|Tom Liptan, ASLA, is a landscape architect who works as a stormwater specialist for the City of Portland?s Bureau of Environmental Services. His own flat 10 x 18' garage greenroof was highlighted in an article in Landscape Architecture Magazine (May, 1998), and I have had the pleasure of speaking with him regarding his positive experiences and feedback.|
Tom's conventional wood frame garage was first braced to support the soil load, and then he placed inexpensive plastic sheeting for waterproofing. He dug up two inches of backyard soil and mixed it together with compost to create his substrate. He initially planted a variety of sedums, and now has a healthy mix including native wildflowers and volunteer grasses mixed in. His extensive greenroof has thrived without any additional irrigation or fertilization.
Tom has been monitoring his greenroof to measure the stormwater retention rates weekly, and the results prove his simple and inexpensive greenroof is effective in capturing stormwater. He uses a 55-gallon drum and a rain gauge to catch and measure runoff, and calculates the flow rate by timing the rainwater over a period of minutes (Tom Liptan, personal communication, February, 1999). After the first storm of four-tenths of an inch of rain, which is approximately forty gallons of rainwater on his 180 square foot greenroof, only three gallons made it into the drum. Following the next storm, two inches of runoff slowly continued to flow from the roof for the next two days. During heavy rainfall events, the greenroof is less effective is retaining stormwater runoff. Depending on the rain intensity, Tom estimates his greenroof retains between 15%-90% of precipitation (LAM, May, 1998).
|In the late 1990's, Tom constructed a small 10 x 10' demonstration greenroof for a local home & garden show and measured people's reactions. He says that approximately 75% had favorable responses to the aesthetics, while others thought it was not attractive at all. His current greenroof plans with the City of Portland include working with developers on two projects, and both involve new multi-family residences. The first is a 10-story building with an 8,000 square foot greenroof, and the second involves a four-story, 150 unit complex in midtown Portland with 30,000 square feet of greenroof. The city is also constructing an 18 x 35' greenroof shelter. Tom is working with both The Garland Company and American Hydrotech to provide the greenroofing systems.|
Tom Liptan believes the United States would greatly benefit from the use of extensive greenroofs due to their stormwater evapotranspiration capabilities. In particular, Portland, Oregon, could use help in managing its sometimes intense rainfall. He is convinced that flooding, combined sewer overflows and related problems would be reduced. He is also promoting the favorable results of the various municipal subsidy programs in Germany.
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|Contact Tom Liptan for specifics: Toml@bes.ci.portland.or.us.|
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