Mary Walker Tower Gets a Green Roof

The City Council proceeded Tuesday with plans to replace the roof on the City Council building with a green roof. Pictured is a modular green roof installation on the Chattanooga Housing Authority’s Mary Walker Towers. Areas covered in the white tarp will have the green roof system installed on top. The full surface of the roof could not be converted to the green system due to structural issues which would not allow those untarped areas to handle any additional load.  Staff photo.

Councilwoman Deborah Scott made a motion Tuesday to move forward with hiring a architect to engineer a green roof for the City Council building.

After weeks of delay, Scott was apparently satisfied with answers to her questions about warranties, load bearing and the need for a new roof on the council building.

“Any discussion,” asked Vice Chairman Jack Benson, who chaired the meeting in the absense of Chairwoman Pam Ladd. “This has certainly been discussed in committee.”

The building’s roof was evaluated by outside experts who said the 20-year-old roof is past its lifetime. The city will pay for the 6,700-square-foot roof repair but the green roof work will be funded by federal stimulus money. The city approved a $26,890 engineering contract for Franklin Architects.

Bob Franklin, of Franklin Architects, said some of the questions will be answered through the engineering process.

“You need to hire us or someone and let us get started on engineering it,” he said in an earlier meeting.

The plan is for this roof to be different from other green roofs, said Leslie Jakobs, urban landscapes coordinator for the city’s Office of Sustainability. She said plans are to put art that will be accessible via webcams installed on the roof.

“We’re looking to put up a green roof system that would be about four inches thick and would absorb most of the rainfall that Chattanooga receives,” Jakobs said. “But we also envision something different like putting art, kinetic art up there.

“We don’t want to just put a lawn up there, it will have a design to it and be attractive. The web cams will be so people can see it.”

Jakobs stressed that the project is in the conceptual stage and nothing has been decided. She said the roof is the first of the 100 green roofs plan motto, “Leave no roof left unused.”

“We’d like to see 100 green roofs in downtown area, and in order to make it really unique we are looking at these different aspects,” she said. “A lot of cities are putting up green roofs and we want to make Chattanooga stand out.”

The office of sustainability is focusing on downtown because the combined sewer overflow area is located in the area. The federal government has raised water quality standards that increased storm water fees for area taxpayers. When rainwater runs into the storm drains, it feeds into the sewer lines, which go through the water treatment plant before being released into the Tennessee River, Jakobs said.

The more water treated, the higher the cost. Green roofs can substantially reduce the amount of runoff water, thus reducing the amount of water needing treatment.

“That means the more water we are able to prevent from going into our storm drains the less gray infrastructure is needed to compensate for our heavy rainfalls,” she said.

There are several green roofs throughout the city including one the Chattanooga Housing Authority installed at Mary Walker Towers. The Battle Academy Elementary School on Market and Main streets also has a green roof.

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