Design of an Intensive Green Roof Based on Native Plant ...
Transcript of Design of an Intensive Green Roof Based on Native Plant ...
Design of an Intensive Green Roof Based on Native Plant Communities
Douglas Daley, P.E., Environmental Resources EngineeringTimothy 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
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 (NYSDECguidelines)
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, backduneforest
• Extreme temperatures, strong winds, shifting sands
American beachgrass, Ammophila breviligulatahttp://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
Color and Texture OptionsSelected 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 hairgrassFragaria virginiana –wild strawberry Geum triflorum – prairie smokeJuniperus communis – common juniper Muhlenbergia glomerata – spike or marshmuhlyOligoneuron album – upland white aster Penstemon hirsutus - hairy beardtongueRosa blanda – meadow rose Saxifraga virginiensis – early saxifrage Solidago hispida – goldenrod Solidago nemoralis – gray goldenrod Sporobolus heterolepis – northern prairie dropseedZigadenus elegans var. glaucus – white camas Zizia aurea – golden alexanders
Saxifraga virginiensis – early saxifrage
Questions
• Name 2 native NYSplant communities that are suitable for climates similar to green roof– Great Lakes Sand Dune
– Alvar
• Alvar communities are characterized by what types of plants and soil?– grasslands, shrublands, 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
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
12))()(( ARvPWQv =
)(009.005.0 IRv +=
P (in) = 90% Rainfall Event NumberI = Impervious Cover = 100 PercentRv = 0.95 Mean Soil Depth = 9 inches
MiraDrain® G4 Drainage Composite storage capacity = 0.32” rain (1.63 lb water/SF)
Dune Plantings
American Beachgrass
Field WormwoodWavy HairgrassCanada Wild Rye
Sand Dune Willow Salix cordata
Eastern Sand Cherry
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 a function of three parameters. These are:– Precipitation – 90% rainfall event number
– Area
– Runoff volume or • impervious cover
• Plant canopy can intercept and store approximately how much annual precipitation?– 10% or more
12))()(( ARvPWQv =
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 ([email protected])
– Tim Toland ([email protected])
– Don Leopold ([email protected])
• SUNY Construction Fund (drawings, access)
• NY Economic Development (incremental construction costs, research funding)