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You are here: Home  > Your Government  > City Departments  > Environment  > Chicago Center for Green Technology  > Water  > Water - Go With the Flow
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How Cisterns Work
How the Green Roof Works


Water - Go With the Flow


In urban areas, rainwater that falls onto sidewalks,streets, parking lots and rooftops flows directly into sewers instead of being absorbed by the ground. As the rain flows across paved surfaces, it picks up pollutants such as oil, gas and other chemicals. The polluted rainwater is carried through the sewer systems and empties into our lakes and rivers.

At Chicago Green Tech, a four-part water conservation system reduces the amount of water flowing into the sewers, which helps prevent water pollution and eases pressure on the sewer system itself. The water conservation system consists of:

Green Roof
One-third of Chicago Green Tech's roof is covered by low-growing sedum, a succulent plant species that absorbs rainwater. Learn about more advantages of having a green roof.

CCGT Cistern

Much of the rain that falls on Chicago Green Tech's roof flows into four 12,000-gallon cisterns and is later used to water the landscape. Thanks to the cisterns, Chicago Green Tech takes less water from the lake to keep the campus lush and green.

Disconnected downspouts
Rainwater on the roof that is not collected by the green roof or in the cisterns flows directly into the landscape via regular downspouts. These downspouts are unique because they are not connected to the sewer system, as are many downspouts in Chicago. By disconnecting your downspout you can save money by using less water in your yard and help keep Chicago's sewer system (and your basement) from flooding during heavy rains. Look here to learn more about disconnecting your downspout.

Bioswales and the wetland
Rainwater falling on the ground at CCGT flows from parking lots and sidewalks into bioswales, which flow into the wetland. Bioswales are essentially ditches featuring water-loving species of plants.

Working together, Chicago Green Tech's water conservation system retains over half of the rainwater that falls on the site. On a rainy day, an average of three inches of rain will fall within a 24-hour period. Without the water conservation system, 175,000 gallons of water would run off of the site into the sewer system.

With the combined system, only 85,000 gallons of rainwater is released into the sewers.

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