CitiesGoGreen - December 2008 - (Page 23)

manual encouraging green infrastructure to meet the requirement. All new municipal buildings are required to have a green “When you start out with sustainable stormwa- roof covering at least 70% of ter approaches, you have to be willing to learn the roof area, and Portland offers zoning bonuses to privateas you go. What has surprised me overall is just ly-owned buildings with green roofs. how effective most of these simple green soluOne of Portland’s most effective programs is a downspout tions have turned out to be.” disconnection incentive: the —Dean Marriott city pays homeowners $53 for every downspout disconcades, that has led to a willingness to take nected from the sewer system. More than 45,000 households participate, resulting on innovative approaches.” Portland’s primary strategy for address- in the annual infiltration of an estimated ing capacity problems associated with one billion gallons of water. The city—which has a stormwater utilcombined sewer overflow (CSO) events was to emphasize decentralized storm- ity—also plans to offer a stormwater fee water management through green infra- discount of up to 35% for properties with structure. Building codes now require on- on-site stormwater management. “We’ve done our share of grey or ensite stormwater management for all new construction, with Portland’s stormwater gineered solutions. Those will always be necessary when you have such an extensive array of infrastructure,” Marriott said. “But we decided a decade ago we liked the multiple benefits that come from the green approaches, particularly those visible to people. For instance, green street features can calm traffic, help with water quality and are good for aesthetics.” Portland’s early objective was to make sustainable techniques visible throughout the city to generate a positive reaction. That is paying off as the techniques demonstrate their effectiveness, and neighborhood and business associations are requesting more of them. Meanwhile, Portland officials monitor their performance to ensure “[W]e’re not just building things that are nice to look at but aren’t really working,” Marriott said. “When you start out with sustainable stormwater approaches, you have to be willing to learn as you go.” He added, “What has surprised me overall is just how effective most of these simple green solutions have turned out to be. A lot of people have suggested it’s mostly for aesthetics and you have to rely on grey infralike-minded people into government and community activism. In the last few deDecember 2008 • • • • • • • • turf, grass or other ground cover. Thick soil layers can support a variety of plant or tree species. One benefit is reduced stormwater run-off. Grass swales: Open, wide channels next to roads and other runoff areas, with plant-covered slopes. Swales filter run-off and reduce flow, allowing infiltration, sedimentation and filtration. They can convey run-off to a downstream discharge location without erosion. Check dams in swales can further slow flow rate, creating small, temporary ponds and promoting infiltration. Roadside infiltration gardens and rain gardens: Captures runoff in often very attractive planted areas, from which it infiltrates. Reducing impervious areas: Minimizing the constructed footprint reduces runoff, as does pervious pavement. Rainwater harvesting: Cisterns (both above and below ground) can collect rainwater from roofs for irrigation and toilet flushing. Tree wells: Depressed areas around trees can collect water and allow it to infiltrate. Caution: A raised ring around the base of a tree will diminish the effectiveness of this method. Depressed parking islands: Capture stormwater and facilitate control. Constructed wetlands: Slowing the flow, these clean water and pass it through a functional habitat. Water quality is maximized through natural aerobic and anaerobic treatment. Wet ponds: Also called stormwater ponds, retention ponds or wet extended detention ponds, these add runoff to a permanent pool and treat and filter the water through settling and nutrient uptake by plants and other aquatic organisms. structure to get environmental performance. We’ve demonstrated we’re going to need to continue to have a mix of grey and green infrastructure, but green infrastructure is more than holding its own.” Even green roofs, which get mixed performance reviews, are effective when properly constructed, says Marriott. While some remove only 10% to 20% of run-off, Portland has others with an 80% peak flow removal. 23 http://citiesgogreen.com

Table of Contents Feed for the Digital Edition of CitiesGoGreen - December 2008

Citites Go Green Contents In Motion We’re Taking Steps 10,000 Rain Gardens in Kansas City Chicago Center for Green Technology Connecticut’s ‘One Thing’ Green Infrastructure for Stormwater Management Philadelphia The Economics of What Matters New Context: New Possibility

CitiesGoGreen - December 2008

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