Design of an Intensive Green Roof Based on Native Plant Communities Douglas Daley, P.E., Environmental Resources Engineering
Timothy Toland, Landscape Architecture
Donald Leopold, Environmental and Forest Biology
SUNY College of Environmental Science and Forestry Syracuse, NY
2013 NYWEA Spring Technical Conference, Syracuse, NY
Summary
• New building stormwater system will meet hydrologic performance requirements, support efforts to conserve unique ecological resources, and educate ESF community.
• Innovative basis of design: Use native plants from communities along the eastern shore of Lake Ontario
• Design process and lessons learned
ESF Plan: Create a Teaching Landscape
• Leadership and innovation in stormwater management
– Onondaga County’s Consent Judgment re CSOs
– Midland Avenue RTF Sewershed (grey infrastructure)
• SUNY ESF Teaching and Research Mission
– Illick Hall (bioretention, 2010)
– Bray parking lot (porous pavement, bioswale)
– Centennial Residence Hall (infiltration, bioswale)
SUNY ESF Gateway Center
• 50,000 SF LEED Platinum
• Biomass‐fueled CHP (65% of campus heat, 20% of campus electricity)
• PV and solar thermal
• Stormwater management through bioretention, green roof, cisterns
SUNY ESF, the Gateway Center and Green Infrastructure
Gateway Center Stormwater Management System
Basis of Design: Need for a Green PRoof
• Original (2009) concept by SUNY Construction Fund – Typical extensive green roof using thin soil, sedums
• Small uprising of scientists and designers at ESF
– Forward‐looking?
– Creativity of design?
– Are we portraying world‐class environmental science and design programs adequately?
ESF Green PRoof
• Consider intensive green roof
– Wider diversity of plant species, including shrubs and trees
– Deeper substrate >4” to 6”
– Park‐like and accessible
– Native vegetation is recommended (NYSDEC
guidelines)
Role of Vegetation
• Water budget
– Promote evapotranspiration
– Interception captures about 10% of annual precipitation
• Growing medium captures about 50%
• Enhance ecosystem services (values)
– Aesthetic
– Habitat
– Conservation
ESF Ecologists and Designers Collaborate
• Long‐term conditions of green roofs:
– Temperature, wind and moisture extremes
– Low soil fertility
– Low organic matter content
– Thin‐soiled
• Ecologists identified 2 NYS native plant communities
– Great Lakes sand dunes
– Alvar ecosystems
Great Lakes Sand Dunes
• World’s largest collection of freshwater dunes
– Hills, mounds or ridges of wind‐
deposited sand
• Variety of plant communities:
– beach, foredune, trough, backdune
forest
• Extreme temperatures, strong winds, shifting sands
American beachgrass, Ammophila breviligulata
http://www.seagrant.sunysb.edu/glhabitat/PDFS/ELODWAFactSheetDunePlants.pdf
• Endangered plant species:
– Champlain beachgrass
(Ammophila breviligulata), – rough avens (Geum
laciniatum),
– woodland bluegrass (Poa
sylvestris), – marsh horsetail (Equisetum palustre), – large twayblade (Liparis
liliifolia), – livid sedge (Carex livida), – giant pine drops (Pterospora
andromedea) – sand dune willow (Salix cordata).
Alvar Communities
• Grasslands, shrublands, limestone woodlands, cedar forests, pavement barrens that develop on flat limestone where soils are very shallow
• Adapted to extreme conditions:
– Shallow soil, regular spring flooding, summer drought
– Flat, thin‐ to no‐soiled, rocky (limestone bedrock)
• Rare, restricted range, vulnerable to extinction, limited acreage, fewer than 100 occurrences in NY – Natural Heritage Program Rank G3, S2, S3
http://www.epa.gov/ecopage/shore/lakeont.html
Alvar Communities:
Chaumont limestone, Jefferson County
Alvar Communities: Grasslands, Pavement and Woodlands
Alvar Communities: Wet tolerant
Alvar Communities: Thin‐soiled
Alvar Communities: Pavement‐
Grassland
Alvar Communities: Shrubs and Trees Rooted in Grikes
Color and Texture Options
Selected Alvar Species
Agropyron trachycaulum – slender
wheatgrass
Aquilegia canadensis – wild columbine
Artemisa campestris var. caudata – tall
wormwood
Aster ciliolatus – aster
Bromus kalmii – brome grass
Carex eburnea – ebony sedge
Carex granularis – sedge
Carex vulpinoidea – brown fox sedge
Danthonia spicata – poverty grass
Deschampsia cespitosa – tufted
hairgrass
Fragaria virginiana –wild strawberry
Geum triflorum – prairie smoke
Juniperus communis – common juniper
Muhlenbergia glomerata – spike or marsh
muhly
Oligoneuron album – upland white aster
Penstemon hirsutus - hairy beardtongue
Rosa blanda – meadow rose
Saxifraga virginiensis – early saxifrage
Solidago hispida – goldenrod
Solidago nemoralis – gray goldenrod
Sporobolus heterolepis – northern prairie
dropseed
Zigadenus elegans var. glaucus – white
camas
Zizia aurea – golden alexanders
Saxifraga virginiensis – early saxifrage
Questions
• Name 2 native NYS
• Alvar communities are plant communities that characterized by what are suitable for climates types of plants and soil?
similar to green roof
– grasslands, shrublands, – Great Lakes Sand Dune
– Alvar
limestone woodlands, cedar forests, pavement barrens
– flat limestone – very shallow soils
Proof: A Race to the Finish
• Ground breaking 8/6/2010
• Proof of Concept started in June 2010
• Intensive Green Roof with native plants included in 100% Construction Documents October 2010
Green Proof – Day 13, 2010
8” Bed
3” Bed
Day 64 (August 18, 2010)
Dune Willow, Salix cordata (3 months)
Sand cherry, Prunus pumila var. depressa
June 6, 2012 (Year 3)
Design Elements
ESF Gateway Building – Green Roof Section Mirafi G4
ESF Gateway Bldg – Dune Profile
Growing Medium Specifications (Intensive)
Property
Metric
Bulk Density (saturated)
74.4 lb/CF
Pore Volume
74%
Maximum Water Holding Capacity
53%
Air‐Filled Porosity at max WHC
20.9%
Permeability
0.02 cm/sec
pH
6.1
Organic Matter
9.3% by mass
Questions
• What is the range of thickness of the lightweight soil medium?
– 6 to 18 inches
• What is porosity?
– Fraction – Volume of voids over the total volume
– 74%
• What is water holding capacity?
– Amount of soil moisture that a soil can hold under freely draining (gravity) conditions
– 54%
Green Roof Runoff Reduction
• A = 9500 SF
• P= 0.9” rainfall
• Water Quality volume (WQv) = 678 CF
• Soil storage: 739 CF
• Drainmat storage: 132 CF
• Total storage: 871 cf
• WQv < Storage
MiraDrain® G4 Drainage Composite storage capacity = 0.32” rain (1.63 lb water/SF)
WQv =
( P )( Rv )( A )
12
Rv = 0.05 + 0.009 ( I )
P (in) = 90% Rainfall Event Number
I = Impervious Cover = 100 Percent
Rv = 0.95 Mean Soil Depth = 9 inches
Placement Autumn 2012
Alvar Community (May 2013)
Dune Plantings
Sand Dune Willow Salix cordata
American Beachgrass
Canada Wild Rye
Wavy Hairgrass
Field Wormwood
Eastern Sand Cherry
Dune Grasses (May 2013)
Lessons Learned so Far
• Use experienced contractor, or watch VERY closely
– Initially installed Miradrain upside‐down
• Grid planting is not a natural feel
• Late season planting when dormant may cause failure of some species, BUT
– It reduces irrigation requirements!
Lessons Learned
• Jute mesh can be wind‐lifted and rolled
• Erosion will occur from sloped surfaces
• Micro‐climates affect plants and soil water
• Management plan: is it a garden, or an ecosystem?
Design Issues
• Designer resistance to stakeholders
– Innovative? Need proof of concept
– What will it look like in 5 years?
• Plant propagation
– Sedums are widely available, easily propagated
• Soil specification
– Organic content high – nutrients high – what effect on these plant communities that are adapted to other conditions?
• Cost – Additional soil and increased structural loads
– In spite of unusual plants, bid came in below estimate. Questions
• Water Quality volume is • Plant canopy can a function of three intercept and store parameters. These are:
approximately how much annual – Precipitation – 90% rainfall event number
precipitation?
– Area
– Runoff volume or • impervious cover
WQv =
( P )( Rv )( A )
12
– 10% or more
Summary
• Native plant communities are developing on the Gateway Center roof, a unique application
• Public access provides education, research and demonstration opportunities to extend knowledge and awareness of threatened ecosystems
• Expect to meet design goals of hydrologic performance, and conservation of unique local ecological resources
Acknowledgments
• Contacts:
– Doug Daley (djdaley@esf.edu)
– Tim Toland (trtoland@esf.edu)
– Don Leopold (djleopold@esf.edu)
• SUNY Construction Fund (drawings, access)
• NY Economic Development (incremental construction costs, research funding)