Soils, Groundwater Recharge,
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
Presentation Dedicated To
Mr. John Pagoda, Jr
Anthracite Mining History Expert
Geologist and Soil Scientist in Training
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
(Chris Watkins, 2002)
– 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
Soils Are A Three Phase System
• 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)
Air and Water – 35 to 55 %
Solid Material – 45 to 65 %
Five Soil Formation
Factors
•
•
•
•
Organisms
Climate
Time
Topography and
Landscape Setting
• Parent Material
R
Point: Soils are Created in Geological Time, but can be
destroyed in a very short time – Keys are Proper Site
Design and Management
Describing Soils
Do Not Rely on Published Soils Mapping
•
•
•
•
•
•
•
Soil Texture
Structure
Consistency
Soil Color
Coarse Fragment Content
Redoximorphic Features
other Diagnostic Properties
Soil Texture
Get Your Hands Dirty
The way a soil "feels" is called the soil texture. Soil texture
depends on the amount of each size of particle in the soil.
The three soil separates: sand, silt, and clay.
Sand are the largest particles and they feel "gritty."
Silt are medium sized, and they feel soft, silky or "floury."
Clay are the smallest sized particles, and they feel "sticky”
when wet and they are hard to squeeze.
Soil Textural Classification
Source: Brady, Nyle. 1990. The Nature and Properties of Soils
Soil Textural Triangle
USDA System
Soil Structures
Water Movement and Structure
Field Photos
Me
Confirmation Testing
Side-by-Side
Testing
Vertical
Permeability
Testing
Nearly 50% of Soil is Space or
Space Filled with Water
• Water – 25+ %
• Air – 25 + %
• Pore Space Makes Up
35 to 55 % of the
total Soil Volume
• This Space is called
Pore Space
Types of Pores
Macropores (> 1,000 microns)-Large
Mesopores (10 to 1,000 microns)- Medium
Micropores (< 10 microns)- Small
Source: http://www2.ville.montreal.qc.ca
How can a
silt loam have
more
macropores
than sand?
Source:
Brady, Nyle,
C. “ The
Nature and
Properties of
Soils” (1990).
Better
Structural
Development
More
Macropores
Source: Brady,
Nyle, C. “ The
Nature and
Properties of
Soils” (1990).
Key Points on Soil Pores
Under gravity, water drains from macropores, where as,
water is retained in mesopores and micropores, via matrix
forces.
Coarse-textured horizons (e.g., sandy loam) tend to have a
greater proportion of macropores than micropores- but they
may not have more macropores than finer textured soils.
Soils with water stable aggregates tend to have a
higher percentage of macropores than micropores.
Proportion of micropores tends to increase with soil depth,
resulting in greater retention of water and slower flow of
water .
Water Stable Aggregates I
Aggregates on left are
more water stable, i.e.,
aggregate stays
together and do not
separate into the its
components, i.e., three
soil separates.
Water Stable Aggregates
Water Stable Aggregates – II
The Classic Photo
Source: Brady, Nyle, C. “ The Nature and Properties of Soils” (1990)
Great Desk Reference Text !!!!
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
• Organic Matter Critical in
Maintaining Water Stable
Peds
Soil Horizons
A Horizons: “ Topsoil”
A Horizon
• Mineral Horizon Near
Surface
• 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
• Mineral Horizon
Bhs Horizon
• Illuviation is Occurring - Movement
into the Horizon
• B Horizon Receives Organic and
Inorganic Materials from Upper
Horizons.
Bs Horizon
Bw Horizon
• 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 Structure and Horizon
Source: http://www.vanaturally.com/soil.html
Soil Physical Properties
• Particle Density (pd)- Approximately 2.65 g/cm^3
mass solid particles /volume soilds
• Dry Bulk Density (bd)
Mass oven dry soils / bulk volume of soil (soils)
Mass wet soil/ bulk volume of soil (engineers)
• Water Content by weight (Og)
Mass of Water/ Mass of dry Soil
• Water content by volume (Ov)
Volume of Water/ Volume of Soil
• Porosity (n)=(1- (Bulk Density /Particle Density))
• Degree Saturation – Volume Wet/ Volume Total
• Depth of Water (dw) = Ov* soil depth (d)
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 are 4
Hydrologic Soil Groups (A, B, C, D).
•Drainage Class and Soil Group were developed
for agricultural applications.
Hydrologic Group A
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 A- Well Drained
Hydrologic Group B
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.
Group B
With Fragipan
Root Limiting / Impermeable
Layers over 50 to 100 cm or 20 to
40 inches.
Hydrologic Group C
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.
Redoximorphic
Perched water table 100 to 150 cm
or 40 to 60 inches; root limiting 20
to 40 inches.
Water
Group D
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).
Gleyed Horizon
Group D - Poorly Drained
Highest Runoff Potential
Hydrologic Soil Terms
•Infiltration - The downward entry of water into the immediate
surface of soil or other materials.
•Infiltration Flux (or Rate)- The volume of water that 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. It is a volume flux of water flowing
into the profile per unit of soil surface area (expressed as velocity).
•Infiltration Capacity (fc)- The amount of water per unit area of time
that water can enter a soil under a given set of conditions at steady state.
•Cumulative infiltration: Total volume of water infiltrated per unit area
of soil surface during a specified time period.
Horton Equation, Philip Equation, Green- Ampt Equation
Flux Density or Permeability
Flux Density (q): The volume of water
passing through the soil per unit crosssectional area per unit of time.
It has units of length per unit time such as mm/sec,
mm/hour, or inches/ day (q = -K(ΔH/L ))
Actually the term is volume/area/time= q = Q/At
Hydraulic Conductivity (K) quantitative measure
of a saturated soil's ability to transmit water
when subjected to a hydraulic gradient. It can be
thought of as the ease with which pores of a
saturated soil permit water movement .
Side by Side (Pagoda, J, 2004)
Percolation Rate
Percolation -Downward Movement of Water
through the soil by gravity. (minutes per inch) at a
hydraulic gradient of 1 or less.
Used and Developed for Sizing Small Flow On-lot
Wastewater Disposal Systems.
Onlot Disposal Regulations (Act 537) has preliminary
Loading equations, but for large systems regulations
typically require permeability testing.
Also none as the Perc Test, SoakAway Test (UK)
Not Directly Correlated to
or a Component of Unsaturated or
Saturated Flow Equations
Comparison Infiltration to Percolation Testing
4.5
4
Infiltraton Test
Rate (in/hr)
3.5
3
Percolation
Testing Over
Estimated
Infiltration
Rate by 40% to
over 1000% *
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)
Recharge and
Recharge Capacity
Soil Factors that Control Recharge:
- Vegetative Cover, Root Development and Organic Content
- Surface Infiltration Rates
- Moisture Content
- Soil Texture and Structure
- Porosity and Permeability
- Soil Bulk Density and Compaction
- Slope, Landscape Position, Topography
Infiltration Rate
Function of Slope & Texture
Source: Rainbird Corporation, derived from USDA Data (Oram,2004)
Infiltration Rate
Function of Vegetation
Source: Gray, D., “Principles of Hydrology”, 1973.
Infiltration
(Compaction/ Moisture Level)
Site Compaction – Can Significantly Reduce Surface Infiltration Rate
Rain Drop Impact Bare Soil
Destroys Soil Aggregates
Disperses Soil Separates
Seals Pore Space
Aids in Loss of Organic Material
Creates a Surface Crust
Source: (D. PAYNE, unpublished)
http://www.geographie.uni-muenchen.de
Infiltration Rate (Time Dependent)
Steady Gravity
Induced Rate
Infiltration with Time Initially
High Because of a Combination of
Capillary and Gravity Forces
f = fc +(fo-fc) e^-kt
fc does not equal K
Final Infiltration Capacity
(Equilibrium)- Infiltration
Approaches q - Flux Density
Infiltration Rate
Decreases with Time
1) Changes in Surface and
Subsurface Conditions
2) Change in Matrix
Potential and Increase in Soil
Water Content and Decrease
in Hydraulic Gradient
3) Overtime - Matrix
Potential Decreases and
4) Reaches a steady-state condition
Gravity Forces
fc – final infiltration rate
Dominate - Causing a
Reduction in the Infiltration
Rate
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)
Double Ring Infiltrometer
Single Rings Infiltrometers
Cylinder - 30 cm in Diameter- Smaller Rings Available.
Drive 5 cm or more into Soil Surface or Horizon.
Water is Ponded Above the Surface- Typically < 6 inches.
Record Volume of Water Added with Time to Maintain a
Constant Head.
Measures a Combination of Horizontal and Vertical Flow
ASTM 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
Very Difficult to Install and Seal – ASTM Double Rings in NEPA
Potential Leaking Areas
Significant Effort is Need to Seal Install and Seal Units
ASTM requires documentation of the
Depth of the Wetting Front
Other Double Rings Small Diameter
Easier to Install and Repeat Testing
6” and 12” Double Ring
3” and 5” Double Ring in
12” Diameter Flooded Pit
Infiltration Data- Double Ring Test
Note: Ring Diameter – 26 cm (Oram 2005)
Infiltration Rate –cm/hr
Cumulative Infiltration
(cm)
Steady-State Rate (slope)
0.403 cm/hr *
Fc = Ultimate Infiltration
Capacity (approx.0.47 cm/hr)
Darcys Law- Saturated Flow
Vertical or Horizontal
Volume of discharge rate Q is proportional to the head
difference dH and to the cross-sectional area A of the column,
but is is inversely proportional to the distance dL of the flow path and
coefficient K is called the hydraulic conductivity of the soil.
The average flux can be obtained by dividing Q with A.
This flux is often called Darcy flux qw .
Estimated Methods- Grain Size
Hazen Method
Applicability: sandy
sediments
• K = Cd10 2
• d10 is the grain diameter
for which 10% of
distribution is finer,
"effective grain size" where D10 is between 0.1
and 0.3 cm
• C is a factor that
depends on grain size
and sorting
Very Fine
Sand, poorly
Sorted
40 - 80
Fine Sand with
fines
40 - 80
Medium Sand,
Well Sorted
80 - 120
Coarse Sand,
Poorly Sorted
80 - 120
Coarse sand,
well
Sorted, clean
120 - 150
Guelph and Amoozegar
Borehole Permeameters
$ 1500
each
Field Testing (Oram, 2000)
Photo Source:http://www.usyd.edu.au
Measuring Permeability
12-inch/ 6-inch Double Ring
Constant or Falling Head Permeameter
Side by Side Testing Mr. Brian Oram and Mr. Chris Watkins, 2003.
Constant Head
Borehole Permeameters
Talsma Permeameter
Modified Amoozegar
Side by Side Testing by Mr. Brian Oram and Mr. John Pagoda, 2004
Darcy Equation- What is Delta H?
Measuring Infiltration Rate
to Estimate/ Calculate the Flux Density
• Infiltrometers- Yes !
– Single ring- Yes !
– Double ring- Yes ! - May be difficult in rocky
terrain.
– Smaller Double Ring in Flood Pit – Yes !
• Flooded Infiltrometers – Yes !
• Adoption of ASTM Methods – Likely not
appropriate, but method should be used as a guide
by professionals.
Percolation Testing
• Does not directly measure permeability or a flux
velocity.
• Has been used to successfully design small flow on-lot
wastewater disposal systems, but equations and designs
have a number of safe factors.
• Results may need to be adjusted to take out an estimate
of the amount of horizontal intake area.
• Without Correction Percolation Data over-estimated
infiltration rate data by 40 to over 1000 % with an
adjustment for intake area error could be reduced to 10
to 200% (Oram, 2003) .
• May need to consider the use of larger safety factors
and equations similar to sizing equations used for onlot disposal systems.
Permeability Testing
• Borehole Permeability Testing can be a Suitable
Method.
• Falling Head and Constant Head Methods may be
suitable.
• Permeability Data for Specific Site should be calculated
using Geometric Average.
• Equations and Methods Based on Darcy’s Law and the
result is a value for K or q.
• Do not recommend estimating permeability based on
particle size distribution.
• Laboratory permeability testing is possible, but it may
be difficult to get a representative sample and account
for induced changes.
How Do We Use this Information?
None Structural
Development Practices
• Maintain Soil Quality and Maximize the Use of
Current Grading to Minimize Loss of O, A, and
upper B horizons.
• Minimize Compaction, Maximize Native
Vegetation, and Use Good Construction Practices
• Consider Hydrological Setting and Existing
Hydrological Features in Site Design and Layout
Answer: New Development/ Construction Practices
Sizing Example I
•
•
•
•
•
•
•
•
Impervious Area – 2500 ft2
Design Storm – 1.3 inch
Volume of Water to Recharge- 2026 gallons
Design Loading
0.1 in3/in2/hour =0.1 in/hr = 1.49 gpd/ft2
Recharge Period – 72 hours
Recharge Volume per day – 675 gpd
Minimum Recharge Area- (675/1.49) = 453 ft2
Minimum Depth to Store 2026 gallons with
Rock Porosity of 35 % - 1.7 feet
Primary Limiting Factor is Not Recharge Capacity
but Providing Recharge Area and Detention
Storage Prior to or as Part of Recharge System
Sizing Example I
•Impervious Area – 2500 ft2
•Design Storm – 1.3 inch
•Volume of Water to Recharge- 2026 gallons
•Design Loading
0.1 in3/in2/hour =0.1 in/hr = 1.49 gpd/ft2
•Recharge Period – 48 hours
•Recharge Volume per day – 1013 gpd
•Minimum Recharge Area- (1013/1.49) = 679 ft2
• Buffer Zone Option- 25 foot wide vegetative zone
•at least 30 feet long (Width/Length Function of Slope)
May Want to Consider- Forested Or Vegetative Overland Flow
or BioRetention / Recharge Systems or Increasing Recharge Period
Sizing Example II
•
•
•
•
•
•
•
•
Impervious Area – 2500 ft2
Design Storm – 1.3 inch
Volume of Water to Recharge- 2026 gallons
Design Loading
0.5 in3/in2/hour =0.5 in/hr = 7.481 gpd/ft2
Recharge Period – 72 hours
Recharge Volume per day – 675 gpd
Minimum Recharge Area- (675/7.48) = 90 ft2 (100 ft2)
Minimum Depth Combination 8 ft * 3 ft Tank in 3 foot
Aggregate Bed
Primary Limiting Factor is Not Recharge Capacity
but Providing Detention Storage Prior to or as Part
of Recharge System
Sizing Example III
• Impervious Area – 2500 ft2
• Design Storm – 1.3 inch
• Volume of Water to Recharge- 2026 gallons
• Design Loading
1.0 in3/in2/hour =1.0 in/hr = 14.9 gpd/ft2
• Recharge Period – 24 hours
• Recharge Volume per day – 2026 gpd
• Minimum Recharge Area- (2026/14.9) = 136 ft2
• Minimum Depth Combination 8 ft * 3 ft Tank in 3 foot
Aggregate Bed
Primary Limiting Factor is Not Recharge Capacity
but Providing Detention Storage Prior to or as Part
of Recharge System
Evaluating Recharge Capacity
•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?
•How does the site currently manage runoff ?
•What are the existing conditions or existing
problems?
Evaluation Recharge Capacity
•Step 3: On-Site Assessment
Deep Soil Testing Throughout Site Based on Soils and Geological
Data
Double Ring Infiltration Testing or Permeability Testing to
calculate q and provide estimate of loading rates
How does the water move through the site ?
•Step 4: Engineering Review and Evaluation
(meet with local reviewers and PADEP)
•Step 5: Additional On-site Testing
•Step 6: Final Design and Final BMP Selection
Artificial Soil Quality Improvement
Aggregate Stability- Using Soil
Conditioner
No Soil Conditioner
Less Soil Conditioner
Source: Brady, N. C., 1990
Soils, Groundwater Recharge,
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
PADEP in the Field