Clean Production and Toxics

Green stormwater management gaining ground

For fifty years, stormwater engineers have considered rain a nuisance. It is something best evacuated quickly from roads and sidewalks and diverted into concrete gutters and underground pipes.

At the end of the pipes though, releases of urban runoff significantly degrade water quality in lakes and rivers. Fortunately, engineers today have started to make peace with stormwater. Together with town planners, landscape architects, biologists, and other experts, engineers are finding natural processes to keep streets and sidewalks clear while improving water quality.

Green infrastructure takes advantage of natural processes such as filtration and infiltration to manage rain on the ground, closer to where it falls. These systems mimic the natural processes of wetlands, marshes and forests, which have kept our water clean and our air fresh for millions of years.

Attractive, cost-effective, and easy to maintain green infrastructure solutions are gaining ground in cities across North America.

Seattle built its first natural drainage system pilot project in 2001 and has redesigned residential developments so that plants, trees, and soil “clean up” runoff. The new vegetated swales, stormwater cascades, and small wetland ponds allow soil to absorb water, slow flows, and filter out many contaminants. The permeable surfaces for residential streets were increased by 11 percent, surface detention in swales was provided, and over 100 trees and 1100 shrubs were planted. These efforts reduced the volume of stormwater leaving the street  by 99 percent.

Delsom Estates, a residential area in Delta, British Columbia, took green infrastructure from idea to reality through a collaborative community process. Approximately one-third of the urban landscape is covered by road rights-of-way, creating opportunities to capture rain where it falls and to restore it to natural hydrologic pathways. Unlike traditional end-of-pipe approaches, permeable pavements allow the water to be filtered through the ground before reaching the water body.

Smaller cities can take advantage of green infrastructure as well. Maplewood, a municipality of about 30,000 in Minnesota, installed 350 rain gardens in public and private lots to help manage their stormwater. With improved water quality in their lakes and an impressive array of rain gardens, the citizens have demonstrated how green infrastructure can make a significant difference to community living and water quality.

Quebec City has also integrated green infrastructure into their design, preventing 6 million cubic metres of wastewater from entering the St.. Charles River. The city replaced 8km of concrete shoreline with 65,000 square metres of native plants, recreating diverse wildlife habitats along the river. Along with retention ponds, such landscape controls efficiently manage wastewater overflows.

Since 2003, the City of Toronto has been integrating green infrastructure into its Wet Weather Flow Master Plan (WWFMP), a 25-year plan to protect the water quality of rivers, streams and other water bodies. A key component of this master plan is raising public awareness about the issue and encouraging participation by Toronto’s residents. Their downspout disconnection program shows that residents, with simple actions, can play an important role to reduce combined sewers overflows.

The integration of such practices requires collaboration among professionals, diverse approaches, incentives, and regulatory changes in order to encourage faster implementation. While local acceptance may be hindered by potential liability issues, lack of performance data, and unfamiliarity with green infrastructure techniques, improvements in design specifications are part of many revised stormwater management and planning guides. Why not consider them in your community as a way to save money, revitalize the economy, prevent pollution and build better living places?

nathalie@solutionsecosmarts.com

© 2009 Great Lakes News.