FFA Soils Presentation Summer 2015
Urban Contest - Slope
Urban Contest - Landform
Urban Contest – Flood Hazard/Soil Stability
Slippage/Subsidence The vast majority of soil conditions in Ohio are typically stable. However, some areas of the state have soil features that create stability issues resulting in landslides, and subsidence. In fact, per capita wise, the Cincinnati area is often called the slip prone capital of the US. • Slippage typically occurs on slopes that are greater than 12 percent, where impervious strata (bedrock) underlie clay or fine textured materials. • Subsidence is settling of organic soils, soils containing semifluid layers or materials that are dissolved in solution.
Urban Contest – Texture, Surface
Soil Texture • Relative proportion of sand, silt and clay in a soil sample • Does not include organic matter
Soil Separates • Most soils have a combination of soil particles sizes • Sand • Silt • Clay
Texture ( Particle Size Distribution ) • Important for determining suitability for various uses • Considered a basic property because it doesn’t change
Soil Texture Classification Systems • USDA Soil Texture Classification System • Unified Soil Classification System • AASHTO (American Association of State Highway and Transportation Officials )
Particle Sizes Sand • Clay: less than 0.002 mm • Silt: 0.002-0.05 mm • Sand: 0.05-2 mm Silt • 0.05 – 0.1 mm very fine . • 0.1 – 0.25 mm fine Clay • 0.25 – 0.5 mm medium • 0.5 – 1 mm coarse • 1 – 2 mm very coarse • Gravels: 2-75 mm • Cobbles:75-250 mm Sand Silt Clay • Stones: 250-600 mm • Boulders: >600 mm Dime Frisbee Beachball
Texture Determination • Laboratory Methods • Pipette method • Hydrometer method • Field • “Feel” of soil when moistened and worked • Graininess, coherence, smoothness, stickiness • Ribboning behavior
Sand + Silt + Clay = 100% 34 % Sand Texture = 33 % Silt CLAY LOAM 33 % Clay
FFA Land Judging Texture • Old Contest • New Contest • 3 textures • 5 textures • Sand (sand, loamy sand) • Coarse (sand, loamy sand) • Clay (sandy clay, clay, silty • Moderately Coarse clay) (sandy loam) • Loam (silt, silt loam, loam, • Medium (loam, silt loam, sandy loam, sandy clay loam, silt) clay loam, silty clay loam) • Moderately Fine (sandy clay loam, clay loam, silty clay loam) • Fine (sandy clay, clay, silty clay)
Triangle Comparison
Urban Contest – Texture, Subsoil
Urban Contest – Texture, Substratum
Urban Contest – Structure, Subsoil
Urban Contest – Structure, Subsoil • Soil Structure is the result of soil particles that bind together to form aggregated soil peds. Structure is a very important characteristic of the soil because it can allow or disallow good air and water movement, and allow for good root penetration.
Structure Types
Granular
Blocky
Platy
Single Grained
Massive
Urban Contest – Drainage Class
Redoximorphic Features • Redoximorphic features are red, yellow and gray colored depletions and concentrations that are indicative of a saturated zone within the soil profile. Redox depletions are gray in color (chromas of < 2) where elements solubilized by anaerobic or reducing conditions have been removed. The redox depletions are the indicator of where the water table is located. Redox concentrations are the red or red-yellow concentrations of iron oxides. Redox features are described by their presence, abundance, and contrast.
Redoximorphic Features
Redoximorphic Features Concentrations and Depletions
Urban Contest – Drainage Class
Urban Contest – Drainage Class
Urban Contest – Depth to Restrictive Soil Features
Urban Contest – Depth to Restrictive Soil Features • Any layer that limits water and roots altogether, or into vertical seams and plains of weakness. • NOT Bedrock! • Dense Glacial Till • Fragipans • Dense Lacustrine Deposits. * The above are only examples of layers that could be considered restrictive. Other layers not listed could still limit water and roots, and would still be considered a restrictive feature.
Urban Contest – Depth to Bedrock
Bedrock • Some bedrock is soft in place and can be excavated. Typically after the material is uncovered, it will harden. • Siltstone, sandstone and shale are examples of soft bedrock. • For this contest, both soft and hard bedrock will be considered bedrock.
Urban Contest – Part II
Urban – BMPs – Buildings with Basements BMP • Moderate to extensive landshaping is required; a protective soil cover should be used to reduce erosion during construction. Condition to call for BMP • Slopes between 6 and 35 percent
Urban – BMPs – Buildings with Basements BMP • Choose an alternate site. - *when this is selected , no other selection should be marked Condition to call for BMP • Areas subject to flooding, slippage, subsidence, seasonal high water table less than 8 inches on nearly level concave slope, or slopes greater than 35 percent
Urban – BMPs – Buildings with Basements BMP • Basement walls should be reinforced and porous material used for backfill to reduce damage from shrinking and swelling. Condition to call for BMP • Fine texture present in the subsoil or substratum
Urban – BMPs – Buildings with Basements BMP • Footer drains, elevated site, exterior waterproofing coatings on the basement walls, and granular porous material for backfill should be used to prevent wet basements. Condition to call for BMP • Seasonal high water table present within 40 inches
Urban – BMPs – Buildings with Basements BMP • Basement excavation should include 3/1 side slopes to decrease the likelihood of soil sloughing and undercutting. • Condition to call for BMP • Single grained soil structure in the subsoil
Urban – BMPs – Buildings with Basements BMP • Moderate to extensive excavation of bedrock is required, or redesign the building to accommodate the site. Condition to call for BMP • Bedrock within 60 inches
Urban – BMPs – Buildings with Basements BMP • Good site; limitations are easy to overcome. Condition to call for BMP • No moderate or severe limitations
Urban – BMPs – Sewage Treatment Systems BMP • Manufacturer’s prohibitions and instructions should be followed when installing components on steep slopes. An alternative method of distribution should be used. Condition to call for BMP • Slopes greater than 18 percent
Urban – BMPs – Sewage Treatment Systems BMP • Choose an alternate site. Condition to call for BMP • Areas subject to flooding, slippage or subsidence
Urban – BMPs – Sewage Treatment Systems BMP • Use an alternative system or design component such as drip distribution, spray irrigation, or an approved pretreatment device to ensure uniform dispersal and water quality standards. Condition to call for BMP • Any of the following present: Slopes 6 to 12 %, coarse or fine texture in any layer, single grained, platy or massive soil structure, moderately deep to restrictive features or bedrock.
Urban – BMPs – Sewage Treatment Systems BMP • Design and implement an engineered drainage system to effectively lower the seasonal water table. Condition to call for BMP • Seasonal high water table within a depth of 16 inches, with no other moderate or severe limitations.
Urban – BMPs – Sewage Treatment Systems BMP • Elevate the infiltrative surface of soil absorption components above the ground surface to increase the vertical separation distance through the use of approved sand fill material. Condition to call for BMP • Less than 20 inches to restrictive soil features or bedrock
Urban – BMPs – Sewage Treatment Systems BMP • Conventional leaching trenches will work well on this site. Condition to call for BMP • No moderate or severe limitations
Urban – BMPs – Driveways and Local Roads BMP • Contruct driveways and local roads across the slope to reduce the angle of incline. Place drainage ditch on the upslope side. Condition to call for BMP • Slopes greater than 6 percent
Urban – BMPs – Driveways and Local Roads BMP • Elevate driveways and local roads above the anticipated high water level Condition to call for BMP • Flood plains
Urban – BMPs – Driveways and Local Roads BMP • Costly measures are needed to reduce the hazard of slippage or subsidence. Condition to call for BMP • Soils subject to slippage or subsidence
Urban – BMPs – Driveways and Local Roads BMP • Replace the surface soil and/or subsoil with suitable base material to prevent damage due to low soil strength. Condition to call for BMP • Any of the following present: medium textured soil in any layer, or moderately fine textured soil in the surface, single grained and granular structure in the subsoil.
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