Brownstown Middle

Brownstown Middle School Green Roof Monitoring Project

Presentation to Alliance of Downriver Watersheds

October 18, 2012

Scott Isenberg & Donald D. Carpenter

Lawrence Technological University

Minimize the negative impact a conventional roof has on our environment

Conserve Energy ($$) and Atmosphere (heat island

effect)

Extend Roof Lifespan (2 times conventional) up to 50 years

Dramatically reduce rain water runoff and improve water quality and erosion issues

Provide habitat for surrounding wildlife

Improve aesthetics of affected area

Introduce unique science curriculum (environmental

science) and provide unique space for learning (on

roof)

Education!

Why did WBSD chose Green Roofs?

Project Goals

1. Determine the overall volume of precipitation retained and detained by the green roof (water quantity)

2. Determine the water quality variable attenuation capabilities, including total suspended solids, pH and temperature (water quality)

3. Determine the reduction in ambient temperature (air quality)

4. Establish how a long-term monitoring station capable of determining green roof performance is a key feature in green infrastructure community education programs and can be integrated into public science curriculum (social impact)

Green Roofs Installed at BMS

Testing Areas • Green roof area was selected because of ease of access,

clear delineation of drainage area and uniform green roof coverage.

• Green roof area: 880 ft2

• Asphalt roof : 3457 ft2

Testing Equipment • Hobo Weather Stations on each roof • 3 Temperature gauges at each station: Air, Roof,

and Drain • A tipping bucket rain gauge was attached to the

green roof station • Data was collected every 5 minutes

Testing Equipment • Palmer Bowlus flumes were installed • ISCO 4230 Bubbler Flow meter • ISCO GLS Compact Composite Sampler • Sampling was triggered by flow rate • Samples were taken at volume intervals

Storm Response • Respond to storm event within 24 hours of

storm • Approx. (2) 200 ml samples collected from

each roof (container stirred before sampling) – (Total Suspended Solids)

• pH tested with NexSens pH/Temp Sensor

Results: Temperature • Black roof temperature were 10 to 20 degrees higher than

the green roof • Average day and night time air temperatures did not show

much variability

Results: Temperature

Results: Temperature

Results: pH • Average black roof pH: 6.26 • Average green roof pH: 7.05 • Michigan natural waters: 6.5 -7.5

Results: TSS • Conservative average green roof TSS: 2 mg/L • Average black roof TSS: 17 mg/L

Results: Flow, Cv by storm size Green roof

Black roof

• Average green roof Cv: 0.481 • Average black roof Cv: 0.885 • Approximately 53% of rainfall was retained by the

green roof compared with approximately 18% of rainfall that fell on the traditional black asphalt roof.

Results: Centroid Delay • Average delay for the black roof: 10 minutes • Average delay for green roof: 1 hour

Flow: Peak Reduction

Sample Storm Hydrographs Large Storm Event

Sample Storm Hydrographs Small Storm Event

Summary • Green roof retained approximately 53% of the rainfall

received • 100% retention of storm events less than 0.10” • pH averaging 1.5 higher for the green roof • With 13,000 ft2 green roof, 19.1 lbs to 1.3 lbs • Average daytime surface temps: 10 to 20 degrees

cooler for fall and spring