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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 Presentation Dedicated To Mr. John Pagoda, Jr.

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Soils groundwater recharge and on site testing l.jpg

Soils, Groundwater Recharge, and On-site Testing

Presented by:

Mr. Brian Oram, PG, PASEOWilkes UniversityGeoEnvironmental Sciences and Environmental Engineering DepartmentWilkes - Barre, PA 18766570-408-4619

Presentation dedicated to mr john pagoda jr l.jpg
Presentation Dedicated ToMr. John Pagoda, Jr

Anthracite Mining History Expert

Geologist and Soil Scientist in Training

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Soils Defined

  • Natural Body that Occurs on the Land Surface that are Characterizedby One or More of the Following:

    • Consists of Distinct Horizons or Layers

    • The ability to support rooted plants in a naturalenvironment

    • 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

(Chris Watkins, 2002)

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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 Positionand Time.

Soil Composed of 4 Components (mineral matter, organic matter, air, and water)

Air and Water – 35 to 55 %Solid Material – 45 to 65 %

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Five Soil Formation Factors

  • Organisms

  • Climate

  • Time

  • Topography and Landscape Setting

  • Parent Material


Point: Soils are Created in Geological Time, but can be destroyed in a very short time – Keys are Proper Site Design and Management

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Describing SoilsDo Not Rely on Published Soils Mapping

  • Soil Texture

  • Structure

  • Consistency

  • Soil Color

  • Coarse Fragment Content

  • Redoximorphic Features

  • other Diagnostic Properties

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Soil TextureGet 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.

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Soil Textural Classification

Source: Brady, Nyle. 1990. The Nature and Properties of Soils

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Field Photos


Confirmation Testing


Vertical PermeabilityTesting

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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

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Types of Pores

Macropores (> 1,000 microns)-Large

Mesopores (10 to 1,000 microns)-Medium

Micropores (< 10 microns)- Small


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How can a

silt loam have more


than sand?

Source: Brady, Nyle, C. “ The Nature and Properties of Soils” (1990).

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Better Structural Development More


Source: Brady, Nyle, C. “ The Nature and Properties of Soils” (1990).

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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 .

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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

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Water Stable Aggregates – IIThe Classic Photo

Source: Brady, Nyle, C. “ The Nature and Properties of Soils” (1990)Great Desk Reference Text !!!!

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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

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Soil HorizonsO- Organic Horizons

  • 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

O Horizon

Dark in Color Because of Humus Material - 1,000,000 bacteria per cm3

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Soil HorizonsA Horizons: “ Topsoil”

  • Mineral Horizon NearSurface

  • 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 HorizonsAlbic Horizon (Latin - White)

  • Mineral Horizon NearSurface

  • 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

E Horizon

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Soil Horizons: B HorizonsZone of Maximum Accumulation

  • 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

Bhs Horizon

Bs Horizon

Bw Horizon

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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

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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.

R Horizon

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Soil Structure and Horizon


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Soil Physical Properties

  • Particle Density (pd)- Approximately 2.65 g/cm^3mass 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)

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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 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 foragricultural applications.

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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

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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.

Root Limiting / Impermeable

Layers over 50 to 100 cm or 20 to

40 inches.

Group B

With Fragipan

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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.

Perched water table 100 to 150 cm

or 40 to 60 inches; root limiting 20

to 40 inches.



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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 DrainedHighest Runoff Potential

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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 flowinginto 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

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Flux Density or Permeability

Flux Density (q): The volume of water passing through the soil per unit cross-sectional 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)

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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

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Comparison Infiltration to Percolation Testing

Percolation Testing Over Estimated Infiltration Rate by 40% to over 1000% *

Source: On-site Soils Testing Data, (Oram, B., 2003)

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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

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Infiltration Rate Function of Slope & Texture

Source: Rainbird Corporation, derived from USDA Data (Oram,2004)

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Infiltration Rate Function of Vegetation

Source: Gray, D., “Principles of Hydrology”, 1973.

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Infiltration (Compaction/ Moisture Level)

Site Compaction – Can Significantly Reduce Surface Infiltration Rate

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Rain Drop Impact Bare Soil

Destroys Soil AggregatesDisperses Soil SeparatesSeals Pore SpaceAids in Loss of Organic Material

Creates a Surface Crust

Source: (D. PAYNE, unpublished)

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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^-ktfc does not equal K

Final Infiltration Capacity(Equilibrium)- InfiltrationApproaches q - Flux Density

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Infiltration Rate

Decreases with Time

1) Changes in Surface and Subsurface Conditions2) Change in Matrix Potential and Increase in Soil Water Content and Decrease in Hydraulic Gradient3) Overtime - Matrix Potential Decreases and Gravity ForcesDominate - Causing a Reduction in the Infiltration Rate

4) Reaches a steady-state conditionfc – final infiltration rate

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Infiltration Rate Function of Horizon A, B, Btx, Bt, C, RC/R Testing - Areas Fractured Rock

Source: On-site Infiltration Testing - Mr. Brian Oram, PG (2003)

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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

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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 HeadRings Driven - 5 cm to 6 inches in the Soil and if necessary sealed

Very Difficult to Install and Seal – ASTM Double Rings in NEPA

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Significant Effort is Need to Seal Install and Seal Units

ASTM requires documentation of the Depth of the Wetting Front

Potential Leaking Areas

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Other Double Rings Small Diameter Easier to Install and Repeat Testing

3” and 5” Double Ring in12” Diameter Flooded Pit

6” and 12” Double Ring

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Infiltration Data- Double Ring Test

Note: Ring Diameter – 26 cm (Oram 2005)

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Cumulative Infiltration


Infiltration Rate –cm/hr

Steady-State Rate (slope)0.403 cm/hr *

Fc = Ultimate Infiltration Capacity (approx.0.47 cm/hr)

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Darcys Law- Saturated FlowVertical 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 .

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Estimated Methods- Grain Size

Hazen Method

Applicability: sandy sediments

  • K = Cd102

  • 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

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Guelph and Amoozegar Borehole Permeameters

$ 1500 each

Field Testing (Oram, 2000)

Photo Source:

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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.

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Constant Head Borehole Permeameters

Talsma Permeameter

Modified Amoozegar

Side by Side Testing by Mr. Brian Oram and Mr. John Pagoda, 2004

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Measuring Infiltration Rateto 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.

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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 on-lot disposal systems.

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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.

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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

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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

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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 Flowor BioRetention / Recharge Systems or Increasing Recharge Period

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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

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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

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Evaluating Recharge Capacity

  • Step 1: Desktop Assessment - GISReview 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?

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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

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Artificial Soil Quality ImprovementAggregate Stability- Using Soil Conditioner

No Soil Conditioner

Less Soil Conditioner

Source: Brady, N. C., 1990

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Soils, Groundwater Recharge, and On-site Testing

Presented by:

Mr. Brian Oram, PG, PASEOWilkes UniversityGeoEnvironmental Sciences and Environmental Engineering DepartmentWilkes - Barre, PA 18766


PADEP in the Field