Soils, Infiltration,
and On-site Testing
Presented 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
Soils Defined
• Natural Body that Occurs on the Land
Surface 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
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 (mineral
matter, organic matter, air, and water)
Five Soil Formation
Factors
•
•
•
•
Organisms
Climate
Time
Topography and
Landscape Setting
• Parent Material
R
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
Climatic Elements
(Energy & Precipitation)
• Annual and Seasonal
Rainfall
• Temperature Range
• Biologic Production
and Activity
• Weathering (Wind,
Water, and Ice)
• Translocation of
Material
Climate and Soil Development
Image Source: University of Wisconsin, 2002
Geologic Time
Time
Landscape and Relief
(Soil Texture)
A- Sandy Texture
and
Loamy Sand
B- Sandy
Textures
C- Clay Loam,
Loam, Silt Loam
Image Source: University of Wisconsin, 2002
Landscape and Relief
(Drainage)
Water Movement
Soil Drainage
Landscape
Configuration
(Convex, Concave)
Elevation
Water Movement
Image Source: NJ NRCS, 2002
Parent Material
• Geological Materials
– Minerals and Rocks
– Glacial Materials
– Loess (wind blown)
– Alluvial Deposits
– Marine Deposits
– Organic Deposits
Glacial Material
• Influences
– Minerals Present
– Colors
– Chemical Reactions
– Water Movement
– Soil Development
Bedrock
Soil Horizons
• Layer of Soil Parallel
to Surface
• Properties a function
of climate, landscape
setting, parent
material, biological
activity, and other soil
forming processes.
• Horizons (A, E, B, C,
R, etc)
Image Source: University of Texas, 2002
Soil Horizons
O- Organic Horizons
O Horizon
Dark in Color Because of
Humus Material - 1,000,000
bacteria per cm3
• Organic Layers of
Decaying Plant and
Animal Tissue
• Aids Soil Structural
Development
• Helps to Retain Moisture
• Enriches Soil with
Nutrients
• Infiltration Capacity
function of Organic
Decomposition
Soil Horizons
A Horizons: “ Topsoil”
A Horizon
• 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
Soil Horizons: E Horizons
Albic Horizon (Latin - White)
E Horizon
• 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 horizon
can be associated with high
water table , use Symbol Eg
(gleyed modifier)
• Underlain by a B (illuvial)
horizon
Soil Horizons: B Horizons
Zone of Maximum Accumulation
Bhs Horizon
•
•
•
•
Bs Horizon
Bw Horizon
•
•
•
•
•
Mineral Horizon
Illuviation is Occurring Movement into the Horizon
B Horizon Receives Organic and
Inorganic 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
Soil Horizons: Bx and Bt Horizons
Horizons Indicate Reduced Infiltration
Capacity and Permeability
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
Area of Highest
Permeability
along Prism
Contact
Bt: Clay accumulation is indicated by
finer soil textures and by clay
coating peds and lining pores
C- Horizons
Distinguished 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
R- Horizons
• Hard, Consolidated
Bedrock
R Horizon
• Typically Underlies a
C Horizon, but could
be directly below an A
or B Horizon.
Soil Hydrologic Cycle
Source: Vepraskas, M.J, et. Al. “ Wetland Soils”, 2001.
Soil Drainage Class
and Soil Group
•Soil Drainage Class - Refers to Frequency
and Duration of Periods of Saturation or Partial
Saturation During Soil Formation. There are 7
Natural Soil Drainage Classes.
•Hydrologic Soil Group-Refers to Soils
Runoff Producing Characteristics as used in the
NRCS Curve Number Method. There area 4
Hydrologic Soil Groups (A, B, C, D).
Group A and B
Group 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
Group C and D
Group C soils are sandy clay loam. They have
low infiltration rates when thoroughly wetted
and 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 high
water 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
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 as
velocity).
Percolation -Vertical and Lateral Movement of water through the
soil by gravity.
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
Infiltration Rate (Time Dependent)
Decreasing Infiltration
Steady Gravity
Induced Rate
Infiltration with Time Rate is Initially
High Because of a Combination of
Capillary and Gravity Forces
Final Infiltration Capacity
(Equilibrium)- Infiltration
Approaches Saturated
Permeability
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
Measuring Infiltration Rate
• Flooding (ring) Infiltrometers
– Single ring
– Double ring
• Flooded Infiltrometers
• Tension Infiltrometers
• Rainfall-Runoff Plot Infiltrometers
Measuring Infiltration Rate
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
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
Other Infiltrometers
Ponded Infiltrometers
Tension Infiltrometer
Unsaturated Flow Of Water
Infiltration Rate by
Soil Group/ Texture
Source: Texas Council of Governments, 2003.
Infiltration Rate
Function of Slope & Texture
Source: Rainbird Corporation, derived from USDA Data
Infiltration Rate
Function of Vegetation
Source: Gray, D., “Principles of Hydrology”, 1973.
Comparison Infiltration to
Percolation Testing
4.5
4
Infiltraton Test
Percolation
Testing
Over
Estimated
Infiltration
Rate by 40
to over
400%
Rate (in/hr)
3.5
3
Percolation Test
2.5
2
1.5
1
0.5
0
1
2
3
4
5
6
Trail
7
8
9
10
Source: On-site Soils Testing Data, (Oram, B., 2003)
Infiltration and Rock Content (Oram, B. 2003)
20
18
Infiltration Rock Content < 20 %
16
Infiltration Rock Content > 60 %
Rate (in/hr)
14
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14
Infiltration
(Compaction/ Moisture Level)
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
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)
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
Evaluation Infiltration
Step 1: Desktop Assessment - GIS
Review Published Data Related to Soils, Geology, Hydrology
Step 2: Characterize the Hydrological 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
Soils, Infiltration,
and On-site Testing
Presented 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
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
k is 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
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 and
the 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
– Darcy’s 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
Philip Equation (1960)
where:
F = total depth of infiltrated water in mm.
t = time in seconds K = hydraulic conductivity in mm/sec
m = the average moisture content of the soil to the depth of the wetting front
m0 = 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
Soils, Infiltration,
and On-site Testing
Presented by:
Mr. Brian Oram, PG, PASEO
Wilkes University
GeoEnvironmental Sciences and
Environmental Engineering Department
Wilkes - Barre, PA 18766
http://www.water-research.net