. There are also four bioretention planters at the back of the building for rainwater to drain into. These planters serve a similar function as a rain garden, but capture roof runoff. They are two duplicated systems with a total of 15 sensors in each planter. Fassman-Beck and her students will be able to use all of those sensors to test the direction of drainage. Her undergraduate students are even working on a system to measure downspout flow, which is really hard. The lab is working directly with the U.S. EPA on this particular project, so their expectations are high. "They're reasonably new as a system to control stormwater," said Fassman-Beck. "There's been very little testing for this kind of setup." Right now, Fassman-Beck and her team are waiting to hear back on several grant proposals. But the good news is that the building is complete. The water retention systems are all installed — and given that they're three separate complex projects installed simultaneously, it's a big deal. "We've been working day and night all summer to get this building the way we want it," said Fassman-Beck. "It's a novelty to have multiple designs tested at the same time. Research setups with real-world inputs being tested side by side are hard to find. But by allowing me to do that, Stevens is really enabling innovation in green infrastructure research." * Living Roofs in Integrated Urban Water Systems is available at https://www.routledge.com/Living-Roofs-in-Integrated-Urban- Water-Systems/Roehr-Fassman-Beck/p/book/9780415535533.

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