Structural Soils Load Bearing Surfaces Engineering Solutions

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1 Arboricultural Associa-on Amenity Arboriculture Conference Structural Soils Load Bearing Surfaces Engineering Solutions James Urban, FASLA, ISA Urban Tree Soils Annapolis, Maryland

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3 Fill our ci,es with large mature trees

4 ca 1986 The soil chart Myth, truth or half truth? 1,000 cf per tree or 3,000 cf? Shared volumes vs isolated volumes?

5 Sky Forest, Japan / PWP 2000

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7 Goals for soil under pavement Load bearing How do you define in the UK? In the US: Suppor-ng material must be compacted to 95% of maximum density (proctor). and / or Structure must support required vehicle weight and mo-on. Example: US H- 20 equivalent 14,500 kg per axle with vehicle traveling 48 km/hr. Support tree growth to maturity Soil quality Loam soil is the standard. Soil quan,ty - 30 Cubic meter Effec1ve volume. Tree root dynamics and sidewalk liking preven-on. Compa,ble with other urban structures, u-li-es, and u-lity repair. Flexible in layout to respond to urban condi-ons and obstruc-ons. Water into and out of the soil. Compa,ble with SUDS goals.

8 Research into systems and soil op,ons Tree growth Amsterdam Tree Soil compacted above 90% Bassuk - CU GBSS soil vs loam soil Smiley - Loam soil vs CU GBSS Smiley/Urban Boston SBSS vs Loam soil Smiley- Loam soil under pavement vs open soil 30 year study Smiley Compara-ve study Silva Cells, Strafa Cells, GBSS and SBSS Oliver Buhler Post construc-on study of structural sol Kristoffersen Growing trees in road founda-on materials Ingerslev 10 year study of GBSS Son- Urban soils Kramer et al Post plan-ng compara-ve study SBSS, GBSS vs loam soil Rahman et al Tree pit design and soil composi-on

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13 When using any of these op,ons you should.. Calculate the soil volume based on efficiency. The following is a reasonable es-mate: Assuming: Loam soil 100% efficient then Silva cells 93% efficient 1 Strata cells 71% efficient 2 Sand based structural Soil 50% efficient 3 Stockholm structural soil 30% efficient 4 Gravel based structural soil 20% efficient 5 Subs&tu&ons must be required to provide the equivalent effec&ve soil volume of the original tender! Efficiency calcula-on assump-ons 1. Silva cells is 7% space devoted to structure. 2. Strata cells is 6% space devoted to structure. In the Bartlef field trial study held 23% less soil than Silva Cells. 3. Sand based structural soil based on observed reduc-ons in growth in the Smiley/Boston study. 4. Stockholm Soil has 30% void space for soil and roots the rest is rock. 5. Gravel based structural soil contains 20% soil the rest is rock.

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The new rain water paradigm is a significant change in the way we build cites. BUT.. Are landscape architects (or engineers) EXPERTS at this? Remember.

16 The new rain water paradigm is a significant change in the way we build cites. BUT.. Are landscape architects (or engineers) EXPERTS at this? Remember. Since ancient -mes, we have evolved solu-ons to conflicts between rain water and human development. The new water paradigm must understand these conflicts and not reintroduce an old problem. I do not think most of us know what we are doing in this area of design!

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19 2 Water to and into the system 6 System maintenance 3 Sediment and debris Ace Maintenance 4 Water distribution 1 Soil / water dynamics Urban Storm Water Systems First principles - What are we doing wrong! 5 Water out of the system

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Water Movement thru the soil Infiltra-on

21 Water Movement thru the soil Infiltra-on rates are set by: Soil type and Soil structure / preserved peds and Soil compac,on Bio- reten-on soils have too much sand and too much compost! Unscreened sandy loam soil Sand/compost bio- reten-on soil mix Screened sandy loam soil mix

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23 2 Water to and into the system M"*C%.J)$N*"C)50N*)0"*&&0,,A$%.), <5*%0'77,0$)E%48G,%$",%*7#85#6,%#7,#% -'7%$",% %85%%$",%4'8)% 2')(3,H% 6'))50J"*C0,C$.$) *(N*1,C$)5*) i*(((%.0 H0*,,'/0)5%,%,)50N*1)50 J"*C0,N%((3*((oo

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25 3 Sediment and debris Clogging at the Entry Point Floatables and silt

26 One mature oak tree dropped: Plus a constant fall of other leaves, tree parts and pollen all year long 200 gallons of leaves 20 gallons acorns 50 gallons of catkins

27 e*"j0=&$.&"0)03$"0 #*1C0,%J.0C)$#0 &(0*.0C L0J0)*)0CX()0"%, "0*((1%/A$")*.)

28 Or use pervious pavers

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James Urban, FASLA, ISA Urban Trees + Soils Annapolis, Maryland

Tree Performance In Load Bearing Paving Tree Growth, Health, Storm Water Results. James Urban, FASLA, ISA Urban Trees + Soils Annapolis, Maryland jimtree123@gmail.com In the medical field there are so