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8/3/2019 Soil Infiltration
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Soils Defined
Natural Body that Occurs on the LandSurface that are Characterized by One or
More of the Following:
Consists of Distinct Horizons or Layers
The ability to support rooted plants in a natural
environment
Upper Limit is Air or Shallow Water Lower Limit is Bedrock or Limit of Biological Activity
Classification based on a typical depth of 2 m or
approximately 6.0 feet
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Another Definition of Soils
A Natural 3 - Dimensional Body at the
Earth Surface
Capable of Supporting Plants
Properties are the Result of Parent Material,
Climate, Living Matter, Landscape Position
and Time.
Soil Composed of 4 Components (mineralmatter, organic matter, air, and water)
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Five Soil Formation
Factors
Organisms
Climate Time
Topography and
Landscape Setting
Parent Material
R
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Soil Food Web - Organisms
Micro &Macroscopic
Decomposition of
Organic Matter
Animals Living in
Soil
Vegetation Types
Human Activity
Redoximorphic
Feature Formation
Image Source: The University of Minnesota, 2003
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Climatic Elements
(Energy & Precipitation)
Annual and Seasonal
Rainfall Temperature Range
Biologic Production
and Activity
Weathering (Wind,
Water, and Ice)
Translocation of
Material
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Climate and Soil Development
Image Source: University of Wisconsin, 2002
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Geologic Time
Time
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Landscape and Relief
(Soil Texture)
Image Source: University of Wisconsin, 2002
A- Sandy Texture
and
Loamy Sand
B- Sandy
Textures
C- Clay Loam,Loam, Silt Loam
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Landscape and Relief
(Drainage)
Image Source: NJ NRCS, 2002
Water Movement
Soil Drainage
Landscape
Configuration
(Convex, Concave)
Elevation
Water Movement
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Parent Material
Geological Materials
Minerals and Rocks
Glacial Materials
Loess (wind blown)
Alluvial Deposits Marine Deposits
Organic Deposits
Influences
Minerals Present
Colors
Chemical Reactions
Water Movement
Soil Development
Glacial Material
Bedrock
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Soil Horizons
Layer of Soil Parallel
to Surface
Properties a function
of climate, landscapesetting, parent
material, biological
activity, and other soil
forming processes. Horizons (A, E, B, C,
R, etc)
Image Source: University of Texas, 2002
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Soil Horizons
O- Organic Horizons Organic Layers of
Decaying Plant and
Animal Tissue Aids Soil Structural
Development
Helps to Retain Moisture
Enriches Soil withNutrients
Infiltration Capacity
function of Organic
Decomposition
O Horizon
Dark in Color Because of
Humus Material - 1,000,000
bacteria per cm3
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Soil Horizons
A Horizons: Topsoil Mineral Horizon Near
Surface
Accumulation of Organic
Material
Eluviation Process Moves
Humic and Minerals from O
Horizon into A horizon
Ap - Plowed A Horizon
Ab - Buried Horizon
Soil dark in color, coarser in
texture, and high porosity
A Horizon
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Soil Horizons: E Horizons
Albic Horizon (Latin - White) Mineral Horizon Near
Surface
Movement of Silicate Clay,Iron, and Aluminum from the A
Horizon through Eluviation
Horizon does not mean a water
table is present, but the horizoncan be associated with high
water table , use Symbol Eg
(gleyed modifier)
Underlain by a B (illuvial)
horizon
E Horizon
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Soil Horizons: B Horizons
Zone of Maximum Accumulation Mineral Horizon
Illuviation is Occurring -
Movement into the Horizon
B Horizon Receives Organic andInorganic Materials from Upper
Horizons.
Color Influence by Organic, Iron,
Aluminum, and Carbonates
Bw - Weakly Colored or Structured
Bhs- Accumulation of illuvial
organic material and sesquioxides
Bs- Accumulation of sesquioxides
Bt- Translocation of silicate clay
Bx- Fragipan Horizon, brittle
Bhs Horizon
Bs Horizon
Bw Horizon
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Soil Horizons: Bx and Bt Horizons
Bx: B horizon with fragipan, a compact,
slowly permeable subsurface horizon that
is brittle when moist and hard when dry.
Prismatic soil structure, mineral coatings
and high bulk density
Horizons Indicate Reduced Infiltration
Capacity and Permeability
Bt: Clay accumulation is indicated by
finer soil textures and by clay
coating peds and lining pores
Area of Highest
Permeability
along Prism
Contact
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C- HorizonsDistinguished by Color,
Structure, and Deposition
Mineral Horizon or Layer,
excluding Rock
Little or No Soil-Forming May be Similar to
Overlying Formation
May be Called Parent
Material
Layer can be Gleyed
Developed in Place or
Deposited
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R- Horizons
Hard, Consolidated
Bedrock
Typically Underlies a
C Horizon, but could
be directly below an A
or B Horizon.RHorizon
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Soil Hydrologic Cycle
Source: Vepraskas, M.J, et. Al. Wetland Soils, 2001.
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Soil Drainage Class
and Soil GroupSoil Drainage Class - Refers to Frequencyand Duration of Periods of Saturation or Partial
Saturation During Soil Formation. There are 7
Natural Soil Drainage Classes.
Hydrologic Soil Group-Refers to SoilsRunoff Producing Characteristics as used in the
NRCS Curve Number Method. There area 4
Hydrologic Soil Groups (A, B, C, D).
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Group A and BGroup A is sand, loamy sand or sandy loam types of
soils. It has low runoff potential and high
infiltration rates even when thoroughly wetted.
Deep, well to excessively drained sands or gravels
and have a high rate of water transmission. Root
Limiting / Impermeable layers over 100 cm or 40
inches*****************
Group B is silt loam or loam. It has a moderate
infiltration rate when thoroughly wetted.
Moderately deep to deep, moderately well to well
drained soils with moderately fine to moderately
coarse textures. Root Limiting / Impermeable e
layers over 50 to 100 cm or 20 to 40 inches
Group A- Well Drained
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Group C and DGroup C soils are sandy clay loam. They have
low infiltration rates when thoroughly wettedand consist chiefly of soils with a layer that
impedes downward movement of water and
soils with moderately fine to fine structure.
Perched water table 100 to 150 cm or 40 to 60
inches; root limiting 20 to 40 inches.
*****************
Group D soils are clay loam, silty clay loam,
sandy clay, silty clay or clay. They have very
low infiltration rates when thoroughly wetted
and consist chiefly of clay soils with a high
swelling potential, soils with a permanent highwater table, soils with a claypan or clay layer at
or near the surface and shallow soils
over nearly impervious material ( < 20 inches).
Group D - Poorly Drained
Highest Runoff Potential
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Definitions
Infiltration - The downward entry of water into the immediate
surface of soil or other materials.
Infiltration Capacity- The maximum rate at which water can
infiltrate into a soil under a given set of conditions.
Infiltration Rate- The rate at which water penetrates the surface of
the soil and expressed in cm/hr, mm/hr, or inches/hr. The rate of
infiltration is limited by the capacity of the soil and rate at which
water is applied to the surface. This is a volume flux of water
flowing into the profile per unit of soil surface area (expressed asvelocity).
Percolation -Vertical and Lateral Movement of water through the
soil by gravity.
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Infiltration Rate and Capacity
Soil Factors that Control Infiltration Rate:
- Vegetative Cover, Root Development and Organic Content
- Moisture Content
- Soil Texture and Structure- Porosity and Permeability
- Soil Bulk Density and Compaction
- Slope, Landscape Position, Topography
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Infiltration Rate (Time Dependent)
Decreasing Infiltration
Infiltration with Time Rate is Initially
High Because of a Combination of
Capillary and Gravity Forces
Final Infiltration Capacity
(Equilibrium)- Infiltration
Approaches Saturated
Permeability
Steady GravityInduced Rate
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Infiltration Rate (Moisture)Infiltration Decreases with Time
1) Changes in Surface and Subsurface Conditions
2) Change in Matrix Potential
3) Overtime - Matrix Potential Decreases and Gravity Forces
Dominate - Causing a Reduction in the Infiltration Rate
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Measuring Infiltration Rate
Flooding (ring) Infiltrometers
Single ring
Double ring
Flooded Infiltrometers
Tension Infiltrometers
Rainfall-Runoff Plot Infiltrometers
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Measuring Infiltration Rate
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Single Rings Infiltrometers
Cylinder - 30 cm in Diameter
Drive 5 cm or more into Soil Surface or Horizon
Water is Ponded Above the Surface
Record Volume of Water Added with Time to Maintain a
Constant Head
Measures a Combination of Horizontal and Vertical Flow
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Double Rings Infiltrometers
Outer Rings are 6 to 24 inches in Diameter (ASTM - 12 to 24 inches)
Mariotte Bottles Can be Used to Maintain Constant Head
Rings Driven - 5 cm to 6 inches in the Soil and if necessary sealed
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Other Infiltrometers
Ponded InfiltrometersTension Infiltrometer
Unsaturated Flow Of Water
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Infiltration Rate by
Soil Group/ Texture
Source: Texas Council of Governments, 2003.
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Infiltration Rate
Function of Slope & Texture
Source: Rainbird Corporation, derived from USDA Data
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Infiltration Rate
Function of Vegetation
Source: Gray, D., Principles of Hydrology, 1973.
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Comparison Infiltration to
Percolation Testing
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1 2 3 4 5 6 7 8 9 10
Trail
Rate(in/hr)
Infiltraton Test
Percolation Test
Percolation
Testing
Over
EstimatedInfiltration
Rate by 40
to over
400%
Source: On-site Soils Testing Data, (Oram, B., 2003)
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0
2
4
6
8
10
12
14
16
18
20
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Rate
(in/hr)
Infiltration Rock Content < 20 %
Infiltration Rock Content > 60 %
Infiltration and Rock Content (Oram, B. 2003)
fil i
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Infiltration
(Compaction/ Moisture Level)
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Case 1 :Myers Proposed Development
Worcester Township, Pennsylvania
Abbottstown Silt Loam,Deep to Moderately Deep, Somewhat Poorly Drained
Some Areas Shallow Depth to Firm Bedrock
Signs of Erosion
Low Surface and Near Surface Infiltration Rates
Associated with Surface Smearing, Btx, Bx Horizons
BC/ C /R Horizons Higher Infiltration Rate.
Readington Silt Loam
Deep Moderately Well Drained
Low Infiltration Surface, Bd, and Btx
High Infiltration in C and R Horizons
I filt ti R t
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Infiltration Rate
Function of Horizon A, B, Btx, Bt, C, R
C/R Testing - Areas Fractured Rock
Source: On-site Infiltration Testing - Mr. Brian Oram, PG (2003)
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Case 2: Country View at Salford
Salford Township, Montgomery County, PA
Soil CrB2 Croton Silt Loam
Deep, Poorly Drained
Diagnostic Features: Bx, Bxg, Bt, R (firm)
Reported Infiltration Rate: < 0.2 to 2.0 in/hr
Field Measured Rate: 0.1 to 0.52 in/hr
Primary Natural Drainage:
Depression Storage, Swale Development, Throughflow
Flow Through Wetland Areas, Overland Flow
Predevelopment Conditions:
Unstable Stream Banks, Overland Flow from Off Site
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Evaluation InfiltrationStep 1: Desktop Assessment - GIS
Review Published Data Related to Soils, Geology, Hydrology
Step 2: Characterize theHydrological Setting
Where are the Discharge and Recharge Zones?
What forms of Natural Infiltration or Depression Storage Occurs?
Step 3: On-Site Assessment
Deep Soil Testing Throughout Site Based on Soils and Geological Data
Double Ring Infiltration Testing
How will water move through the site ?
Step 4: Engineering Review and Evaluation
Step 5: Additional Infiltration or On-site Testing
Step 6: Final Design
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Soils, Infiltration,
and On-site TestingPresented by:
Mr. Brian Oram, PG, PASEO
Wilkes University
GeoEnvironmental Sciences and
Environmental Engineering Department
Wilkes - Barre, PA 18766
570-408-4619
http://www.water-research.net
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Horton Equation (1939)
Infiltration is a Function of Time as defined by:
f(t) = fc + (fo fc)e^-kt
f(t) = infiltration rate for any time t from beginning of infiltration
fc = infiltration capacity
fo = initial infiltration rate at (t=0)
e = 2.71 =base of natural log
kis a measure of the rate of decrease in infiltration rate(constant that depends on soil type)
Large Watershed Application - Replaced by Philip and Green-Ampt
Horton Method Used in EPA Storm Water Management Model
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Green-Ampt Equation Green-Ampt model was the first physically-based model/equation describing
the infiltration of water into soil. The model yields cumulative infiltration andthe infiltration rate as an implicit function of time. The volume of infiltration
was a function of:
Soil pores are saturated behind wetting front;
Wetting front moves in response to capillary forces; and
Darcys flow governs that headloss in the saturated zone.
Approx. Equation: f = (A/F)+B; f = infiltration rate, F -
accumulative infiltration, and A and B are fitted parameters
The Green-Ampt Model has been modified to calculate water
infiltration into non-uniform soils by several researchers . In 1989,GALAYER was developed for heterogenous soils
Models Available at:
http://www.epa.gov/ada/csmos/ninflmod.html
http://www.bae.ncsu.edu/soil_water/drainmod/dmversions.htm
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Philip Equation (1960)
where:
F = total depth of infiltrated water in mm.
t = time in seconds K = hydraulic conductivity in mm/secm = the average moisture content of the soil to the depth of the wetting front
m--0 = initial soil moisture content - based on API calculation or input
Pot = capillary potential at the wetting front in mm
Pot = 250 log (K) + 100
D1 = depth of water on the soil surface
Takes into account the Ponding Head
Models Available at:
http://www.epa.gov/ada/csmos/ninflmod.html
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Soils, Infiltration,
and On-site Testing
Presented by:
Mr. Brian Oram, PG, PASEO
Wilkes University
GeoEnvironmental Sciences and
Environmental Engineering DepartmentWilkes - Barre, PA 18766
http://www.water-research.net