Metro Council considers financial incentive for green roofs

Monday, August 20, 2012 at 5:57pm

Metro officials have mapped out a system to offer financial incentives to businesses and homeowners that build green roofs under an ordinance the Metro Council will consider Tuesday.

The bill, which Metro Water Services helped draft, would deliver a reduction of sewer charges for up to five years to customers in large swaths of Davidson County’s urban core that have green roofs covering at least 50 percent of their rooftops. The reduction would apply to new and existing green roofs.

Sonia Harvat, spokeswoman for the water department, told The City Paper the measure is aimed at encouraging the construction of green roofs.

“Not only will this reduce overflows to the Cumberland River, but green roofs improve air quality, reduce heating and cooling costs, mitigate the city’s heat island effect and provide green space to urban areas,” she said.

The legislation, set for a second of three council votes on Tuesday, offers a credit of $10 for each square foot of the green roof. The measure would apply only to customers who live in the older parts of Nashville that are part of the city’s combined sewer system. This includes much of downtown and surrounding neighborhoods, East Nashville, and the area along West End Avenue near Vanderbilt University.

The measure would not offer financial aid for the 178,000-square-foot green roof set to go atop Nashville’s Music City Center, which does not feed into the city’s combined sewer system. In addition, bill sponsors –– council members Sean McGuire and Walter Hunt –– have proposed an amendment that would exclude all publicly owned buildings from the incentive.

Monthly charges for water and sewage are based on metered water consumption. Rates vary between commercial and residential property owners.

The green-roof credit would be awarded each month to ratepayers until their full credit expires or 60 months have lapsed –– whichever comes first. The water department has set a cap of $500,000 annually for distribution collectively among all properties that qualify for the program. The reduction would be delivered on a first-come-first-served basis.

Revenues collected from water and sewer fees goes toward the water department’s operating budget.

Mayor Karl Dean’s Green Ribbon Committee on Environmental Sustainability encouraged ways to spur more green roofs in a 2009 report.

Customers would need to submit documentation annually to receive the credit. Eligible green roofs, in addition to covering half a rooftop, would need the following components:

• a waterproof membrane layer;

• a drainage layer designed such that roof drains can be inspected and cleaned;

• a growth medium at least four inches in depth; and

• a vegetation layer, at least 80 percent of which must consist of live, hardy, drought-resistant plants. 

6 Comments on this post:

By: JeffF on 8/20/12 at 4:11

Please, please, please use your heads and don't give sewer credits for this. Make stormwater maintenance a public works issue with its own billing and give building owners a credit on that amount. If you need help with this talk with one of the hundreds of other cities who were wise enough to identify stormwater runoff as something not pertaining to their water delivery enterprise funds. If you call Franklin it would be a local call.

Damn this city is so set to do things as illogical as possible sometimes. It will not make you look dumb to do things like our more successful immediate neighbors every now and then.

By: Kosh III on 8/21/12 at 7:04

Where does water from the new convention center go?

Why only certain neighborhoods? Most new construction is NOT downtown or in West End but in the suburbs--that would seem a good place to offer the incentive.

By: Jughead on 8/21/12 at 8:51

Greentards. Glad taxpayers funded those STUPID free charging stations for electric cars that nobody owns. That was a good use of tax dollars---thousands to a California company that laughs all the way to the bank.

I am SO sick of greentards--insincere preaching based entirely on emotion, and not fact.

By: dogmrb on 8/21/12 at 8:35

It appears you three are just looking backwards!

By: JConman on 8/27/12 at 3:13


This actually is a logical approach for the combined sewer overflow zone (CSO zone). In those areas, the stormwater runoff drains into the sanitary sewer system and goes to the treatment plant and is treated as sewer. This has a major impact on the sewage treatment plant and the amount of water that is treated there. In other parts of town, where the storm sewer is separate from the sanitary sewer, when you pay your water bill, part of that bill also pays for sewage. There is no meter on sewage so they go by the amount of water you use since it is metered. They know that if you flush your toilet or run your sink then that amount of water (minus some minimal loss) goes down the drain and to the sewer plant. However, the businesses in the CSO zone also have stormwater runoff that goes to the sewer plant. Therefore, they are charged extra for sewer to account for this (but remember, sewage is not metered so they have to come up with another means of estimating how much runoff leaves the site). By using a green roof you are intercepting some of this flow that gets used by the planting material and plants and is not directed to the sewer plant. Therefore, Metro is offering a credit to businesses that intercept the stormwater and keep it from going to the sewage plant. So for this unique area it does make sense. As far as the Stormwater User's fee you are referring to, that might make sense in other areas of town where the storm and sewer are separate lines. Murfreesboro has a fee structure like you're referring to (not sure about Franklin).

By: JConman on 8/27/12 at 3:16

Kosh III,

See my previous post. Stormwater runoff that doesn't go into the combined system goes straight to the river or creek or lake. For the convention center, I believe it goes directly to the Cumberland River. It doesn't go to the sewage treatment plant to get treated first. That is why Metro has started making developments treat the stormwater before it is dumped directly into the waters of the state. It helps decrease pollutants generated by development. A green roof aids in this treatment process.

Trust me ... I'm a civil engineer ...