Structural Soils

NINA BASSUK,CORNELL UNIVERSITYURBAN HORTICULTURE INSTITUTEROOTS GROWING INCU-STRUCTURAL SOIL

Volume effects on tree growth. Honeylocust inSyracuse, NY. Those on the right are in tree pits.Those on the left are in tree pits but with small park“break-out” area to their left.

Effect of soil volume on willow oaks planted onPennsylvania Ave,Washington DC

Tree pit in New York City. B and B tree going into 4’ x 5’ tree pit.

Required compaction prior to laying pavement.

Tree ball placed into tree pit opening.

Tree blown down showing restrictedand shallow root growth.

Tree root s coming to the edge of a treepit, making a right angle turn.

Close up of root restrictionin tree pit.

Tree roots in paver surface followingthe weakness in the jointing mixture.

Cross sectioned conceptual detail of tree in tree pit.Compacted soil under compacted base course,under pavement.

Tree roots heaving sidewalk.

Using space under the sidewalk for rootgrowth is the only place for trees to findadequate soil.

Example of uniformly gradedcrushed stone (3/4”-1 1/2”) withno fines

Screened topsoil of a loam to clay-loamtexture to be added to the stone.

Structural soil close up after 3years under pavement.

English oak root system fromearly trials in containers.Structural Soil was compacted to100% proctor density.

Three year field study comparing normal soilprofile under sidewalk with structural soil andagricultural field soil. Species used werehedge maple, little leaf linden and crabapple.

Crab apple root systemgrowing downward instructural soil.

NY State Dept of Transportationinstallation of CU Structural Soil inIthaca,, NY 1997. Fifty trees of fivespecies planted into continuoustrenches.

Sidewalk “bumpouts” where thestructural soil trench widened out.Soil was placed on 3, 8” lifts andcompacted to 95% proctor density ateach lift.

Hedge maple in second yearof growth in Ithaca trench.

Sydney Olympic sitewithout structural soilSydney Olympic sitewith structural soil

Pyramidal black locust planted intostructural soil in Ithaca parking lot next totrain tracks.

Asphalt removed 15’ into the parkinglot from the tracks, continuously for60’. Structural soil placed 30” deepand asphalt reload. Trees in secondyear of growth after transplanting.

Tree planted in CU-Structural Soil with porous asphalt

Structural Soils:• Increases Macropores and Infiltration Rate forRoot Growth, Drainage, Air Circulation andStormwater DetentionCU-Structural Soil Stalite Structural Soil Soil AloneMean Total Porosity@ 95%-100% Proctor: 26% 34% 34%Mean MacroporesBased on TotalPore Volume @95%-100% Proctor: 31% 38% 2%Infiltration rate:>24”/hr >24”/hr 0.5”/hr

Porous Asphalt Research -Planting in CU-StructuralSoil

Piezometers installed tomeasure depth of water tableWater flowing freely throughPorous asphalt

WEB SITE:WWW.HORT.CORNELL.EDU/UHI

Finished grade aftercompaction before concrete ispoured.

Retro-fitting structural soil30” deep around existingtrees in Ithaca.

Soil Water Retention CCU Structural Soil4540353025201510500 5 10 15 20% Soil Water Content by VCU 1CU 2*CU 3CU 4CU 5CU 6CU 7CU 8CU 9CU 10CU 11CU 12CU 13CU 14CU 15CU Structural Soil availablewater holding capacity=9%

Profile of CU-Structural Soil parking lot withporous asphalt surface

Plant selection is an important part of creating a successfullandscape

Palms planted inCU-Structural SoilSouth Pointe Park,Miami Beach

Compacted soil showing loss of structure.

Potential use of structural soil toenlarge planting islands in parkinglots without taking up parking space.