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Under court order to make $3 billion in sewer improvements to better handle stormwater runoff, Atlanta is joining the growing ranks of the ''ecoroof'' movement, reports Larry Copeland in today's USA TODAY.
Ecoroofs, also called living roofs or green roofs, turn the tops of commercial buildings into gardens with plants growing right out of the roof.
Proponents of these roofs say they address several problems that occur in developed or urban areas:
The roofs are natural sponges in heavy rainstorms and reduce water runoff by up to 90 percent.
The greenery, soil and root system filter out pollutants picked up by rainwater as it drops through the atmosphere.
They combat the dreaded "heat island effect" that can raise temperatures significantly in heavily developed areas.
Copeland reports that county buildings in Anne Arundel County, Md., and Arlington County, Va., have adopted the concept. So has the Heinz 57 building in Pittsburgh. Chicago, Toronto and Seattle have ecoroofs on their city halls and courthouses. Ford Motor is building a 10-acre ecoroof on its truck plant in Dearborn, Mich.
Portland, Ore., is the national leader in ecoroof technology, David Beattie, director of the Center for Green Roof Research at Pennsylvania State University told Copeland. In the middle of its own $1 billion, federally mandated sewer project, Portland is vigorously pushing ecoroofs. The city recently began offering tax breaks and grants to developers who use them.
Many builders are resistant, according to Copeland. They say green roofs which consist of liners, dirt and plant cover are twice the cost. The biggest expense? It's reinforcement of the roof to handle the added weight of soil and cover.
Experts say there are other compensations. Ecoroofs last twice as long. They can eliminate the need for costly retaining ponds, which many local laws require developers to create to handle stormwater runoff. They also can cut a building's energy costs.
When it rains heavily in a city like Atlanta where developers have paved millions of acres for a population that has more than doubled since 1980 to 4.1 million the water cannot be absorbed by the ground. It runs off pavement and rooftops into the city's drainage system, often overwhelming the system's ability to carry it off.
The drainage also mixes into the sewer system that carries wastewater from homes and businesses to sewage treatment plants. Unable to handle the deluge of sewage and rainwater, the plants often divert the mixture untreated into rivers and streams. Ecoroofs, proponents say, absorb such runoff.
Rainwater can also bring with it high levels of pollutants as it drops to the ground. Pollutants such as sediment and bacteria from stormwater runoff cause more than 80 percent of the water quality violations that landed Atlanta in violation of the Clean Water Act over the past decade.
Then there is the heat-island effect. It occurs where there are impenetrable surfaces on the ground, such as parking lots or roofs, and a layer of smog particulates in the air above. The two together prevent heat from dissipating and cause a temperature buildup.
With a living roof, summer temperatures on city rooftops can be reduced by as much as 70 degrees, proponents say.
Atlanta is starting small. Officials hope to begin construction of a 3,000-square-foot living roof atop City Hall in January. They plan to integrate green roofs into the ongoing stormwater management plan for the city.